Évaluation du potentiel de rétablissement de la sous-population de tortue luth (Dermochelys coriacea) de l'Atlantique Nord-Ouest

Abstract

In 2017, Leatherback Sea Turtles were re-listed under the Species at Risk Act (SARA) as two populations (Atlantic and Pacific), both Endangered. Leatherback Sea Turtles in Atlantic Canada belong to the Northwest Atlantic (NWA) subpopulation, which is listed as Endangered through the International Union for Conservation of Nature (IUCN) Red List. A Recovery Potential Assessment according to current guidance was not completed for the Leatherback Sea Turtle prior to its listing under SARA. • The NWA Leatherback subpopulation is in decline, with a recent index abundance estimate of 20,659 mature nesting females at consistently monitored beaches and a regional nesting abundance decrease of 9.32% (CI: -12.9% to -5.57%) annually from 2008–2017. • In the Northwest Atlantic, Leatherbacks use Canadian waters seasonally in the summer months. High use areas of core foraging habitat have been identified throughout Atlantic Canadian waters. • There is no existing evidence to suggest that Leatherbacks are habitat limited in Atlantic Canadian waters. • In Atlantic Canada, Leatherbacks do not come ashore and are broadly distributed through coastal and offshore waters. As such, there is no current method to accurately determine the number of turtles using these waters. Efforts are underway to correct for biases in estimating abundance of various species in aerial survey areas, which may produce a minimum estimate of the number of Leatherbacks using these waters. • Throughout their range, Leatherbacks encounter a variety of natural and anthropogenic threats, with incidental fishery interactions identified as a leading cause of mortality within this subpopulation. • While interactions do occur between Leatherbacks and fisheries in Atlantic Canadian waters, available data suggest that fishery interactions occur most frequently outside of Canadian waters, especially in waters adjacent to some high-density nesting beaches. • At-sea mortality in Canada, and elsewhere, may be reduced through adaptive fishing methods (i.e., ropeless fishing gear, time-area closures, reduction of ghost gear). • A spatial-temporal analysis of the overlap between fishery and Leatherback distributions should occur prior to the establishment of any new fisheries or potential changes in the seasonality or spatial extent of existing fisheries are considered. • There is some scope for harm to Leatherbacks in Atlantic Canadian waters; however, human-induced threats should be reduced to the fullest extent possible throughout the Northwest Atlantic and regular assessments should be conducted to evaluate the impact of Canadian fisheries on this subpopulation. • A recovery goal is to increase the number of Leatherbacks in the broader NWA subpopulation by maintaining or increasing the number of adult and subadult Leatherbacks using Atlantic Canadian waters. Progress towards this goal may be achieved by reducing human-induced interactions and mortalities in Atlantic Canada, supporting Leatherback persistent use of Canadian waters as core foraging habitat, and continuing efforts to monitor Leatherback spatial and temporal distributions. • The NWA Leatherback subpopulation is not currently on course to meet the recovery goal. International collaboration (through activities such as nesting beach monitoring and protection, increased survey efforts throughout foraging habitats, and reduction of fishery interactions throughout the NWA Leatherback range) is necessary for the recovery of this subpopulation.