Study of Reef Fish Spawning Aggregations and Connectivity ... Palau SPAGS Final … · Ulong...

Study of Reef Fish Spawning Aggregations and Connectivity on the

Palauan Reef Tract

Final Report & Addendum

January 2006 TNC Pacific Island Countries

Report No. 2/06

Prepared by: Patrick L. Colin1

Coral Reef Research Foundation

For the Pacific Island Countries Coastal Marine Program The Nature Conservancy

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Author Contact Details: 1 Coral Reef Research Foundation, P.O. Box 1765, Koror, PW 96940, Republic of Palau.

Email: [email protected] Citation: Colin, P.L. 2006. Study of reef fish spawning aggregations and connectivity on the Palauan reef tract: Final Report and Addendum. Report prepared for the Pacific Island Countries Coastal Marine Program, The Nature Conservancy. TNC Pacific Island Countries Report No. 2/06. © 2006 The Nature Conservancy

All Rights Reserved. Reproduction of this publication for educational or other non-commercial purposes is authorized without prior permission from the copyright holder(s). Reproduction for resale or other commercial purposes is prohibited without prior written permission of the copyright holder(s). Donors Financial assistance was provided by the Office of Strategic Planning, Operations and Technical Support, Bureau for Asia and the Near East, U. S. Agency for International Development, under the terms of Award No. LAG-A-00-99-00045-00. The opinions expressed herein are those of the author(s) and do not necessarily reflect the view of the U. S. Agency for International Development. The Oak Foundation. The David and Lucile Packard Foundation. Report Available From: Indo-Pacific Resource Centre The Nature Conservancy 51 Edmondstone Street South Brisbane, QLD 4101 Australia Or via the worldwide web at: www.conserveonline.org Cover photo: Typical “bubble plot’ distribution of Plectropomus areolatus and Epinephelus fuscoguttatus fish densities at Ngerumekaol (Ulong Channel) aggregation site on 2 July 2005. (P.L. Colin/CRRF).

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TABLE OF CONTENTS

Table of Contents .................................................................................................................................... ii List of Figures .................................................................................................................................... ii

1. Introduction ......................................................................................................................................... 1 2. Results of Field Work.......................................................................................................................... 3

2.1. Spawning Aggregation Documentation and Time/Location of Spawning.................................. 3 2.2. Assessment and Monitoring of Spawning Aggregations ............................................................ 6 2.3. Oceanography of Spawning Aggregation Sites and Dispersal of Eggs After Spawning ............ 9

2.3.1. Barrier Reef Dynamics........................................................................................................ 9 2.3.2. Dispersal of Eggs after Spawning from Resident Aggregation Sites - Experimental Approaches ................................................................................................................................. 10 2.3.3. Barrier Reef Channel Dynamics ....................................................................................... 11 2.3.4. Dispersal of Eggs after Spawning from Transient Aggregation Sites............................... 13

2.4. Comparison of Resident and Transient Aggregation Site Dynamics........................................ 13 3. Outcomes and Follow Up Recommendations ................................................................................... 14 4. References ......................................................................................................................................... 16 5. Addendum to original Final Report................................................................................................... 17

5.1 Additional Research Information Obtained During This Project............................................... 17 5.2 Oceanography of Spawning Aggregation Sites.......................................................................... 21 5.3 Publications ................................................................................................................................ 25

5.3.1 Abstract for Seventh Indo-Pacific Fish Conference........................................................... 25 5.4 References .................................................................................................................................. 25

6. Appendices ........................................................................................................................................ 27 Appendix 1: Study Terms of Reference .......................................................................................... 27

Background ................................................................................................................................. 27 Connectivity ................................................................................................................................ 27 Scope of Work ............................................................................................................................ 28

Appendix 2: Letter of Response to Final Report Review Comments ............................................. 31 Appendix 3: Interim Report 1 – Spawning Aggregation Connectivity Project (19 January 2004) 37

General ........................................................................................................................................ 37 Bathymetric Mapping of Grouper Aggregation Sites ................................................................. 37 New Methods for Quantifying Aggregation Surveys ................................................................. 37 Oceanography of Aggregation Sites ........................................................................................... 37 Investigations of Aggregation Sites Reported to be "Fished Out".............................................. 38 Future Efforts .............................................................................................................................. 38

Appendix 4: Interim Report 2 – Spawning Aggregation Connectivity Project (20 September 2005).......................................................................................................................................................... 39

LIST OF FIGURES

Figure 1: Ocean conditions associated with the spawning of Cheilinus undulatus................................. 2 Figure 2: Aggregations of Epinephelus polyphekadion at Ulong Channel, 3 July 2005......................... 2 Figure 3: Typical GPS Density Survey swim track with one-minute rectangles (white lines) delineated.

.......................................................................................................................................................... 4 Figure 4: Typical GPS density bubble plot for two species of groupers on the same day at the Ulong

Channel aggregation site................................................................................................................... 4 Figure 5: Bubble plots showing distribution and relative abundance of Epinephelus fuscoguttatus at

Ulong Channel on the same lunar phase during five months of 2005 .............................................. 5 Figure 6: Bubble plots showing distribution and relative abundance of Epinephelus polyphekadion at

Ulong Channel on the same lunar phase during five months of 2005. ............................................. 6 Figure 7: Bubble plots showing distribution and relative abundance of Plectropomus areolatus at

Ulong Channel on the same lunar phase during five months of 2005. ............................................. 7

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Figure 8: Comparison of distribution and relative numbers of three species of groupers at the Ulong Channel aggregation site between 2003 and 2005 on the same lunar phase (1 day before new moon) in August. .............................................................................................................................. 8

Figure 9: Comparison of distribution and relative numbers of three species of groupers at the Ulong Channel aggregation site between 2003 and 2005 on the same lunar phase (2 days before new moon) in August. .............................................................................................................................. 9

Figure 10: Tracks of GPS logging drifter from areas near humphead wrasse aggregation sites at Saes Reef, western barrier reef, Palau..................................................................................................... 11

Figure 11: Current meters at the Ulong Channel site. ........................................................................... 12 Figure 12: Tracks of drifters started at the mouth of Ulong Channel at half hour intervals starting 15

minutes after sunset, 7 May 2005. .................................................................................................. 12 Figure 13: Tracks for current drifters from resident aggregation site of Cheilinus undulatus (upper

tracks) and a transient grouper aggregation site (lower tracks), Ulong Channel. ........................... 14 Figure 14: Results of surveys concerning the geomorphological aspects of spawning aggregation

occurrence at Ebiil Channel, Ngerechelong State, Palau................................................................ 18 Figure 15: The West Channel (Toachel Lengui) area of the western barrier reef of Palau................... 19 Figure 16: Bathymetric map of the Denges Channel area on the eastern barrier reef of Palau.

Occurrence of aggregating species of reef fishes are not yet shown on this figure. ....................... 20 Figure 17: Bathymetric survey of the Cemetery Reef area in the southern Rock Island area of Palau. 21 Figure 18: Oceanographic data from the Sae's Reef aggregation site of Cheilinus undulatus for a

period of 14 days (April 2004)........................................................................................................ 22 Figure 19: Oceanographic parameters at the Ulong Channel spawning aggregation site, 2-6 May 2005.

