Introduction Greenland halibut (Reinhardtius hippoglossoides; GH) have declined significantly since...
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GH larvallength (mm) 10 12 14 16 18 20 22 24 D epth Range (m) 400-530 300-400 200-300 100-200 46-100 10-45 GH larvallength (mm) 10 12 14 16 18 20 22 24 D epth Range (m) 400-530 300-400 200-300 100-200 46-100 10-45 N = 63 N = 12 N = 8 N = 13 N = 27 N = 6 Introduction Greenland halibut (Reinhardtius hippoglossoides; GH) have declined significantly since the 1970’s in the eastern Bering Sea (EBS) . The reasons for the strong decline of GH in this region are unknown, and there is also very little information about the GH life history in the EBS. Objectives of this study are to examine transport pathways from spawning to potential nursery locations of GH egg, larvae, and early-juveniles in the EBS, and to determine what factors affect patterns of larval transport, dispersal and survival of the early life history stages. Methods - Historical data on GH adults and larvae were available from NMFS surveys conducted by scientists at the AFSC - Ichthyoplankton data (1982-2005): 60cm Bongo Net (60BON), Modified Bottom Trawl (MBT; samples the midwater), Conclusions • Potential spawning area (vertically and horizontally) is the continental slope (below 500m) near Bogoslof Is. and potential nursery area is the middle shelf (50-100m) near Pribilof Is. in the EBS. • GH spawn in deep water (below 500m), and it is likely that larvae slowly rise after hatching. The presence of larger larvae in the upper water column (<45 m depth) suggest some degree of diel migration of larger larvae, possiby associated with feeding. •GH larvae in the EBS have a long duration in the plankton and are subject to extended drift pathways. Larvae likely drift along the continental shelf edge, eventually crossing from the slope to the shelf to settle as age-0s. • Mechanisms of slope-shelf connectivity are still being investigated, though the larvae could be physically influenced by the ANSC and BSC. Eddies, transport through canyons, and/or wind- induced transport may all play a role in shelf-slope connectivity. •Patterns observed for GH may be indicative of strategies by other Dongwha Dongwha Sohn Sohn 1 , Lorenzo Ciannelli , Lorenzo Ciannelli 1 , Janet T. Duffy-Anderson , Janet T. Duffy-Anderson 2 , Ann Matarese , Ann Matarese 2 and Kevin M. and Kevin M. Bailey Bailey 2 1 Oregon State University, Oregon State University, E-mail: [email protected], E-mail: [email protected], 2 NOAA, NMFS, Alaska Fisheries Science Center (AFSC) NOAA, NMFS, Alaska Fisheries Science Center (AFSC) Distribution and Drift Pathways of Larval and Juvenile Greenland halibut 2. Vertical Distribution by MOC Fig. 4. Mean (±SD) standard length (mm) related with vertical depth . A paradigm for slope spawning flatfish species? B T (June to A ugust) M B T (July to A ugust) 60B ON (M arch to M 1982 1986 1988 1990 1992 1984 1996 1998 2000 1994 2002 2004 2006 MOC (A pril) July) -175 -170 -165 -160 54 56 58 60 62 ALASKA Pribiof Is. St.Matthew Unimak Is. Bogoslof Is. BT MBT 60B O N -175 -170 -165 -160 54 56 58 60 62 ALASKA Pribiof Is. St.Matthew Unimak Is. Bogoslof Is. G eartypes 60B O N MBT BT GH larvallength (m m) 20 40 60 80 100 G eartypes 60B O N MBT BT GH larvallength (m m) 20 40 60 80 100 Fig. 1. Larval distribution and drift pathways by gear. Fig. 2. Mean (±SD) standard length (mm) by gear . Fig. 3. Schematic of mean circulation the upper 40 m. Aleutian North Slope Current (ANSC), Bering Slope Current (BSC) (Stabeno et al., 1999). Results – 1. Horizontal Distribution 60BON: Early larvae (8.8-22.4mm SL) found on the continental slope (<500m) and drift northward during spring. MBT: Late larvae & early juveniles (18-54mm SL) found on the middle shelf (50m - 100m) near the Pribilof Is. during summer. BT: Age>0 (60-90mm SL) occurred on the middle shelf near St. Matthew Is. during summer. Reference - Stabeno, P.J., Schumacher, J.D. and Ohtani, K., 1999. The physical oceanography of the Bering Sea. In: Loughlin, T.R. and Ohtani, K., Editors, 1999. Dynamics of the Bering Sea, University of Alaska Sea Grant Press, Fairbanks, AK, pp. 1–28 AK- SG-99-03 . Larvae from vertically stratified MOC tows were found throughout the water column between 0-500m, but highest concentrations were noted upper 45m vertical depth. Also, larvae length is bigger at shallower depths .
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Transcript of Introduction Greenland halibut (Reinhardtius hippoglossoides; GH) have declined significantly since...
GH larval length (mm)
10 12 14 16 18 20 22 24
Dep
th R
ange
(m
)
400-530
300-400
200-300
100-200
46-100
10-45 N = 63
N = 12
N = 8
N = 13
N = 27
N = 6
GH larval length (mm)
10 12 14 16 18 20 22 24
Dep
th R
ange
(m
)
400-530
300-400
200-300
100-200
46-100
10-45 N = 63
N = 12
N = 8
N = 13
N = 27
N = 6
Introduction
Greenland halibut (Reinhardtius hippoglossoides; GH) have
declined significantly since the 1970’s in the eastern Bering Sea (EBS) .
