Understanding the movement of aquatic organisms is crucial for assessing mortality risks, population structure, and resilience. When populations exhibit diverse behaviors, such as partial migration, individuals can exhibit different movement strategies, forming behavioral contingents; these may distribute mortality risks across space and time, potentially influencing population fluctuations and resilience. Although partial migration and behavioral contingents have been documented in many bony fish species, their role in elasmobranch populations is less explored. Bull sharks Carcharhinus leucas are large-bodied, upper trophic-level predators whose general movement patterns have been studied in the western North Atlantic (WNA). We investigated the movement ecology of bull sharks, focusing on partial migration and contingent movement behaviors in the WNA. We analyzed passive acoustic telemetry detections of bull sharks (n = 61) tagged at multiple sites on the US east coast and in The Bahamas from 2009 to 2023. Network and hierarchical cluster analyses identified 6 distinct clusters of bull sharks based on their movement behavior, ranging from highly mobile to highly resident groups. Spatial network analysis revealed seasonal overlap of all clusters on the east coast of Florida and The Bahamas during winter. Tagging site, sex, size, and temporal effects were not significantly related to cluster membership, suggesting that individual variation drove movement groups. We hypothesize that partial migration exists and clusters represent behavioral contingents within the WNA bull shark population. Diverse movement behaviors of bull sharks may influence resilience to fishing pressures or changes in environmental conditions and should be considered in future stock assessments.

Diverse natural and anthropogenic factors threaten the viability of Atlantic and Pacific salmon populations during their anadromous life cycle, but other than fisheries, the proximate cause of mortality for free-swimming salmon is most likely predation. Salmon predation is frequently mediated by environmental conditions. Large-scale atmospheric forces affect salmon predation indirectly by altering streamflow, thermal regimes, and oceanographic features that then effect salmon food-webs, physiology, and interactions with other taxa. Direct effects of predation are difficult to track confidently over time due to variability in predator and salmon cooccurrence in time and space, and complicating dynamics, such as competition among predators, alternative prey, and undiagnosed compensatory and additive mortality. This synthesis of predation on salmon emphasizes the importance of considering interactive effects of predation, environmental factors, and predator abundance and distribution through the salmon life-cycle to support effective salmon management and conservation efforts. We identify actions that may promote salmon recovery and sustainability, including (i) increasing the diversity of juvenile salmon size and timing at ocean entry, (ii) quantifying the role of contact points and alternate prey availability, and (iii) upgrading ecosystem models to evaluate alternative ecosystem management strategies. Importantly, considering additive predation impacts due to predator behaviors (e.g. predators moving inshore, upstream) and foraging responses (i.e. Holling’s functional and numerical responses) should be part of management evaluations as these processes control the potential impacts of interactions with salmon at contact points modulated by salmon growth and alternate prey availability. Key objectives for future research include identifying connections with predator populations and their community spatiotemporal patterns of abundance and distribution, and understanding environmental influences on predator–salmon interactions.

Warming ocean conditions have resulted in rapid borealization of Arctic seas, with fish assemblages reorganizing as sub-Arctic fish species expand into new territories, such as in the Chukchi Sea in the Pacific Arctic. During the summer months, this region has seen increases in the presence and abundance of groundfishes, including Pacific cod (Gadus macrocephalus) and walleye pollock (Gadus chalcogrammus), with the possibility of Pacific halibut (Hippoglossus stenolepis) arriving in coming years. To assess this potential, thermal conditions occupied by Pacific halibut in the adjacent northern Bering Sea were compared to modeled bottom-water temperatures in the Chukchi Sea to determine if suitable thermal habitat is available in the region. Pacific halibut in the Bering Sea primarily occupied waters from 6.0 to 8.2 °C, but were regularly found in conditions from 3.8 to 9.8 °C during the summer and temperatures around 0.9 °C during the winter. The availability of these conditions in the Chukchi Sea was relatively limited during a recent cold year, constrained to eastern coastal waters near Alaska with maximal availability during August and September. In contrast, suitable thermal conditions were 2.5 to 7.8 times more prevalent during a warm year, comprising a large portion of the Chukchi Sea from July to October. Findings suggest that suitable thermal conditions are currently available for Pacific halibut in the Chukchi Sea, indicating the potential for range expansion into the region. However, the current absence of the species suggests that alternative factors are currently discouraging this movement, such as prey availability or substrate type.

