Biological and physical processes in and around Astoria submarine ...

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Journal of Marine Systems 50 (2004) 21–37

Biological and physical processes in and around Astoria

submarine Canyon, Oregon, USA

Keith L. Bosleya,*, J. William Lavelleb, Richard D. Brodeurc, W. Waldo Wakefielda,Robert L. Emmettc, Edward T. Bakerb, Kara M. Rehmked

aNOAA Fisheries, Northwest Fisheries Science Center, Fishery Resource Analysis and Monitoring Division,

Hatfield Marine Science Center, 2032 S.E. OSU Drive, Newport, OR 97365, USAbNOAA Pacific Marine Environmental Laboratory, OAR 7600 Sand Point Way NE, Seattle, WA 98115-6349, USA

cNOAA Fisheries, Northwest Fisheries Science Center, Fish Ecology Division, Hatfield Marine Science Center, 2030 S.E. OSU Drive,

Newport, OR 97365, USAdOregon State University, Hatfield Marine Science Center, 2030 S.E. OSU Drive, Newport, OR 97365, USA

Received 13 February 2003; accepted 10 June 2003Available online 21 July 2004

Abstract

Astoria Canyon represents the westernmost portion of the Columbia River drainage system, with the head of the canyon

beginning just 16 km west of the mouth of the Columbia River along the northern Oregon and southern Washington coasts.

During the summer of 2001, physical, chemical, and biological measurements in the canyon were taken to better understand the

hydrodynamic setting of, and the feeding relationships among, the pelagic and benthic communities. Results show that currents

were strongly tidal, and transport, where measured, was primarily up and into the canyon below shelf depth as previous studies

in the canyon have shown. Temperature time series suggests that the largest diurnal oscillations occurred at, or were trapped

near, the bottom of the canyon. Within the upper canyon, subtidal temperature was correlated with upper-level shelf-edge

currents, linking subtidal upwelling events in the canyon with near-surface subtidal along-shore flow. Invertebrates, such as

shrimp, euphausiids, and squid, as well as mesopelagic fishes, dominated the Isaacs–Kidd midwater trawl catches along the

canyon walls. Large trawl catches were comprised mainly of hake and rockfishes (shallow trawls) and macrourids, scorpaenids,

stomiids, and zoarcids (bottom trawls). Gut-content analysis of rockfishes and lanternfishes revealed substantial use of

midwater prey such as euphausiids and mesopelagic fishes. The d13C values of fishes and invertebrates reflected local primary

production, as indicated by particulate organic matter (POM) d13C values from samples collected at various depths along the

axis of the canyon, as well as across the canyon at several sites. The d15N values of fishes and invertebrates indicated

lanternfishes, along with euphausiids, amphipods, shrimp and squid, may be important dietary components of higher-trophic-

level fishes in both the benthic and benthopelagic food webs. The d13C and d15N values of Sebastes species showed significant

enrichment in the adults of species that are largely piscivorous relative to the values of adults of more omnivorous species.

D 2004 Elsevier B.V. All rights reserved.

Keywords: Submarine canyons; Astoria canyon; Currents; Zooplankton; Micronekton; Fish; Stable isotopes

0924-7963/$ - see front matter D 2004 Elsevier B.V. All rights reserved.

doi:10.1016/j.jmarsys.2003.06.006

* Corresponding author. Tel.: +1-541-867-0506; fax: +1-541-867-0505.

E-mail address: [email protected] (K.L. Bosley).

K.L. Bosley et al. / Journal of Marine Systems 50 (2004) 21–3722

1. Introduction

Canyons represent just one type of abrupt topog-

raphy in which enhanced productivity is often found.

Factors that lead to enhanced productivity in canyons

are the regional and local topography, the regional

and local nutrient supply, vertical migration habits of

species, and the ocean currents within and above the

canyon. Genin (2004) has reviewed the biophysical

mechanisms by which fishes and their prey resources

become aggregated near abrupt topography. These

include funneling and trapping of plankton (Koslow

and Ota, 1981; Greene et al., 1988; Macquart-Mou-

lin and Patriti, 1996) and counter-upwelling depth

retention (Allen et al., 2001). The topographic com-

plexity of canyons, the time-varying nature of flow

and forcing, and the difficulty in sampling behavior-

ally dynamic biological populations in physically

dynamic environments, however, make fully unrav-

eling trophic pathways in these environments a

challenge.

Compared to neighboring shelf and slope regions,

submarine canyons exhibit intensified flow and tur-

bulence. Wind-driven, pressure-driven, and tidal

flows dominate motion (e.g., Hickey et al., 1986;

Hunkins, 1988; Noble and Butman, 1989; Lafuente

et al., 1999). Focusing of flow by canyon topography

makes canyons a major site in cross-slope/cross-shelf

exchange (e.g., Hickey, 1997). Freeland and Denman

(1982), noting the persistent pool of nutrients on the

shelf at the head of the Juan de Fuca Canyon in the

Northeast Pacific Ocean, recognized that canyons

may serve as conduits of deep nutrients to shelf

water (see also Sobarzo et al., 2001). Internal tide

focusing and breaking in canyons (Gardner, 1989)

can lead to intensified mixing near canyon bottoms

(Lueck and Osborn, 1985; Carter and Gregg, 2002;

Kunze et al., 2002; Petruncio et al., 1998). Increased

turbulence in the bottom f 100 m leads to resus-

pension, a slowing of the deposition of particulate

matter descending from the euphotic zone, and to

higher levels of particulates and nutrients in the

water column within the canyon. Density-driven,

down-canyon flows are also not uncommon and they

can temporarily change habitats along a canyon floor

by scouring the seafloor, by increasing turbidity, and

through sediment deposition (Kampf and Fohrmann,

2000).

Astoria Canyon, along the west coast of North

America and just beyond the mouth of the Colum-

bia River, is considered to be a steep and narrow

canyon (Hickey, 1997). Flow is marked by spatial

variability at length scales of a few kilometers or

less; diurnal and semi-diurnal tidal motions account

for much of the variance (Hickey, 1997). This

results in suspended matter fields that are marked

by considerable temporal variability (Plank et al.,

1974).

During times of maximum upwelling (southward

along-shore near surface flow), flow across the entire

width of the canyon is landward, but prior to and after

maximum upwelling, canyon flow is marked by

strong lateral shear (Hickey, 1997). A cyclonic vortex

at the head of canyons is typical of flow during such

times (Allen, 1996; Hickey, 1997; She and Klink,

2000) and, in the case of Astoria Canyon, it extends as

much as 50 m above canyon rim depth. Water

properties are domed upward at the head of some

canyons (Hickey, 1995) in response to upwelling. In

Astoria Canyon, shelf flows crossing the canyon in

the near surface (0–100 m) are not deflected (Hickey,

1997).

Stable-isotope ratios present a useful tool for

studying the processes, connections, and energy flow

within aquatic ecosystems (see reviews by Fry and

Sherr, 1984; Owens, 1987; Peterson and Fry, 1987).

Two elements, carbon and nitrogen, are particularly

useful as natural tracers of both the flow of organic

matter and food-web structures in marine ecosystems.