........................................................................................................................................................ 23 Figure 20: Complete data showing oceanographic parameters at the Ulong Channel aggregation site,

summer 2005................................................................................................................................... 24 Figure 21: Acknowledgement pages from power point presentations presented at international

meetings by P. Colin....................................................................................................................... 25

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1. INTRODUCTION

This is a final report for the contract "Study of Reef Fish Spawning Aggregations and Connectivity on the Palauan Reef Tract", Palau Projects - Marine contract. Work was initiated in March 2003 on this contract and, after a number of extensions, concluded on 31 August 2005. This final report has been delivered on 14 January 2006. The final report summarizes all the information gathered during this project, however, full analysis of the data are not complete. A number of scientific publications will be prepared detailing the results of this project which will include the final analysis. This project was part of an ongoing effort investigating spawning aggregations and, as such, there is often no clear conclusion to the work. The knowledge obtained, equipment purchased and methods developed from this project will be used immediately to continue this effort. Spawning aggregations of reef fishes are known throughout the world's tropical oceans. In a spawning aggregation greatly increased numbers of fish come together at specific times and locations for purposes of reproduction (Domeier and Colin 1997). Those species which aggregate include most of the larger species of bony fishes found on reefs and are the species most important in subsistence and commercial fisheries. The smaller species on reefs (damselfishes, gobies, blennies, etc) produce demersal (benthic) eggs and do not generally aggregate to spawn. Reef fishes which aggregate produce small (generally less than 1 mm diameter) planktonic (pelagic) eggs which are slightly buoyant and drift away with the currents, hatching within about 24 hours into pelagic larvae which spend a few to several weeks in the water column. These eventually recruit from the plankton to benthic habitats as juveniles. The egg and early larval stages are passive drifters with no ability to swim relative to currents. Later stages of reef fish larvae may be able to swim sufficiently well to affect their dispersal. The biological advantages of this behavior are not well known, however given its broad geographic occurrence among many different families of reef fishes, there must be some benefit to reproductive success from this activity. Spawning aggregations fall into two basic types, resident and transient (Domeier and Colin 1997). Resident aggregations occur over prolonged periods of time during the year, often daily, and generally involve only short migrations from home ranges to the spawning site. Typical families with resident aggregations include wrasse (Labridae), parrotfishes (Scaridae) and surgeonfishes (Acanthuridae). Transient aggregations occur only for a relatively short periods of time (usually no more than a few months), often have a lunar component (a particular lunar phase), and can involve lengthy migrations (to 100's of km) to and from spawning sites. Transient aggregations are found in groupers (Serranidae) and snapper (Lutjanidae) among other families. This project was focused on obtaining new information regarding the importance of spawning aggregation as sources of fish larvae, and their connections with areas outside the actual aggregations sites. The timing and location of spawning determines when and where eggs are released into water masses and local oceanography determines where they will go from the spawning site while they undergo their pelagic life history phase. Such considerations should be an integral part of the design of marine protected area (MPA) networks. The work fell into several different categories. Important resident and transient aggregations would be examined, for the former group using humphead wrasse (Cheilinus undulatus) and three species of groupers (Epinephelus fuscoguttatus, E. polyphekadion and Plectropomus areolatus) for the latter. The resident aggregations of the humphead wrasse, Cheilinus undulatus (also commonly known as the Maori wrasse and/or Napoleon fish), through earlier work supported by the National Fish and Wildlife Foundation, were found to aggregate, often daily, at many location along the ocean side of the western barrier reef of Palau, spawning about 2-2.5 hours after high for a period of nearly one hour. They migrate distances of up to 4-5 km to these daily aggregations, which consists of as many as 15 males and 100-150 females. They spawn at the water's surface some distance out from the reef as moderate

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tidal currents bring a lens of warmer, murkier water from lagoon to ocean cross the reef and carrying the eggs somewhat offshore (Fig. 1). In this case, the time and location of spawning was well known and current drifters could be started in the area of water with the freshly spawned eggs to track their dispersal. With both resident and transient aggregations, the intention was to then couple of small scale oceanography of egg dispersal into the larger hydrodynamic investigations of Palau to provide a rough idea of dispersal potential during the 3-4 weeks larvae remain in the water column. Such basic information as whether or not larvae are found in the lagoon, the ocean near Palau ("sticky water") or far offshore it is not known and has tremendous potential for affecting the success of the early life history (spawning to settlement) of reef fishes.

Figure 1: Ocean conditions associated with the spawning of Cheilinus undulatus.

Left. Rising tide has water moving from ocean to lagoon without any stratification of the water column, no spawning occurs at this time. Right. Falling tide has lagoon water moving across the reef to the ocean as a lens of warmer and murkier (compared to oceanic water). C. undulatus spawns at the surface out from the reef on the falling tide.

For the three species of groupers forming transient aggregations at the mouths of the major barrier reef channels (Fig. 2), one objective had been to try to establish the exact time and location of spawning. Despite repeated attempts to observe actual spawning, no unquestioned observations of grouper spawning had been made in Palau. Elsewhere, grouper spawning has been documented to occur at sunset for at least one of the species aggregating in Palau. Why has spawning not yet, despite the effort of making observations on many days at sunset, been observed in Palau? From the information on the time and location of spawning, the initial trajectory of the planktonic eggs would be determined by releasing current following drifters at the time and location of spawning, then following them for up to several hours.

Figure 2: Aggregations of Epinephelus polyphekadion at Ulong Channel, 3 July 2005.

A. Mouth area of channel with sand bottom sloping downward at the lower portion of the photograph to the drop off. B. Portion of channel inshore about 100 m from mouth with E. polyphekadion facing into the slight current coming from the ocean into the channel.

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Since spawning aggregations are considered an important potential reason for locating a MPA to provide for protection of the aggregation (and hence reproductive output), it was evident that work intended to document when spawning might be occurring could easily and logically be expanded to quantify the numbers and distribution of fish within aggregations. A new method for documenting the numbers of fish and extent of an aggregation (the GPS density survey) was developed and this project was used as the first real test of its practicality as a monitoring technique. The results indicate such surveys are very useful in documenting the dynamics of aggregations over the course of days, lunar months and years. The data are quantitative, with some caveats, and surveys can be repeated at later times by other observers with high confidence any changes detected represent actual differences in aggregation size, rather than some factor associated with different observers or a different area. The work was concerned with two basic aspects of reef fish spawning important in any consideration of MPA's, their design and Protected Area Networks in general. The first concerned documentation of the time and location of spawning aggregations to learn when and where spawning actually occurs and to quantitatively document the numbers of fish in aggregations over time and space for future comparison. Second, oceanographic aspects of spawning aggregation occurrence and dispersal of eggs were examined with respect to how they might relate to the connectivity of aggregation sites into general ocean and lagoon circulation and eventually recruitment areas. While we may know some details of the small scale features of spawning, integrating this into the larger picture, even for a relatively small area such as Palau, has not been done with any certainty. This work does not answer these questions, but does provide new information related to these considerations. 2. RESULTS OF FIELD WORK

2.1. SPAWNING AGGREGATION DOCUMENTATION AND TIME/LOCATION OF SPAWNING

Most estimates of populations of fishes at aggregation have either been qualitative estimates, based on a rough approximation of numbers present (Colin et al. 2003) or some type of semi-quantitative transect or area count with little ability to assess accuracy of data or to repeat surveys again at a later date (example Johannes et al. 1999 for Palau). At the time this project started, I was beginning to use a new method for assessing spawning aggregations in a more quantitative, and just importantly, a repeatable manner. It was decided to apply this new method to the Ulong Channel grouper spawning aggregations to provide base line data on the numbers of fishes present, their distribution and dynamics over the course of days, lunar months and years. While slightly peripheral to the original intent of this project, the application of this method to spawning aggregation work should be extremely useful to the overall goal of increasing knowledge of spawning aggregations for the benefit of MPA considerations. In the end considerable resources were focused on gathering these data which provide new insight into the dynamics of transient aggregating species that will allow better consideration of the role of currents in dispersing eggs from spawning sites. The techniques used in doing a GPS Density Survey are detailed in an included PowerPoint presentation (Colin et al. 2005). Basically the observer, swims a series of transects across the area of an aggregation while towing a small float with a position logging GPS receiver. The observer counts and records the number of individuals of selected species each minute within a chosen distance (usually 10 m either side) of the swim track. After return to shore the GPS data are downloaded, the distance during each minute (during which fish counts were made) determined and the area surveyed calculated from the swath width (Fig. 3). This provides the area surveyed each minute (a rectangle), the numbers of fishes within that area and the location of the area on the reef. From these data, the density of fishes can be plotted for any given survey and an estimate of the total numbers of fishes in the aggregation (Fig. 4.). Since the data are quantitative, within certain limits, surveys from different

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days, months and years can be compared and with some confidence, it can be said whether numbers of fish are changing and if aggregations are of the same spatial extent and location.

Figure 3: Typical GPS Density Survey swim track with one-minute rectangles (white lines) delineated.

Area of rectangles is determined by distance surveyed each minute by swath width, while the numbers of fishes are counted during each minute to calculate density.

Figure 4: Typical GPS density bubble plot for two species of groupers on the same day at the Ulong Channel aggregation site.

Plectropomus areolatus in shown in the upper panel while Epinephelus fuscoguttatus is in the lower panel. The difference in their respective distributions, as determined by the GPS Density Survey method, is evident.

