Population growth of an endangered pinniped—the New Zealand sea lion (Phocarctos hookeri)—is limited more by high pup mortality than fisheries bycatch

Population growth of the endangered New Zealand sea lion (Phocarctos hookeri) on Campbell Island is primarily constrained by high pup mortality, not fisheries bycatch. A precautionary Potential Biological Removal (PBR) analysis revealed that current bycatch levels—even with a strong male bias (98%)—remain below sustainability thresholds, particularly after mitigation measures were implemented. Population Viability Analysis (PVA) modeling further supported this, indicating that reducing pup mortality, such as through ramp installations in wallows to prevent drowning, could significantly boost population growth. While long-term research is needed for more precise demographic data, the study underscores the critical need for ongoing conservation efforts focused on pup survival and bycatch mitigation, alongside robust observer coverage to ensure accurate annual estimates.

Hamilton, S., & Baker, G. B. (2019). Population growth of an endangered pinniped—the New Zealand sea lion (Phocarctos hookeri)—is limited more by high pup mortality than fisheries bycatch. ICES Journal of Marine Science, 76(6), 1794–1806. https://doi.org/10.1093/icesjms/fsz039