In recent years, the northern Bering Sea (NBS) fish assemblage has changed, where rising water temperatures have correlated with increases in abundance of sub-arctic fish species. One such species is the Pacific halibut (Hippoglossus stenolepis), a commercially important flatfish that has largely been unstudied within the NBS. To assess Pacific halibut within the region, we attached pop-up satellite telemetry tags on large individuals in the NBS during the summer months. Our objectives were to characterize depths and temperatures occupied by Pacific halibut, identify the timing, magnitude, and destination of Pacific halibut migratory movements, and assess the scale of those movements compared to current management practice. Tagged Pacific halibut remained within the Bering Sea but made relatively large-scale seasonal movements within the basin. During autumn, all Pacific halibut made offshore migrations to the continental shelf edge, reaching as far south as the Pribilof Islands and as far north as Russian waters along the Kamchatka Peninsula. Individuals remained in offshore waters throughout the winter, likely for spawning purposes, where they occupied conditions as cold as − 1.9 °C and as deep as 696 m. Fish returned to relatively warm, shallow waters near their initial tagging locations in early summer, an indication of inter-annual site fidelity and homing to NBS foraging areas. This study provides the first evaluation of Pacific halibut at their northernmost extent, with findings indicating that individuals in the NBS display fine-scale spatial dynamics representative of migratory foraging contingent behavior.

Many species have reduced reproductive potential at the poleward extreme of their range, where they exhibit unique spawning dynamics. However, recent poleward range expansions have resulted in many species being unstudied in these regions, such as the Pacific halibut (Hippoglossus stenolepis) in the northern Bering Sea (NBS). To characterize Pacific halibut spawning dynamics at the northern extreme of their range, we attached pop-up satellite telemetry tags to large females in the NBS, with time series data and tag reporting locations being used to infer spawning behavior and to identify occupied spawning habitat conditions, location, and timing. Pacific halibut in the NBS occupied spawning habitat later and farther north than previously described, where spawning habitat was occupied from January to May and reached as far north as the Russian continental shelf edge. Additionally, 42% of mature individuals never occupied presumed spawning habitat, suggesting the presence of skip spawning behavior. These findings suggest that Pacific halibut exhibit unique spawning dynamics in the NBS, which may result in a reduced reproductive potential within this northern population component.

Although steelhead (Oncorhynchus mykiss) is a culturally and recreational important species throughout North America, less is known about its ocean than its freshwater ecology. To provide insights into migratory routes and habitats occupied by steelhead in the North Pacific Ocean, we attached pop-up satellite archival tags (PSATs) to female steelhead kelts from three watersheds on the east coast of Prince of Wales Island, in southern southeast Alaska. PSATs successfully recorded extensive westward post-spawning migrations of nine female kelts across the Gulf of Alaska to areas near the Alaska Peninsula and Aleutian Islands. From the months of June to October, tagged steelhead occasionally dived to 10–20 m, but spent approximately 90