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GPS Density Surveys of the Ulong Channel grouper aggregations were made during the aggregation season on 24 days in 2003, 6 days in 2004 and 26 days in 2005. The data from 2003 and 2005 are the robust, but for 2004, despite intensive efforts, weather conditions (strong westerly winds and seas) severely limited access to Ulong Channel at the times of aggregation. It is impossible to present all these distribution data in this report, however, a PowerPoint presentation is attached which has bubble plots of the distribution of each of the three species of groupers for each survey day during 2003 and 2005. These plots, some examples of which are shown as Figures 5-9, provide a visual indication of fish numbers present, but not total numbers found within the aggregation on a given day. Contour analysis, which will provide those data with some confidence, has not yet been completed. Resident spawners, particularly those species do not aggregate, produce on any given day a pulse of eggs around much of the margin of Palau and many areas inside of the barrier reefs. These eggs, which like most others, are slightly positively buoyant and will float to near the water surface. Only surface waves and chop will serve to keep them suspended in the water column. On extremely calm days we would expect the vast majority of eggs to occur within the upper 1 m of water.

2005- 2 days before New Moon

Epinephelus fuscoguttatus

Figure 5: Bubble plots showing distribution and relative abundance of Epinephelus fuscoguttatus at Ulong Channel on the same lunar phase during five months of 2005

Refer to Figure 4 for relationship between the plots and location of the channel.

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Epinephelus polyphekedion

Figure 6: Bubble plots showing distribution and relative abundance of Epinephelus polyphekadion at Ulong Channel on the same lunar phase during five months of 2005.


2.2. ASSESSMENT AND MONITORING OF SPAWNING AGGREGATIONS

The protection of spawning aggregations of reef fishes has been well accepted as desirable and helping to promote conservation of the species which engage in this behavior. It is poorly known how much fishing pressure spawning aggregations can sustain without decreasing greatly or disappearing, however the most recent study (Sadovy and Domeier 2005) suggests that even low levels of exploitation of aggregations will have negative effects in the future. Where aggregations are protected it is not well known whether this protection translates into stable or increasing numbers of individuals in the aggregation. These fishes are subject to fishing pressure and lack of suitable habitat outside the aggregations, so although they are protected while reproducing, numbers of individuals still continue to decrease if fishing pressure is high. Among resident aggregation species, the humphead wrasse (Cheilinus undulatus) was a natural choice for a definitive species from this group. It is the largest wrasse in the world, has recently been listed as a CITES II species, is an iconic species and has eggs and larvae typical of other resident aggregators. The present work builds upon knowledge gathered from an earlier National Fish and Wildlife Foundation funded study by looking at the role of "micro-oceanography" as it's relates to spawning occurrence and egg dispersal. Most of the results from the C. undulatus portion of this study are reported under section 2.3.2.

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Plectropomus areolatus

Figure 7: Bubble plots showing distribution and relative abundance of Plectropomus areolatus at Ulong Channel on the same lunar phase during five months of 2005.

Refer to Figure 4 for relationship between the plots and location of the channel. For the species of groupers in transient aggregations, the data provide a clear picture of the peak lunar days of aggregation and strong evidence for peak lunar months. Despite the effort put into assessing aggregation occurrence and watching fish behavior, we have still not seen any grouper spawn at Ulong Channel. It is possible the interaction between tide and currents at that site is unusual, since the channel is not open at its inner end. There is a shallow sill which affects the timing of current direction change relative to the tide which may cause the groupers there to spawn at some time other than close to sunset. They may be spawning sometime after sunset and hence, not observed by divers. The aggregation size for the three species of groupers is evident from the size of density "bubbles" shown in Figures 5-7. For E. fuscoguttatus few fish were aggregated in April 2006. But on the same lunar phase in May and June large numbers occurred in the channel. During July and August, significant numbers were still there, but appeared to be slightly less abundant than during the earlier two months (Fig. 5). For E. polyphekadion, few fish were seen during April and May, however very large numbers were present in June and July, with a greatly reduced number in August (Fig. 6). For contrast to the previous two species, P. areolatus significant numbers were found from April through August with peak abundance in June and July. The plots indicate the ability of the GPS Survey Technique to provide data that allow more sophisticated comparisons between days and months during any spawning season. Comparison of data between years, when the same lunar phase and lunar month are compared (Figs. 7 and 8), provide some strong evidence whether populations of aggregating fishes are stable, decreasing or increasing. For the two lunar phase days indicated in Figs. 7 and 8 it appears likely there has been an increase in fish number at the aggregation sites between 2003 and 2005. Contour analysis will provide (hopefully) corroboration of this indication and may be strong evidence that protection (Ulong Channel is a no fishing zone at all times) of aggregation sites is helping to

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reverse the general trend towards decreased populations of fishes within aggregations.

2003 1 Day Before New Moon 2005

Figure 8: Comparison of distribution and relative numbers of three species of groupers at the Ulong Channel aggregation site between 2003 and 2005 on the same lunar phase (1 day before new moon) in August.


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2003 2 Days Before New Moon 2005

Figure 9: Comparison of distribution and relative numbers of three species of groupers at the Ulong Channel aggregation site between 2003 and 2005 on the same lunar phase (2 days before new moon) in August.


2.3. OCEANOGRAPHY OF SPAWNING AGGREGATION SITES AND DISPERSAL OF EGGS AFTER SPAWNING

Relatively little has been published regarding the current patterns at spawning aggregation sites, particularly concerning the immediate fate of planktonic eggs after release. Transient and resident spawning aggregation sites have different current regimes. In Palau, those species spawning on the barrier reef, resident aggregations are in areas with cross reef tidal currents, but also influenced by the along reef components of current while transient aggregations at the mouths of channels are in an environment strongly dominated by the tidal currents in the channels. Typically these channel currents are considerably stronger than the cross reef currents, although both are driven by the same mechanism, the tides. One aspect of this work was the first comparison of their relative effectiveness in transporting eggs away from the spawning sites (and shallow reefs). 2.3.1. Barrier Reef Dynamics

The depth of water over the shallow barrier reefs of Palau is determined by the state of the tide. At spring low water many areas of the barrier reef are exposed, making it a true barrier to the passage of water between lagoon and ocean. Neap low tides do not have the reef emergent, but are sufficiently low that the depth of water over the reef is very small compared to the width of the reef, and water can move across the reef only with difficulty and slowly. At high tide, water is a few meters deep across the barrier reef and currents can move large amount of water relatively easily between lagoon and ocean. Intermediate stages of the tide (or neap high tides) have more restricted cross reef circulation, and there is a complex relationship between the hydrostatic heads of the lagoon and ocean, the depth

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of water over the reef and the effects of wind and waves on water transport. It is far beyond the focus of this project to deal with this relationship in detail, however, it would be a subject of great relevance to future considerations of egg transport after spawning of the many species of reef fishes which spawn on the barrier in relation to the tide. Nearly all fishes known to spawn planktonic eggs on the shallow barrier reefs of Palau spawn after high tide, from the time the current slowly starts to move off the reef to near the mid-tide stage where currents are at their highest velocity. The later stages of the falling tide do not seem to be a time of any significant spawning. The many smaller reef fishes, particularly parrotfishes, surgeonfishes and wrasses, that do not aggregate (but still spawn on the falling tide) produce a pulse of floating eggs coming off the barrier reef for a period of 1-2 hours, which can be thought of as moving slowly offshore as a band as the tide falls. For species which form resident aggregations, such as the humphead wrasse, there will be a pulse of eggs coming off the reef a few hundred meters (or less) in width issuing from the limited segment of the barrier reef. Whether resident aggregation sites are "superior" locations for spawning has been a matter of scientific debate for many years (Shapiro et al. 1988) and data regarding this question have been relatively few since. An effort was made to gather additional information relative to this important question of whether or not there are superior spawning sites. From the present work it appears for the single humphead wrasse site investigated in detail there is no clear difference in the transport of eggs off the reef between aggregation sites and nearby areas outside of the aggregation site, nor any difference in transport from spawning sites for times when the aggregation is spawning and both before and after spawning. It appears, based on the limited data collected during this project, that the western barrier reef of Palau has a net outflow from lagoon to ocean during at least the spring season. The currents across the barrier reef are largely tidally driven, although wind speed and direction may have a presently undocumented effect on current flow. If this is the case, it has many implications for fishes spawning along the barrier reef with regard to where their eggs (and larvae) go after spawning. The lagoon water is slightly less dense than the oceanic water outside the barrier reef. Lagoon water is usually warmer and more turbid and when the tide is falling, it comes across the barrier reef. The entrainment of eggs within this lagoon water may have significant effects regarding the potential return of eggs to the reef, as the density differences between lagoon and oceanic water may serve to reduce dispersal of the lens of lagoon water away from the reefs. 2.3.2. Dispersal of Eggs after Spawning from Resident Aggregation Sites - Experimental Approaches

