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Maintenance of genetic variation may provide resilience of populations to natural environmental variability. We used Pacific ocean perch (POP; Sebastes alutus) to test for the maintenance of adaptive variation across overlapping generations. POP are a long‐lived species characterized by widespread larval dispersal in their first year and a longevity of over 100 years. In order to understand how early marine dispersal affects POP survival and population structure, we used restriction site‐associated DNA sequencing (RADseq) to obtain 11,146 single‐nucleotide polymorphisms (SNPs) from 401 young‐of‐the‐year (YOY) POP collected during surveys conducted in 2014 (19 stations) and 2015 (4 stations) in the eastern Gulf of Alaska. Population clustering analysis showed that the POP samples represented four distinct ancestral populations mixed throughout the sampling area. Based on prior work on larval dispersal of POP, these larvae are most likely from distinct parturition locations that are mixing during their pelagic dispersal life stage. Latent factor mixed models revealed that POP larvae face significant selection during their first year at sea, which is specific to the year of their birth. Thus each adult cohort's genetic composition is heavily influenced by the environmental conditions experienced during their first year at sea. Long‐lived species relying on broadcast spawning strategies may therefore be uniquely resilient to environmental variability by maintaining a portfolio of cohort‐specific adaptive genotypes, and age truncation due to overfishing of older cohorts may have detrimental effect on the population viability., We found that marine fish larvae and young‐of‐the year Pacific ocean perch (Sebastes alutus) experience strong selection acting during their pelagic stage. This selection is dependent on the environmental conditions encountered during their first year of life. We present evidence of fluctuating selection acting on Pacific ocean perch young‐of‐the year life stage resulting in cohort‐specific genetic selection patterns.

On March 24, 1989, the Exxon Valdez grounded on Bligh Reef in Prince William Sound, Alaska, spilling an estimated 10.8 million gallons of crude oil. Contrary to early projections, subsequent studies over several decades have shown subsurface oil persisting on impacted beaches. Here we present findings from a lingering oil survey conducted during the summer of 2015 at a small set of beaches in Prince William Sound known to have persistent subsurface Exxon Valdez oil. The objectives of the survey were to estimate how much oil remains at these sites, the oil composition, and oil retention rates compared to previous studies. Results from the survey found lingering oil was present at 8 of 9 sites that were revisited. Surveys revealed little evidence of change in oil area or mass over the last 14 years, nor has there been a change in the distribution of oiling intensities or their location on the beach. Detailed analysis of the oil indicated it has not weathered since 2001. Subsurface oils collected in 2015 have enriched concentrations of phenanthrenes and chrysenes relative to oil originating in the cargo hold indicating that buried oil has retained some toxic potential over the last two decades, but it is not currently bioavailable. Subsurface oil appears to be sequestered in sediments and protected from hydrological washing and low oxygen and nutrient levels inhibiting biodegradation. These findings are consistent with previous surveys and predictive geomorphic models suggesting the estimated 0.6% Exxon Valdez oil remaining is sequestered and not bioavailable unless disturbed and will likely persist in the environment on a decadal scale.

Unmanned aircraft systems (UASs) were tested for counting Chinook salmon ( Oncorhynchus tshawytscha) redds as a more accurate, safer alternative to manned helicopter flights. Counting redds from the helicopter was less expensive and time consuming, but of the total redds counted at selected sites with a UAS, an average (± SD) of only 77% ± 14% was counted from the helicopter. A river-wide census of redds was not possible with a UAS because the study area was too large for the single field crew to survey. Simulation analyses were used to compare stratified random sampling (STRS) and sampling proportional to size (PPS) for estimating annual total redd counts from data collected with a UAS. The STRS estimates were more accurate and precise, whereas the PPS estimates, though biased, had 95% CIs that included the observed redd count more frequently. We strongly recommend that researchers conduct simulation analyses to evaluate alternative survey sampling methods if they are considering replacing census counts made from manned aircraft with counts estimated from data collected with a UAS. We conclude that UAS application reduces the risk inherent to manned aircraft flights, but the reduction in risk can come at the cost of estimates of population parameters that can sometimes be inaccurate and lack 95% CI coverage.

Chinook salmon (Oncorhynchus tshawytscha, Salmonidae) returns to western Alaska were historically high and variable but recently reached record lows. Understanding the differential influence of climatic and oceanic conditions on the growth of juvenile Chinook salmon in the north and south eastern Bering Sea is key to understanding mechanisms and factors affecting the production dynamics of Chinook salmon from western Alaska and the Arctic. Summer growth was lower and more variable among years for Chinook salmon in the south than the north eastern Bering Sea. Summer growth decreased with a rise in sea temperatures in the north and south and increased with more sea ice coverage and a later time of ice retreat in the south but not in the north. Capelin (Mallotus villosus), an important prey for juvenile Chinook salmon in the north and during cold years may link increased growth to cooler sea temperatures. Reduced and more variable summer growth of juvenile Chinook salmon from the eastern Bering Sea with warming may have implications on overwintering survival.