Northern high-latitude glaciers impact nearshore marine ecosystems through the discharge of cold and fresh waters, including nutrients and organic matter. Fishes are important integrators of ecosystem processes and hold key positions in the transfer of energy to higher trophic positions in such systems. This study used a natural gradient in space and time, including watershed glacial cover (0–60%) of five adjacent estuaries and three sequential discharge periods (pre-peak, peak, post-peak) in the northern Gulf of Alaska (Kachemak Bay) to test whether differences in glacial cover of watersheds upstream of estuaries affect dietary resource use of nearshore fishes. Dietary resource use was assessed using stomach content and stable carbon and nitrogen isotope analyses to determine fish diet composition and trophic niche width. Crescent gunnel (Pholis laeta), a mostly sedentary species, was our focal species for comparisons across estuaries and discharge periods. Discharge period had a greater influence on diet composition and trophic niche width of crescent gunnels than watershed glacial coverage. Niche width of crescent gunnel was larger during the post-peak discharge period compared to pre-peak and peak periods, coincident with a shift in prey spectrum. However, watershed glacial cover was not a suitable predictor of niche width of crescent gunnel. Trophic resource use was also considered along this glacial cover gradient for two other fish species, Pacific staghorn sculpin (Leptocottus armatus) and starry flounder (Platichthys stellatus), but within the post-peak discharge period only. These species exploited a larger prey base compared to crescent gunnel, likely due to their greater mobility. Similar to crescent gunnel, there were no relationships in trophic niche width associated with watershed glacial coverage for these other species during the post-peak discharge period. Instead, trophic resource use of these three nearshore fish species was influenced by a more complex set of dynamic environmental variables (salinity, temperature, turbidity, and discharge), as well as static watershed characteristics, especially vegetation cover. Such drivers can act through changes in metabolic rates, modulating foraging strategies and trophic connectivity, as well as terrestrial nutrient delivery to support estuarine production. The environmental conditions associated with the glacially influenced estuaries during our study period (2020−2021) seemed within a range that allowed nearshore fishes to maintain energy pathways and prey bases across these estuaries, but it is unknown how these estuarine food webs may be influenced in years of extreme conditions such as during heat waves, droughts, or floods.

Climate change is impacting marine ecosystems throughout the circumpolar Arctic, altering seasonal habitats and the food bases for fishes, seabirds, and marine mammals. Arctic and Subarctic regions provide resources for resident species and for species that migrate to the north from more southerly regions. Changes in northerly latitudes thus impact endemic as well as non-endemic animals. Herein, we review what is known about climate-driven changes in the migration patterns of Arctic and Subarctic marine vertebrates, including: 1) Arctic residents with seasonal movements – those fishes, seabirds, and marine mammals that complete their entire life cycle within the Arctic but exhibit seasonal movements; 2) Breeding migrants – many seabirds enter the Arctic to breed and subsequently migrate south in the fall; and 3) Summer visitors for feeding – certain species of boreal fishes, seabirds and marine mammals arrive during the northern summer to feed on abundant prey though they breed elsewhere. Migratory movements are often driven by the timing and extent of sea ice, which defines suitable habitat for some animals and limits access to open water and prey for others. Longer open-water seasons, warmer ocean temperatures, and stronger winds have resulted in earlier production blooms in spring and often, extended open-ocean plankton blooms into late summer, resulting in altered prey types and distributions. A common thread among taxa is that shifts in distribution and timing of migrating animals indicate they are traveling farther north, or shifting longitudinally, and migrations are occurring over longer seasonal time frames. Species performing multiple lifetime migrations or long-distance migrants may need to adjust migration timing or routing iteratively to match changes in marine productivity. Altered animal distributions or phenology, and reduced sea ice, affects access to animals that are critical nutritional, economical, and cultural components of Indigenous people’s lives in the Arctic. Ongoing changes challenge the resilience and adaptability of Arctic people and ecosystems, and will require adaptive research and management approaches.

