Review of a Small-scale Pelagic Longline Fishery off Northeastern Brazil

The annual catches of four small longliners operating off northeast Brazil from 1983 to 1997 were examined across different areas and locations. The total catch comprised tunas (30%), sharks (54%), billfishes (12%), and other fish species (4%). Fishing strategy and annual composition of catches showed large spatial and temporal variabilities with the dominant catches alternating among yellowfin tuna, Thunnus albacares; gray sharks, Carcharhinus spp.; and blue shark, Prionace glauca. Catches of blue and gray sharks showed a significant interaction among seamounts, with gray sharks occurring in maximum abundance around those seamounts that had relatively deep summits and lowsloping depth profiles. Results are discussed in terms of the various factors that may have influenced distribution of effort. gan to operate from Natal (Fig. 1) using relatively small vessels to target tunas and other large pelagic species of fish. This fleet expanded throughout the following 10 years and by 1997 consisted of 10 boats ranging in size from about 16 to 26 m. As part of management regulations governing the present fishery, operators have been required to complete logsheets for each fishing trip. Information requested include location of fishing grounds, number of hooks used on the longline, time of setting and retrieving the gear, and composition of catches. In addition, at the end of fishing trips, biological data on the various species captured have routinely been collected by researchers. Although some of these data have been used in studies examining biological aspects of the main species, including their relative distribution and abundance (Hazin et al., 1990; 1994a), reproductive biology (Hazin et al., 1994b), and feeding habits (Hazin et al., 1994c), no studies have been done describing temporal and spatial variabilities in composition of catches. To provide a brief overview of the changes in fishing strategy and catches, including some analysis of relative abundance and distribution of the main species, our aims in this paper were to collate yearly catch data from four vessels that have operated in the fishery since 1983 and compare these across defined areas and locations. Material and Methods This study was done using data from the logsheets of four longliners, (Alfa, Argus, Rio Turi, and Soloncy Moura) operating off northeastern Brazil from 1983 to 1997 (Fig. 1). All vessels used similar configurations of Japanese-style multifilament longlines (Shapiro, 1950; Suzuki et al., 1977). Each longline consisted of a multifilament mainline (Fig. 2A) with secondary lines (Fig. 2B) attached in clusters of 6–7 (termed “baskets”) over approx. 360 m. Styrofoam bouys, each attached to a 25 m line were tied to the mainline after every cluster of hooks (Fig. 2A). The types of hooks used varied among 3 main brands (depending on availability) however, relative sizes remained similar throughout the period examined (Fig. 2C). The mean number of hooks (± SE) set per vessel per day was 975 ± 7. Fishing methods and operations were similar across the fleet with the mainline-set begining at about 0200 h and ending at dawn. The gear was then left to fish for about 6 h, before retrieval began at noon and ended at dusk. The primary bait was the Brazilian sardine, Sardinella brasiliensis, although some other species, including flying fish, Cypselurus cyanopterus, and squid, Loligo sp., were occasionally used. Due to different oceanographic and biological conditions (Paiva and Le Gall, 1975; Hazin1) and for the purposes of this study, the total area fished (Fig. 1) was divided into the following three subareas for analysis: 1 Hazin, F. H. V. 1993. Fisheries-oceanographical study on tunas, billfishes and sharks in the southwest equatorial Atlantic Ocean. D. Sc. Thesis, Tokyo Univ. Fish., 286 p.