Resumo
This paper demonstrates results obtained in studies of the size and age of first sexual maturity for some of the more important commercial species landed at Santos, and gives some information about destruction of immature fish caused by Brazilian and foreign vessels fishing from Santos. Figures 1A, 1B, 1C and 1D indicates the length at which 50% of the fish are immature (virgins) and 50% are mature, that is, the mean length at first sexual maturity. For the sardine, it occurs at 17 cm, in the second year; for "pescada-foguete" (weak fish) at 26 cm and "corvina" (with-mouth drum) at 28 cm, both in the third year; and for "goete" (another weak fish), for which there are as yet no age data, at 18 cm. The slopes of the curves suggest that "pescada-foguete" and "goete" mature in a interval of length classes briefer than do the other two. The percentage of immatures landed by Brazilian vessels and sold as identified species is high for sardine, "percada-foguete" and "corvina", but low for "goete". Although the role of small parejas is small in the landings of the other species, it is considerable for "goete" (Table II). With the exception of sardines, the other species are landed as "mistura" (mixed fish) by the Brazilian fishermen. Within this market category, it may be noted that almost all of the "pescada-foguete" and "corvina" are immature, although this is not true for "goete" (Table III and Fig. 3). The numbers of fish of the three species landed mixed by small parejas is lower than for other vessels, but more individuals of the three species by weight are landed by small parejas in comparison with other vessels. Foreign boats land large amounts of "pescada-foguete" and less of "corvina". It may be seen that the percentage of immature fish remained practically constant for "pescada-foguete" but "corvina" shows a slight increase (Table IV, Fig. 4). The fish landed by the foreign boats are sorted for size, and it may be noted that "pescada-foguete" is landed almost entirely in the medium category, "corvina" as medium in 1958, but small in the latter two years The yield of the foreign boats, compared to the Brazilian one, shows an increase during the period under study in the quantities of "pescada-foguete" and a decrease for "corvina". However, the percentage of immatures landed increased for both species. Part of the catch is discarded at sea by the Brazilian fishermen, and all of the discarded fish, so far as the three main species are concerned, are immature. No sardines are discarded. The data for small parejas, all Brazilian, show a high percentage of immatures in relation to the total caught, both landed and discarded (Table VII, Fig. 7). On the other hand, the foreign boats, using a much larger mesh (68 mm), do not find it necessary to discard fish, and also, as may be seen by comparing Tables IV and VII, the percentage of immatures caught is much lower. It is evident that small fish caught and discarded are of no commercial value, while those landed yield little profit because of their small size. On the other hand, it is possible that large destruction of immature fish may be prejudicial to the fishery, both because they are not spared to grow to larger and more valuable sizes and because they are lost to the stocks as reproducers. The problem posed here might be solved by an increase in the mesh size of the Brazilian vessels, giving small fish a chance to escape without very much effect on the overall yield. Fifty percent points for these species have been calculated as: "pescada-foguete"........................... 70 mm "corvina"........................................ 95 mm "goete".......................................... 55 mm
Sobre a primeira maturação sexual e destruição de peixes imaturos
A. E. A. de M. Vazzoler
Instituto Oceanográfico da Universidade de São Paulo. Membro do Grupo de Pesquisas sôbre a Pesca Marítima (G.P.P.M.)
SUMMARY
This paper demonstrates results obtained in studies of the size and age of first sexual maturity for some of the more important commercial species landed at Santos, and gives some information about destruction of immature fish caused by Brazilian and foreign vessels fishing from Santos.
Figures 1A, 1B, 1C and 1D indicates the length at which 50% of the fish are immature (virgins) and 50% are mature, that is, the mean length at first sexual maturity. For the sardine, it occurs at 17 cm, in the second year; for "pescada-foguete" (weak fish) at 26 cm and "corvina" (with-mouth drum) at 28 cm, both in the third year; and for "goete" (another weak fish), for which there are as yet no age data, at 18 cm. The slopes of the curves suggest that "pescada-foguete" and "goete" mature in a interval of length classes briefer than do the other two.
The percentage of immatures landed by Brazilian vessels and sold as identified species is high for sardine, "percada-foguete" and "corvina", but low for "goete". Although the role of small parejas is small in the landings of the other species, it is considerable for "goete" (Table II).
