Science & Data

Join Alaska Fisheries Science Center researchers in their attempt to better understand hatchery-reared salmon marine survival.

Join Alaska Fisheries Science Center researchers in their attempt to better understand hatchery-reared salmon marine survival.

Although decreasing length at maturity has been observed in some Alaska salmon populations, the generality of this trend is poorly understood. This study was undertaken to determine whether this pattern holds for multiple species of salmon from a small watershed in Southeast Alaska (Auke Creek), and if so, what abiotic and biotic factors are contributing to this phenomenon.

Pelagic fish and jellyfish were sampled using a trawl net towed in the upper 20 m of the eastern Bering Sea during the Alaska Fisheries Science Centers’ Bering Arctic Subarctic Integrated Surveys (BASIS) during late summer, 2002–2016. Stations were approximately 30 nautical miles apart and a trawl was towed for approximately 30 minutes. Area swept was estimated from horizontal net opening and distance towed.

A radio telemetry study was conducted on Yukon River Chinook salmon during 2002–2004 to provide information on migration patterns.

This annual survey, conducted by the Southeast Coastal Monitoring (SECM) project, marks 20 consecutive years of systematically monitoring how juvenile salmon utilize marine ecosystems during a period of climate change.

Pacific salmon (Oncorhynchus spp.) are prohibited species in the federally managed Bering Sea groundfish fisheries, which are subject to complex management rules (NPMFC 2017a) that are in part designed to reduce prohibited species catch, hereafter referred to as “bycatch”. It is important to understand the stock composition of Pacific salmon caught in these fisheries, which take place in areas that are known feeding habitat for multiple brood years of Chinook salmon (Oncorhynchus tshawytscha) from many different localities in North America and Asia (Myers et al. 2007, Davis et al. 2009). Chinook salmon are economically valuable and highly prized in commercial, subsistence, and sport fisheries. Determining the geographic origin of salmon caught in federally managed fisheries is essential to understanding the effects that fishing has on Chinook salmon stocks, especially those with conservation concerns (NPFMC 2017a). This report provides genetic stock identification results for the Chinook salmon bycatch samples collected from the U.S. Bering Sea walleye pollock (Gadus chalcogrammus) trawl fishery. National Marine Fisheries Service (NMFS) geographical statistical areas (NMFS area) associated with the Bering Sea groundfish fishery (NMFS areas 509-524) and Alaska Department of Fish and Game (ADF&G) statistical areas1 are shown in Figure 1 and are used later in the report to describe the spatial distribution of the Chinook salmon bycatch and genetic samples.

The Gulf of Alaska (GOA) is serves as a feeding habitat for multiple brood years of Chinook salmon (Oncorhynchus tshawytscha) originating from many different localities in North America and Asia. Determining the geographic origin and stock composition of Pacific salmon caught in federally managed fisheries is essential to understanding whether fisheries management could address potential conservation concerns. This report provides genetic stock identification results for Chinook salmon Prohibited Species Catch (bycatch) samples collected in the GOA from the trawl fisheries for walleye pollock (Gadus chalcogrammus) and catcher vessel (CV) trawl fisheries for rockfish (Sebastes spp.). The National Marine Fisheries Service (NMFS) and Alaska Department of Fish and Game (ADF&G) geographical statistical areas associated with the groundfish fishery are shown in Figure 1 and are used later in the report to describe the spatial distribution of the Chinook salmon bycatch and genetic samples. All analyses used a single nucleotide polymorphism (SNP) baseline provided by ADF&G (Templin et al. 2011; Appendix 1), the same baseline used to estimate previous stock compositions of samples from the Chinook salmon bycatch of the federally managed GOA trawl fisheries (Guthrie et al. 2013, 2016-18; Guyon et al. 2014, 2015a,b; Larson et al. 2013). For additional information regarding background and methodology refer to the Chinook salmon bycatch report prepared previously for the 2008 Bering Sea trawl fishery (Guyon et al. 2010).

Juvenile Pacific salmon (Oncorhynchus spp.), ecologically-related species, and associated biophysical data were collected from the marine waters of the northern region of southeastern Alaska (SEAK) in 2015. This annual survey, conducted by the Southeast Coastal Monitoring (SECM) project, marks 19 consecutive years of systematically monitoring how juvenile salmon utilize marine ecosystems during a period of climate change. The survey was implemented to identify the relationships between year-class strength of juvenile salmon and biophysical parameters that influence their habitat use, marine growth, prey fields, predation, and stock interactions. Up to 13 stations were sampled monthly in epipelagic waters from May to August (total of 23 sampling days). Fish, zooplankton, surface water samples, and physical profile data were collected during daylight at each station using a surface rope trawl, bongo nets, a water sampler, and a conductivity-temperature-depth profiler. Surface (3-m) temperatures and salinities ranged from approximately 8 to 15 ºC and 15 to 32 PSU across inshore, strait, and coastal habitats for the four months. A total of 17,228 fish and squid, representing 25 taxa, were captured in 92 rope trawl hauls fished from June to August. Juvenile salmon comprised approximately 89% of the catch. Over all months and habitats, juvenile pink (O. gorbuscha), chum (O. keta), sockeye (O. nerka), and coho (O. kisutch) salmon occurred in 51-92% of the hauls, while juvenile Chinook salmon (O. tshawytscha) occurred in about 22% of the hauls. Abundance of juvenile salmon was low in 2015; peak CPUE occurred in June strait and coastal habitats. Coded-wire tags were recovered from 51 juvenile coho salmon and 5 juvenile and immature Chinook salmon, that primarily originated from hatchery and wild stocks in SEAK sampled in the strait habitat; an additional 18 adipose-clipped juvenile salmon without tags were present. The only non-Alaskan stocks were recovered off Icy Point, a juvenile Chinook salmon from the Willamette River, OR and a juvenile coho salmon from the Satsop River, Washington. Of the juvenile salmon examined for otolith marks, Alaska enhanced stocks comprised 56% of the juvenile chum (373 of 663) and 38% of the juvenile sockeye salmon (202 of 532). Of the 380 potential predators of juvenile salmon, predation on juvenile salmon was not observed in the six fish species examined. The long term seasonal time series of SECM juvenile salmon stock assessment and biophysical data is used in conjunction with basin-scale ecosystem metrics to annually forecast pink salmon harvest in SEAK. Long term seasonal monitoring of key stocks of juvenile salmon and associated ecologically-related species, including fish predators and prey, permits researchers to understand how growth, abundance, and interactions affect year-class strength of salmon in marine ecosystems during a period of rapid climate change.

Scientists from the National Oceanic and Atmospheric Administration (NOAA) and the Alaska Department of Fish and Game partnered with the Yukon Delta Fisheries Development Association to study the diets, health, and seasonal cycles of juvenile Chinook salmon on the Yukon River Delta beginning in summer 2014.