Data from: Hidden demographic impacts of fishing and environmental drivers of fecundity in a sea turtle population

Fisheries bycatch is a critical threat to sea turtle populations
worldwide, particularly because turtles are vulnerable to multiple gear
types. The Canary Current is an intensely fished region, yet there has
been no demographic assessment integrating bycatch and population
management information of the globally significant Cabo Verde loggerhead
turtle (Caretta caretta) population. Using Boa Vista island (Eastern Cabo
Verde) subpopulation data from capture-recapture and nest monitoring
(2013–2019), we evaluated population viability and estimated regional
bycatch rates (2016–2020) in longline, trawl, purse-seine, and artisanal
fisheries. We further evaluated current nesting trends in the context of
bycatch estimates, existing hatchery conservation measures, and
environmental (net primary productivity) variability in turtle foraging
grounds. We projected that current bycatch mortality rates would lead to
the near extinction of the Boa Vista subpopulation. Bycatch reduction in
longline fisheries and all fisheries combined would increase finite
population growth rate by 1.76% and 1.95%, respectively. Hatchery
conservation increased hatchling production and reduced extinction risk,
but alone it could not achieve population growth.  Short-term
increases in nest counts (2013–2021), putatively driven by temporary
increases in net primary productivity, may be masking ongoing long-term
population declines. When fecundity was linked to net primary
productivity, our hindcast models simultaneously predicted these opposing
long-term and short-term trends. Consequently, our results showed
conservation management must diversify from land-based management. The
masking effect we found has broad-reaching implications for monitoring sea
turtle populations worldwide, demonstrating the importance of directly
estimating adult survival and that nest counts might inadequately reflect
underlying population trends.