Joseph A. Orsi

Distribution and Migration of Juvenile Chinook Salmon Derived from Coded Wire Tag Recoveries along the Continental Shelf of Western North America

Abstract The effects of ocean conditions on highly migratory species such as salmon are difficult to assess owing to the diversity of environments they encounter during their marine life. In this study, we reconstructed the initial ocean migration routes of juvenile Chinook salmon Oncorhynchus tshawytscha originating from Oregon to Southeast Alaska using coded wire tag recovery data from Canadian Department of Fisheries and Oceans and National Marine Fisheries Service research surveys conducted between 1995 and 2006. Over this 12-year period, 1,862 coded-wire-tagged juvenile Chinook salmon were recovered along the coasts of Oregon, Washington, British Columbia, and Alaska from March to November. Except for those from the Columbia River, most juvenile Chinook salmon remained within 100–200 km of their natal rivers until their second year at sea, irrespective of their freshwater history and adult run timing. Northward migration of most coastal stocks was initiated during their second or possibly third year ...

Marine Vertical Distribution of Juvenile Chinook and Coho Salmon in Southeastern Alaska

Abstract Vertical distributions of chinook salmon Oncorhynchus tshawytscha of marine ages x.0, x.1, and x.2 and coho salmon O. kisutch of age x.0 are reported for the marine waters of southeastern Alaska. (The number or letter preceding the decimal point indicates number of winters spent in freshwater, that following the decimal point indicates winters spent in salt water.) Understanding vertical distribution of prerecruit salmon may be useful in minimizing fishery bycatch. Salmon were caught to a depth of 36.6 m from chartered commercial power trollers fishing small hooks and lures. Sampling occurred throughout inside waters of the Alexander Archipelago and adjacent coastal waters during September 1986 and in inside waters near Ketchikan during February, May, and September 1987. Vertical distribution of salmon differed significantly by species and age-group: in September, age-x.0 coho salmon (mean fork length, 28.4 cm) were caught shallower than age-x.0 chinook salmon (27.3 cm); age-x.1 (44.2 cm) and age...

Modifications in Electrical Anesthesia for Salmonids

Abstract Modifications in the electrified basket for anesthetizing fish make it more portable and easier to use. Modifications include the use of six electrodes instead of two and the addition of a circuit switch, removable handles, and webbing that makes fish easier to reach for tagging. The basket can anesthetize juvenile chinook salmon (Oncorhynchus tshawytscha) and coho salmon (O. kisutch) as small as 20 cm.

Small versus Large Trolling Lures for Sampling Juvenile Chinook Salmon and Coho Salmon

Abstract The effectiveness of small versus large trolling gear (hooks and lures) was compared for sampling juvenile chinook salmon Oncorhynchus tshawytscha and coho salmon O. kisutch in the marine waters of southeastern Alaska during 23 d in spring and fall 1985. Sizes, marine ages, and numbers of salmon caught by each gear size were compared. Reducing the size of terminal gear resulted in the capture of smaller and younger salmon. Additionally, more salmon were caught in fall by the small gear than by the large gear; however, catch rates in spring were not significantly different between gear types. Results demonstrate the potential for using scaled-down trolling gear for sampling.

Contrasting Early Marine Ecology of Chinook Salmon and Coho Salmon in Southeast Alaska: Insight into Factors Affecting Marine Survival

Abstract To identify processes potentially contributing to the differential marine survival rates of Chinook salmon Oncorhynchus tshawytscha and coho salmon O. kisutch originating from Southeast Alaska, we compared the early marine ecology of the two species during the critical first summer in marine waters. We predicted that the higher survival rates for coho salmon relative to Chinook salmon were related to the larger size, faster growth, or different habitat or species associations of coho salmon. Our size and growth expectations were largely substantiated: juvenile coho salmon were larger than juvenile Chinook salmon and had faster length-based growth, although weight-based growth rates were similar. The most obvious difference was in their distributions. Juvenile coho salmon overlapped spatially and temporally with abundant juvenile pink salmon O. gorbuscha and chum salmon O. keta, whereas juvenile Chinook salmon were geographically separated from other salmonids. This suggests that coho salmon benefited from a predation buffer that did not extend to Chinook salmon. Our results indicate that factors influencing marine survival of juvenile Chinook salmon and coho salmon in Southeast Alaska are attributable to species-specific differences in their early marine distribution patterns and species interactions.