With the exception of sardines, the other species are landed as "mistura" (mixed fish) by the Brazilian fishermen. Within this market category, it may be noted that almost all of the "pescada-foguete" and "corvina" are immature, although this is not true for "goete" (Table III and Fig. 3). The numbers of fish of the three species landed mixed by small parejas is lower than for other vessels, but more individuals of the three species by weight are landed by small parejas in comparison with other vessels.
Foreign boats land large amounts of "pescada-foguete" and less of "corvina". It may be seen that the percentage of immature fish remained practically constant for "pescada-foguete" but "corvina" shows a slight increase (Table IV, Fig. 4). The fish landed by the foreign boats are sorted for size, and it may be noted that "pescada-foguete" is landed almost entirely in the medium category, "corvina" as medium in 1958, but small in the latter two years
The yield of the foreign boats, compared to the Brazilian one, shows an increase during the period under study in the quantities of "pescada-foguete" and a decrease for "corvina". However, the percentage of immatures landed increased for both species.
Part of the catch is discarded at sea by the Brazilian fishermen, and all of the discarded fish, so far as the three main species are concerned, are immature. No sardines are discarded. The data for small parejas, all Brazilian, show a high percentage of immatures in relation to the total caught, both landed and discarded (Table VII, Fig. 7).
On the other hand, the foreign boats, using a much larger mesh (68 mm), do not find it necessary to discard fish, and also, as may be seen by comparing Tables IV and VII, the percentage of immatures caught is much lower.
It is evident that small fish caught and discarded are of no commercial value, while those landed yield little profit because of their small size. On the other hand, it is possible that large destruction of immature fish may be prejudicial to the fishery, both because they are not spared to grow to larger and more valuable sizes and because they are lost to the stocks as reproducers.
The problem posed here might be solved by an increase in the mesh size of the Brazilian vessels, giving small fish a chance to escape without very much effect on the overall yield. Fifty percent points for these species have been calculated as:
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VI - AGRADECIMENTOS
A autora agradece a orientação prestada por Mr. Ian Dennis Richardson, técnico da "Food and Agriculture Organization of the United Nations" e a todos os elementos do Grupo de Pesquisas sobre a Pesca Marítima, que colaboraram na execução dêste trabalho.
VII - BIBLIOGRAFIA
(Recebido em 6/6/61)
Publ. nº 161 do Inst. Ocean. da USP.
Contr. nº 13 do G.P.P.M.
- BRAGA, A. S. 1962. Métodos de compilação e computação de dados estatísticos de desembarque de pescado no porto de Santos. Bol. Inst. Ocean., vol. XII, n.ş 2, p. 39-64.
- LARA, F. J. S. 1951. A study of the life history of Macrodon ancylodon (Bloch & Schneider), a sciaenid fish occurring on the coast of southern Brazil. An. Acad. Bras. Ci., vol. 23, n.ş 3, p. 291-322.
- MOREIRA, P. S. Quantidade dos peixes rejeitados pela frota comercial de Santos e observações sobre a seletividade de malhas de 54 mm. (Em preparação).
- NOMURA, H. 1960. Considerações sobre amostragem de peixes marinhos (I). Bol. Inst. Ocean., vol. XI, n.ş 1, p. 99-120.
- RICHARDSON, I. D. & SANTOS, E. P. Note on the selectivity of meshes used by the Santos fishing fleet. Bol. Inst. Ocean., vol. XII, n.ş 1, p. 33-52, figs. tabs.
- RICHARDSON, I. D., VAZZOLER, G., FARIA, A. & MORAES, M. N. 1959. Report on sardine investigations in Brazil. FAO, Rome, v + 7 p., figs. tabs. (Experience paper, n.ş 13).
- VAZZOLER, G. 1962. Sôbre a biologia da corvina da costa sul do Brasil. Bol Inst. Ocean., vol. XII, n.ş 1, p. 53-102, figs. tabs.
Datas de Publicação
-
Publicação nesta coleção
14 Jun 2012 -
Data do Fascículo
1962
Histórico
-
Recebido
06 Jun 1961
