Abstract
AbstractThe Smooth Dogfish Mustelus canis is an abundant, small coastal shark occurring along the U.S. Atlantic coast. Despite being targeted by a directed fishery and having recently undergone a stock assessment that found the population neither overfished nor experiencing overfishing, little is known about the spatial and temporal distribution of this species. Here, we used catch data from the spring and fall Northeast Area Monitoring and Assessment Program's fishery‐independent trawl surveys conducted between 2007 and 2016 and various environmental factors to perform hierarchical Bayesian modeling as a first attempt to spatially predict adult Smooth Dogfish CPUE in U.S. northwest Atlantic Ocean waters by sex and season. Relevant environmental variables differed between both sexes and seasons. Male and female CPUEs were similarly associated with lower salinity and shallower depth in the spring. During fall, male CPUE was associated with sea surface temperature and bottom rugosity, and female CPUE was associated with chlorophyll‐a concentration, bottom rugosity, and year. Habitat modeling results predicted that areas of high male and female CPUEs would overlap during spring but strongly diverge during fall, when greater predicted CPUEs for males were distributed considerably farther north. These results suggest sexual segregation among Smooth Dogfish during fall, with the springtime overlap in distribution coinciding with the pupping and mating season in this population. This difference in distribution during fall may allow for a male‐only directed fishery for Smooth Dogfish in the northern extent of the species’ range in waters near southern New England and Georges Bank.
Highlights
Inhabiting mostly shallow and estuarine coastal waters, the Smooth Dogfish is considered a nocturnal bottom feeder, primarily consuming crustaceans, including crabs, shrimps, and lobsters, and more opportunistically feeding on molluscs, bony fishes, cephalopods, and polychaete worms (Gelsleichter et al 1999; Kiraly et al 2003; Castro 2011)
In 1999 the Smooth Dogfish was included on the list of shark species that were protected from finning and for which all landed sharks must have a fin-to-carcass-weight ratio of not more than 5%; in 2003, the species was further included on the list of species protected under the Shark Finning Prohibition Act (SFPA)
The results of the U.S Atlantic assessment indicated that the stock is likely neither overfished nor experiencing overfishing, the review panel recommended caution due to uncertainty in the catches as well as uncertainty associated with the stock–recruitment relationship that resulted from the analysis (SEDAR 2015c)
Summary
Inhabiting mostly shallow and estuarine coastal waters, the Smooth Dogfish is considered a nocturnal bottom feeder, primarily consuming crustaceans, including crabs, shrimps, and lobsters, and more opportunistically feeding on molluscs, bony fishes, cephalopods, and polychaete worms (Gelsleichter et al 1999; Kiraly et al 2003; Castro 2011). The Smooth Dogfish has not been of high economic value for the U.S Atlantic commercial shark fishery (though it is the second most abundant shark species in U.S Atlantic coastal waters after the Spiny Dogfish Squalus acanthias). The review panel’s recommendations included the need to increase efforts for monitoring and recording of various environmental variables (e.g., bottom water temperature and salinity) in fishery-independent surveys (SEDAR 2015a). This information may be used to enhance indices of relative abundance that serve as proxies for the CPUE, which is commonly used as the index in stock assessment modeling and in the process of determining stock abundance status. Despite the knowledge that many shark populations have been observed to be or are suspected to be characterized by the presence of sexual segregation (Pratt and Carrier 2001; Sims 2005; Wearmouth and Sims 2008; Mucientes et al 2009; Dell’Apa et al 2014), there is a paucity of studies that have investigated the spatiotemporal
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