Objective: Estimates of Pacific salmon Oncorhynchus spp. stock composition in coastal fishery harvests are needed to balance fishing opportunities against conservation. Catch partitioning in some small-scale fisheries can be hindered by insufficient resolution of modern stock classification tools (e.g., genetic stock identification). Methods: We used acoustic telemetry to investigate the stock composition of commercial landings in the Norton Sound district of Alaska by mimicking local fisheries to capture and tag 578 Coho Salmon O. kisutch in the contiguous Shaktoolik and Unalakleet commercial subdistricts over two seasons. Result: In total, 341 individuals that were last detected in demarcated spawning areas were assigned to a stock of origin based on putative natal site fidelity. Sex, location of capture, and timing of capture were predictors of stock membership. Models that were fitted to commercial harvest data from the project years (2020 and 2021) estimated that 32.9% of the Shaktoolik subdistrict catch was Shaktoolik stock, 51.5% was Unalakleet stock, and the remainder consisted of other transitory stocks. Conversely, 86.7% of landed Coho Salmon in the Unalakleet subdistrict were Unalakleet stock, whereas the Shaktoolik stock and transitory stocks made up less than 10%, respectively. Conclusion: These findings suggest that coastal salmon fisheries in Norton Sound have access to a variable mixture of stocks whose unique characteristics can be leveraged to examine the effects of directed harvest effort on stock health and diversity.

Arctic freshwater ecosystems and fish populations are largely shaped by seasonal and long‐term watershed hydrology. In this paper, we hypothesize how changing air temperature and precipitation will alter freeze and thaw processes, hydrology, and instream habitat to assess potential indirect effects, such as the change to the foraging and behavioral ecology, on Arctic fishes, using Broad Whitefish Coregonus nasus as an indicator species. Climate change is expected to continue to alter hydrologic pathways, flow regimes, and, therefore, habitat suitability, connectivity, and availability for fishes. Warming and lengthening of the growing season will likely increase fish growth rates; however, the exceedance of threshold stream temperatures will likely increase physiological stress and alter life histories. We expect these changes to have mixed effects on Arctic subsistence fishes and fisheries. Management and conservation approaches focused on preserving the processes that create heterogeneity in aquatic habitats, genes, and communities will help maintain the resilience of Broad Whitefish and other important subsistence fisheries. Long‐term effects are uncertain, so filling scientific knowledge gaps, such as identifying important habitats or increasing knowledge of abiotic variables in priority watersheds, is key to understanding and potentially mitigating likely impacts to Arctic fishes in a rapidly changing landscape.

Arctic lamprey (Lethenteron camtschaticum) is an important dietary resource for rural and indigenous communities in parts of Alaska, with some commercial use. As with many fish species harvested for human consumption, there are concerns regarding mercury concentrations ([Hg]) in Arctic lamprey that may impact human health. To date, information regarding the life cycle and diet of Arctic lamprey is scarce, with no published studies examining [Hg] in Arctic lamprey tissues. Our goals were to investigate the feeding ecology of Arctic lamprey from the Bering Sea, determine how diet and potential dietary shifts might influence [Hg] in muscle, and determine if current [Hg] may pose a human health risk. The mean total [Hg] in Arctic lamprey muscle (n = 98) was 19 ng/g wet-weight. Log transformed total [Hg] were not associated with any measured biological variables including length, mass, δ13C values, or δ15N values. A stable isotope mixing model estimated that capelin (Mallotus villosus) accounted for 40.0 ± 4.0% of the Arctic lamprey diet, while Pacific sand lance (Ammodytes hexapterus) and Pacific herring (Clupea pallasii) accounted for 37.8 ± 3.1% and 22.2 ± 3.5% respectively. Finally, diet percentage compositions shifted based on size class (i.e., medium versus large). These results indicated that feeding location, bioaccumulation, and biomagnification are not important drivers of [Hg] in Arctic lamprey and current [Hg] do not pose a human health risk. Taken together, this research further expands our knowledge of Arctic lamprey trophic ecology in the eastern Bering Sea.