It is possible to obtain time-integrated descriptions of

diets, sources of prey, and the trophic status of a fish

by quantifying the ratios of 15N/14N and 13C/12C. The

carbon sources in a geographic area can be distin-

guished isotopically because the relative amount of13C in the tissues of primary producers varies depend-

ing on the mechanism of carbon fixation and often

varies substantially between habitats that are domi-

nated by different types of primary producers (Fry and

Sherr, 1984). The trophic level of a secondary con-

sumer can be inferred because heavier isotopes, espe-

cially 15N, are retained in the tissues of a consumer in

increasing amounts relative to the amount of heavier

isotopes found in its diet, a process referred to as

fractionation (DeNiro and Epstein, 1981). A one-

trophic-level difference in nitrogen stable isotope

levels is generally considered to be 3.0 to 3.5 per

K.L. Bosley et al. / Journal of Marine Systems 50 (2004) 21–37 23

mil (x) (DeNiro and Epstein, 1981). That is, if a

primary producer had a value of 0x, a primary

consumer that feeds on it should have a value of

3.0x to 3.5x. A secondary consumer feeding on the

primary consumer would be expected to have a value

of 6.0x to 7.0x, and so on.

Hill and Wheeler (2002) examined organic carbon

and nitrogen in surface waters off of Oregon and

Washington to characterize three distinct water sour-

ces: oligotrophic offshore water, the Columbia River

plume, and the coastal upwelling region. They found

that the river plume had the highest levels of both

total and dissolved organic carbon. Previous studies

have shown that potential sources of carbon in marine

and coastal ecosystems will have different d13Csignatures, and they used the carbon isotopic compo-

sition of suspended particulate organic matter (POM)

and sediments as a means of calculating the amount

of terrestrial carbon that is contributed to freshwater

and marine systems (Fry and Sherr, 1984). A prereq-

uisite for using isotope ratios as tracers in food webs

is a detectable and consistent difference in the isoto-

pic signature between its components. In areas of the

oceans where there are different sources of primary

production, along with diverse assemblages of con-

sumers, such as along a continental shelf or slope,

stable isotopes can be used in conjunction with

traditional methods (i.e. stomach content analysis) to

study feeding relationships and the relative contribu-

tions of different primary producers (Perry et al.,

1999; Polunin et al., 2001; Davenport and Bax,

2002).

Astoria Canyon is a highly productive fishery

region. The canyon is home for many pelagic fish

species, and many years of surveys have found

extensive groundfish resources there as well. Despite

the importance of its fisheries resources, we know

little about the pathways leading from primary

nutrients to higher trophic levels in Astoria Canyon.

To date, the only study of the food habits of fishes in

Astoria Canyon was that of Pereyra et al. (1969),

which examined the feeding ecology of adult yellow-

tail rockfish that utilized mesopelagic prey resources.

In this work, we report on biological, chemical, and

physical measurements taken in Astoria Canyon

aimed at further elucidating feeding relationships

and the physical environment in which these trophic

transfers occur.

2. Materials and methods

2.1. Study area

This study was conducted during a NOAA Ocean

Exploration cruise aboard the R/V Ronald H. Brown

from June 27 through July 3, 2001 in Astoria Canyon.

The head of the canyon begins at a bottom depth of

120 m just 16 km west of the present river mouth (Fig.

1). The axis of the canyon extends from well within

the continental shelf zone, west-southwest for approx-

imately 110 km, where, at a bottom depth of more

than 2000 m, it transitions into a deep-sea channel.

The width of the canyon ranges from 9 km where it

cuts across the shelf to 70 km where it transitions into

Astoria Channel (Carlson, 1968). Astoria Canyon is

the southern-most submarine canyon of a series of

canyons that bisect the continental margin of the

Pacific Northwest off British Columbia and Washing-

ton. Rogue Canyon, far to the south, is the only other

significant canyon feature on the Oregon margin

(Underwood, 1991). Astoria Canyon lies within a

major upwelling region and underlies the Columbia

River Plume, a major hydrographic feature along the

coasts of Oregon and Washington (Hickey, 1989). Our

study was confined to the eastern portion of the

canyon.

2.2. Physical measurements

Two taut-wire moorings were deployed in the

canyon on June 29 to measure currents and temper-

atures. The moorings collected data during the inten-

sive 1-week biological sampling period (June 27–July

3) and remained in the canyon through August 2 in

order to sample during one entire lunar cycle. The

Aanderaa RCM-7 current meters recorded speed,

averaged over the sampling interval, and instanta-

neous direction half-hourly. Moorings M-118 and

M-119 were located at 46j13.8VN, 124j27.0VW and

46j11.0VN, 124j39.40VW, respectively. M-118, in

337-m water depth, recorded currents at a depth of

275 m, and M-119 recorded currents at 50, 275, and

325 m in 400-m water depth. M-118 was located

nearer the head of the canyon, and M-119 was located

where the canyon and upper slope intersect (Fig. 1).

Temperatures were recorded using Miniature Temper-

ature Recorders (MTR) and Miniature Autonomous

Fig. 1. Sampling locations in Astoria Canyon. The CTD stations are indicated by single upper-case letters/open circles; the IKMT trawl sites

begin with the letter ‘‘I’’/solid star; the Sea Eagle trawl sites begin with the letter ‘‘R’’/solid triangle (midwater rope trawl) or ‘‘B’’/open square

(bottom trawl); and the mooring locations begin with the letter ‘‘M’’/solid square. Bathymetry is adapted from NOAA National Ocean Survey

Seamap Series for the North Pacific Ocean, no. 12042-12B. Depth contours are in meters. Only the 150-, 1000-, and 2000-m contours are

featured on the inset map to show the relative position of the shelf break.


Plume Recorders (MAPR) (Baker and Milburn,

1997). On M-118, temperatures were sampled half-

hourly at depths of 60, 100, 125, 160, 200, 250, 290,

and 340 m, and on M-119, at depths of 100, 150, 190,

and 270 m. Wind speed and direction 5 m above sea

level were sampled hourly from Buoy 46029 by the

NOAA National Data Buoy Center. Buoy 46029 at

46j07V00UN and 124j30V36UW in 128 m of water is

located 13 km SSW of M-118 and 13 km ESE of M-

119. The buoy’s location makes its measured winds

representative of those over the canyon (Fig. 1).

Spectral analysis of time series involved removing

the mean and a linear trend from each time series,

cosine tapering 10% of both ends of the resulting

record, Fourier analyzing, and then band smoothing

the resulting periodograms using a Hanning spectral

window with an 11-point width (e.g. Emery and

Thomson, 1997).

CTD casts were made at several stations across the

canyon and along its axis from the R/V Brown. A CTD

rosette containing multiple Niskin bottles was lowered

at each station and water samples were collected from

just below the sea surface, from the midwater (based

on station depth) and from just above the sea floor.

Replicate water samples were first filtered through 28-

Am mesh to remove larger particulates and then

through Whatman GF/F filters to collect particulate

organic matter (POM). The filters were frozen for

further processing on land for isotopic analysis (see

below).

