Warming Ocean Conditions Relate to Increased Trophic Requirements of Threatened and Endangered Salmon

Daly, Elizabeth A.; Brodeur, Richard D.

doi:10.1371/journal.pone.0144066

Cited by 36 publications

(31 citation statements)

References 66 publications

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“…Secondary productivity in salt water is important to the survival of kelts to the next spawn (Chaput and Benoît ). Furthermore, warm ocean conditions can increase metabolic demands with implications for survival of salmonids (Daly and Brodeur ). Ocean survival of kelts in our study was highest for cohorts reentering the ocean during 2010–2012.…”

Section: Discussionmentioning

confidence: 99%

Patterns of Iteroparity in Wild Snake River Steelhead

et al. 2019

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Some anadromous salmonids are iteroparous (repeat spawners); however, postspawn individuals are often not considered in management plans because of the lack of long‐term studies of this life history. The balance of factors affecting survival between spawns and fecundity of repeat spawners should determine the percentage of iteroparous individuals in a population. Steelhead Oncorhynchus mykiss are capable of iteroparity, but Snake River populations in the interior Columbia River basin in the Pacific Northwest have the lowest iteroparity rates. Managers are interested in augmenting the incidence of iteroparity as a conservation measure. However, there is little information about repeat‐spawning steelhead to guide and evaluate management. In this study, we elucidated patterns and characteristics of repeat‐spawning steelhead in the Snake River basin. Repeat spawners were overwhelmingly female and were found in all 10 stocks. Most iteroparous fish first spawned after 1 year in the ocean (51.4%) and skipped a year between spawns (55.4%). Growth between spawns declined for longer, older steelhead. Survival from the first spawning migration to postspawn emigration increased during the study. However, survival in the Columbia River estuary and Pacific Ocean declined such that overall survival to second spawn varied little. Small females were most likely to survive to a second spawning migration. We hypothesized that iteroparity in Snake River steelhead was constrained by the energetic costs of the spawning migration (distance, elevation, timing, dam passage) combined with a lack of timely postspawn recovery. Hence, survival to second spawning migration is low for Snake River steelhead and most postspawn steelhead needed a full year to recover. Management programs intended to augment the incidence of iteroparity should account for (1) factors that increase stress and metabolic demand on spawning and postspawn fish and (2) factors that increase the time it takes for emigrating kelts to effectively refuel and recover.

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Section: Discussionmentioning

confidence: 99%

Patterns of Iteroparity in Wild Snake River Steelhead

et al. 2019

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“…This could skew the average body condition of the surviving subyearling salmon for these years: the total number of survivors could be lower, potentially leading to decreased adult returns, but survivors would be in better body condition on average. This hypothesis agrees with the results presented here and by Daly and Brodeur ().…”

Section: Discussionmentioning

confidence: 97%

“…These results are consistent with those of a similar study (Daly and Brodeur, ) focusing on May and June, which determined that higher piscivory rates did not necessarily lead to better body condition of yearling Chinook salmon. However, this previous study found that yearling Chinook salmon collected in warmer years were in worse body condition than those from cool years, a result contradictory to the findings presented here.…”

Section: Discussionmentioning

confidence: 99%

“…Daly and Brodeur () found that prey species driving interannual differences in yearling Chinook salmon diets included several fish species (Pacific sand lance, flatfish, and rockfish) as well as invertebrates. Interestingly, while SST and PDO aligned with diet composition variation, Columbia River outflow was also found to be a significant abiotic factor affecting diet in yearling Chinook salmon.…”

Section: Discussionmentioning

confidence: 99%

“…Off Central California, (MacFarlane, 2010) found that northern anchovy were a critical prey of subyearling Chinook salmon emigrating from the San Francisco estuary and estimated that each salmon would need to consume three anchovies per day to sustain observed energetic gains and growth rates. Daly and Brodeur (2015) found that prey species driving interannual differences in yearling Chinook salmon diets included several fish species (Pacific sand lance, flatfish, and rockfish) as well as invertebrates. Interestingly, while SST and PDO aligned with diet composition variation, Columbia River outflow was also found to be a significant abiotic factor affecting diet in yearling Chinook salmon.…”