Understanding spawning behavior of commercial fish populations provides a basis for making management decisions related to these stocks. Archival tags can be used to define spawning behavior when depth-specific movements are involved. Spawning behavior of Greenland halibut (Reinhardtius hippoglossoides) in the eastern Bering Sea and the Aleutian Islands was inferred from archival tag data. The predominant period of identified spawning activity, based on abrupt vertical rises of females, occurred in January and February, and females reached apexes in their upward movement (spawning rises) at depths of approximately 200-350 m below the surface, indicating that the release of eggs could occur at depths shallower than previously assumed. Females had a single spawning rise annually, a result supporting the notion that this species is a total (single-batch) spawner. Male Greenland halibut exhibited spawning behavior, rises to shallower depths one or more times, for an average of 20 d. For large female Greenland halibut (>80 cm in fork length), spawning rises occurred in consecutive years, indicating that, despite oocyte development taking more than 1 year, spawning occurs annually. Inferring spawning behavior by using data collected with archival tags can aid in understanding the maturity of Greenland halibut.

Interactions between spatial dynamics and stock structure in marine fishes have largely focused on stocks in decline; stock structure is rarely re-visited for expanding species. Here, the spatial ecology of Atlantic halibut (Hippoglossus hippoglossus L.), managed as four stocks in the Northwest Atlantic, is reviewed. Halibut collapsed under high exploitation in the mid-19th century, but the Canadian fisheries value has increased seven-fold since the early 2000s. Atlantic halibut's thermal habitat has increased due to warming, possibly contributing to its expansion. Genomic evidence differentiates two populations in the four management units, whereas there is non-genetic spatial structure within each of the stock boundaries. There are different core juvenile areas and a diversity of spawning migration patterns influenced by timing, fish size, maturity state, and distance between summer-feeding and over-wintering habitats. From tagging studies, multiple estimates of median distance at recapture (similar to 3-90 km) are much less than the spatial domain of each stock. Growth rates are faster in the warmer south, as predicted by growing degree day. The current perspective of Atlantic halibut spatial structure is that there are two distinct populations, and within each, there are subpopulations composed of multiple migratory contingents. The level of mixing on common spawning grounds both among and within subpopulations is only partly understood.

The development of hydrokinetic turbines has been motivated by the desire to reduce fossil fuel reliance, energy production costs, and greenhouse gas emissions. Detailed information about fish interactions with hydrokinetic turbines is limited; therefore, this study sought to characterize the interactions between a turbine (RivGen; Ocean Renewable Power Company) and Sockeye Salmon Oncorhynchus nerka from one of the most productive populations in the world-that in the Kvichak River, Alaska. By viewing real-time video imagery, our objectives were to quantify the number of Sockeye Salmon smolts that interacted with the turbine and to assess the behaviors/outcomes of these interactions during the species' smolt out-migration. From May 21 to June 10, 2021, a total of 2,374 Sockeye Salmon smolts passed through the field of view of cameras placed immediately downstream of the hydrokinetic turbine. The majority of these observed events occurred over a short (5-d) time period from late May to early June during periods of darkness (0000-0400 hours). Fish were observed passing through the hydrokinetic turbine in both normal and disoriented manners, with the rotational status/speed of the hydrokinetic turbine appearing to influence passage behavior. Blade strikes on fish were also observed, all of which occurred when the turbine was rotating at high "production" speeds. After temporally and spatially extrapolating the observed fish interactions to account for our subsampling, the results suggest that when monitoring was conducted, the hydrokinetic turbine interacted with approximately 200,000 Sockeye Salmon smolts during this species' smolt out-migration period. This study adds to the sparse knowledge base on fish interactions with emerging riverine hydrokinetic devices and may inform strategies to mitigate the impacts of developing energy projects on socially and culturally important fisheries.

