Informing Conservation Strategies for the Endangered Atlantic Sturgeon Using Acoustic Telemetry and Multi‐state Mark–recapture Models

Summary Causes of non‐intentional mortality may pose conservation challenges for long‐lived, migratory species. Recovery attempts for Atlantic sturgeon Acipenser oxyrinchus oxyrinchus populations in the USA have mainly involved closures of targeted fishing, but bycatch mortality from fisheries targeting other species remains a significant obstacle. Natural and fishing mortality levels are highly uncertain and difficult to separate, but quantifying spatial and temporal patterns of movements and total mortality can directly inform management policies regarding fishing activity that affects sturgeon. Subadult sturgeon were tagged with acoustic transmitters to track their movements with receivers deployed in active fishing areas within the New York Bight. Multi‐state mark–recapture models were used to quantify seasonal patterns in survival and migration while accounting for detection probabilities of tagged fish. Movement patterns of sturgeon were highly variable among seasons along the Long Island Coast, with frequent south‐westward movements during the increase in sea surface temperature in spring. North‐eastward movements were most pronounced during winter, when temperatures were lowest. Sturgeon were less common along coastal Long Island during summer. Larger fish transitioned among strata more frequently, but also had slightly lower survival than smaller fish, which may result from selectivity for larger individuals caught incidentally in bottom trawl or gillnet fisheries. Weekly total mortality rates, including both natural and fishing mortality, averaged 0·24%. Highest weekly survival rates were observed during periods of decreasing sea surface temperature in autumn and winter, while lowest survival was observed during periods of increasing temperature in spring and summer while sturgeon migrated through areas of known bycatch. Policy implications. Movement and survival patterns of Atlantic sturgeon suggest that late spring, coinciding with periods of ocean bycatch in fisheries along the coast of Long Island, is a particularly sensitive period for Atlantic sturgeon. Conservation efforts could target these few weeks using real‐time observations from acoustic telemetry and remote sensing technologies to implement in‐season fishery closures, thereby reducing incidental mortality of Atlantic sturgeon. Such bycatch management measures would aid in recovery attempts of a long‐lived, migratory population with endangered status.