Catch, bycatch, and indices of population status of blue shark (Prionace glauca

• Main Author: Steven E. Campana
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2004
• Subjects: Petersen; North Atlantic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.622.1120; http://nefsc.noaa.gov/nefsc/Narragansett/sharks/refpdfs/Campana et al 2005.pdf

The nominal catch of blue sharks in the Canadian Atlantic grossly underestimates the actual catch mortality; the sum of landed catch and by-catch mortality in the Canadian Atlantic has averaged about 1000 t annually since 1986. Several indices of population health suggest that blue shark abundance has declined, and mortality has increased, in the past decade. Median size in the catch has declined, as have standardized catch rates from both commercial longline fisheries and recreational shark tournaments. Catch curve analysis suggests a very high fishing mortality on the population. However, Petersen analysis of tag recaptures indicates that the exploitation rate in Canadian waters was <1%. Two independent approximations of total North Atlantic blue shark catch mortality suggest North Atlantic catches of more than 100,000 t and catch mortalities of 26,000-37,000 t. Blue sharks have low commercial value and are discarded in great numbers by commercial pelagic fisheries. Life table analysis indicates that blue shark populations are both productive and resilient compared to other shark species, a fact which may help explain their persistence in the face of a high overall catch mortality and a decline in relative abundance. Nevertheless, steps to reduce their mortality appear to be warranted. RÉSUMÉ