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While juvenile white sharks (JWS) can display regional endothermy, the need to maintain internal temperatures within an energetically favorable range likely drives thermoregulatory movements to maximize growth and foraging efficiency. Many JWS from the northeastern Pacific population aggregate seasonally in nearshore nursery habitats throughout the Southern California Bight and historic data show that inter-seasonal movement patterns may be heavily dependent on ambient water temperature. However, the degree to which micro-scale (e.g., ~10 m²) water temperature heterogeneity influences JWS three-dimensional movement within nearshore aggregation sites is unknown. High-resolution temperature and passive acoustic-telemetry geo-positional data were used to quantify how temperature and vertical thermal stratification influenced JWS movement using several modeling approaches. JWS selected for water temperatures between 16 - 22°C and depths shallower than 2 m. Sharks occupied deeper waters during dawn and dusk periods, and their distance from the seafloor and spatial orientation of their depth distribution was significantly related to the thermal structure of the water column across the monitored area. Tagged sharks remained above a 16°C thermal threshold and altered their horizontal and vertical distributions accordingly. While high-resolution movement and environmental data provide improved predictability of microscale habitat use and distribution, other variables such as prey distribution, behavior, and competition would further improve habitat use models for this highly mobile species. [ABSTRACT FROM AUTHOR]

Abstract.--Ocean fishing piers are ubiquitous along the world's coastline, yet little research has examined how these structures can attract and retain fishes. Fishers routinely use these human-made structures as a [...]

Abstract.--Many batoid species will form aggregations while resting on the seafloor; however, the environmental variables that drive resting habitat selection behavior, and how it varies among species are not well [...]

No-take marine reserves have become a popular tool in fisheries management worldwide; ever, many aspects of their design, including optimal size and location, are still debated. This is due, in part to a lack of critical knowledge on behavior of many exploited marine organisms. Because a primary application of no-take marine reserves is to protect adult reproductive stock, which may serve to supply larvae and juveniles to adjacent unprotected areas, reserves must be large enough at minimum to encompass the daily movement patterns of adult fishes. Previous studies on home range sizes and site fidelity of kelp bass and sheephead in California marine reserves have suggested that habitat composition may influence the size and shape of home ranges, and that breaks in habitat may serve as natural barriers, restricting the home ranges of some fishes. Surprisingly, little is known about how habitat composition, quality and gradients may influence home range sizes and site fidelity of nearshore kelp bed fishes. Knowing fish-habitat relationships and how habitat edges affect fish movement will allow managers to site reserves knowledgeably with goals of optimizing “leaky” boundaries that allow for spillover into the fishery or “tight” boundaries that minimize movements of fish across the boundary.

Green sea turtles, Chelonia mydas, are known to inhabit populated and often urbanized areas. To understand turtle habitat use and behavior within these unique habitats, seven juvenile green turtles were fitted with acoustic transmitters (September 2012-August 2014), of which two transmitters included an accelerometer (AP transmitter). One individual fitted with an AP transmitter was tracked using a passive acoustic array in an urbanized river, the San Gabriel River, Long Beach, CA (33[degrees]45' N, 118[degrees]05' W). Three additional turtles in this river and three turtles (one with AP transmitter) in a restored estuary (33[degrees]44' N, 118[degrees]03' W) in southern California were actively tracked for two nonconsecutive 24-h periods. Those fitted with AP transmitters indicated that turtles were less active at night (0.58 [+ or -] 0.56 m/[s.sup.2] and 0.50 [+ or -] 0.63 m/[s.sup.2]) than during the day (0.86 [+ or -] 0.63 m/[s.sup.2] and 0.78 [+ or -] 0.60 m/[s.sup.2]) at both sites. Activity data and corresponding movements of the actively tracked turtle fitted with the AP transmitter were used to infer resting periods for other tracked individuals. Turtles rested near bridge pilings and runoff outflows in the river to potentially shelter from tidal flow. Turtles used significantly larger daily areas in the urbanized river (0.046 [+ or -] 0.023 [km.sup.2]) where resources may be patchier and less abundant, compared to turtles in the estuary (0.024 [+ or -] 0.012 [km.sup.2]) where large, dense eelgrass beds are present. Based on the habitat use and behaviors of green sea turtles, it appears that some green sea turtles are able to make use of both highly developed and restored habitats and likely benefit from certain aspects of development., Green sea turtles, Chelonia mydas, have been listed and protected in the United States under the Endangered Species Act (ESA) since 1978 (FWS andNMFS, 80 FR 15271). Through decades of [...]

Juvenile white sharks (JWS) of the Northeastern Pacific population are present in nearshore southern California waters and form mixed size class (~1.5–3 m) aggregations for weeks to months, often within 500 m of shore. These nearshore beach habitats are heavily used for human recreation (e.g., surfing, swimming, body boarding, wading, and standup paddleboarding) and the amount of spatio-temporal overlap between JWS and humans is currently unknown. Increases in human population and the Northeastern Pacific population of white sharks have raised concern over human beach safety. To determine spatio-temporal JWS-human overlap at various spatial scales (e.g., across the entire southern California coastline, across different distances from shore, and within specific beach locations), 26 beach locations across southern California were surveyed monthly resulting in 1644 aerial drone surveys between January 2019 to March 2021. Thirteen environmental variables were assessed to predict when spatio-temporal overlap between JWS and water users was highest. Coast-wide distribution of JWS was clumped, limiting human-shark co-occurrence to specific locations, with 1096 of 1204 JWS observations occurring at Carpinteria and Del Mar Beach locations. Nearshore distribution indicated JWS are often close enough to the wave break to interact with some water users (median = 101 m, range = 2–702 m), although JWS had the most spatial overlap with stand-up paddlers. Daily human-shark co-occurrence was 97% at beaches where JWS aggregations had formed, and human activity showed high spatial overlap at shark aggregation sites. Although there is higher seasonal human-shark spatio-temporal overlap where aggregations form in southern California, the number of unprovoked shark bites across southern California is extremely low. This study provides evidence that high human-shark spatio-temporal overlap does not lead to an increased bite frequency in southern California, and there are a number of possible explanations as to why JWS are not biting water users despite daily encounters. [ABSTRACT FROM AUTHOR]