Two experiments were run at the humphead wrasse aggregation site at Saes Reef examining the question of whether there were differences in transport of water from aggregation spawning sites and non-spawning sites, plus the effect of time of spawning on transport from spawning sites. Four sites on the ocean edge of the barrier reef were chosen for drifter release. Two were within the aggregation and spawning site, which encompasses about 250 m of reef edge drop off, while one both north and south of the spawning areas, where aggregation has never been observed, also selected. The timing of spawning at the aggregation site is well known and it was decided to do a time staggered release of drifters before, during and after spawning from areas both inside and outside the aggregation area. This was to examine whether there were any obvious differences in the tracks of drifters started within spawning times and areas with those started outside, but near to that "box". Twelve drifters with GPS logging units recording their positions at 1 minute intervals were used, allowing three successive "launches" of four drifters each. The four start positions mentioned above were marked by small floats tied to the reef for consistent drifter release locations. Two boats were used in the operation, one with an observer who was watching the behavior of the fish, for both aggregation and then spawning, while the second boat was used to launch at the direction of the observer and then to keep track of the drifters. The observer told the crew in the second boat when to start drifters and three

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successive launches were made, for a total of twelve drifters. Each launch of four drifters was started within 2-3 minutes, as fast as the boat could move between the floats and put the gear over the side.

Figure 10: Tracks of GPS logging drifter from areas near humphead wrasse aggregation sites at Saes Reef, western barrier reef, Palau.

A1. Generalized map showing arc of barrier reef (dark green) with tracks of drifters on 11 April 2005 with respect to the overall extent of reef. A2. Detail of drifter tracks on 11 April 2005, with different colors started as groups at different times (30 min apart), showing the similarity of all tracks started at the same time. B1. Generalized map showing arc of barrier reef (dark green) with tracks of drifters on 12 April 2005 with respect to the overall extent of reef. B2. Detail of drifter tracks on 12 April 2005 with only slight evidence of along reef transport.

Drifters tracked off the reef initially due to the current moving across the reef from the lagoon to the ocean (Figure 10) on both days. On one day (11 April 2005) after moving a few hundred meters off the reef, they stalled and then started moving slowly along the reef, with a minor component of off reef movement still present (Fig. 10A-1,A-2). On the other day, the drifters continued to move slowly off the reef for well over one hour without any noticeable along reef component. The gear was only run for a few hours since the purpose of the experiment was to establish the initial off reef trajectory of eggs. Where these drifters (and eggs, and eventually larvae) would be after one or more days is unknown. 2.3.3. Barrier Reef Channel Dynamics

The occurrence of grouper aggregations around the mouths of channels between lagoon and ocean in Palau implies that the channels provide some sort of benefit to these fishes. Usually there are implications cited about the increased transport of eggs away from the reef in tidal channels, but such have never been proven, nor has the actual trajectory of eggs spawned at a channel been documented.

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Two current meters (Fig. 12) were deployed in the channel for the entire 2005 grouper aggregation season (April to September). The first was a single point current meter stationed mid-way in the channel in an area of high grouper density. The second was an acoustic Doppler current profiler situated at 40 m depth below the mouth of the channel. The single point meter provided a nearly continuous record of currents (except for one day when it was serviced before redeployment in mid-summer).

Figure 11: Current meters at the Ulong Channel site.

A. Single point current meter in 8 m depth in mid-channel in an area of high grouper density. B. Acoustic doppler current profiler at 40 m depth below the mouth of the channel.

Figure 12: Tracks of drifters started at the mouth of Ulong Channel at half hour intervals starting 15 minutes after sunset, 7 May 2005.

After two hours, the first drifter deployed (red track) was recovered and started again at the mouth of the channel. Squares on the figure are 1 km square.

Since spawning had never been observed in groupers at Ulong Channel, it was decided to try an alternative method to direct observation of spawning, by seeing if large numbers of fish eggs of the sort of size produced by groupers could be detected in water exiting the channel during the first two hours after sunset. Since the eggs float they will eventually reach the surface, however, if spawned several meters deep, it might take an hour or more to float to the surface. It was decided to start

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drifters at the channel mouth (Fig. 12) at half hour intervals after sunset, allow them to drift for at least one hour and then sample around the drifter for fish eggs using a plankton net towed behind the boat. This additionally would provide information on the movement of water out of the channel during the time the fish were likely to be spawning. 2.3.4. Dispersal of Eggs after Spawning from Transient Aggregation Sites

The successively launched drifters took very similar track outward from the channel. The night of this experiment was very calm, so there was little to no effect from wind on the transport of the water out the channel. Although the current coming out of the channel mouth seems quite strong (and it is in the narrow portion of the channel), once it reaches the open ocean it slows considerably. Over the course of 1-2 hours, the drifters only moved 1-1.5 km. Ulong channel may be anomalous in its tide/current regime compared to other channels and this may be a major factor why grouper spawning has not yet been observed there. The current meter in the channel indicated the current direction switches from incoming (ocean to lagoon) to outgoing about one hour prior to high tide in the channel. This implies that the tide level in the lagoon is actually higher than in the channel as the tide rises towards high water. As the tide rises in the channel, this increases the depth of water across the inner sill, allowing the higher water level damned up behind the barrier reef in the lagoon to start flowing more freely across the sill and into the channel and then out to sea via the channel. Because the lagoon tide level is higher than the channel, this can cause the tide level in the channel to still increase while the current reverses from incoming to outgoing through the channel to the ocean.

2.4. COMPARISON OF RESIDENT AND TRANSIENT AGGREGATION SITE DYNAMICS

Although the analysis of current information is not yet complete, one interesting comparison can be made between cross reef and reef channel dispersal of fish eggs. Figure 13 shows the tracks of drifters from the C. undulatus spawning site (upper tracks) over the first few hours after spawning and drifter tracks from Ulong Channel from when spawning was presumably occurring (lower tracks). While it might be expected the channel tracks would indicate more rapid and greater dispersal from the reef, this does not seem to be the case on superficial examination of the tracks. The cross reef tracks actually seem to go further offshore (if there was no along reef component) than the channel tracks. This does not take into account effects of wind, which could not be quantified, nor other day to day variation. There certainly is not a major (a few to several times more) difference in transport from either type of aggregation site.

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Figure 13: Tracks for current drifters from resident aggregation site of Cheilinus undulatus (upper tracks) and a transient grouper aggregation site (lower tracks), Ulong Channel.

Tracks are shown over 2-3 hours. Map grid is 1 square km. 3. OUTCOMES AND FOLLOW UP RECOMMENDATIONS

The work provides some insight into the complexities of reef fish spawning aggregations and their incorporation into protected areas. The new GPS Density Survey method worked well in its application at Ulong Channel, and it is recommended, that whenever possible, others workers involved with spawning aggregations in Palau and elsewhere with TNC funding, attempt to document their local aggregation size and location using this technique. The method would be very applicable to the work ongoing in Pohnpei and that in Ebiil Channel in Palau. Ann Kitalong of The Environment, Inc. has recently received a grant from NOAA to do community-based monitoring of rabbitfish (Siganidae) aggregations which occur during the spring near seagrass beds in Palau. Her work includes using GPS Density Surveys to monitor distribution of rabbitfishes, and is the first incorporation of this method into a community based monitoring project. Using the GPS float during field work is easy, and the training involved in doing the surveys is minimal. The set up and analysis is more complicated, but this part of the project can easily be done by trained workers, and does not detract from the strength of the data obtained, since the observers main responsibility is to take accurate fish counts on a minute by minute basis, and record the data. I will be working closely with Ann to assess and modify if need be the technique as a result of her work. The present work gives strong indication the Ulong Channel grouper aggregations are increasing in size over the last two years. Continued monitoring work, focused on the times when fish are most abundant, will allow refinement of this conclusion in future years. Resident and transient aggregations represent two different life history strategies for coral reef fishes. As such the probably require separate consideration when they are included in planning for protected areas. The also require different management strategies for any sustainable local subsistence

