Auke Bay Laboratory  (cont.)

Sablefish Longline Survey Completed

Personnel from the ABL and the Center’s RACE Division  recently completed the twenty-third annual longline survey of the upper continental slope of the GOA of Alaska and eastern Bering Sea (EBS). The survey consisted of six legs of 12-14 days each from the Bering Sea to Dixon Entrance in Southeast Alaska and one special experiment. One hundred fifty-three longline hauls (sets) were completed between 2 June and 3 September 2001 by the chartered fishing vessel Ocean Prowler. Sixteen km of groundline containing 7,200 hooks baited with squid were set each day.

Sablefish (Anoplopoma fimbria) was the most frequently caught species, followed by giant grenadiers (Albatrossia pectoralis), Pacific cod (Gadus macrocephalus), and arrow- tooth flounder (Atheresthes stomias). A total of 94,033 sablefish were caught during the survey.   A total of 4,170 sablefish, 626 shortspine thornyhead (Sebastolobus alascanus), and 128 Greenland turbot (Reinhardtius hippoglossoides) were tagged and released during the survey.  Length-weight data and otoliths were collected from approximately 2,500 sable- fish.  Sperm whales (Physeter macrocephalus) and killer whales (Orcinus orca) took fish from the longline at several stations as in previous years. Data have been processed and reports are being prepared for the North Pacific Fishery Management Council.

By Chris Lunsford

 
Tags From Seamount Sablefish Appear in Commercial Fishery

Tagging of sablefish near seamounts began in 1999 in an effort to determine the extent, if any, of emigration from and exchange of sablefish between seamounts in the Northeast Pacific Ocean.  To date, about 2,700 tagged fish have been released on five seamounts: Giacomini, Surveyor, Pratt, Welker, and Dickens. Eight tags have been recovered in the commercial fishery so far, verifying that seamount to continental slope migration does occur. Although a number of tagged fish have been recaptured on the same seamounts where they were released, none have been recovered on different seamounts. Four of the slope recoveries were of fish tagged on Giacomini Seamount in 1999.  Three of these were recovered in the central Gulf of Alaska between long. 147º and 149ºW.  Time at liberty ranged from 329 to 452 days. Recovery data for the fourth Giacomini-area tagged fish were missing. Recoveries of fish released on Surveyor Seamount were made in the western, central, and eastern Gulf of Alaska .  Time at liberty ranged from 300 days for the central gulf recovery to nearly 2 years for the eastern gulf recovery.  One fish tagged on Welker Seamount in 2000 was recovered 283 days later in the central gulf.

By Nancy Maloney.

 
Trawl Survey Design for Rockfish Studied

ABL staff are examining ways to improve trawl survey design for slope rockfish, including methods for efficiently increasing sample size and precision.  One way to increase sample size  with minimal effort is to collect hydroacoustic signals, both during trawl hauls and between trawls. Raw data were collected during the AFSC Gulf of Alaska groundfish trawl survey in summer 2001 with a Simrad ES60 echosounder. On the chartered fishing vessel Morning Star, a split-beam transducer was used, and data were collected during and between trawls.  On the chartered fishing vessel Vesteraalen, a single-beam transducer was used, and data were collected only during trawl hauls.   Global Positioning System (GPS) coordinates and time-stamps were recorded with the raw data.  The data collected for the entire survey are on 55 CDs and will be analyzed as part of a doctoral dissertation at the University Alaska Fairbanks, Juneau Center for Fisheries and Ocean Sciences.

By Jon Heifetz.

 
Multibeam Echosounder Surveys Conducted in  Gulf of Alaska

Portions of the seafloor in the Gulf of Alaska were surveyed using multibeam echosounder technology during summer 2001 aboard the chartered survey vessel Davidson.  The surveys were designed to enable production of detailed bathymetric and habitat maps in support of ongoing research on the effects of fishing gear on seafloor habitat, identification of Habitat Areas of Particular Concern, and stock assessment of rockfish.  In cooperation with the ADF&G, the surveys were conducted off Southeast Alaska in the vicinity of Cape Ommaney and in the central GOA near Portlock Bank.  The Cape Ommaney site is the locality of extensive colonies of red-tree coral (Primnoa willeyi). The Portlock Bank site is an important commercial fishing area. Approximately 1,200 km² of seafloor were mapped during 12 survey days. To aid in habitat classification, dives were conducted using the submersible Delta to collect video data of the seafloor.  Benthic grab samples were also collected in the vicinity of the dive
sites.

By Jon Heifetz.

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AFSC Quarterly
Research Reports
July-Sept 2001