ESTRUCTURA Y DINAMICA DE LA PESQUERIA DEL CALAMAR (Loligo plei) EN SANTA CATARINA, SUR DE BRASIL
by J. A. A. PEREZ
Centro de Ciências Tecnológicas da Terra e do Mar (CTTMar), Universidade do Vale do Itajaí (UNIVALI).
Cx. Postal 360, Itajaí, Santa Catarina, CEP 88.302-202, Brasil (e-mail: angel@mbox1.univali.rct-sc.br)
in which squid was most likely to be the main target.
Results and discussion
The Fishery. The squid L. plei is caught offshore by double rig trawlers, licensed for shrimp and/or fish, and by pair trawlers. Inshore squid is caught incidentally in the multiespecific fish traps and by the directed hand jigging fishery.
Inshore and offshore squid fisheries occur from December to March. Catch peaks may occur in all months with a clear inter-annual variability.
Offshore catches concentrate off the northern coast, in sandy bottoms between the 20 and 45 m isobaths. Fish traps and hand jigging operate near the coast, the latter being normally conducted around coastal islands (Perez et al.1997, Perez et al.1999).
Directed vs. Incidental catch. The pattern of squid targeting in the summer trawling fishery was assessed by correlating the number of fishing trips with total catch in each summer. Pair trawlers presented the strongest linear correlation (r2=0.89, n=7) and were clearly the main squid trawlers. In both shrimp and fish double rig trawlers the same correlation was considerably weaker (r2=0.21 and 0.24 respectively) and probably affected by a mixture of fishing targets.
When only landings above 500kg were considered, linear correlation improved substantially, indicating that a certain number of vessels do target squid during the summer.
Squid biomass vs. Fishing Dynamics.The fishing season occurs within a 17 weeks period. Shrimp trawlers are the first vessels to land significant squid catches every summer, which in turn probably stimulate other trawlers to join the fishery later in the season.
Summer squid catches are sustained by a single cohort of spawning individuals that become available in the trawling areas in December and disappear in March-April. Peaks of squid biomass during each season, assessed by the variation of standardized CPUE, showed considerable inter-annual variation. When weeks of biomass (CPUE) peaks during seven seasons
were compared to the weeks when 50% of the total catches had been taken by each fleet, it was observed that (a) whereas shrimp trawler catches generally preceded biomass peaks, (b) fish and pair trawlers normally reached their 50% catch after these peaks. In recent years, however, all fleets tended to adjust their effort to periods of highest abundance which suggested that this seasonal fishery is going through a period of development and improvement (Fig. 1).
Fig. 1. Relationship between weeks of biomass peaks and weeks of 50% cumulative catch of shrimp trawlers, fish trawlers and pair trawlers, from 1990 to 1997.
Seminario Final Proyecto INIDEP - JICA, 1999 167 Catch peaks of the inshore fishery have always
approached biomass peaks, probably because squid fishing at the communities occur only when squid is abundant and easily available (Perez et al. 1999).
Acknowledgements
I am grateful to Edilson José Branco (CEPSUL /IBAMA) for providing both inshore and offshore catch records.
References
IBAMA 1994. Informe sobre os desembarques controlados de pescados no estado de Santa Catarina, nos anos de 1988 a 1992. Ministério do Meio Ambiente, Brasília, DF, 100 p.
Perez, J. A. A. & Pezzuto, P.R. 1998. Valuable shellfish in the by-catch of the shrimp fishery off southern Brazil: spatial and temporal patterns. J. Shell. Res. 16(2):527-532
Perez, J. A. A., Schettini, C. A. F., Buratto, J. R.
& Machado, M. 1997. A pesca de lulas (Mollusca: Cephalopoda) na Ilha do Arvoredo, SC: Características e relações ecológicas, verão de 1996. Not. Téc. FACIMAR 1:9-22 Perez, J. A. A., Lucato, S. H. B., Andrade, H. A.,
Pezzuto, P. R. & Rodrigues-Ribeiro, M. 1998.
Metodologia de Amostragem Biológico-Populacional dos Desembarques no Porto Pesqueiro de Itajaí, SC). Not. Téc. Facimar. 2:
93-108.
Perez, J. A. A., Martins, R. S. & Buratto, J. R.
1999. Estrutura e dinâmica da pesca artesanal de lulas em Santa Catarina. Anais do XI Congresso Brasileiro de Engenharia de Pesca.
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Sparre, P. & Venema, S. C. 1992. Introduction to tropical fish stock assessment. Part 1-Manual.
FAO Fish. Tech. Pap. 306/1. Ver. 1:376p.
Seminario Final Proyecto INIDEP - JICA, 1999 169
Introducción
La falta de controles de las medidas de regulación pesquera o la carencia de las mismas facilita la sobrepesca.
La sobrepesca afecta a la biomasa del efectivo pesquero produciendo necesariamente una disminución de la misma. La sobrepesca afecta también a la estructura de edades poblacional, modificándola por la disminución de los ejemplares de edades mayores.
Cambios en la estructura de edades y la disminución de biomasa pueden cambiar la densidad de peces.
Aunque permanentemente los barcos pesqueros tratan de aumentar su eficiencia, las medidas de regulación pueden restringir este cambio. Cuando existe sobrepesca, los barcos pesqueros tratan de adaptarse a los cambios biológicos por la disminución del recurso con el
objetivo de mantener su captura. En este contexto aumenta también la competencia entre los pescadores y en la fase terminal (hacia el colapso) aparecen conflictos sociales y económicos que agravan la competencia.
Bajo este escenario de explotación (descontrolada), se comentará el efecto del mismo sobre la captura por unidad de esfuerzo de flota pesquera y su utilización para la calibración de modelos de evaluación y la normalización del esfuerzo pesquero.
El poder de pesca
El poder de pesca de un barco se define como:
res la captura por unidad de esfuerzo y unidad de densidad, de donde