Valuable shellfish species in the by-catch of shrimp fishery in southern Brazil : spatial and temporal patterns

The pink-shrimp (Penaeus paulensis and P. brasiliensis) is the most important shellfish resource in southern Brazil. Highly unselective, the pink-shrimp trawl fishery produces an abundant and diverse by-catch that includes valuable and poorly known shellfish species. Landings of pink-shrimp trawlers in the Itajaf harbor (26°S, southern Brazil) were monitored regularly from May 1995 to March 1997, to study temporal and spatial patterns of the catches of pink-shrimp and the squids, Loligo plei and L. sanpaulensis; the scallop, Pecten ziczac; the deep-sea lobster, Metanephrops rubellus; and the slipper lobster, Scyllarides depressus. Shrimp trawlers operated year round except for a period between March and part of May, when fishing is closed to protect shrimp recruitment periods. Trawling took place from southern Sao Paulo coast (23°S) to northern Rio Grande do Sul (30° S) at depths ranging from 14 to 120 m concentrating seasonally in six main fishing areas according to patterns of penaeid shrimp distribution. Such seasonal displacement determined the patterns of incidental exploitation of all shellfish species and has originated: (a) a directed scallop fisheries, whose uncontrolled effort lead to its collapse; and (b) an emerging L. plei fishery stimulated by their massive seasonal presence in by-catch. The slipper lobster and the deep-sea lobster are potential resources whose fishery development depend on favourable markets and incentives. Adequate biological and ecological information on these shellfish populations is urgently required to prevent future collapses of promising shellfish fisheries.