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exploitation. Persons involved in the planning and design of MPA's need to be aware of these differences and consider the various species and their spawning strategies in this regard. It is also important for planners to understand that the dispersal and eventual recruitment of fish larvae is very different from what may be occurring in most species of scleractinian corals. Although many corals have a drifting dispersal stage, often they persist only a few days in the plankton, and may recruit much closer to their source point than reef fish larvae, which typically spend a minimum of 2-4 weeks in the plankton. It is not yet possible to couple the micro-oceanography of spawning into the generalized hydrodynamic model prepared for Palau (Skirving et al. 2005). The model focuses more on questions of mixing and does not provide an easy method of assessing 2D movement of water within the lagoon. It also does not cover the area outside the barrier reefs, the area where salient topography (headlands of reefs, irregular reef lines, etc.) cause eddying and small scale modification of the generalized ocean flow around Palau (Skirving and Heron 2005). During the period of this grant, I have tried to interest other works in what I feel is a very powerful tool for documenting in a repeatable manner aggregations and a number of other marine phenomena. I gave a presentation on this method to the Palau Conservation Society lunch-time seminar series and there was great interest in using it for future aggregation work, such as the ongoing program at Ebiil. I hope to work with PCS this coming year to do additional surveys at Ebiil (some preliminary work was done with Jason Kuartei on this contract a few year ago mapping out the limits of aggregations there). I also plan to go to the Ulong Channel site with Asap from PCS to try to delineate the areas surveyed by Johannes et al (1999) so we can attempt to make comparisons of fish data from their surveys. From their publication, it is not possible to identify the area where they did their surveys, and by taking a participant in the work, we may be able to narrow the location of the surveys and make a quantitative measurement of the distance and area surveyed. If this can be done, then we can make an approximate comparison using the data gathered during this survey, since the exact location of each density measurement is known. The methods put into use would be easily applied to other work supported by TNC and others in the Micronesia region. The grouper aggregation sites in Pohnpei would be easily surveyed. I also hope to expand this work, without outside funding, during this year to look at some other aggregation areas in Palau. While attention has focused on the Ulong channel site for attempts to document spawning, this site was used mostly because of convenience to Koror. The lack of spawning observations may be related to the somewhat anomalous current conditions there, due to the sill effect of the inner channel, and we need to do sunset observations at a more "typical" channel area with a grouper aggregation. The GPS Density Survey method is being tried elsewhere. I have given out several of the waterproof housings and some GPS units to workers in the Caribbean, Hawaii, Florida, Papua New Guinea and Indonesia. While the method has not yet been published (it will be) I have given several presentations on the method, including the Gulf and Caribbean Fisheries Institute in November 2004 and the Indo-Pacific Fish Conference in Taiwan in 2005. The PowerPoint presentation prepared for the IPFC is the most definitive documentation of the method and has been distributed to many individuals. There is a great need for some basic research on the distribution and oceanographic conditions associated with reef fish larvae in Palau. We have some idea where and when a limited suite of species spawns, but virtually nothing about any aspect of their early life history. This is a major deficiency and such information is of critical importance in planning protected areas and the overall network of them. This work also points out the need to establish a long term monitoring of weather conditions over the marine environment. The location of the present wind measuring instruments at the Palau Weather Station is inadequate for any considerations of weather (principally wind speed and direction) on shallow water environments.

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4. REFERENCES

Colin, P.L., T.J. Donaldson and L.E. Martin. 2005. GPS density surveys: A new method for quantitatively assessing reef fish spawning aggregations (and other populations of reef fishes) [PowerPoint – Conference Presentation]

Colin, P.L., Y. Sadovy and M.L. Domeier. 2003. Manual for the study and conservation of reef fish

spawning aggregations. Society for the Conservation of Reef Fish Aggregations, Special Publ. 1: 1-99.

Domeier, M.L. and P.L. Colin. 1997. Tropical reef fish spawning aggregations: defined and reviewed.

Bull. Mar. Sci. 60(3): 698-726. Johannes, R.E., L. Squire, T. Graham, Y. Sadovy and H. Rengull. 1999. Spawning aggregations of

grouper (Serranidae) in Palau. Marine Conservation Research Series Publ. No. 1, The Nature Conservancy, 144 pp.

Sadovy, Y and M. Domeier. 2005. Are aggregation-fisheries sustainable? Reef fish fisheries as a case

study. Coral Reefs 24: 254-262. Shapiro, D.Y; D.A. Hensley and R.S. Appeldoorn. 1988. Pelagic spawning and egg transport in coral-

reef fishes: a skeptical overview. Envir. Biol. Fishes 22(1): 3-14. Skirving, W., S. Heron, C. Steinberg, A.E. Strong, C. McLean, M. Heron, S. Choukroun, F. Arzayus

and A. Bauman. 2005. Palau modeling final report. The Nature Conservancy, 46 pp. Associated documents submitted on CD-R: 1. GPS Density Survey PowerPoint Presentation [Colin, P.L., T.J. Donaldson and L.E. Martin. 2005.

GPS density surveys: A new method for quantitatively assessing reef fish spawning aggregations (and other populations of reef fishes)]

2. PowerPoint Presentation with Ulong Channel grouper density graphs 2003-2005.

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5. ADDENDUM TO ORIGINAL FINAL REPORT

This addendum covers aspects of work done during the period of the grant in question which were not included in the original Final Report. While not totally inclusive of all work done, this addendum should provide a clear idea of the scope of work undertaken during the grant. It must also be emphasized that this work has not come to a halt. Rather the information obtained is being built upon to increase our knowledge of spawning aggregations in Palau without further grant support from TNC or any other agency other than internal funds of Coral Reef Research Foundation. Spawning aggregations of reef fishes should be an important element of any program developing a network of marine protected areas. Many of the larger reef fishes important for human fisheries (often subject to high fishing pressure) aggregate to spawn and for some it is believed aggregation spawning constitutes the great majority of their reproductive output. Understanding the early life history of reef fishes, those stages from spawning to the recruitment of juveniles from the plankton, is critical to achieve any understanding of how a MPA network should be designed. The reproductive potential of reef fishes is very high (usually millions of eggs per female), yet recruitment from the plankton is much smaller and year to year population strength can vary greatly due to what happens during the month or so between spawning and recruitment.

5.1 ADDITIONAL RESEARCH INFORMATION OBTAINED DURING THIS PROJECT

Figure 14 shows the typical process of developing a GPS referenced bathymetric map of a possible spawning aggregation area through the inclusion of habitat information (in the form of a vertical aerial photomosaic) and addition of GPS derived data on the physical limits of spawning aggregations of two species of groupers on a given day. It is normally quite difficult to obtain an overall perspective of the distribution of a spawning aggregation, particularly its relationship to geomorphological features of reef areas nearby. Just as important are the geomorphological features of areas where aggregations DO NOT OCCUR. This inability to assess the areas where aggregations do and do not occur has resulted in a number of fallacies having been put forward regarding the relationship of spawning aggregations to bottom features. This sort of information is invaluable, although that may not be evident at the time it is collected, in that this is a quantitative record of aggregation occurrence and distribution which can be used in future years to track changes (or stability) of aggregations. Some basic principles guide the preparation of such aggregations surveys. Bathymetric surveys need to be done over a wider geographic area than the area known or believed to represent the spawning aggregation site. Without this broader coverage, it is not known how "typical" or "unique" the actual aggregation site might be. Figure 14a shows a typical survey of a channel mouth area (Ebiil Channel). While the spawning aggregation is known or believed to occur on only one side of the channel, it is very important to include both sides of the channel in the survey. Similarly it is important to include the entire mouth of the channel, particularly the deeper portions central in the channel, so that the depth to which the aggregation occurs can be placed in perspective with the full mouth depth of the channel. In this case (Fig. 14) the aggregations do not occur deeper than about 25 meters while the channel bottom is in excess of 30 meters. Hence the fishes do not form an aggregation across the entire channel mouth, but rather bunch up on one shoulder of the channel mouth. Why do they not also occur on the other side of the channel? Possibly current patterns are different on the two sides of the channel, or one area may be a "traditional" aggregation site which is used simply because it is where the fishes have always aggregated and may not be superior to the opposite side of the channel. If aggregation build up over time with protection, will aggregating fish also start occurring on the other side of the channel? In some areas of Palau, bathymetric surveys were done of areas reported to be spawning aggregation sites, but during this work no aggregations of fishes were found in those areas. Consequently no fish distribution could be plotted against the bathymetric features (Figure 15), but the mapping of the area is now complete and can eventually be used to plot out aggregation distribution when it becomes known. Just as importantly, if surveys are conducted at times when no aggregating

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fishes are encountered, then this becomes quantitative information which can be used in the future as strong evidence of return of aggregations (if they start forming again in the areas previously surveyed).

