Atlantoraja castelnaui, Spotback Skate

Abstract

The Spotback Skate (Atlantoraja castelnaui) is a medium-sized (to 147 cm total length) skate that occurs in the Southwest Atlantic from Rio de Janeiro, Brazil, to Buenos Aires, Argentina. It inhabits the continental shelf and upper slope from inshore to 300 m depth. It is captured in intense and largely unmanaged demersal trawl fisheries throughout its geographic range. Two lines of evidence indicate a population reduction. First, in Santa Catarina State, Brazil, catch-per-unit-effort (CPUE) declined by an estimated 54% between 1974 and 1981. Second, a 75% decline in CPUE was estimated from 1994 to 1999 in Rio Grande do Sul, Brazil. Both declines are consistent with a population reduction of >99% over three generation lengths (48 years). This large skate has a slow life history, and many skates with similar characteristics have undergone severe population reductions and face increased extinction risk. It is highly susceptible to exploitation and does not have any refuge from fishing at depth. Overall, due to declining abundance from intense and largely unmanaged fishing through most of its range combined with its large size and presumed late age-at-maturity (and therefore high sensitivity to fishing pressure), it is suspected that the Spotback Skate has undergone a population reduction of >80% over the past three generation lengths (48 years), and it is assessed as Critically Endangered A2bd.