Predicting Extinction Vulnerability in Skates

Abstract

Abstract:Relatively few marine fishes have been assessed under World Conservation Union criteria, yet it is believed that marine fish extinction rates have been underestimated by one order of magnitude (McKinney 1999). Given the paucity of data required for traditional assessment methods, we explored the use of potential correlates of extinction vulnerability to prioritize species for conservation assessment. We focused on the world's 230 species of skates and rays (Rajidae) because they have been identified as one of the most vulnerable groups of marine fishes. We searched for all documented cases of local extinction and compiled a database of body size and latitudinal and depth ranges for all species for which data were available. We found that species that have disappeared from substantial parts of their ranges ( “locally extinct” ) have large body sizes compared with all other skates, but that latitudinal and depth ranges were similar to those of other species. The body size correlate may be due to higher mortality rates and correlations with life‐history parameters such as late age at maturity. We used the locally extinct species that had the smallest size or ranges as benchmarks to generate lists of other species that may be vulnerable. Body size generated the smallest species list (7), excluding the known local extinctions, compared with lists generated by size of latitudinal (150) or depth range (63). Body size was the only trait that correctly identified the known local extinctions, suggesting that it is more useful than range sizes for identifying potentially vulnerable fishes. This provides a simple, objective method of prioritizing species for further assessment, which complements direct methods that are more data‐intensive and time‐consuming.