Resumo em Inglês:

A fishery research programme requires an accurate picture of the length distribution of the fish caught and landed. Each boat is considered a sampling unit. It is therefore necessary to know how to draw a sample from the fish landed in such a way as to give an accurate assessment of the length distribution of the boat's landing. This is the purpose of the present paper, which refers to the sampling of "pescada-foguete" (Macrodon ancylodon) caught by parejas of "Sociedade de Pesca Taiyo Ltda.", and landed on the fish market of Santos, State of São Paulo, Brazil. By courtesy of that firm two voyages were made during which observations on the length distribution of the fish caught were carried out. Independently, samples were taken of the fish landed from these voyages, after landing. In this way an evaluation of the sampling techniques used on the fish market was obtained. Due to the selection of the nets used, there is no rejection of "pescada-foguete" at sea and therefore the fish measured represent a boat's catch. Methods: 1 - Samples from the hauls were taken on board, at random, during two voyages, to find out if there is a significant difference in the length distributions between hauls on the same voyage. 2 - At the fish market three boxes of each size category: large - G, medium - M, and small - P, were measured: one (1) series at the beginning, the second (2) at the middle, and the third (3) at the end of the landing operation. The purpose was to see if there is a significant difference between the length distributions of each size category or if the same length distribution occurred in a given category during the entire process of landing. 3 - The grand mean, calculated according to the procedure and example given in Table VIII, for the sample quoted in item 2 above, was compared with that taken from the same vessel at sea. This shows whether the market sampling for length distribution differs significantly from that estimated from non-selected samples on the boat. The results were as follows: 1 - In the first voyage seven samples (Table I) were obtained from seven different hauls, and the means of the samples are plotted in Figure 2; the means of the second voyage (fifteen samples) drawn at random on the following trip, are plotted in Figure 3. The t test was applied for the comparison between the means and the results are shown in Tables II and III. The first three means show (Figure 2) a significant difference because at the beginning of the fishing operation several hauls were made at random to locate the shoals (Figure 1). The other four show no significant difference. The means of the second trip do not show, in general, a significant difference, probably due to the fact that the fishing was done at the same distance from the coast during the whole trip. For estimation of the variability of all samples together, analysis of variance was used (Table IV). The value of F is high in the first voyage, but not very high in the second. 2 - The difference between the mean length of the same size category taken at the beginning (1), at the middle (2), and at the end (3) of the landing was not highly significant (Tables V and VI). 3 - Table IX shows the comparison between the grand mean (see how it was computed in Table VIII) and the mean resulting from the gathering of samples obtained aboard the ship, in the first and in the second voyage. Those concerning the first trip do not show a significant difference; the same is true of two [(1) and (2)] from the second trip. The other (3) shows a significant difference because at the end of the landing some fish of bigger size than those normally considered as small were placed in the box of small fish measured. A percentage length frequency distribution of the raised market data and the boat samples (Figs. 4 and 5) shows practically no difference. Also, there is no significant difference between the samples obtained on board and those obtained on the fish market (grand mean for the two stratified samples of the first voyage, and for the three samples of the second one), as shown in Table X, i.e., the mean of two stratified samples taken at the fish market at the return from the first trip, when compared with the one obtained aboard, showed no significant difference. The same is evident with the three stratified samples obtained at the return from the second trip. The size distribution within a category is not the same for every landing (Tables VII and VIII). Therefore, from every landing a stratified sample must be drawn. Table V shows that two general means present no significant difference, but this is not so when compared with the third one. This suggests that more than one box is necessary to represent the catch of a pareja belonging to "Sociedade de Pesca Taiyo Ltda.". Table XI I shows, however, that the measurements of half a box of 25 kg, and the counting of the other half (to raise the total number of fish landed at each size category) are sufficient enough to represent the box. The most important conclusion is that a better representative sampling can be achieved by reducing the number of fish measured from each box, and increasing the number of boxes measured for fish. Thus the variance between boxes will be reduced and it will fall nearer to the variance within each box.

Resumo em Português:

Neste trabalho, adotou-se o método empregado por Lucas et al. (1954), Margetts (1957) e Beverton & Holt (1957), para o estudo da seletividade, produzida pelas malhas das redes da frota pesqueira de Santos, sobre as seguintes espécies: "Corvina" (Micropogon furnieri), "Pescada-foguete" (Macrodon ancylodon), "Goete" (Cynoscion petranus), "Tortinha" (Isopisthus parvipinnis), Cangauá" (Bairdiella ronchus), "Maria Luísa" (Paralonchurus brasiliensis) e "Oveva" (Larimus breviceps). O estudo baseou-se nas seguintes hipóteses: primeiramente, que a malha fosse completamente flexível, em segundo lugar, completamente rígida, com as proporções de 2:3 entre as diagonais e em terceiro lugar, que o peixe pudesse tomar secção transversal circular. Através de retas de regressão, foram estabelecidas correlações entre a malha, nas duas situações e o comprimento do peixe, com 50% de probabilidade de escape. Concluiu-se que os barcos brasileiros da frota, devido à malhagem pequena, capturam peixes de comprimento inferior ao aceito pelo mercado, produzindo depredação, o que não acontece com os barcos japoneses.

