Post-release survival of juvenile Loggerhead Sea Turtles (Caretta caretta) incidentally hooked by Atlantic Canadian pelagic longline gear

Abstract

Estimating post-release survival is essential to understand how bycatch may impact sea turtle populations. Pelagic longline gear is the only documented source of anthropogenic harm and mortality to Loggerhead Sea Turtles in Atlantic Canadian waters. Mortality affecting juvenile Loggerhead Sea Turtles in Atlantic Canadian waters may ultimately translate to population-level impacts for the Loggerhead Sea Turtle population in the northwest Atlantic. Pop-up satellite archival tags (PSATs) were attached to 62 juvenile Loggerhead Sea Turtles incidentally hooked by Atlantic Canadian pelagic longline gear (2012–2018) to estimate associated post-release survival. Analysis of diving behaviour, ocean temperature, and ambient light level was used to assign fates to hooked Loggerhead Sea Turtles. Application of the Kaplan-Meier estimator with right censoring indicated that the annual probability of an individual hooked Loggerhead surviving post-release was 87.7%. There was no significant difference in probability of survival between shallow-hooked and deep-hooked Loggerhead Sea Turtles. PSATs are valuable tools to investigate post-release survival of a variety of marine animals, however, there are some limitations associated with tag performance and acquisition of tag data via satellite.