Incidental mortality of franciscana (<i>Pontoporia blainvillei</i>) in the artisanal fishery of Praia Grande, São Paulo State, Brazil

Abstract

The artisanal fishery in Praia Grande, Sao Paulo State, southeastern Brazil, was monitored between August 1998 and June 2001 through interviews with fishermen and onboard observations. The objective was to describe the fleet, the gear and the fishing activities, and to monitor the bycatch of small cetaceans. The Praia Grande fishing community has 20 fishermen who operate five aluminum and one wooden open boat. Seven types of gillnet and one beach seine net are used. Nets are made of nylon monofilament; net length and height range from 60-1800m and 1.5-10m, respectively. Mesh sizes vary from 7-30cm. Each type of net is set up according to target species and weather conditions. Fish of the families Sciaenidae, Carangidae, Carcharhinidae, Trichiuridae and Ariidae are the main species captured. The incidental mortality of 31 franciscanas was recorded. Thirteen specimens were collected: 8 males (106-122cm) and 5 females (71-134cm). Captures took place in depths of up to 20m and along 31km of the coast. Catch per unit of effort for the period July 1999-June 2001 indicated a higher mortality in autumn and in gillnets with 14cm stretched mesh size ('malha 14') Three franciscanas were captured and released alive from beach seine nets. Several fishing communities with similar operational methods along the southeastern coast of Brazil remain unmonitored. This suggests that franciscana mortality may be substantial on a regional basis and emphasizes the urgency of systematic monitoring.