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We conducted monthly fishery-independent sampling using scientific gillnets and longlines at two seagrass shoals and surrounding soft-bottom habitat in the northeast Gulf of Mexico. Using non-metric multidimensional scaling, we explored the effects of abiotic variables on temporal patterns of fish community structure, analyzed temporal patterns using permutational multivariate analysis of variance, and tested for cyclicity in community structure. Additionally, we used generalized additive models to explore the effects of environmental variables on immigration and emigration phases of dominant taxa. We found strong seasonality and cyclicity in assemblages captured by both gear types, with depauperate winter communities and diverse assemblages in warmer month. Our results suggest that temperature may determine the timing of immigration and duration of the residency period of dominant taxa, but photoperiod may cue immigration and emigration in adults when the purpose of those migrations includes predicable reproductive functions (e.g., parturition). We found evidence of partial migration in juvenile life stages of some coastal sharks and hypothesize that rising temperatures due to climate change may have variable effects on residency patterns over ontogeny. Key words: community ecology, marine fishes, migration, seasonality, Introduction Knowledge of species habitat use and movement patterns is important for effective fisheries management and conservation. Migrations structure populations (Frisk et al. 2014; Chapman et al. 2015; Secor 2015), [...]

Fisheries-independent data on the diversity, relative abundance, and demographic structure of poorly studied, threatened oceanic sharks are absent from much of the western North Atlantic Ocean, where multiple oceanic shark species have experienced significant population declines. Resource-limited management approaches require the identification of critical habitats or aggregation sites worthy of protection and enforcement. Data were collected on oceanic sharks using pelagic longline surveys, targeted baiting, and opportunistic encounters in oligotrophic open-ocean habitats of north-eastern Exuma Sound (NES), The Bahamas. The oceanic epipelagic shark community was also characterized using targeted baiting off Columbus Point, Cat Island (CI), a seamount north of San Salvador (SSSM), and the northwestern tip of Mayaguana. Pelagic longline surveys suggested that the relative abundance of sharks at NES was low (shark catch-per-unit-effort: 0.0007 sharks hook−1 h−1; 2.3 sharks per 1000 hooks). Silky sharks Carcharhinus falciformis, particularly juveniles (134 ± 39 cm stretched total length; mean ± SD STL), were the most common. Targeted baiting suggested oceanic whitetip sharks C. longimanus were abundant at CI, where large adults (245 ± 23 cm STL), most of which were females (83.8%, n = 98 of 117) that were gravid (65.7%; n = 46 of 70 assessed for pregnancy), dominated the aggregation. Many (20.5–26.5%, n = 24–31 of 117 depending on assumptions regarding tag loss) were recaptured or resighted at CI for up to five years. Silky sharks dominated catches at SSSM. Oceanic sharks, particularly adults, were sometimes caught or observed alongside short-finned pilot whales Globicephala macrorhynchus or tunas. Although The Bahamas offers threatened oceanic sharks refuge from fishing across its entire jurisdiction, these data suggest that some fixed features, including sites such as CI and potentially SSSM, are important aggregation sites with high regional conservation value and should be prioritized by fisheries managers and enforcement officials. [ABSTRACT FROM AUTHOR]

This study describes growth and reproductive characteristics of a facultative elasmobranch symbiont, Echeneis naucrates. Females grew slower but achieved a larger size than males (growth coefficient, K = 0.25 and 0.38 year−1, and mean maximum size, L∞ = 603 and 477 mm, respectively). Mean relative batch fecundity was 39.5 (s.d. = 13.1). Gonadosomatic indices peaked in July and August for males and females, respectively, with histology evidence of readiness to spawn or active spawning in August. Host‐symbiont length ratios increased linearly with sharksucker length (y = 0.0402 + 0.0003x, adjusted R2 = 0.56). [ABSTRACT FROM AUTHOR]