Section: Discussionmentioning

confidence: 99%

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Interannual variability in the feeding and condition of subyearling Chinook salmon off Oregon and Washington in relation to fluctuating ocean conditions

Dale

Daly

Brodeur

2016

Fisheries Oceanography

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Chinook salmon (Oncorhynchus tshawytscha) is one of several economically‐important species of salmon found in the Northeast Pacific Ocean. The first months at sea are believed to be the most critical for salmon survival, with the highest rate of mortality occurring during this period. In the present study, we examined interannual diet composition and body condition trends for late‐summer subyearling Chinook salmon caught off Oregon and Washington from 1998 to 2012. Interannual variability was observed in juvenile salmon diet composition by weight of prey consumed. Juvenile subyearling Chinook salmon were mainly piscivorous, with northern anchovy (Engraulis mordax) being especially important, making up half the diet by weight in some years. Annual diets clustered into two groups, primarily defined by their proportion of invertebrate prey (14% versus 39% on average). Diet composition was found to influence adult returns, with salmon from high‐invertebrate years returning in significantly larger numbers 2–3 yrs later. However, years that had high adult returns had overall lower stomach fullness and poorer body condition as juveniles, a counterintuitive result potentially driven by the enhanced survival of less fit individuals in better ocean conditions (top‐down effect). Ocean conditions in years with a higher percentage of invertebrates in salmon diets were significantly cooler from May to August, and bottom‐up processes may have led to a fall plankton community with a larger proportion of invertebrates. Our results suggest that the plankton community assemblage during this first fall may be critical in predicting adult returns of Chinook salmon in the Pacific Northwest.

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Two Anomalously Warm Years in the Northern California Current: Impacts on Early Marine Steelhead Diet Composition, Morphology, and Potential Survival

2020

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Juvenile steelhead Oncorhynchus mykiss enter the northern California Current ecosystem from the Columbia River and other Pacific Northwest coastal rivers and include several populations that are listed under the U.S. Endangered Species Act. However, relatively little is known about the response of these populations to interannual variability in ocean conditions. In 2015 and 2016, anomalous ocean conditions, called the warm “Blob,” persisted in the northern California Current, increasing ocean temperatures by over 2.5°C. To determine how steelhead respond to such major shifts in temperature, we compared diet composition, stomach fullness, size, and body condition of juvenile steelhead collected in 2015 and 2016 to those of a subset of steelhead collected in previous surveys (2001, 2002, 2004, and 2006–2011) that included warm, cool, and neutral ocean years. In addition, we used bioenergetics models to assess the importance of the marine environment in contributing to changes in steelhead condition under different ocean temperature scenarios. Steelhead from 2015 and 2016 exhibited some of the poorest body condition values but were the largest sizes across all years evaluated. Steelhead diet composition varied between warm and cold years and between warm and average years, with steelhead consuming more insects, juvenile rockfishes, and rare and unidentified fish in warm years. Unusual taxa, including gelatinous salps (2015 and 2016) and juvenile smelts (2016), were consumed during Blob‐influenced years. Bioenergetics models indicated that interannual variability in growth was influenced by changes in temperature and feeding conditions in the marine environment, with significant differences in growth between warm and cold ocean years apparent as early as day 2 of the simulated marine residence. These findings highlight the potential for warm ocean years to influence the diet composition and morphology of Columbia River steelhead populations and may lead to a better understanding of factors influencing survival of juvenile steelhead during early marine residence.

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Warming Ocean Conditions Relate to Increased Trophic Requirements of Threatened and Endangered Salmon

Cited by 36 publications

References 66 publications

Patterns of Iteroparity in Wild Snake River Steelhead

Patterns of Iteroparity in Wild Snake River Steelhead

Interannual variability in the feeding and condition of subyearling Chinook salmon off Oregon and Washington in relation to fluctuating ocean conditions

Two Anomalously Warm Years in the Northern California Current: Impacts on Early Marine Steelhead Diet Composition, Morphology, and Potential Survival

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