2.3. Biological sampling

Most of the biological samples and data were

collected from the R/V Brown. Multi-frequency acous-

tic data were collected from continuous transects

across the canyon using an EK-500 echosounder

receiving data from 38-, 120-, and 200-kHz trans-

ducers. Complete analyses of these acoustic data are

beyond the scope of this paper and will be presented

elsewhere. The acoustics were employed to target

midwater and bottom trawling on particular signals

and acoustic layers. Three horizontal tows for micro-

nekton were made with an IKMT (Isaacs–Kidd mid-

water trawl) with a mouth area of 5.4 m2. The main

body of the net was comprised of 10-mm stretch


mesh, with 500-Am mesh in the codend. A large V-fin

depressor situated at the front of the net increased the

sampling depth for the given amount of wire out. A

calibrated General Oceanicsk flow meter suspended

in the mouth of the net provided data on the amount of

water filtered by the trawl. The depth of each tow was

determined using a MAPR device. All fishes and

invertebrates caught were identified by species and

weighed in the laboratory to determine biomass.

Selected species from these tows had white muscle

tissue dissected for stable-isotope analysis and stom-

achs dissected for content analysis and were handled

as described above. Whole invertebrates also were

frozen for further processing and isotopic analysis.

Some biological sampling was carried out from a

commercial fishing vessel, the F/V Sea Eagle, during

the same time period. Fishes and invertebrates were

collected from the Sea Eagle using a bottom trawl that

featured a ‘‘rock hopper’’ footrope (number of

tows = 2) and using a Nordic 264 rope trawl (n = 7)

to assess species diversity and abundance around the

canyon. Fish that were collected in the trawls were

sorted by species and then weighed, measured, and

counted. Selected species had white muscle tissue

dissected for stable-isotope analysis and stomachs

dissected for content analysis. The muscle tissue

was dissected from just below the dorsal spines or

fins of each fish and then frozen. The stomachs were

preserved in 10% formalin. Whole invertebrates also

were sorted by species, and selected animals were

frozen for further processing and isotopic analysis.

2.4. Laboratory analyses

Prior to analysis, muscle-tissue samples were first

thawed and then dried completely at 55 jC. The

samples were ground using a Wig-L-Bugk (Dents-

ply) automated mortar and pestle and then loaded into

tin capsules. Filter samples also were thawed and

dried completely at 55 jC and then acidified with 1

N HCl to remove any inorganic carbon. The stable-

isotope analysis was carried out using a Costech

elemental analyzer coupled to a Thermo Finnegan

stable-isotope-ratio mass spectrometer in the continu-

ous-flow mode, with ultra-high-purity helium as the

carrier gas. The stable-isotope ratios (15N/14N and13C/12C) were reported as d15N and d13C, with units

of per mil (x) difference relative to standards; N2 in

air for nitrogen and PDB (Peedee belemnite) (Craig,

1957) for carbon. Lipids are depleted in 13C relative to

other biochemical fractions (DeNiro and Epstein,

1977, 1978; Tieszen et al., 1983). Since lipids were

not removed prior to the analysis of muscle-tissue

samples, final fish and invertebrate d13C values were

normalized (McConnaughey and McRoy, 1979) to

account for the depletion effect of lipids.

3. Results

3.1. Physical environment of the canyon

Surface winds measured south of the canyon had a

vector-averaged speed of 3.4 m s� 1 and direction of

149j (Fig. 2A), typical of southward winds along the

Oregon coast during spring and summer (Hickey,

1997). The spectra of wind over the interval June–

August 2001 exhibited both diurnal and semidiurnal

peaks.

Currents measured at 50-m depth on M-119 (Fig.

2C) showed a strong vector-averaged flow of 16.4 cm

s� 1 to the south (181j), with no indication of flow

reversal. Spectra analysis of the record confirmed a

strong semi-diurnal, nearly linear, oscillatory compo-

nent, a substantial inertial frequency signal, but a very

weak diurnal oscillation. Currents at 225 m (Fig. 2D)

and 325 m (not shown) at M-119 flowed primarily to

the NNE (24j and 17.6j, respectively) along the trend

of the slope isobaths at vector-averaged speeds of 6.8

and 3.6 cm s� 1, possibly showing evidence of the

influence of the California undercurrent.

Currents in the upper canyon (M-118) at 225-m

depth (Fig. 2B) were weaker (mean speed = 0.8 cm

s� 1) and more variable in direction, with the overall

vector-averaged direction of 96j in the direction of

the canyon wall. Spectra of data from the three deep-

est meters showed almost no inertial oscillation, a

strong rectilinear semi-diurnal signal, and strong di-

urnal signals as well. Diurnal motions, which were

clearly intensified by the canyon topography, were

rectilinear at 225 and 275 m but nearly circular at the

325-m deep site (not shown).

Temperatures (T) recorded at M-118 (Fig. 3A)

showed substantial temporal variability and sizeable

vertical gradients. Between 50 and 325 m, the temporal

mean of T differed by 1.5 jC (Fig. 3B), roughly

Fig. 2. Vector time series of (A) winds measured offshore, just south of Astoria Canyon (46j07V, 124j30.6VW); (B) currents in the upper part of

the canyon at M-118 and 275-m depth; (C) currents in the upper water column (50-m depth) over the canyon but farther offshore at M-119; (D)

currents at M-119 but below shelf depth (225 m).


equivalent to the magnitude of the temporal variance

around that mean at each depth. The sequence of

spectra (Fig. 3C) showed a semi-diurnal signal at all

depths, and a diurnal signal that was very weak at the

upper meters but intensified below shelf depth in the

canyon.

Tidal oscillations in T recorded at 200-m depth on

the upper canyon mooring (M-118) were made more

clearly visible in Fig. 4 (solid line). Tidal oscillations

in the north–south component of currents measured in

the near surface waters (50m depth) at mooring M-

119, nearer the canyon mouth, were even more

apparent (dotted line).

CTD observations showed high spatial (vertical

and horizontal) and temporal variability in both the

hydrography and turbidity of the canyon waters. In

the upper canyon, a broad layer of intense light

scattering was common between 200- and 300-m

depth, likely a remnant of resuspension and advection

of adjacent shelf sediments. Just above the canyon

floor, a 50-m-thick layer of sharply increased light

scattering, lower temperature, and increased salinity

Fig. 3. (A) Eight time series of temperatures (T) recorded at M-118 at depths (starting with the uppermost series) of 60, 100, 125, 160, 200, 250,

290, and 340 m. (B) Profiles of temperature representing the mean, maximum, and minimum T from each of the time series. (C) Spectra of time

series each successively offset by one unit on the y-axis. The lowest curve (not offset) represents data from 60-m depth.


suggest up-canyon flow vigorous enough to create a

thick layer of resuspended bottom sediments. Light-

scattering values in this layer increased with decreas-

ing canyon depth. Even in the upper canyon, vertical

stratification was sufficient to maintain pronounced

layering of the fine-grained suspended particulate

matter.

