Preliminary recovery of coastal sharks in the south‐east United States

Abstract

Relative abundance of many shark species in the Atlantic is assessed by compiling data from several independently conducted, but somewhat spatially limited surveys. Although these localized surveys annually sample the same populations, resulting trends in yearly indices often conflict with one another, thereby hindering interpretation of abundance patterns at broad spatial scales. We used delta‐lognormal generalized linear models (GLMs) to generate indices of abundance for seven Atlantic coastal shark species from six fishery‐independent surveys along the US east coast and Gulf of Mexico from 1975 to 2014. These indices were further analysed using dynamic factor analysis (DFA) to produce simplified, broad‐scale common trends in relative abundance over the entire sampled distribution. Effects of drivers including the North Atlantic Oscillation index, the Atlantic Multidecadal Oscillation index, annually averaged sea surface temperature and species landings were evaluated within the DFA model. The two decadal oscillations and species landings were shown to affect shark distribution along south‐east US coast. Estimated common trends of relative abundance for all large coastal shark species showed similar decreasing patterns into the early 1990s, periods of sustained low index values thereafter and recent indications of recovery. Small coastal shark species exhibited more regional variability in their estimated common trends, such that two common trends were required to adequately describe patterns in relative abundance throughout the Gulf of Mexico and Atlantic. Overall, all species’ (except the Gulf of Mexico blacknose shark) time series concluded with an increasing trend, suggestive of initial recovery from past exploitation.

Defining Sex-Specific Habitat Suitability for a Northern Gulf of Mexico Shark Assemblage

“…The most recent assessment for blacknose shark was unable to determine the status of the GoM stock (SEDAR, 2011); consequently, commercial retention of blacknose sharks in the GoM is currently prohibited. Despite preliminary signs of shark recovery as indicated by increasing population trends for GoM Atlantic sharpnose shark, the relative abundance of GoM blacknose shark is declining (Peterson et al, 2017). Yet, of the six species we examined, blacknose shark possesses the largest FIGURE 7 | Predicted relative abundance from BRT models for female (red) and male (blue) (A) blacktip shark and (B) sandbar shark during spring, summer and autumn.…”

Global priorities for conserving the evolutionary history of sharks, rays and chimaeras

“…The global scale of IUCN assessments belies regional and local variation in status due to variation in fishing pressure and strength of management 48 . MPAs are but one widely lauded tool for protecting chondrichthyans, but broad scale conservation and sustainable fisheries management have great potential when effectively enforced 40,42,49 . For example, Australia, Canada, New Zealand, and USA already have enforced fisheries and conservation management in place for many chondrichthyan species 42,50 19,20 .…”

Community interactions and density dependence in the southeast United States coastal shark complex

“…The LCS complex was found to recover more quickly from environmental or anthropogenic disturbances (i.e., faster resiliency and return rate). In general, these stability measures were extremely close in magnitude, likely reflecting that the species examined are migratory and avoid unfavorable environmental conditions (Peterson et al 2017), such that these environmental variables may have a limited effect on equilibrium conditions. Environmental insensitivity of the SCS complex was reflected in the smaller variance of the stationary distribution.…”