Figure 14: Results of surveys concerning the geomorphological aspects of spawning aggregation occurrence at Ebiil Channel, Ngerechelong State, Palau.

A. Base bathymetric map derived from running a series of transect lines logging data on latitude, longitude and depth at intervals of approximately 1-2 seconds. Data are plotted in a contour plotting program with depth contour intervals selected to reflect the depths at which geomorphological features of relevance to the spawning aggregation occur. B. Bathymetric contour lines placed upon a vertical aerial photomosaic which indicates the habitat types present at and near the spawning aggregation site. C. Limits of aggregations, determined by swimming around the outer edge of the spawning aggregation sites of two species of groupers

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Figure 15: The West Channel (Toachel Lengui) area of the western barrier reef of Palau.

A. Bathymetric survey of the channel with depths in meters. The central portion of the channel is generally 60-75 m in depth, by far the deepest channel through the Palau barrier reef and is a major conduit of deeper, cool oceanic water on rising tides. B. Bathymetric of the West Channel placed on an aerial photomosaic of the channel area. No spawning aggregations have been positively located in this channel as yet, although there are verbal records of their occurrence.

More problematic are areas where only a modest number of fishes are surveyed. Is this a spawning aggregation or not? Using the generally accepted criteria of Domeier and Colin (1997), a spawning aggregation must represent at least a 3 x increase in fish abundance in a given area (and the fish must also be gathered for spawning). Without reasonably quantitative data, it is hard to verify and document an actual increase in numbers of a given species. The Denges Channel area (Figure 16) was reported to be "fished out" of grouper spawning aggregations during the 1990's (see Johannes et al. 1999), yet during this work a number of groupers of species which were aggregating elsewhere at the same time were seen during a few surveys carried out in this area. Unfortunately we do not have any quantitative data to back up this assertion that the aggregations were extirpated, just the vague qualitative observations that no fish were seen in some part of the aggregation area at that time.

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Figure 16: Bathymetric map of the Denges Channel area on the eastern barrier reef of Palau. Occurrence of aggregating species of reef fishes are not yet shown on this figure.

Nearly all work on spawning aggregations in Palau has focused on outer reef areas. This is the area where traditional knowledge reports aggregations to occur. However, for questions of marine protected areas it is important to know whether aggregation and spawning might be occurring within lagoon areas, as the early life history of fishes spawned in such locations would be very different from those originating on the barrier reef. It might be that lagoon spawned fishes have a much higher chance of successfully recruiting in Palau, and lagoon aggregation sites may be much more important than barrier reef sites for some species. I might also note here that aspects of this question could be answered by isotopic analysis of otoliths of recently recruited reef fishes, the area where the larvae grow up imparting a distinctive isotopic composition to the otolith. Over the last several years I have been investigating the aggregation and spawning of humphead wrasse, Cheilinus undulatus (subsequently referred to as "HHW"). All aggregation sites discovered have been on the western barrier reef of Palau. However, small populations of adult fish occur in lagoonal areas of Palau and whether or not these populations are spawning within the lagoon has been a matter of some interest. The species is a resident aggregator, spawning nearly daily and undergoing only short migrations. It is unfeasible, using that spawning strategy, to reach the barrier reef and the lagoon population was either spawning at lagoonal sites or not spawning at all. The lagoon also lacks distinct tidal cues for spawning, such as occur on the barrier reef, so the fish there might have a totally different spawning regime. A population of at least one large male and several female HHW occurred at Cemetery Reef in the Rock Islands and several days were spent observing the behavior and possible spawning of this group. A bathymetric survey done on the entire area (Figure 17) to better understand the possible spawning area for HHW at Cemetery Reef. Despite this effort, no spawning has yet been observed there and whether or not HHW are spawning within the lagoon is still unknown. This will be investigated further in the future.

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Figure 17: Bathymetric survey of the Cemetery Reef area in the southern Rock Island area of Palau.

The possible aggregation and spawning location of Cheilinus undulatus is indicated, however, spawning has not yet been observed.

5.2 OCEANOGRAPHY OF SPAWNING AGGREGATION SITES

One major component of the work on the grant was to document the "microoceanography" of spawning sites and attempt to tie the transport of spawned eggs into the more general circulation within and around Palau. Very little has been done previously on this aspect of spawning aggregations, so these efforts represent the first attempts to rigorously document the relationship between aggregation and oceanography. Since there was a significant knowledge base for the Ulong Channel grouper aggregations (transient) and the barrier reef HHW aggregations (resident), it was decided to focus on these two types of aggregations for the oceanographic work.

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Figure 18: Oceanographic data from the Sae's Reef aggregation site of Cheilinus undulatus for a period of 14 days (April 2004).

Temperature, current speed, current direction and water depth (tide) are shown. At the C. undulatus aggregation site north of Sae's Tunnel, a single point current meter was located on the shallow reef where the fish aggregate for two weeks (Fig. 18). This is an area adjacent to the shallow barrier reef where the tides cause currents to move back and forth across the reef. Over the course of a tidal cycle, water moves from the ocean across the reef into the lagoon on a rising tide, while on the falling (ebbing) tide the water moves the opposite direction, from lagoon to ocean. At the aggregation site the temperature can vary 1-1.5 0C over the cycle of the tide (see top Fig. 18 above). Current speed and direction vary with the tide, with maximum current speeds of about 40-50 cm sec-1 across the reef. Generally the currents are much gentler, usually in the range of 0-15 cm sec-1. The HHW typically spawn at the mid stage of the falling tide, when the water moving across the reef from lagoon to ocean is at its fastest. This causes the eggs, which are spawned seaward on the shallow reef, to move quickly off the reef into open water within a few 100 meters of the reef (this was covered in the Final Report). Alongshore currents then tend to pick up the eggs and move them in whatever direction they are going. It is believed the strategy of spawning on the falling tide is a mechanism for removing eggs quickly from the range of benthic based particulate planktivores which might otherwise eat them. An abundance of oceanographic data was obtained during the 2005 aggregation season for three species of groupers (P. areolatus, E. fuscoguttatus and E. polyphekadion) at Ulong Channel. The

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similarities and differences in the aggregation timing and population size to this site were discussed in the earlier Final Report.

Figure 19: Oceanographic parameters at the Ulong Channel spawning aggregation site, 2-6 May 2005.

Current direction is quite distinct, depending on tidal state, compared to the Sae's Reef site (Fig. 18). The current reverses (see current direction graph) to outgoing before the high tide peaks (depth graph), indicating an unusual relationship between tide and current probably controlled by the lagoon side sill of the channel.

The study of oceanographic factors at Ulong Channel reveals some unusual aspects to currents and tides there (Figs 19 and 20). These hitherto unknown factors may affect spawning behavior and timing. Despite several years of attempting to make observations of spawning by groupers at Ulong Channel, no grouper has ever been positively observed to spawn there. Most groupers, for which there is knowledge, are known to spawn at the time of sunset. Indeed, some of the species occurring at Ulong Channel have been recorded to spawn at sunset elsewhere (Samoilys and Squire 1994). Why these species have never been seen to spawn at Ulong Channel has been a real mystery. The answer may well lie in the unusual current patterns occurring there. Figure 19 shows plots of temperature, current speed and direction and tide for 5 days in May 2005. These data are typical for other days, but if too many days are shown in one graph, the details of what is happening are not visible (Fig. 20). As the data for current direction indicate, the current is going out the channel from lagoon to ocean about twice as much as from ocean to lagoon. On a rising tide, the current actually reverses and starts moving from lagoon to ocean BEFORE high tide. The tide continues to rise for as much as an hour, but the current acts as though the tide is falling. This anomalous pattern may be a result of Ulong Channel being only a partial channel, having a sill at its inner end which acts as an inhibitor of flow at most times. During 2006 I will be attempting to observe spawning of groupers at sites other than Ulong Channel, to see whether the conditions there might be correlated with the lack of spawning at dusk.

