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1. Juvenile Chum Salmon and Pink Salmon use of submerged vegetative habitats and the influence of an apex predator

   https://doi.org/10.1093/mcfafs/vtaf001  

   Domke, Lia_K; Cates, Rebecca_J; Raymond, Wendel_W; Eckert, Ginny_L (April 2025, Marine and Coastal Fisheries)

   ABSTRACT ObjectiveApex-predator-initiated trophic cascades occur in many nearshore marine habitats that simultaneously serve as critical habitat and food sources for commercially and ecologically important species, including juvenile Pacific salmon Oncorhynchus spp. Yet the potential relationships among apex predators (e.g., sea otters Enhydra lutris), submerged aquatic vegetation, and juvenile salmonids are not well understood. In Southeast Alaska, we investigated (1) juvenile salmonid abundance in eelgrass Zostera marina meadows and understory kelp beds and (2) potential drivers of juvenile Chum Salmon Oncorhynchus keta and Pink Salmon O. gorbuscha abundance in eelgrass meadows. MethodsWe analyzed historic (1998–2007) beach seine surveys to compare juvenile salmonid abundance in nearshore habitats. We then employed the same survey (2017, 2019) in eelgrass to quantify juvenile salmonid abundance alongside the influence of sea otter density (number/km2), distance from anadromous stream (km), seasonality, sediment categorization, and aboveground eelgrass biomass (g/m2). ResultsWe found greater abundance of Chum Salmon in understory kelp compared with eelgrass, whereas Pink Salmon abundance was similar between habitats. In eelgrass, Chum Salmon abundance peaked in June and was positively associated with sea otter density. Pink Salmon abundance varied seasonally, peaking in May. We found increased Pink Salmon abundance with increasing sea otter density and distance from anadromous stream and decreased abundance with increased eelgrass biomass. ConclusionGrowth and survival while juvenile salmonids are out-migrating from streams and relying on nearshore vegetated habitats can determine if they recruit to fisheries as adults. Here, we highlight the use of multiple habitats, eelgrass and understory kelp, indicating that both should be explored as critical nursery habitat. We present evidence of indirect effects of sea otters influencing the abundance of juvenile salmonids, with potential further implications as sea otter populations expand. Apex predators, quality of vegetated habitats, and their structuring roles in the nearshore are critical for informing adaptive coastal fisheries management. 

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2. Body size and early marine conditions drive changes in Chinook salmon productivity across northern latitude ecosystems

   https://doi.org/10.1111/gcb.17508  

   Feddern, Megan L; Shaftel, Rebecca; Schoen, Erik R; Cunningham, Curry J; Connors, Brendan M; Staton, Benjamin A; von_Finster, Al; Liller, Zachary; von_Biela, Vanessa R; Howard, Katherine G (October 2024, c)

   Abstract Disentangling the influences of climate change from other stressors affecting the population dynamics of aquatic species is particularly pressing for northern latitude ecosystems, where climate‐driven warming is occurring faster than the global average. Chinook salmon (Oncorhynchus tshawytscha) in the Yukon‐Kuskokwim (YK) region occupy the northern extent of their species' range and are experiencing prolonged declines in abundance resulting in fisheries closures and impacts to the well‐being of Indigenous people and local communities. These declines have been associated with physical (e.g., temperature, streamflow) and biological (e.g., body size, competition) conditions, but uncertainty remains about the relative influence of these drivers on productivity across populations and how salmon–environment relationships vary across watersheds. To fill these knowledge gaps, we estimated the effects of marine and freshwater environmental indicators, body size, and indices of competition, on the productivity (adult returns‐per‐spawner) of 26 Chinook salmon populations in the YK region using a Bayesian hierarchical stock‐recruitment model. Across most populations, productivity declined with smaller spawner body size and sea surface temperatures that were colder in the winter and warmer in the summer during the first year at sea. Decreased productivity was also associated with above average fall maximum daily streamflow, increased sea ice cover prior to juvenile outmigration, and abundance of marine competitors, but the strength of these effects varied among populations. Maximum daily stream temperature during spawning migration had a nonlinear relationship with productivity, with reduced productivity in years when temperatures exceeded thresholds in main stem rivers. These results demonstrate for the first time that well‐documented declines in body size of YK Chinook salmon were associated with declining population productivity, while taking climate into account. 

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3. Prey tell: what quillback rockfish early life history traits reveal about their survival in encounters with juvenile coho salmon

   https://doi.org/10.3354/meps13300  

   Fennie, HW; Sponaugle, S; Daly, EA; Brodeur, RD (June 2020, Marine Ecology Progress Series)