The vertical and horizontal variability was not as

evident in the d13C data from the POM that was

collected, but there were some measurable differences

(Table 1). Overall though, the POM data varied little

between the stations around the canyon, regardless of

depth. The mean d13C was � 23.82x with a standard

deviation (S.D.) of 1.10x (n = 22). The station with

the greatest d13C variability between surface and

bottom POM was station J, which ranged from a

low of � 25.25x near the bottom to a high of

� 21.40x near the surface. Station J was the deepest

station sampled and was located in the heart of the

canyon (see Fig. 1). Several stations had surface POM

Fig. 4. Along-shore current speeds (dotted line) at 50-m depth on M-119, plotted over temperatures (solid line) measured in the upper part of

Astoria Canyon on M-118 at 200-m depth.


d13C that were nearly identical to bottom POM d13C.One was station G, located just up-canyon from

station J, with a depth of more than 700 m. Two of

these were stations B and F, which were the north-

ernmost and southernmost stations, respectively,

along a cross-canyon transect and were among the

shallowest sites sampled.

3.2. Biological observations

An example of the bioacoustic data collected for

choosing trawl locations is shown in Fig. 5. In this

example (from a 120 kHz profile, taken over the north

wall of the canyon), several distinct layers at shelf

depth, along the canyon wall, over a pinnacle at

f 225-m depth and at approximately the same depth

Table 1

Particulate organic matter d13C values from water samples collected

at stations located around Astoria Canyon at the surface, midwater,

and near the bottom

Surface Midwater Bottom

Station A � 22.83 � 22.95 � 24.44

Station B � 23.38 � 23.14 � 23.81

Station C � 22.37 � 23.79 � 24.94

Station D – – � 25.14

Station E – � 24.43 �Station F � 22.27 � 24.29 � 22.48

Station G � 24.48 – � 24.63

Station I � 23.96 � 25.24 � 25.06

Station J � 21.40 � 23.66 � 25.25

Dashed lines represent locations that could not be sampled.

within the canyon proper can be seen. On the basis of

the IKMT and trawl data (described below), the layers

were later found to be correlated with catches of

rockfishes in close proximity to the canyon walls

and pinnacles and with euphausiids and Pacific hake

(Merluccius productus) in the layers farther away

from these topographic features, but still within the

canyon.

Two IKMT trawls were made along the northern

side of the canyon and one on the south side (Fig. 1).

Tow 1 (to 89 m) targeted shallow acoustic layers

along the northern canyon wall, and caught mostly

larger zooplankton (decapod larvae, euphausiids,

hyperiids, chaetognaths, and fish larvae), but no large

nekton (Table 2) were collected in this tow. The two

deeper tows (to 222 and 264 m) caught a variety of

large mesopelagic organisms, including midwater

shrimps, squids, and fishes (Table 2). The northern

lampfish (Stenobrachius leucopsarus) dominated the

catch by number and weight in tow 3 (Table 2).

However, in tow 2, the catch was predominantly made

up of the offshore species of euphausiid, Euphausia

pacifica; the trawl apparently passed through a layer

of this species.

Nine fish/decapod trawls (Fig. 1) were made from

the Sea Eagle. Data from only three of the hauls (R1,

B1, and B2) are reported here (Table 3) because they

were the only ones from which tissue samples and

stomachs were collected for comparing stable-isotope

data to stomach content data. Similar to the IKMT

tows, tow R1 fished in midwater and caught a low

diversity of taxa, which with the exception of some

Fig. 5. A 120-kHz bioacoustic profile taken on a north-to-south transect across the north wall of Astoria Canyon, Oregon. The vertical gridlines

represent 10-min time intervals.


Pacific hake, was comprised entirely of rockfishes of

the genus Sebastes. The deepest bottom tow, B1 (max.

depth = 549 m), caught a relatively high diversity of

fishes, including grenadiers, thornyheads (Sebastolo-

obus alascanus, Sebastolobus altivelis), sablefish

(Anoplopoma fimbria), viperfish (Chauliodus

macouni), and snailfishes (Family Liparididae), but

no rockfishes. There was also a fairly substantial catch

of tanner crabs (Chionoecetes spp.) in that haul.

Finally, the last tow (B2) contained mostly thorny-

heads, eelpouts (Family Zoarcidae), and Dover sole

(Microstomus pacificus) but few other species.

The stomach content data are presented in Table 4.

Of the rockfish stomachs that were analyzed, widow

rockfish (Sebastes entomelas) were found to have

primarily unidentifiable gelatinous material; yellow-

tail rockfish (Sebastes flavidus) were found to have

euphausiids, myctophids, and squids; and bocaccio

rockfish (Sebastes paucispinis) were found to have

only Pacific ocean perch (Sebastes alutus) and other

fish remains in their stomachs. The stomach contents

of the myctophid, California headlightfish (Diaphus

theta), were found to contain primarily euphausiids

(E. pacifica) and hyperiid amphipods, while the

northern lampfish (S. leucopsarus) had a similar diet

but also consumed copepods to some extent (Table 4).

3.3. Stable-isotope analyses

The carbon and nitrogen stable-isotope data for

individual fishes and invertebrates are presented in

Fig. 6A. The isotopic values of most of the fishes that

were sampled were enriched in heavier isotopes of

both carbon and nitrogen relative to the invertebrates

that were collected. To better compare the trophic

position of the rockfishes, d13C and d15N values of

only the Sebastes species are presented in Fig. 6B.

Both the d13C and d15N values were significantly

different between rockfish species ( p < 0.0001, SAS

General Linear Model). Of the five species of rockfish

that were sampled in the pelagic tow, bocaccio rock-

fish (n = 9) was the most enriched in 13C and 15N,

which is in agreement with the findings of the

stomach-content analysis indicating substantial pisci-

vory by this species. A post-hoc, pairwise comparison

determined that bocaccio rockfish d13C values were

significantly enriched relative to both yellowtail rock-

fish (n = 17) and widow rockfish (n = 17), and canary

Table 2

Standardized densities (number per 1000 m3) and biomass (grams per 1000 m3) of zooplankton and micronekton collected in each Isaacs–Kidd

Midwater Trawl (IKMT) in Astoria Canyon in 2001

Tow 1 (max. depth = 89 m) Tow 2 (max. depth = 222 m) Tow 3 (max. depth = 264 m)