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Figure 20: Complete data showing oceanographic parameters at the Ulong Channel aggregation site, summer 2005.

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5.3 PUBLICATIONS

There have not yet been any peer-reviewed publications resulting from this work, however several manuscripts are in preparation. Two major talks were given using materials from this project and the acknowledgement pages of each PowerPoint presentation are shown in Figure 21 indicating acknowledgement of The Nature Conservancy.

Figure 21: Acknowledgement pages from power point presentations presented at international meetings by P. Colin

5.3.1 Abstract for Seventh Indo-Pacific Fish Conference

A new method for quantitatively assessing reef fish spawning aggregations and other populations of reef fishes. Patrick L. Colin, Terry J. Donaldson and Laura E. Martin Spawning aggregations of several species of grouper (Serranidae: Plectropomus and Epinephelus) and humphead wrasse (Cheilinus undulatus) were assessed in Palau using a new GPS-based density quantification technique. Divers or snorkelers towed on the surface waterproof GPS units logging positions at 15 sec intervals, while surveying fishes on a minute by minute basis. Fishes were counted in a swath either side of the swim path at one minute intervals. Concurrent notes were taken on the type of bottom present and other data of interest. GPS positions were downloaded and the distance traveled each minute was determined. Distance traveled each minute times the width of the swath determined the area surveyed, while the number of fishes counted allowing a determination of fish density in that area. Density values, which are tied to a GPS determined position, can then be plotted on aerial or satellite images, bathymetric maps, or habitat maps. Surveys are repeatable at any time in the future. This technique can also be used for surveys of distribution, density and habitats of any type of reef fish which can be visually counted. An example is shown using the technique to map out the distribution of juvenile C. undulatus over a broad area of Palau. The technique described provides a more quantitative assessment of populations than is obtained with commonly used underwater visual survey (UVS) techniques.

5.4 REFERENCES

Domeier, M.L. and P.L. Colin. 1997. Tropical reef fish spawning aggregations: defined and reviewed. Bull. Mar. Sci. 60(3): 698-726.

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Johannes, R.E. 1998. The case for data-less marine resource management: examples from tropical nearshore finfisheries. Trends Ecol. Evol. 13(6): 243-246.

Johannes, R.E., L. Squire, T. Graham, Y. Sadovy and H. Renguul. 1999. Spawning Aggregations of

Groupers (Serranidae) in Palau, Marine Conservation Research Series Publication # 1, 156 pp. Samoilys, M.A. and L.C. Squire. 1994. Preliminary observations of the spawning behavior of coral

trout, Plectropomus leopardus (Pisces: Serranidae), on the Great Barrier Reef. Bull. Mar. Sci. 54(1): 332-342.

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6. APPENDICES

APPENDIX 1: Study Terms of Reference

Background

The Nature Conservancy has initiated a highly collaborative program to transform the way marine protected areas (MPAs) for coral reefs and associated habitats are selected, designed, managed, and financed. The goal of this initiative – called Transforming Coral Reef Conservation – is to catalyze a worldwide effort to establish and protect networks of MPAs within high biodiversity tropical marine ecoregions that are designed to survive, managed to last, and inter-connected. We recognize that coral reef conservation must effectively address local needs and threats, their underlying causes and build resilience in the face of large-scale, unmanageable global threats to biodiversity, such as coral bleaching. Building on traditional and legislative protection already in place, the establishment of Palau’s MPA network will be the first application of the Transforming Coral Reef Conservation concepts of coral bleaching resistance, survivability, connectivity and sustainability. It will be a model for other countries to follow. The guiding principles for implementing this initiative include: • Establishing effective MPAs must address local management needs and build on pre-existing use

rights and management systems, and will only be effective and sustainable with the support of communities, state and national governments.

• Working closely with a range of partners in Palau to facilitate the establishment of the MPA network and to apply the latest design criteria.

• Establishing a number of MPAs that are representative of the area’s marine biodiversity, mutually replenishing, and managed as an integrated network.

• Building resilience to threats into MPA networks. Four fundamental requirements need to be met: they must be self or mutually replenishing; of sufficient size; have connectivity between areas for larval or juvenile recruitment; and be effectively managed.

• Creating sustainable financing and management approaches to allow MPA networks to cover their costs while providing incentives for human development and poverty reduction compatible with long-term conservation.

• Strengthening local capacity of institutions and individuals to manage MPAs effectively. • Adaptive management must be applied, requiring regular monitoring to measure performance and

the impact of management actions. Connectivity

A research program is needed to examine the role of physical and biological parameters and processes in controlling the transport of biological materials, such as fish and coral larvae, between areas of Palau. This is directly related to the "connectivity question": the interconnections of different shallow-water marine areas that allow for exchange between them and repopulation in cases where areas have been impacted. The coupling of biological systems to physical systems is poorly understood, hence our ability to interpret whether MPA's might be biologically connected with one another and either be sources or recipients of larval propagules or adult organisms is rudimentary. Two biological phenomena, the formation of spawning aggregations by reef fishes and the mass spawning of stony corals, provide focus events to help elucidate biological connectivity. Reef fish spawning aggregations result in the production of planktonic eggs and larvae, which remain in the water for a number of weeks (depending on species). Many locations of spawning aggregations are consistent over time and the gathering of numerous large fishes allows monitoring of the populations in ways that would not normally be feasible. Since a large part of their propagules are committed to a limited volume of water, we can examine whether there might be particularly reasons for the timing

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and location of spawning which influence a successful recruitment outcome. Knowledge of the biology of spawning and associated physical oceanography associated with the spawn is important in refining any concepts of connectivity. Without such real information, most connectivity modeling is doomed to give invalid information. Coral spawning, in which corals of many species over a wide area nearly simultaneously release their planktonic gametes or larvae, provides similar opportunities to assess the ability to disperse or retain propagules. The seasonal and lunar timing of coral spawning in Palau is being investigated by others, but once gametes are released, their duration and dispersal can be tracked to some extent to estimate the area where new coral colonies might result of spawning elsewhere in Palau. Scope of Work

The contractor will be responsible for performing the study and research as outlined below in accordance with the Budget, parameters, and requirements contained below, and be responsible for any necessary sub-contractors. Methods and Materials

The study will apply multiple approaches to 1) use new twists in known technology to enhance our ability to learn about this coupling between spawning and recruitment, and 2) focus on biological phenomena as they relate to the physical environment. The planned methods will have an increased chance of demonstrating levels of coupling, and at the very least, enhance our knowledge of where information is needed regarding the fate of spawn from fishes, corals and others. Many of the methods to be used are described in the recent SCRFA spawning aggregation study manual (Colin, P.L., Y.J. Sadovy and M.L. Domeier. 2002. Manual for the Study and Conservation of Reef Fish Spawning Aggregations. Society of the Conservation of Reef Fish Aggregations, Spec. Pub. 1, 98 pp.). The basic tools required includes GPS receivers of various types, the "current-following" drifter, the CTD (conductivity-temperature-depth) profiler and stationary current meters. These allow the assessment of the movement of a single parcel of water (Lagrangian) or the movement of water at a single site (Eulerian). The movement of eggs and larvae will be estimated using "current following drifters", a simple device consisting of a sea anchor, to tie the drifting device to the water mass in which it sits, and a float or pole which can be tracked. The float can have a small strobe light, a GPS logging device, and a radio beacon for location and recovery. A stationary current meter and an acoustic doppler current profiler (ADCP), and digital flow meters will be used to examine the coupling of the small scale to the larger scale. These instruments will be used at spawning sites to record current condition, and provide data supplementary to drifter information. Spawning Site Physical Parameters

Reef fish aggregation sites would be assessed through production of detailed bathymetric maps of each area, habitat mapping using aerial photographs and underwater surveys, and monitoring of physical conditions such as temperature profiles and currents. By gathering information on all these factors at as many sites as possible, a generalized picture of the range of physical factors for each species of concern will be obtained. Such information is useful in searching for unknown aggregation sites, based on physical factors (geomorphology, currents). Spawning Site Biological Parameters

As much biological information as possible shall be collected for as many spawning sites as feasible in accordance with the Budget. These would include things such as seasonal and lunar timing of

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aggregations, numbers of fish, sizes and sexes. The time, location and descriptions of spawning behavior for as many sites and species as feasible should be documented. Scaling Considerations

