No evidence of cryptic bycatch causing New Zealand sea lion population decline

Abstract

In PNAS, Meyer et al. (1) analyze whether exclusion devices in trawl nets contributed to New Zealand sea lion (NZSL; Phocarctos hookeri ) population decline at the Auckland Islands. We refute the primary conclusion from their correlative assessment: that annual pup production changes (as a measure of population size) were primarily driven by cryptic bycatch of adults in sub-Antarctic trawl fisheries. We also contest their interpretation that sea lion exclusion devices (SLEDs), used throughout the Auckland Islands squid trawl fishery since 2004, “…can obscure rather than alleviate fishery impacts on marine megafauna” (1). Meyer et al. (1) compare annual pup estimates with factors that could impact NZSL populations, reporting that when the fisheries interaction rate (IR; NZSL interactions per trawl) was high in one year, … [↵][1]1To whom correspondence should be addressed. Email: sheryl.hamilton{at}utas.edu.au. [1]: #xref-corresp-1-1