Density Biomass Density Biomass Density Biomass

Cnidaria

Hydromedusae unidentified 2.562 1.209

Atolla sp. 0.031 0.010

Siphonopora

Siphonophora unidentified 0.213 0.341

Cephalopoda

Gonatus onyx 0.384 0.207 0.063 0.124

Taonius pavo 0.085 0.437 0.094 0.044

Crustacea

Cancer magister 0.914 0.038 2.050 0.098

Munida quadrispina 0.000 0.283 0.045

Sergestes similis 2.263 0.805 4.534 1.871

Pasiphaea pacifica 11.785 4.699 1.385 2.725

Pandalus jordani 3.886 0.360 1.354 0.688

Thysanoessa spinifera 0.229 0.011 1.228 0.075

Euphausia pacifica 320.239 47.881 1.008 0.057

Boreomysis califonica 0.031 0.003

Holmesiella anomola 0.063 0.006

Phronima sedentaria 0.114 0.001 0.128 0.013 0.252 0.028

Paraphronima gracilis 0.686 0.008

Primno macropa 0.343 0.010 0.085 0.003

Themisto pacifica 0.914 0.006 0.085 0.000

Cyphocaris challengeri 0.171 0.009

Ampelisca sp. 0.031 0.001

Karoga megalops 0.126 0.010

Stilipes distincta 0.220 0.024

Chaetognatha

Eukhronia hamata 0.114 0.001

Sagitta elegans 1.942 0.003

Sagitta scrippsae 0.686 0.002

Osteichthyes

Sebastes spp. 0.114 0.007

Stenobrachius leucopsaurus 6.917 11.060 8.533 11.710

Stenobrachius nannochir 0.031 0.006

Diaphus theta 0.384 1.077 0.063 0.018

Tarletonbeania crenularis 0.031 0.019

Bathylagus stilbius 0.189 0.056

Chauliodus macouni 0.043 0.015 0.031 0.017

Lycodapus spp. 0.031 0.010

Nectoliparis pelagicus 0.128 0.018 0.063 0.001

Lyopsetta exilis 0.043 0.003

Glyptocephalus zachirus 0.114 0.016 0.043 0.011


rockfish (Sebastes pinniger, n = 4) d13C values were

also significantly enriched relative to widow rockfish

(Tukey’s Studentized range test, a = 0.05). The d15Nvalues of bocaccio rockfish were also significantly

enriched relative to both yellowtail rockfish and

widow rockfish.

4. Discussion

4.1. Currents and hydrography

Current and temperature time series in Astoria

Canyon exhibit strong, semi-diurnal components at

Table 3

Standardized densities (number per 106 m3) of fish and decapods collected in midwater (R) and bottom (B) trawls in Astoria Canyon in 2001

Common name Scientific name Tow R1

(max. depth = 89 m)

Tow B1

(max. depth = 549 m)

Tow B2

(max. depth = 340 m)

Density Density Density

Tanner crab Chionoecetes spp. 22.01 0.54

Myxinidae

Pacific hagfish Eptatretus stouti 0.51 0.54

Scyliorhinidae

Brown cat shark Apristurus brunneus 5.63 0.54

Alepocephalidae

California slickhead Alepocephalus tenebrosus 0.51

Stomiidae

Pacific viperfish Chauliodus macouni 65.52

Neoscopelidae

Blackchin Neoscopelus macrolepidotus 1.09

Pacific blackchin Scopelengys tristis 0.10

Moridae

Pacific flatnose Antimora microlepis 0.51 1.09

Gadidae

Pacific hake Merluccius productus 19.30

Macrouridae

Giant grenadier Albatrossia pectoralis 8.70

Grenadiera Coryphaenoides spp. 748.32

Scorpaenidae

Rougheye rockfish Sebastes aleutianus 0.27

Brown rockfish Sebastes auriculatus 19.99

Darkblotched rockfish Sebastes crameri 0.69

Widow rockfish Sebastes entomelas 31.02

Yellowtail rockfish Sebastes flavidus 51.70

Bocaccio Sebastes paucispinis 4.14

Canary rockfish Sebastes pinniger 2.07

Shortspine thornyhead Sebastolobus alascanus 1.33 12.75

Longspine thornyhead Sebastolobus altivelis 149.66 13.29

Anoplopomatidae

Sablefish Anoplopoma fimbria 12.80 2.17

Cyclopteridae

Unidentified snailfish Cyclopteridae 11.26 0.27

Zoarcidae

Snakehead eelpout Lycenchelys crotalinus 2.56 2.17

Black eelpout Lycodes diapterus 6.65 4.07

Unidentified eelpout Zoarcidae 3.80

Pleuronectidae

Dover sole Microstomus pacificus 4.07

Deepsea sole Embassichthys bathybius 1.02 0.27

Arrowtooth flounder Atheresthes stomias 1.02 0.27

a Possible complex of two species: Coryphaenoides acrolepis (Pacific grenadier) and C. cinerus (popeye grenadier).


all measured locations, have inertial frequency com-

ponents only above shelf depth, and have a diurnal-

frequency content that is weak above but strong

within the canyon.

The topography of Astoria Canyon, like other

deep, narrow canyons, clearly intensifies diurnal

motions (Fig. 3C). Results are consistent with the

much more extensive physical oceanographic inves-

tigations of Astoria Canyon by Hickey (1997).

One interesting aspect of Fig. 4 is the apparent

correlation of the subtidal signals in the two records,

with a slight time lead of current on T changes. Both

Table 4

Prey composition (percent of total weight) of three species of rockfishes (Sebastes spp.) and two mesopelagic myctophids from Astoria Canyon

collected in midwater and bottom trawls in June 2001

Prey items Predator S. entomelas S. flavidus S. paucispinis D. theta S. leucopsarus

Number examined 16 18 6 25 27

Length range (mm) 341–398 384–496 382–415 48–81 53–96

Copepoda

Calanus marshallae 2.41

Clausoalanus spp. 1.12

Candacia spp. 1.12

unidentified calanoid 0.43 4.18

Hyperiidae

Themisto pacifica 0.02 3.75 2.94

Primo macropa 1.33

unidentified 1.32 18.43 2.94

Euphausiacea

Euphausia pacifica 62.06 57.68 29.41

unidentified 0.14 19.45 35.29

Decapoda

Pasiphaea pacifica 2.98

Cephalopoda

unidentified squid 8.46

Siphonophora 0.06

Other gelatinous material 95.27

Osteichthyes

Nectoliparis pelagicus 1.44

Stenobrachius leucopsarus 23.39

Sebastes alutus 91.02

unidentified fish remains 8.74 0.68

Unidentified material 3.10 0.25 20.59


Hickey (1997) and Allen et al. (2001) have noted a

similar correlation in their measurements. The expla-

nation begins by noting that currents in the near-surface

layer should be in approximate geostrophic balance

with the cross-shore pressure gradient (dp/dx). The

subtidal, along-shore, near-surface current record can

serve as a surrogate for dp/dx. Fluid in the canyon is

subject to overlying pressure gradients (dp/dx) and

other forces, but as Freeland and Denman (1982) note,

the walls of the canyon prevent the primary force

balance in the canyon from being geostrophic as it is

near-surface. Instead, dp/dx forcing in the canyon

opposes frictional forces and along-axis baroclinic

pressure gradients, which together determine along-

axis flow. Changes in dp/dx can therefore alter the

strength and possibly the direction of along-axis flow,

with one consequence being changes in T. Larger,

negative dp/dx drive stronger, up-canyon flow, causing

isopycnals to bend upward and T at a fixed location to

decrease. The correlation of surface currents and T in

the canyon shown in Fig. 4 occurs in this way.

The correlation of subtidal T at 200 m and along-

axis currents at M-118 at 225 m was not nearly as

good. The poor correlation of those two time series

(not shown) makes it quite unlikely that changes in T

in Fig. 4 were caused by horizontal advection past the

measurement site. The reason instead must be the

vertical displacement of isopycnals, a displacement

documented by Hickey (1997) using CTD measure-

ments. Therefore, in the upper canyon, T primarily

recorded the vertical movement of isotherms in re-

sponse to up- or down-canyon flow. Temperature at

M-118 at 200-m depth over the time period June 29th

to July 6th decreased by as much as 0.4 jC (Fig. 4).

Using a dT/dz of 4.1�10� 3 jC m� 1 at 200-m depth

estimated from the central profile of Fig. 3A, the

corresponding vertical displacement of isopycnals at

M-118 would be 98 m.