Sablefish Predation on Juvenile Pacific Salmon in the Coastal Marine Waters of Southeast Alaska in 1999

Abstract At-sea observations of predation by age-1 and older (age-1+) sablefish Anoplopoma fimbria on juvenile Pacific salmon Oncorhynchus spp. were combined with laboratory studies to determine gastric evacuation rates and were used to estimate summer predation impact in the northern region of Southeast Alaska. In June and July 1999, up to 63% of sablefish examined from trawl catches in strait habitat had each consumed one to four juvenile pink salmon O. gorbuscha, chum salmon O. keta, or sockeye salmon O. nerka. In two laboratory experiments, field-captured sablefish were acclimated without food in compartmentalized flow-through tanks with conditions manipulated to reflect the photoperiod and temperature regimes of summer. These sablefish were each offered one whole, preweighed juvenile chum salmon; consumption events were observed, and the sablefish were then sacrificed at predetermined time intervals. Prey biomass remaining in the stomach of each sablefish predator was weighed, and an exponential mode...

Chinook Salmon First-Year Production Indicators from Ocean Monitoring in Southeast Alaska

Understanding migration and abundance of Chinook salmon stocks during critical early marine periods is important because declining returns in some regions of Alaska have eff ectuated commercial fi shery disaster declarations since 2012. Annual ocean catch data of juvenile and immature Chinook salmon pre-recruits were examined from research surface trawling in Icy Strait, Southeast Alaska (SEAK), from 1997 to 2014 to examine how ocean survival depends on critical early periods. In total, 1,108 Chinook salmon were sampled in 1,037 trawl hauls from May to September. Data on the release location and timing for 50 fi sh recovered with coded-wire tags (CWTs) indicated most to be of SEAK origin (48), and either immature (ocean age-1) or juvenile (ocean age-0). Based on monthly CWT Chinook salmon recoveries and catch, juvenile fi sh occurred in increasing abundance from June to September, whereas immature fi sh occurred in decreasing abundance from May to September. There was strong coherence in the ocean survival rates of wild and hatchery SEAK stocks of Chinook salmon, and average regional survival was signifi cantly (p < 0.05) correlated to the abundance of ocean age-1 fi sh, but not ocean age-0 fi sh. This study indicates SEAK Chinook salmon stocks have initial localized marine distributions as juveniles, and they are present as immature fi sh in the ensuing spring and summer. Research catch rates of pre-recruits have the potential to be useful as a leading ecosystem indicator stock assessment tool for managers.

Using Salmon Survey and Commercial Fishery Data to Index Nearshore Rearing Conditions and Recruitment of Alaskan Sablefish

Abstract We examined physical and biological indices from Pacific salmon Oncorhynchus spp. surveys and commercial fisheries to index nearshore rearing habitats used by age-0 and age-1 Sablefish Anoplopoma fimbria in the eastern Gulf of Alaska and as indicators for their recruitment to age2 during the period 2001–2013. The best-fitting general linear model used to estimate age-2 Sablefish recruitment included chlorophyll-a concentration during late August and an index of juvenile Pink Salmon O. gorbuscha abundance during the age-0 stage of Sablefish. The model and biophysical indices from 2012 and 2013 produced a forecast of 23 million age-2 Sablefish for 2014 and a forecast of 8 million Sablefish for 2015. This study highlights the opportunity to use proxies for direct ambient physical and biological observations of rearing habitats in estimating groundfish recruitment to older ages.