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: dsohn@coas.oregonstate.edu, E-mail: dsohn@coas.oregonstate.edu, 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 .