Fig. 6. (A) d13C vs. d15N of all of the fish and invertebrates that had tissue samples collected from sites in and around Astoria Canyon. Species

that are followed by a (B) are benthic and those that are followed by a (BP) are benthopelagic. (B) d13C vs. d15N of rockfish that had tissue

samples collected.



Typical southward summer winds during the mea-

surement period signal a persistent, but variable,

onshore atmospheric-pressure gradient. Subtidal cur-

rents in the upper water column move southward over

the canyon, and currents in the canyon should upwell

as a result. An expectation based on previous meas-

urements and models for this and other deep, narrow

canyons (e.g. Allen, 1996; Hickey, 1997; She and

Klinck, 2000) is that deep, upwelled water and the

nutrients contained therein will continue upward, spill

onto the shelf, and nourish the shelf downstream of

the southern canyon edge, resulting in elevated pro-

ductivity there. For example, it was along the southern

side of Astoria Canyon where Pereyra et al. (1969)

reported much higher catches of fish. The subtidal

current and T record in Fig. 4 suggests that the rate of

upwelling varies. Hickey (1997) shows from measure-

ments in Astoria Canyon that under such conditions,

upwelling is not laterally uniform. In fact, at times

before and after maximum upwelling, down-canyon

flow occurs on the upstream side of the canyon,

leading to a cyclonic eddy that extends downward

into it and as much as 50 m above it near the canyon

head. This recirculation (Hickey, 1997) may prolong

the residence time of nutrients and biota within the

canyon.

4.2. Water chemistry

The d13C values of POM were typical of marine

phytoplankton, which have been shown to range

anywhere from � 24x to � 18x (Fry and Sherr,

1984; Rau et al., 1990). The station (J) with the greatest

variability between d13C values of surface and bottom

POM was the deepest site that was sampled and was

located along the axis of the canyon. With the excep-

tion of Station G (which had nearly identical d13Cvalues of surface and bottom POM), the other stations

along the axis of the canyon that had samples collected

from multiple depths (C and A) had a 1.6x to 2.5xdifference between surface and bottom POM. The

shallow stations on the north and south sides of the

canyon showed the greatest homogeneity between

d13C values of surface and bottom POM.

Assuming 1–2x enrichment in 12C between tro-

phic levels (DeNiro and Epstein, 1978), it appears that

many of the animals at higher trophic levels, particu-

larly invertebrates and small fish, were probably deriv-

ing their carbon from localized primary production

rather than from distant sources, based on the range

of POM d13C values that were measured. This deter-

mination is dependant on the length of time necessary

to incorporate the isotopic signature of a diet. A long-

lived rockfish would probably reflect an integration of

isotopic signatures over a longer period of time, where-

as invertebrates and smaller (i.e. micronektonic) fish

would reflect integration over shorter time periods.

The importance of localized primary production to

the food web around the canyon may have been

elevated during 2001. Terrestrial and riverine inputs

of carbon were expected to be anomalous as it was a

drought year. Indeed, the average monthly flow of the

Columbia River in June 2001 was 4296 m3 s� 1,

which makes it one of the lowest on record. River

flow was substantially lower than the June averages

from the previous 10 years (1991–2000 ranged from

5775 to 14570 m3 s� 1; data from United States

Geological Survey station at Beaver, Oregon).

4.3. Biological sampling

Many of the zooplankton and micronekton collect-

ed in the IKMT tows in the canyon are known to

occupy the epipelagic (upper 200 m) layers of the

ocean off Oregon although a number of these taxa are

known to vertically migrate down to the mesopelagic

zone during daytime (Pearcy and Laurs, 1966; Kry-

gier and Pearcy, 1981). However, many of the micro-

nektonic fishes are rarely found over the continental

shelf (Brodeur et al., 2003); some (e.g. Stenobrachius

nannochir) are not known to migrate up into epipe-

lagic waters (Pearcy et al., 1979) and are not likely to

occur this close to the coast except in canyons or other

areas with substantial on-shelf transport. Brodeur et al.

(2003) found that the distribution of several of the

dominant myctophids we collected in this study was

displaced farther onto the shelf on a transect near

Astoria Canyon than on other transects along the coast

of Oregon, and speculated that they may be advected

onshore by way of the canyon. Although our micro-

nekton sampling in Astoria Canyon was limited, we

observed densities and biomasses of some taxa that

were high relative to nearby areas (Pearcy and Laurs,

1966; Kalish et al., 1986), indicating perhaps an

interaction between behavior of these organisms and

currents affected by the canyon topography (see also


Greene et al., 1988; Macquart-Moulin and Patriti,

1996; Mackas et al., 1997). These high densities were

corroborated by cross-canyon acoustic transects,

which indicated substantial scattering layers in the

canyon and which often intersected the canyon walls,

especially during daytime (Brodeur, personal obser-

vation and example in Fig. 5).

There appear to be trophic effects associated with

the cross-canyon horizontal structure in Astoria

Canyon. High densities of several species of pelagic

rockfishes were collected in our shallow trawls and

were often observed in remotely-operated-vehicle

video transects during this cruise (Wakefield, unpub-

lished data). Dense swarms of euphausiids were also

observed near the bottom at the rim of the canyon

during daytime deployments (Gomez-Gutierrez et

al., 2003). Stable-isotope and dietary data suggest

that the rockfish species may utilize either euphau-

siid aggregations or mesopelagic prey that are

advected up the canyon and toward the canyon

walls, where the shallow bottom blocks their vertical

descent (Genin, 2004), or where they are then

advected onto the adjoining shelf and trapped, mak-

ing them vulnerable to predation by rockfishes

(Pereyra et al., 1969). This trophic interaction be-

tween rockfishes and mesopelagic prey has been

observed numerous times in the North Pacific, both

on offshore banks (Brodeur and Pearcy, 1984; Genin

et al., 1988) and in canyons (Pereyra et al., 1969;

Lorz et al., 1983; Brodeur, 2001), which may point

to these areas as being critical habitats for these

heavily exploited rockfish species (Yoklavich et al.,

1999).

It is also clear from the stable-isotope and dietary

data that some rockfish species occupy a higher

trophic position relative to other rockfish species

feeding in the same general area. These data show

that adult bocaccio rockfish were at a higher trophic

position than any of the other rockfish species that

were sampled, consistent with other dietary studies of

this species (summarized by Love et al., 2002). The

lower-trophic positions of widow rockfish and yel-

lowtail rockfish relative to bocaccio, as indicated by

their significantly lower d13C and d15N values, are

also consistent with other dietary studies (Love et al.,

2002; Lee, 2003) that found their diets to be com-

prised of gelatinous zooplankton and micronekton,

including smaller fishes, euphausiids and amphipods.

The d15N values of myctophids, sergestid and

pasiphaed shrimp, and squid (Gonatus onyx) were

clustered between the other fish species and most of

the other invertebrates, indicating that they all play an

intermediary role in energy flow within the canyon

food web. In an earlier study off Oregon, Tyler and

Pearcy (1975) observed three species of myctophids

(two in common with the current study, D. theta and

Stenobrachius leucopsaurus) to feed primarily on

euphausiids, copepods, and hyperiid amphipods. Our

stable-isotope data, along with diet studies off Oregon

(Nishida et al., 1988), indicate that shrimp and squid

may also represent a link between zooplankton that

graze on primary producers and higher trophic levels.