Abundances of large sharks are reported to have declined worldwide, and in response various levels of fisheries management and conservation efforts have been established. For example, marine-protected areas have been suggested as a means to protect large expanses of ocean from fishing and other industrial activities (e.g., habitat destruction), and in 2011 The Commonwealth of The Bahamas established The Bahamas Shark Sanctuary. Nonetheless, assessing the effectiveness of conservation efforts is challenging because consistent long-term data sets of shark abundances are often lacking, especially throughout the Caribbean and The Bahamas. In this study, the authors investigated the catch rates and demographics of tiger sharks Galeocerdo cuvier caught in a fishery-independent survey near Bimini, The Bahamas, from 1984 to 2019 to assess relative abundance trends following the banning of longline fishing in 1993 and the subsequent establishment of the shark sanctuary. To contextualize the relative abundance trends near Bimini, the authors compared this to the relative abundance of tiger sharks in a fishery-dependent survey from the Southeastern USA (SE USA), conducted from 1994 to 2019. The data of this study suggest that local abundance of tiger sharks has been stable near Bimini since the 1980s, including after the ban of longline fishing and the implementation of the shark sanctuary. In comparison, the abundance near the SE USA has slowly increased in the past decade, following potential declines in the decade preceding the USA Shark Management Plan. The results of this study provide some optimism that current conservation efforts in The Bahamas have been effective to maintain local tiger shark abundance within the protected area. In addition, current fisheries management in the SE USA is allowing this species to recover within those waters.

Knowledge of the three-dimensional movement patterns of elasmobranchs is vital to understand their ecological roles and exposure to anthropogenic pressures. To date, comparative studies among species at global scales have mostly focused on horizontal movements. Our study addresses the knowledge gap of vertical movements by compiling the first global synthesis of vertical habitat use by elasmobranchs from data obtained by deployment of 989 biotelemetry tags on 38 elasmobranch species. Elasmobranchs displayed high intra- and interspecific variability in vertical movement patterns. Substantial vertical overlap was observed for many epipelagic elasmobranchs, indicating an increased likelihood to display spatial overlap, biologically interact, and share similar risk to anthropogenic threats that vary on a vertical gradient. We highlight the critical next steps toward incorporating vertical movement into global management and monitoring strategies for elasmobranchs, emphasizing the need to address geographic and taxonomic biases in deployments and to concurrently consider both horizontal and vertical movements.

Understanding space use and movement behavior can benefit conservation and management of species by identifying areas of high importance. However, this can be challenging for highly mobile species, especially those which use a wide range of habitats across ontogeny. The Bahamas is hypothesized to be an important area for tiger sharks, but the utility of the area for this species within the broader western North Atlantic is not fully understood. Therefore, we assessed (1) whether the area near Bimini serves as an important pupping location for tiger sharks, (2) their level of residency and site fidelity to the area, and (3) regional dispersal across ontogeny. Frequent captures of young-of-year tiger sharks, as well as ultrasonography showing near-term and recently postpartum females supports the hypothesis that pupping occurs in the area. However, small juveniles had low overall recapture rates and sparse acoustic detections near Bimini, indicating they do not reside in the area for long or may suffer high natural mortality. Large juvenile and sexually mature tiger sharks had higher overall local residency, which increased during cooler water winter months. The probability of dispersal from Bimini increased for larger individuals. Repeated, long-term site fidelity was displayed by some mature females, with several returning to Bimini across multiple years. Satellite tracking showed that tiger sharks extensively used areas outside of The Bahamas, including traveling more than 12,000 km. Together, these results show that Bimini is an important area for tiger sharks, serving as a pupping ground, rather than a nursery ground, a finding which could be incorporated into future conservation and management efforts.

Although steelhead (Oncorhynchus mykiss) is an iconic species found throughout the North Pacific rim, little is known about its ocean ecology. To provide insights into migratory routes and habitats occupied by steelhead in the North Pacific Ocean, we attached pop-up satellite archival tags (PSATs) to steelhead kelts in 2018 (n = 16), 2019 (n = 12), and 2020 (n = 35) from the Situk River, a robust Alaskan population. PSATs recorded extensive post-spawning migrations extending to the western North Pacific Ocean, and as far north as the central Bering Sea. While at sea, tagged steelhead spent the majority of their time in surface waters (< 5 m) and occasionally dived to 15–20 m, but displayed no observable diel depth-based behaviors. Tagged steelhead kelts experienced a thermal environment of 4–16 °C from June to January, after exiting the Situk River. Results from this project corroborate the limited past research suggesting that steelhead predominantly occupy surface waters and that their distribution is largely influenced by sea-surface temperatures of ~5–15 °C. Additionally, results from this study suggest that the waters near the Aleutian Islands are important feeding grounds for steelhead kelts from the Situk River, and thus may play a critical role in the successful reconditioning of repeat spawners in this population. These results provide the first detailed insights into the ocean ecology of steelhead and may be used for a variety of applications (e.g., niche construction, and forecasting future range dynamics under climate scenarios).

