AFSC/ABL: Gulf of Alaska Diel Trawl Survey, 2005-2006

Metadata Updated: November 17, 2018

Diel epipelagic sampling for juvenile Pacific salmon (Oncorhynchus spp.), rockfish (Sebastes spp.), sablefish (Anoplopoma fimbria), and associated species was conducted in order to identify factors that may affect year-class success of these commercially important species. Sampling occurred in offshore marine habitats of the coastal northeast Pacific Ocean from 10-20 August 2005 and was conducted with a surface trawl fishing the upper 20 m of the water column along transects up to78 km offshore near 58 N. Three habitats were sampled along each transect over a 24-hr period: the continental shelf (2,000 m depth). A total of 38,747 fish and squid representing 24 species were sampled in 56 trawl hauls. Of the targeted juvenile fish species, a total of 587 salmon, 11 rockfish, and 70 sablefish were captured. Sampling during day (1500-1900) and night (2200-0200) periods indicated that biomass of fish and squid was 2-4 times higher at night at (each?)all habitat types pooled across transects. No distinct patterns between day or night occurrence were noted for juvenile pink salmon (O. gorbuscha), chum salmon (O. keta), sockeye salmon (O. nerka), or coho salmon (O. kisutch), however, juvenile Chinook salmon (O. tshawytscha) were encountered only at night. Catches of juvenile rockfish and juvenile sablefish were quite low in this study, and larger sample sizes of these fish are needed to adequately determine their diel distribution. Diel differences were apparent with forage species such as Pacific herring (Clupea pallasi), capelin (Mallotus villosus), and eulachon (Thaleichthys pacificus) that were almost exclusively sampled at night. The offshore distribution patterns of target species were distinctly different, with the most common occurrences of juvenile salmon over continental shelf habitats, juvenile sablefish over continental shelf and slope habitats, and juvenile rockfish over slope and abyss habitats. Pacific herring, capelin, eulachon, and Pacific sardines (Sardinops sagax) were found over continental shelf habitats, whereas small squid and myctophids occurred primarily at slope and abyssal habitats. The greatest overall catch biomass was of gelatinous species (jellyfish), which was consistently higher than that of all fish and squid combined, usually by an order of magnitude. Individual fish or squid species with highest average weight per haul were pomfret (Brama japonica), adult coho salmon, Humboldt squid (Dosidicus gigas), and blue sharks (Prionace glauca). The occurrence of the latter two warm-water species and Pacific sardines were of interest because this study occurred during an anomalously warm year and the capture of Pacific sardines and Humboldt squid represent northern range extensions for these species. Stomach content analysis of potential predator species of the target species showed that only adult coho salmon were predating on juvenile salmon and sablefish, and only pomfret were predating on juvenile rockfish. Further sampling of the target species is needed in these habitats during more normal environmental conditions to validate these observations.

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Metadata Date February 28, 2018
Metadata Created Date May 31, 2016
Metadata Updated Date November 17, 2018
Reference Date(s) (publication)
Frequency Of Update notPlanned

Metadata Source

Harvested from NOAA CSW Harvest Source

Additional Metadata

Resource Type Dataset
Metadata Date February 28, 2018
Metadata Created Date May 31, 2016
Metadata Updated Date November 17, 2018
Reference Date(s) (publication)
Responsible Party Alaska Fisheries Science Center (Point of Contact, Custodian)
Contact Email
Access Constraints Access Constraints: Contact the Point of Contact for data request form. | Use Constraints: User must read and fully comprehend the metadata prior to use. Data should not be used beyond the limits of the source scale. Acknowledgement of NOAA, as the source from which these data were obtained, in any publications and/or other representations of these data is suggested. | Distribution Liability: The user is responsible for the results of any application of this data for other than its intended purpose.
Bbox East Long -134.986
Bbox North Lat 58.35035
Bbox South Lat 57.44538
Bbox West Long -137.893
Coupled Resource
Frequency Of Update notPlanned
Guid gov.noaa.nmfs.inport:17231
Harvest Object Id ed8a9cbd-e7b0-4424-9ada-d40d295c3880
Harvest Source Id 2aed8e29-fc5b-4cde-aa66-fb1118fd705e
Harvest Source Title NOAA CSW Harvest Source
Metadata Language eng
Metadata Type geospatial
Progress completed
Spatial Data Service Type
Spatial Reference System
Spatial Harvester True
Temporal Extent Begin 2005
Temporal Extent End 2006

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