5. Conclusions

This study illustrates the potential of physical

processes to concentrate marine organisms in and

around undersea canyons. Recirculation (Hickey,

1997), for example, favors a prolonged residence time

of nutrients and biota within the canyon. At the time

of this study, local primary production appeared to

have a predominant effect on the canyon food web

compared to other potential sources. Species compo-

sition was shown to vary both vertically in the water

column and spatially. Stable-isotope and dietary data

suggest that rockfish may utilize either euphausiid

aggregations or mesopelagic prey that are advected up

the canyon and towards the canyon walls, and show

species-specific differences in the trophic position of

fishes. Fish that were found to be primarily piscivo-

rous (based on gut contents) had d15N and d13Cvalues that were enriched relative to fish that were

found to be omnivorous. Fish that were shown to be

entirely planktivorous had d15N values that were

depleted relative to other fish. It is hoped that the

information presented here may serve to support

future studies in this and possibly other highly pro-

ductive undersea canyons.

Acknowledgements

Funding for this work was provided by the NOAA

Northwest Fisheries Science Center, NOAA Office of

Ocean Exploration, NOAA Pacific Marine Environ-


mental Laboratory, the West Coast and Polar Under-

sea Research Center of NOAA’s National Undersea

Research Program, Oregon State University, and

NOAA Oceanic and Atmospheric Research Office

of Marine and Aviation Operations for R/V Brown

ship time.

The authors wish to thank the following individ-

uals for assisting with various aspects of this project:

Doug Burrows, Julia Clemons, Bob Embley, Chris

Goldfinger, Chris Harvey, Gordon Hendler, Greg

Krutzikowsky, Phil Levin, Bruce McCain, Susan

Merle, Todd Miller, William Pearcy, Bill Peterson,

Kevin Piner, Bill Reichert, Joe Resing, Josie Thomp-

son and Sharon Walker. Additional thanks go to the

Canadian Scientific Submersible Facility; Capt. Dan

Parker and the crew of the F/V Sea Eagle; Jennifer

Bloeser and Dave Douglas for assistance with sample

collection on the Sea Eagle, the officers and crew of

the R/V Ronald H. Brown, and Bill Pearcy, Bill

Peterson, Karen Bosley and three anonymous

reviewers for comments on earlier versions of the

manuscript. This is contribution no. 2542 from

NOAA Pacific Marine Environmental Laboratory.

References

Allen, S.E., 1996. Topographically generated subinertial flows

within a finite-length canyon. J. Phys. Oceanogr. 26,

1608–1632.

Allen, S.E., Vindeirinho, C., Thomson, R.E., Foreman, M.G.G.,

Mackas, D.L., 2001. Physical and biological processes over a

submarine canyon during an upwelling event. Can. J. Fish.

Aquat. Sci. 58, 671–684.

Baker, E.T., Milburn, H.B., 1997. MAPR: a new instrument for

hydrothermal plume mapping. Ridge Events 8, 23–25.

Brodeur, R.D., 2001. Habitat-specific distribution of Pacific ocean

perch (Sebastes alutus) in Pribilof Canyon, Bering Sea. Cont.

Shelf Res. 21, 207–224.

Brodeur, R.D., Pearcy, W.G., 1984. Food habits and dietary overlap

of some shelf rockfishes (Genus Sebastes) from the northeastern

Pacific Ocean. Fish. Bull. 82, 269–293.

Brodeur, R.D., Pearcy, W.G., Ralston, S., 2003. Abundance and

distribution patterns of nekton and micronekton in the Northern

California current transition zone. J. Oceanogr. 59, 515–535.

Carlson, P.R., 1968. Marine Geology of Astoria Submarine

Canyon. PhD thesis, Oregon State University, Corvallis,

OR, 259 pp.

Carter, G.S., Gregg, M.C., 2002. Intense, variable mixing near the

head of Monterey Submarine Canyon. J. Phys. Oceanogr. 32,

3145–3165.

Craig, H., 1957. Isotopic standards for carbon and oxygen and

correction factors for mass spectrometric analysis of carbon

dioxide. Geochim. Cosmochim. Acta 12, 133–149.

Davenport, S.R., Bax, N.J., 2002. A trophic study of a marine

ecosystem off southeastern Australia using stable isotopes of

carbon and nitrogen. Can. J. Fish. Aquat. Sci. 59, 514–530.

DeNiro, M.J., Epstein, S., 1977. Mechanism of carbon isotope

fractionation associated with lipid synthesis. Science 197,

261–263.

DeNiro, M.J., Epstein, S., 1978. Influence of diet on the distribution

of carbon isotopes in animals. Geochim. Cosmochim. Acta 42,

495–506.

DeNiro, M.J., Epstein, S., 1981. Influence of diet on the distribution

of nitrogen isotopes in animals. Geochim. Cosmochim. Acta 45,

1885–1994.

Emery, W.J., Thomson, R.E., 1997. Data Analysis Methods in

Physical Oceanography. Pergamon Press, New York, p. 634.

Freeland, H.J., Denman, K.L., 1982. A topographically controlled

upwelling center off Southern Vancouver Island. J. Mar. Res.

40, 1069–1093.

Fry, B., Sherr, E., 1984. d13C measurements as indicators of carbon

flow in marine and freshwater ecosystems. Contrib. Mar. Sci.

27, 13–47.

Gardner, W.D., 1989. Periodic resuspension in Baltimore Canyon by

focusing of internal wavers. J. Geophys. Res. 94, 18185–18194.

Genin, A., 2004. Trophic focusing: the role of bio-physical cou-

pling in the formation of animal aggregations over abrupt top-

ographies. J. Mar. Syst. (this issue).

Genin, A., Haury, L., Greenblatt, P., 1988. Interactions of migrat-

ing zooplankton with shallow topography: predation by rock-

fishes and intensification of patchiness. Deep-Sea Res. 35,

151–175.

Gomez-Gutierrez, J., Peterson, W.T., De Robertis, A., Brodeur,

R.D., 2003. Mass mortality of krill caused by parasitoid ciliates.

Science 301, 339.

Greene, C.H., Wiebe, P.H., Burczynski, J., Youngbluth, M.J.,

1988. Acoustical detection of high-density krill demersal layers

in the submarine canyons off Georges Bank. Science 241,

359–361.

Hickey, B.M., 1989. Patterns and processes of circulation over the

shelf and slope. In: Landry, M.R., Hickey, B.M. (Eds.), Coastal

Oceanography of Washington and Oregon. Elsevier, Amster-

dam, pp. 41–116.

Hickey, B., 1995. Coastal submarine canyons. In: Mueller, P., Hen-

derson, D. (Eds.), Proceedings Hawaii Winter Workshop, Janu-

ary 17–10, 1995, Univ. Hawaii, pp. 95–100.

Hickey, B., 1997. The response of a steep-sides, narrow canyon to

time variable wind forcing. J. Phys. Oceanogr. 27, 697–726.