The study shall examine connectivity at a number of scales. Using drifters, the fine scale will include learning about the track taken by planktonic fish eggs (the type released by nearly all large food fishes) released from a spawning aggregation site or the way coral eggs are transported away from their natal reef. The large scale, using drifters, current meters and satellite data, for an island group such as Palau will seek to determine the extent of the "sticky water" phenomenon – the extent to which the island ecosystem couples with the larger oceanic circulation it sits inside. There are levels of scale in between and they are all important in overall examination of connectivity. Most large reef fishes have planktonic eggs and larvae, spending about 1-2 months in the plankton before settling out and becoming bottom-dwelling juveniles. Coral spawn can have considerably shorter time in the plankton, as little as a few days, but some species can remain some months in the plankton. Less is known about other types of larvae, but certainly they range from short to long lived in the plankton. Field Approaches

Drifters will be launched at times before, during and after spawning events, such as mass spawning of groupers, and tracked for as long as possible. The drifters, and presumably the eggs, would follow wherever the currents carry them and the first few days will almost certainly determine whether larvae are retained in the waters around an island like Palau or else swept into the general oceanic circulation. If retained around the islands, these propagules would be entrained in what is commonly known as the "sticky water", that ocean water which has distinctive characteristics of temperature, salinity, plankton and nutrients that come only from water which has resided in the lagoon and nearshore areas of Palau. Very few estimates exist of the likelihood of inshore "sticky" water becoming part of the general oceanic circulation. The study will begin to address retention versus dispersal of eggs and larvae. During a period of several months of the initial project, drifters will be used on increasing risky "missions". Missions would run from inshore current studies, such as in the Rock Islands of Palau, to the large lagoon, outer reef areas and finally offshore "sticky" water deployments where recovery is unlikely. Deliverables

Contractor shall deliver the following deliverables: 1. A detailed report at the completion of the study containing, at a minimum, the following:

• Descriptions and maps of the physical parameters and characteristics of all known reef fish spawning aggregation sites in Palau (including, but not limited to: bathymetric and habitat maps of each site; temperature profiles; current regimes – direction and speed at different depths – during spawning times)

• Descriptions and maps of the biological parameters and characteristics of the aggregations at as many sites as possible (including, but not limited to: species; seasonal, lunar and diurnal timing; numbers of fish, sizes and sex ratios; extent and limits of the species aggregations; confirmation of spawning and descriptions of spawning behavior for as many species as feasible)

• Documentation of new aggregations (including, but not limited to: places, species and timing; and testing of remote identification methods)

• Documentation and mapping of egg/propagule transportation and dispersal patterns over the first 24 to 36 hours for as many aggregations as feasible, and during coral spawning events.

• Descriptions of all methods used and new approaches, methods and materials developed • Summary Financial Report (as an Appendix)

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2. Brief quarterly progress reports (end of August 2003, November 2003, February 2004, May 2004) 3. Publications: The contractor is encouraged to publish in the scientific literature the information

collected during this research, with the following conditions: • The information used is for non-profit purposes • The Nature Conservancy is allowed to review drafts prior to submission • Appropriate acknowledgement of the donors, including but not limited to USAID, and The

Nature Conservancy are included. This acknowledgment requirement shall also apply to any other external communications in connection with this project.

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APPENDIX 2: Letter of Response to Final Report Review Comments

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APPENDIX 3: Interim Report 1 – Spawning Aggregation Connectivity Project (19 January 2004)

General

Initial field work was started in April 2003 and continued actively through the end of the grouper spawning season in late August 2003. This work focused on several different aspects of spawning aggregations. With the assessment of connectivity of spawning aggregation sites with recruitment areas as the ultimate objective, work started on aspects of these questions. In some cases, we need to obtain some basic information, such as exactly when species of groupers are spawning at known aggregation sites, before we can fully examine the dispersal of eggs and larvae Bathymetric Mapping of Grouper Aggregation Sites

Bathymetric maps were prepared for some of the grouper aggregation sites. Maps are completed for Ebiil, West Channel and Ngerumekaol (Ulong) Channel. Maps of other grouper sites will be prepared early in 2004 in time for the spring/summer spawning season. The bathymetric maps are used to plot distribution of aggregations as determined by GPS transects. New Methods for Quantifying Aggregation Surveys

A new method of surveying aggregation sites has been developed. The method uses GPS based survey transects to produce a density measure of aggregated fishes during a free swimming process. This method has great potential for making truly repeatable and quantitative surveys possible. During the summer of 2003 numerous surveys were done on grouper density at aggregation sites. The most effort was put into surveys at Ngerumekaol (Ulong Channel) as this site is reasonably close to Koror and adequate numbers of fishes to provide significant data. Preliminary work was done at Ebiil Channel also. Working with Dr. Terry Donaldson of the University of Guam, transect surveys were undertaken on 20 days. The number of fishes encountered in a 20 m wide swath (10 m on either side of the line of swimming or drifting) are recorded on a minute by minute basis. A logging GPS receiver in a waterproof float is towed by the diver/snorkeler, logging the position of the observer at a 15second interval. Later the GPS positions are downloaded and the distance traversed in each minute (while the fish count was being made) is determined. The distance and swath width gives an area surveyed, and the fish count used to determine a density, with the location of the survey area determined by the GPS coordinates. Successive densities can be plotted against bathymetric maps or vertical aerial photos to provide an overall picture of the distribution of fish within an aggregation, its relationship to environments at the aggregation site and through contour plotting arrive at an estimated number of fish(es) at the survey site. Since the survey locations are referenced by GPS coordinates, the same areas can be resurveyed daily, yearly or at any time interval chosen. Oceanography of Aggregation Sites

Two current meters have been purchased to document currents at aggregation sites. This portion of the research has not yet really started as the two current meters were diverted for use in the "hydrodynamic modeling" project supported by TNC. While the equipment placed out for this project was recovered in January 2004, one of my meters was needed to continue sampling a station where the original current meter had failed. This meter will be recovered in mid-February 2004. Current following drifters are being readied for work this spring. One preliminary study was done in which four drifters were started from a Humphead wrasse spawning site. All four drifters gradually moved offshore and along the reef on the western barrier reef. There was no indication of them altering direction as the tide changed from outgoing to incoming. This indicates that at least at some

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times C. undulatus eggs can be taken into offshore circulation. More days of drifter runs are needed to ascertain whether this is a general pattern. Investigations of Aggregation Sites Reported to be "Fished Out"

The question of whether spawning aggregations will reestablish themselves after being fished out is quite important with regard to whether conservation measures, despite apparent loss of an aggregation, might be useful in bringing back aggregations. Two areas, reported to be fished out grouper aggregation sites, were examined. The first was in the Denges (Ngerelong) Channel reported by Johannes et al. (1996) and other local informants to have been fished out by a live reef fish trade operation in the early 1990's. Since we did not know exactly where the aggregation previously occurred, it was decided to bathymetrically map the site and then make a series of exploratory diving transects to assess the presence of grouper during the period when aggregation should be occurring. Dives were made on two day using GPS tracked scooter transects. The first day did not reveal any significant numbers of groupers, but many thousands of bigeyes, Priacanthus cruentatus, were found in separate schools of about 200 individuals each along the front of the reef. Aggregation of this species is not previously reported in Palau (or elsewhere as far as I know), but the numbers of fish seen were indicative that this species might be occurring in spawning aggregations. This species will be examined further during the spring-summer of 2004. The second dive transect at Denges Channel revealed that there were groupers present in modest numbers whose dispersal and behavior was indicative of spawning aggregations. While we were limited in the amount of data that could be gathered at this site, due to our unfamiliarity with it, we intend to examine this area more closely in 2004. Our preliminary information indicates that groupers are again aggregating here. We do not actually know whether the aggregations found at this channel truly ceased to exist after fishing, but if they did, the apparent fact that aggregation have reappeared gives some hope that other areas might have grouper aggregations reestablish themselves after being fished out. A fished out grouper aggregation area at German Channel was examined on two occasions. The first time, a GPS track scooter transect was swum from ocean to near the lagoon, in the area that was reported to previously have grouper aggregations. No groupers were seen on this transect. Later, a report of a humphead wrasse aggregation site near the previous location was investigated late in the grouper spawning season, and it was discovered that some groupers consistent with aggregating individuals were found in this area. It is possible the grouper aggregations in this area are starting to recover or the ori

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