Diagnóstico dos recursos pesqueiros marinhos, Cynoscion jamaicensis, Macrodon ancylodon e Micropogonias furnieri (perciformes: sciaenidae), da região sudeste-sul do Brasil entre as latitudes 23° e 28° 40'S

Abstract

The Sciaenid fish species Cynoscion jamaicensis (Jamaica weakfish), Macrodon ancylodon (king-weakfish) and Micropogonias furnieri (whitemouth croaker) are marine fishing resources traditionally exploited off Southeastern and Southern regions of Brazil. Their importance was verified in the time series of the extractive fisheries production of Brazil. So, they were selected to have many of their fisheries biology aspects re-evaluated by REVIZEE Programme - Programme of Assessment of the Sustainable Potentiality of Living Resources in the Exclusive Economic Zone off Southeastern Coast of Brazil (23° to 28° 40 S). In this context the Fisheries Institute of the Secretary of Agriculture and Supply (IP) performed biological and biometrical samplings, disposed statistical data of extractive production and the diagnosis results concerning to these species in the State of São Paulo. After a General Introduction which places the reference landmarks on the issue, three similarly structured diagnosis on each of the concerned species are presented. They were formatted as scientific articles which may slightly differ from each other in the fisheries description or in the methods used to describe life cycle previously defined by REVIZEE. Biological and biometrical data collected from 1993 to 2003 were used to characterize life cycle. The marine extractive production was described by using the available fisheries time series and those published by IBAMA and IP. Additional information on the fishing effort associated to the catches landed in the State of São Paulo was also provided by IP through the System of Data Bank Management for Statistical Control of the Marine Fisheries Production ProPesq®. This information was useful to verify the level of fisheries performance. These articles aim at characterizing the stocks exploitation status considering: geographical distribution; catch evolution; length structure and length-weight relationship; growth; mortality and survival rates; and reproduction. Among the three species, king weakfish belonging to the Southeastern stock lacked information on reproductive biology which is detailed in the fourth chapter. After the four articles Final Considerations summarizes the diagnosis and presents management recommendations, in agreement with the results presented in the Executive Report of REVIZEE Programme, which is the official final document published by the Programme facing the commitments which Brazil assumed with the international community when ratified the United Nations Convention on the Law of the Sea. Jamaica weakfish is one of the main demersal resources exploited in the Southeastern region. In the last 20 years, its production reached a peak at 5,000 t in 1998, which decreased to 2,800 t in 2005 (reduction: 44 %). The State of São Paulo received a little more than half the total catch, mostly from pair trawlers. This fleet has shown yield trend since 1996, which accompanies the landed catch. Both sexes reach gonadal maturity at 193.1 mm total length within 2.5 years; they can live up to 14 years, with 389.57 mm maximum theoretical length; total mortality was estimated as Z=1.24 ano-1 (M=0.54 ano-1; F=0.70 ano-1), corresponding to a 0,56 exploitation rate, which indicates the stock is overexploited. These results point out that fishing effort on this species must not increase in order to keep catch on a sustainable level. The king weakfish production and yield presented decreasing trend, which was chiefly observed in the last 10 years. Its mortality rate increased, associated to the exploitation rate (E=0.58), higher than 0.5; the length at first maturity (L50=284.5 mm) shortened between 5% and 10% of the maximum theoretical length value (L∞=506.59 mm). All this pack of information is enough to characterize the Southeastern stock of king weakfish as overexploited. Even though, one can infer this stock responses positively to effort decrease based on the signs of possible yield recovery which were observed in the late decade of 1990. The decrease of fishing effort can be even more efficient for stock recovery if it is associated to the protection of the area from 23°S and 25°S, and between 18 m and 28 m deep and from december to april, which is the intensive reproduction period. Whitemouth croaker is the main demersal fishing resource at Southeastern and Southern regions. It occupies the second rank among the fish landed in the State of São Paulo and it is caught by boats using different kinds of fishing gears. The Southeastern stock was intensely exploited in the 1960 and 1970 decades but it showed signs of recovery after a reduction of fishing effort. However, in the last 10 years, once again whitemouth croaker has been excessively caught, what has pulled the yield down. Most of that is due to many fishing fleets, which did not have whitemouth croaker as the main target, having aimed their effort to this species. The average length of whitemouth croaker landed in São Paulo is around 290 mm, nearly the same length at first maturity for females (Lt50=292.24 mm). The maximum theoretical length is 389.57 mm. The total mortality rate is 0.59 and the exploitation rate is 0.63, what points out that stock is overexploited and that fishing effort control is needed to keep capture sustainable.