The reasons for the strong decline of GH in this region are unknown, and
there is also very little information about the GH life history in the EBS.
Objectives of this study are to examine transport pathways from
spawning to potential nursery locations of GH egg, larvae, and early-
juveniles in the EBS, and to determine what factors affect patterns of
larval transport, dispersal and survival of the early life history stages.
Methods
- Historical data on GH adults and larvae were available from NMFS surveys conducted by scientists at the AFSC
- Ichthyoplankton data (1982-2005): 60cm Bongo Net (60BON), Modified Bottom Trawl (MBT; samples the midwater),
Multiple Opening/Closing Net Environmental Sampling System (MOC)
- Groundfish survey data (1982-2006): Bottom trawl (BT)
Conclusions
• Potential spawning area (vertically and horizontally) is the continental slope (below 500m)
near Bogoslof Is. and potential nursery area is the middle shelf (50-100m) near Pribilof Is.
in the EBS.
• GH spawn in deep water (below 500m), and it is likely that larvae slowly rise after
hatching. The presence of larger larvae in the upper water column (<45 m depth) suggest
some degree of diel migration of larger larvae, possiby associated with feeding.
•GH larvae in the EBS have a long duration in the plankton and are subject to extended drift
pathways. Larvae likely drift along the continental shelf edge, eventually crossing from the
slope to the shelf to settle as age-0s.
• Mechanisms of slope-shelf connectivity are still being investigated, though the larvae
could be physically influenced by the ANSC and BSC. Eddies, transport through canyons,
and/or wind-induced transport may all play a role in shelf-slope connectivity.
•Patterns observed for GH may be indicative of strategies by other deep living flatfishes
(arrowtooth flounder, Pacific halibut, Kamchatka flounder) which share a common goal of
dispersing larvae toward nursery areas over the continental shelf.
Dongwha Dongwha SohnSohn11, Lorenzo Ciannelli, Lorenzo Ciannelli11, Janet T. Duffy-Anderson, Janet T. Duffy-Anderson22 , Ann Matarese , Ann Matarese22 and Kevin M. Bailey and Kevin M. Bailey22
11Oregon State University, Oregon State University, E-mail: [email protected], E-mail: [email protected], 22NOAA, NMFS, Alaska Fisheries Science Center (AFSC)NOAA, NMFS, Alaska Fisheries Science Center (AFSC)
Distribution and Drift Pathways of Larval and Juvenile Greenland halibut
2. Vertical Distribution by MOC
Fig. 4. Mean (±SD) standard length (mm) related with vertical depth .
A paradigm for slope spawning flatfish species?
BT (June to August)
MBT (July to August)
60BON (March to May)
1982 1986 1988 1990 19921984 1996 1998 20001994 2002 2004 2006
MOC(April)
BT (June to August)
MBT (July to August)
60BON (March to May)
1982 1986 1988 1990 19921984 1996 1998 20001994 2002 2004 2006
MOC(April)
July)
BT (June to August)
MBT (July to August)
60BON (March to May)
1982 1986 1988 1990 19921984 1996 1998 20001994 2002 2004 2006
MOC(April)
BT (June to August)
MBT (July to August)
60BON (March to May)
1982 1986 1988 1990 19921984 1996 1998 20001994 2002 2004 2006
MOC(April)
July)
BT (June to August)
MBT (July to August)
60BON (March to May)
1982 1986 1988 1990 19921984 1996 1998 20001994 2002 2004 2006
MOC(April)
BT (June to August)
MBT (July to August)
60BON (March to May)
1982 1986 1988 1990 19921984 1996 1998 20001994 2002 2004 2006
MOC(April)
July)
BT
MBT
60BON
-175 -170 -165 -160
54
56
58
60
62 ALASKA
Pribiof Is.
St. Matthew
Unimak Is.Bogoslof Is.
BT
MBT
60BON
-175 -170 -165 -160
54
56
58
60
62 ALASKA
Pribiof Is.
St. Matthew
Unimak Is.Bogoslof Is.
Gear types
60BON MBT BT
GH
larv
al l
en
gth
(m
m)
20
40
60
80
100
Gear types
60BON MBT BT
GH
larv
al l
en
gth
(m
m)
20
40
60
80
100
Fig. 1. Larval distribution and drift pathways by gear.
Fig. 2. Mean (±SD) standard length (mm) by gear .
Fig. 3. Schematic of mean circulation the upper 40 m. Aleutian North Slope Current (ANSC), Bering Slope Current (BSC) (Stabeno et al., 1999).
Results – 1. Horizontal Distribution
60BON: Early larvae (8.8-22.4mm SL)found on the continental slope (<500m)and drift northward during spring.
MBT: Late larvae & early juveniles (18-54mm SL) found on the middle shelf(50m - 100m) near the Pribilof Is. during summer.
BT: Age>0 (60-90mm SL) occurred on the middle shelf near St. Matthew Is. during summer.
Reference - Stabeno, P.J., Schumacher, J.D. and Ohtani, K., 1999. The physical oceanography of the Bering Sea. In: Loughlin, T.R. and Ohtani, K., Editors, 1999. Dynamics of the Bering Sea, University of Alaska Sea Grant Press, Fairbanks, AK, pp. 1–28 AK-SG-99-03 .
Larvae from vertically stratified MOC tows
were found throughout the water column
between 0-500m, but highest
concentrations were noted upper 45m
vertical depth.
Also, larvae length is bigger at shallower
depths .