   Predation is a major source of mortality in the early life stages of fishes and a driving force in shaping fish populations. Theoretical, modeling, and laboratory studies have generated hypotheses that larval fish size, age, growth rate, and development rate affect their susceptibility to predation. Empirical data on predator selection in the wild are challenging to obtain, and most selective mortality studies must repeatedly sample populations of survivors to indirectly examine survivorship. While valuable on a population scale, these approaches can obscure selection by particular predators. In May 2018, along the coast of Washington, USA, we simultaneously collected juvenile quillback rockfish Sebastes maliger from both the environment and the stomachs of juvenile coho salmon Oncorhynchus kisutch . We used otolith microstructure analysis to examine whether juvenile coho salmon were age-, size-, and/or growth-selective predators of juvenile quillback rockfish. Our results indicate that juvenile rockfish consumed by salmon were significantly smaller, slower growing at capture, and younger than surviving (unconsumed) juvenile rockfish, providing direct evidence that juvenile coho salmon are selective predators on juvenile quillback rockfish. These differences in early life history traits between consumed and surviving rockfish are related to timing of parturition and the environmental conditions larval rockfish experienced, suggesting that maternal effects may substantially influence survival at this stage. Our results demonstrate that variability in timing of parturition and sea surface temperature leads to tradeoffs in early life history traits between growth in the larval stage and survival when encountering predators in the pelagic juvenile stage. 

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4. Efficacy of baits and lures for weasel detection

   https://doi.org/10.1002/wsb.1580  

   Bergeson, Scott M; Kays, Roland; Jachowski, David S; Anderson, Courtney D; Williamson, Chad R; Burket, Ashley; Butfiloski, Joseph W; Cheeseman, Amanda E; Cotey, Stacy R; Dennison, Catherine C; et al (June 2025, Wildlife Society Bulletin)

   Abstract Small mustelids are difficult to survey due to their low density and cryptic nature. Population status of North American weasels (Mustela erminea,Mustela nivalis, andNeogale frenata) are believed to be in decline, but there are no standardized monitoring protocols to evaluate their status. To support weasel monitoring, we compared the attractiveness of various combinations of baits and lures to weasels in sites located throughout the eastern and central USA. We baited a total of 122 clusters of 4 camera traps, across 14 states, with random combinations of 4 baits and 3 scent lures in the winters of 2022 and 2023. Cameras baited with meat were 3.5 times more likely to detect both short‐ and long‐tailed weasels on average (mean percentage of cameras detecting weasels: 20–30%) than those with scent lures (3–11%). Red meat was twice as effective at attracting short‐tailed weasels (50%) as chicken or cat food (20%; Z = 2.49,p < 0.01). While red meat marginally increased detections of long‐tailed weasels (21%) compared to chicken and cat food (19%), its effectiveness was influenced by whether the bait was stolen (Z = 2.08,p = 0.04). Additionally, long‐tailed weasels were detected in half the time when raw chicken was used (median days to detection: red meat = 39.5 days, raw chicken = 14.5 days). When salmon oil was added to meat bait, it increased the likelihood of detecting short‐tailed weasels and reduced the time to detection for both species. A variety of non‐target species stole meat bait during the survey, making the camera traps less effective. The addition of salmon oil may have allowed for continual attraction of weasels until stolen meat bait could be replenished. In summary, red meat was the best all‐purpose bait for weasels, although raw chicken is similarly effective for long‐tailed weasels, and the addition of salmon oil is helpful. We also recommend a specific bait enclosure design that was the most effective at minimizing theft of bait. We propose our baiting strategy can be used as a survey standard to evaluate the distribution and population status of weasels. 

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5. Longevity of Bioretention Depths for Preventing Acute Toxicity from Urban Stormwater Runoff

   Maguire, L.M. (August 2024, EWRI Low Impact Development Congress)

   Urbanization poses increasing threats to aquatic ecosystems, including increased chemical loading. Of relatively recent concern is the potential of urban stormwater runoff to facilitate the spread of microplastics (MPs), including tire wear particles. Previous studies have demonstrated the effectiveness of bioretention treatment systems in treating runoff, thereby reducing chemical loading into surface waters and preventing acutely lethal and sublethal effects to aquatic organisms. In this study, we aimed to determine the effectiveness and longevity of bioretention soil media (BSM) at various infiltration depths, including the shallower depth currently required by the Washington Department of Ecology (18”). Experimental columns containing three different BSM depths were dosed with roadway runoff at an accelerated rate to simulate nine water years in approximately 30 calendar months. The chemical and biological effectiveness of the columns in treating runoff was assessed by analyzing influent/effluent chemistry and characterizing the health of juvenile coho salmon (Oncorhynchus kisutch). Bioretention treatment efficiently removed copper, zinc, total PAHs, and total suspended solids (> 70% removal). Influent stormwater runoff was acutely lethal to juvenile coho salmon (88, 90, 100, and 56.3% mortality in four exposures across the nine accelerated years). However, bioretention treatment was protective of coho, altogether preventing mortality for all treatment depths in three exposures and all but one depth in the last exposure, likely due to overflow when influent flow exceeded the ponding capacity of some of the columns. This study is ongoing and will continue to assess bioretention effectiveness through 10 accelerated years. Future research should consider the ability of bioretention systems to remove MPs and associated pollutants in runoff and explore the fate of MP-contaminant complexes in bioretention systems. Although contaminants themselves, MPs can also act as vectors of other contaminants of concern in aquatic ecosystems, including antibiotic resistance genes (ARGs). Contaminants co-occurring in runoff (e.g., heavy metals) can stimulate the selection or amplification of these ARGs. If left untreated, runoff carrying ARGs to surface waters could increase resistance in environmental bacteria and risks to human health. 

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