We sampled fish at eight locations in western Prince William Sound (PWS), Alaska, in April, July, and September 2006, and July 2007, to identify species assemblages and habitat use. At each location, fish were sampled with a 37-m long variable mesh beach seine in three nearshore habitats: bedrock outcrops, eelgrass meadows, and cobble beaches with kelp. A total of 49,060 fish representing 45 species were captured in 95 beach seine hauls. Catch-per-unit-effort (CPUE, all species) did not differ by season but did differ by habitat type–CPUE was greater in eelgrass and kelp than in bedrock. Seasonal pulses in catch were evident for some species; pink salmon were captured only in spring and summer, Pacific herring only in summer and fall, and capelin only in fall. Species richness was greater in summer (34) than in spring (23) or fall (28), and greater in eelgrass (34) than in bedrock (22) or kelp (33). Species that were good discriminators among seasonal collections were pink salmon, saffron cod, crescent gunnel, and Pacific herring, whereas species that were good discriminators among habitat collections were crescent gunnel, tubesnout, bay pipefish, saffron cod, and Arctic shanny. Of the most abundant species captured, most were juveniles based on estimated size at maturity. The summer fish assemblage in western PWS has changed over the last 20 years, especially with the appearance in large numbers of saffron cod. Sites in this study can be monitored periodically to track future changes in fish assemblages and habitat that may result from local and regional human disturbance.

Extracts from semi-permeable membrane devices (SPMDs) deployed on beaches in Prince William Sound (PWS), Alaska, were used to evaluate if complex contaminant mixtures from different sources can be distinguished by the resulting cytochrome P450 1A (CYP1A) activity in exposed test animals. Deployment sites included canneries, salmon hatcheries, and beaches where lingering oil remains from discharges during the 1964 earthquake or the 1989 Exxon Valdez oil spill. Other sites were selected at random to evaluate region-wide contaminant inputs or were located in salmon streams to evaluate contaminants carried and released by migrating salmon carcasses following reproduction. Following standard deployments of approximately 28 d, an aliquot of the accumulated contaminants was intraperitoneally injected without cleanup into juvenile rainbow trout (Oncorhynchus mykiss). After 2 d and 7 d, the activity of CYP1A was measured by the ethoxyresorufin-o-deethylase (EROD) assay. Exposure to extracts from the oiled sites and one hatchery site with numerous creosote pilings elicited strong EROD responses, whereas fish exposed to salmon stream extracts elicited weak but significant responses during late summer compared to late spring. Responses from the other sites were not significant, indicating contaminants from these sources are unlikely to cause CYP1A induction in resident biota. Rather than simply assessing extant contaminants, this method evaluates the potency of the different sites for bringing about aryl hydrocarbon receptor responses in resident biota.

Oil stranded by the 1989 Exxon Valdez spill has persisted in subsurface sediments of exposed shores for 16 years. With annualized loss rates declining from approximately 68% yr(-1) prior to 1992 to approximately 4% yr(-1) after 2001, weathering processes are retarded in both sediments and residual emulsified oil ("oil mousse"), and retention of toxic polycyclic aromatic hydrocarbons is prolonged. The n-alkanes, typically very readily oxidized by microbes, instead remain abundant in many stranded emulsified oil samplesfrom the Gulf of Alaska. They are less abundant in Prince William Sound samples, where stranded oil was less viscous. Our results indicate that, at some locations, remaining subsurface oil may persist for decades with little change.

We examined 32 shorelines selected at random in 2003 from shorelines in Herring Bay, Lower Pass, and Bay of Isles in Prince William Sound, Alaska, to examine the vertical distribution of oil remaining from the 1989 Exxon Valdez oil spill and to estimate the probability that sea otters and ducks would encounter oil while foraging there. On each shoreline, sampling was stratified by 1-m tide height intervals and randomly located 0.25 m2 sampling quadrats were examined for evidence of surface and subsurface oil. Oil from the T/V Exxon Valdezwasfound on 14 shorelines, mainly in Herring Bay and Lower Pass, with an estimated 0.43 ha covered by surface oil and 1.52 ha containing subsurface oil. Surface and subsurface oil were most prevalent near the middle of the intertidal and had nearly symmetrical distributions with respect to tide height. Hence, about half the oil is in the biologically rich lower intertidal, where predators may encounter it while disturbing sediments in search of prey. The overall probability of encountering surface or subsurface oil is estimated as 0.0048, which is only slightly greaterthan our estimated probability of encountering subsurface oil in the lower intertidal of Herring Bay or Lower Pass. These encounter probabilities are sufficient to ensure that sea otters and ducks that routinely excavate sediments while foraging within the intertidal would likely encounter subsurface oil repeatedly during the course of a year.