Landscape-level geomorphic processes influence the spatial and temporal arrangement of fish habitats in freshwater ecosystems and fishes move across riverscapes, selecting a suite of habitats to maximise fitness. Here, we explore the influence of geomorphology on stream channel attributes and assess Broad Whitefish (Coregonus nasus) spawning habitat potential in the Colville River in Arctic Alaska. Using high-resolution digital surface models (5 m(2)), we quantified the stream network extent and summarised channel habitat attributes continuously across the drainage network. Next, we developed an intrinsic potential (IP) model for Broad Whitefish by using geomorphic channel parameters previously understood to be associated with spawning habitats (channel width, median substrate size and channel braiding) to estimate the potential of streams across the Colville River watershed to provide spawning habitat. Our model results show the majority of habitat with high IP (>= 0.6) was located within the braided sections of the main channel, which encompass >1548 km, but only 2% of the total channel network. The IP model was tested by tracking radio-tagged Broad Whitefish using aerial surveys. Prespawn fish moved into the watershed starting mid-July and mostly used habitat with moderate to very high IP in the middle and lower watershed. Several individuals were relocated in smaller multichannels with vegetated bars that contained very low IP (<= 0.2), suggesting that other factors, such as hyporheic flow, may also influence spawning habitat selection. Our study demonstrates that IP modelling offers a useful method to quantify spawning habitat potential in data-poor riverscapes, providing useful information for managers to assess potential anthropogenic impacts and develop conservation plans to protect essential Broad Whitefish habitat.

A diversified energy portfolio may include marine energy in the form of current energy converters (CECs) such as tidal or in-river turbines. New technology development in the research stage typically requires monitoring for environmental effects. A significant environmental effect of concern for CECs is the risk of moving parts (e.g., turbine blades) colliding with animals such as fishes. CECs are installed in energetic locations in which it is difficult to operate sensors to fulfill monitoring requirements for informing collision risk. Collecting data (i.e., about blade strikes or near-misses) that inform interactions of fishes with CECs is usually attempted using active acoustic sensors or video cameras (VCs). Limitations of low-light conditions or water turbidity that preclude effective use of VCs are overcome by using high-resolution multibeam echosounders (or acoustic cameras (ACs)). We used an AC at two sites to test its ability to detect artificial and real fish targets and determine if strike, near-miss, and near-field behavior could be observed. Interactions with fish and artificial targets with turbines have been documented but strike confirmation with an AC is novel. The first site was in a tidal estuary with a 25 kW turbine and water clarity sufficient to allow VC data to be collected concurrently with AC data showing turbine blade strike on tethered artificial fish targets. The second site was a turbid, debris-laden river with a 5 kW turbine where only AC data were collected due to high water turbidity. Data collection at the second site coincided with downstream Pacific salmon (Oncorhynchus spp.) smolt migration. Physical fish capture downstream of the turbine was performed with an incline plane trap (IPT) to provide context for the AC observations, by comparing fish catches. Discrimination between debris and fishes in the AC data was not possible, because active movement of fishes was not discernable. Nineteen fishes were released upstream of the turbine to provide known times of possible fish/turbine interactions, but detection was difficult to confirm in the AC data. ACs have been used extensively in past studies to count large migratory fish such as Pacific salmon, but their application for small fish targets has been limited. The results from these two field campaigns demonstrate the ability of ACs to detect targets in turbid water and observe blade strikes, as well as their limitations such as the difficulty of distinguishing small fishes from debris in a high-energy turbid river. Recommendations are presented for future applications associated with CEC device testing.