Hickey, B., Baker, E., Kachel, N., 1986. Suspended particle move-

ment in and around Quinault submarine canyon. Mar. Geol. 71,

35–83.

Hill, J.K., Wheeler, P.A., 2002. Organic carbon and nitrogen in the

northern California current system: comparison of offshore, riv-

er plume, and coastally upwelled waters. Prog. Oceanogr. 53,

369–387.

Hunkins, K., 1988. Mean and tidal currents in Baltimore Canyon. J.

Geophys. Res. 93, 6917–6929.


Kalish, J.M., Greenlaw, C.F., Pearcy, W.G., Holliday, D.V., 1986.

The biological and acoustical structure of sound scattering

layers off Oregon. Deep-Sea Res. 33, 631–653.

Kampf, J., Fohrmann, H., 2000. Sediment-driven downslope flow

in submarine canyons and channels. J. Phys. Oceanogr. 30 (9),

2302–2319.

Koslow, J.A., Ota, A., 1981. The ecology of vertical migration in

three common zooplankters in La Jolla Bight, April –August

1967. Biol. Oceanogr. 1, 107–134.

Krygier, E.E., Pearcy, W.G., 1981. Vertical distribution and biology

of pelagic decapod crustaceans off Oregon. J. Crustac. Biol. 1,

70–95.

Kunze, E., Rosenfeld, L.K., Carter, G.S., Gregg, M.C., 2002. In-

ternal waves in Monterey submarine canyon. J. Phys. Oceanogr.

32, 1890–1913.

Lafuente, J.G., Sarhan, T., Vargas, M., Plaza, F., 1999. Tidal

motions and tidally induced fluxes through La Linea Submarine

Canyon, western Alboran Sea. J. Geophys. Res. Oceans 104,

3109–3119.

Lee, Y.W., 2003. Oceanographic effects on the dynamics of food

habits and growth condition of some groundfish species of the

Pacific Northwest. PhD thesis, Oregon State University.

Lorz, H.V., Pearcy, W.G., Fraidenburg, M., 1983. Notes on the

feeding habits of the yellowtail rockfish, Sebastes flavidus, off

Washington and in Queen Charlotte Sound. Calif. Fish Game

69, 33–38.

Love, M.S., Yoklavich, M., Thorsteinson, L., 2002. The Rockfishes

of the Northeast Pacific. The University of California Press,

Berkeley, CA.

Lueck, R.G., Osborn, T.R., 1985. Turbulence measurements in a

submarine canyon. Cont. Shelf Res. 4, 681–695.

Mackas, D.L., Kieser, R., Saunders, M., Yelland, D.R., Brown,

R.M., Moore, D.F., 1997. Aggregations of euphausiids and Pa-

cific hake (Merluccius productus) along the outer continental

shelf off Vancouver Island. Can. J. Fish. Aquat. Sci. 54,

2080–2096.

Macquart-Moulin, C., Patriti, G., 1996. Accumulation of migratory

micronekton crustaceans over the upper slope and submarine

canyons of the northwestern Mediterranean. Deep-Sea Res.

43, 579–601.

McConnaughey, T., McRoy, C.P., 1979. Food-web structure and the

fractionation of carbon isotopes in the Bering Sea. Mar. Biol. 53,

257–262.

Nishida, S., Pearcy, W.G., Nemoto, T., 1988. Feeding habits of

mesopelagic shrimps collected off Oregon. Bull. Ocean Res.

Inst. 26 (II), 99–108.

Noble, M., Butman, B., 1989. The structure of subtidal currents

within and around Lydonia Canyon, Evidence for enhanced

cross-shelf fluctuation over the mouth of the canyon. J. Geo-

phys. Res. 94, 8091–8110.

Owens, N.J.R., 1987. Natural variations in 15N in the marine envi-

ronment. Adv. Mar. Biol. 24, 390–451.

Pearcy, W.G., Laurs, R.M., 1966. Vertical migration and distri-

bution of mesopelagic fishes off Oregon. Deep-Sea Res. 13,

153–165.

Pearcy, W.G., Nemoto, T., Okiyama, M., 1979. Mesopelagic fishes

of the Bering Sea and adjacent northern North Pacific Ocean. J.

Oceanogr. 35, 127–135.

Pereyra, W.T., Pearcy, W.G., Carvey Jr., F.E., 1969. Sebastodes

flavidus, a shelf rockfish feeding on mesopelagic fauna, with

consideration of the ecological implications. J. Fish. Res. Board

Can. 26, 2211–2215.

Perry, R.I., Thompson, P.A., Mackas, D.L., Harrison, P.J., Yelland,

D.R., 1999. Stable carbon isotopes as pelagic food web tracers

in adjacent shelf and slope regions off British Columbia, Can-

ada. Can. J. Fish. Aquat. Sci. 56, 2477–2486.

Peterson, B.J., Fry, B., 1987. Stable isotopes in ecosystem studies.

Ann. Rev. Ecolog. Syst. 18, 293–320.

Petruncio, E.T., Rosenfeld, L.K., Paduan, J.D., 1998. Observations

of the internal tide in Monterey Canyon. J. Phys. Oceanogr. 28,

1873–1903.

Plank, W.S., Zaneveld, J.R., Pak, H., 1974. Temporal variability of

suspended matter in Astoria Canyon. J. Geophys. Res. 79,

4536–4541.

Polunin, N.V.C., Morales-Nin, B., Pawsey, W.E., Cartes, J.E., Pin-

negar, J.K., Moranta, J., 2001. Feeding relationships in Medi-

terranean bathyal assemblages elucidated by stable nitrogen and

carbon isotope data. Mar. Ecol., Prog. Ser. 220, 13–23.

Rau, G.H., Teyssie, J.-L., Rassoulzadegan, F., Fowler, S.W., 1990.13C/12C and 15N/14N variations among size fractionated marine

particles: implications for their origin and trophic relationships.

Mar. Ecol., Prog. Ser. 59, 33–38.

She, J., Klinck, J.M., 2000. Flow near submarine canyons driven by

constant winds. J. Geophys. Res. 15, 28671–28694.

Sobarzo, M., Figueroa, M., Djurfeldt, L., 2001. Upwelling of

subsurface water into the rim of the Biobio submarine can-

yon as a response to surface winds. Cont. Shelf Res. 21,

279–299.

Tieszen, L.L., Boutton, T.W., Tesdahl, K.G., Slade, N.A., 1983.

Fractionation and turnover of stable carbon isotopes in animal

tissues: implications for d13C analysis of diet. Oecologia 57,

32–37.

Tyler Jr., H.R., Pearcy, W.G., 1975. The feeding habits of three

species of lanternfishes (Family Myctophidae) off Oregon,

USA. Mar. Biol. 32, 7–11.

Underwood, M.B., 1991. Submarine canyons, unconfined turbidity

currents, and sedimentary bypassing of forearc regions. Rev.

Aquat. Sci. 4, 149–200.

Yoklavich, M., Greene, G., Calliet, G.M., Sullivan, D.E., Lea, R.N.,

Love, M.S., 1999. Habitat associations of deep-water rockfishes

in a submarine canyon: an example of a natural refuge. Fish.

Bull. 98, 625–641.

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