Pink salmon Oncorhynchus gorbuscha fry from Auke Creek, Alaska, were marked with coded wire tags (CWTs) and, in some cases, thermally induced otolith marks, to investigate the effects of the CWT process on survival and straying. Pink salmon from Gastineau Hatchery that had been thermally marked provided a point of comparison. Marked fish were also used to estimate the natal composition of fish in nearby streams and at Auke Creek and Gastineau Hatchery. The survival of fish with both CWTs and thermal marks was significantly lower than that of fish with thermal marks alone but not significantly different from that of fish with CWTs alone. No effect of CWTs on straying was detected. The estimated straying rates were 4.4% and 6.7% for early-run and late-run Auke Creek fish, respectively, and 6.9% for Gastineau Hatchery fish. The observed straying and run composition estimates indicated a large-scale interchange of adult pink salmon among local streams, which may promote rapid colonization and recover...

Numbers of strays (adult salmon returning to a nonnatal stream), straying rates, and distribution of strays were estimated for pink salmon incubated in oil-contaminated gravel and for an unexposed control group. The treatment groups were incubated in oiled gravel, which resulted in initial aqueous exposures for total polynuclear aromatic hydrocarbons (TPAHs) of 5 and 19 μg/L for a low and high dose, respectively; the control group was incubated in gravel without oil. Fry from each treatment group were marked with coded wire tags (CWTs). The numbers of tagged fish released were 65,409 from the control; 69,441 from the low-dose group; and 70,414 from the high-dose group. A total of 288,492 pink salmon were sampled for CWTs when returning to spawn in the natal stream of the experimental fish, when returning to streams within 60 km of the natal stream, and when returning to two hatcheries within 100 km of the natal stream. The frequencies of observed strays were 0.023, 0.030, and 0.025 for the contro...

The Arctic ecosystem is changing rapidly, yet information on nearshore fish assemblages for the northeastern Chukchi Sea is extremely limited. To address this information gap, we sampled nearshore fish assemblages with a beach seine and a small bottom trawl at six stations in the northeastern Chukchi Sea in August 2007, 2008, and 2009, and in September 2009. Catch and species composition differed by gear type and between sample periods, including the two in 2009. A total of 16 039 fish representing 18 species were captured in 24 beach seine hauls, and 3108 fish representing 24 species were captured in 48 trawl tows. Beach seine catch was dominated by capelin (83%), and trawl catch was dominated by Arctic cod (56%). Species that were good discriminators between gear types were capelin (seine) and slender eelblenny (trawl), and unidentified small sculpins were the most common taxa caught with both gear types. Capelin and Arctic cod captured by either gear type were mostly juveniles (judging by size). Variability among sampling periods in catch and species composition within gear types can likely be attributed to annual variations in environmental conditions, including differences in water temperature (range: 2˚–9˚C). The shallow nearshore environment of the northeastern Chukchi Sea provides important habitat for many fish species and is extremely vulnerable to disturbance. Loss of sea ice from global warming may open up formerly inaccessible areas to oil and gas exploration, vessel traffic, and commercial fishing. Thus, long-term monitoring of nearshore fish assemblages in the Alaskan Arctic is necessary for managers to make informed decisions in this fragile environment.

We estimated the amount of oil remaining in Prince William Sound, Alaska, 12 yr after the 1989 Exxon Valdez spill to assess its importance as a long-term reservoir of toxic hydrocarbons. We found oil on 78 of 91 beaches randomly selected according to their oiling history. Surface oiling was recorded for randomly placed quadrats, which were then excavated and examined for subsurface oil. The cumulative area of beach contaminated by surface or subsurface oil was estimated at 11.3 ha. Surface oil varied little with tide height, but subsurface oil was more prevalent at the middle tide heights. The mass of remaining subsurface oil is conservatively estimated at 55 600 kg. Analysis of terpanes indicated that over 90% of the surface oil and all of the subsurface oil was from the Exxon Valdez and that Monterey Formation oil deposited after the 1964 Alaska earthquake accounted for the remaining surface oil. These results indicate that oil from the Exxon Valdez remains by far the largest reservoir of biologically available polycyclic aromatic hydrocarbons on beaches impacted by the spill and that biota dependent on these beaches risk continued exposure.