Resumo em Inglês:

In this paper the relationship between total length and girth (circumference) of seven species: "Corvina" (Micropogon furnieri), "Pescada-foguete" (Macrodon ancylodori), "Goete" (Cynoscion petranus), "Tortinha" (Isopisthus parvipinnis), "Cangaua" (Bairdiella ronchus), "Maria Luisa" ("Paralonchurus brasiliensis), and "Oveva" (Larimus breviceps), are expressed in the form of fitted regressions. Theoretical selection lengths assuming, at the one extreme, the mesh to be completely flexible, and at the other extreme to be rigid with axes of 2:3 are calculated. The fish is assumed to be able to adopt a circular cross section. If the fish is not circular but retains its normal form, the difference in the selection length is shown to be little different. The Brazilian commercial boats fishing from Santos are shown to use a mesh which has a very low selection point well below the size of fish which are acceptable on the fish market. The Japanese boats use a much larger mesh, which select fish of marketable size.

Resumo em Português:

Os dados estudados neste trabalho foram coletados desde agosto de 1958 até agosto de 1959, e provieram da área compreendida entre os paralelos 23ºS e 34ºS, para uma faixa de poucas milhas distante da costa brasileira. A distribuição dos comprimentos para o total de 10.521 peixes medidos no Entreposto de Pesca de Santos, durante o período já referido, mostrou um valor modal de 30,4 cm, e os limites de comprimentos foram de 16 até 70 cm. A mistura (categoria comercial que inclui várias espécies, englobando corvinas pequenas), representa 12,93% do total em número da corvina desembarcada, com valor modal de 20,4 cm, tendo por limites de comprimento 12 e 38 cm (distribuição viciada). Tanto as médias mensais de comprimentos, como os valores modais das curvas mensais de distribuição dos comprimentos mostram que a corvina cresce no período compreendido entre o outono e parte do inverno. No início do período aparece um valor modal baixo, correspondendo a uma queda brusca das médias mensais de comprimento, sugerindo que peixes de pequeno tamanho são recrutados para a pesca nessa época. O exame das escamas mostrou a existência de marcas, que possibilitaram a determinação da idade. Supondo-se que o crescimento das escamas e do peixe se faz obedecendo a uma relação linear, usou-se os métodos do "retro-cálculo" e de von Bertalanffy para a construção da curva de crescimento. Através das médias mensais de comprimento por grupo de anel determinou-se a periodicidade da formação do anel, que é anual, correspondendo a meados do verão até meados do outono, portanto, antes de abril, mês em que as médias de comprimentos possuem valores baixos. Para o total de corvinas desembarcadas verificou-se serem as classes de 2 e 3 anéis as que predominaram, com percentagens altas, seguidas das classes de 1 e 4 anéis. Na distribuição mensal observou-se que as classes de 2 e 3 anéis predominaram, alternando suas freqüências em alguns meses e que a partir do mês de abril de 1959 as classes de 0 e 1 anel são mais regulares e mostram percentagens relativamente altas. As relações comprimento-pêso, comprimento-perímetro, pêso-perímetro e o crescimento do peso e do perímetro foram tratadas matematicamente, tendo-se calculado os coeficientes de correlação das equações correspondentes.

Resumo em Inglês:

The purpose of this paper is to present the first results obtained on the length/frequency distribution, age and growth, and the relations length/weight, length/girth, and girth/weight, of Corvina (Micropogon furnieri = M. opercularis), a fish of the family Sciaenidae caught off the Brazilian coast. This work is part of a long term programme designed to assess the size of the fishable stocks, to suggest the proper management of these stocks, and to aid the fishing industry in their rational exploitation. The data were obtained at the fish market of Santos in the period from August 1958 to August 1959. They were obtained from an area which extends between the parallels 23º S and 34º S and a few miles off the Brazilian coast; the area exploited by the Santos fishing fleet (Fig. 1). The data, however, are insufficient to define all the biological parameters of the fish under consideration. Nevertheless, they are a beginning towards assessment of the marine resources of Brazil. The author does not try to draw final conclusions, but only to present the first results of the research under way. Corvina is landed at the fish market in two forms: 1) Corvina as such, and sold under that name, and this comprises the bulk of the landing; and 2) Corvina included in "mistura" (a market category composed of a number of different species). These fish are of a small size and may be up to 12.93% of the total landed by numbers. The Corvina landed as "mistura" suffers from a selection made by the fishermen and therefore it was difficult to obtain good sampling of the numbers of Corvina landed of the lower lenghts. For this reason little use has been made of the data referring to Corvina landed as "mistura". For the period of thirteen months the length range was from 16 to 70 cm, with a modal value of 30.4 cm for corvina. For corvina included in "mistura" the range was 12 to 38 cm, with a modal value of 20.4 cm (Tables IV and V, and Fig. 2). The monthly length distributions (Table IV and Fig. 3) show the main modal values shifting to the right. This shifting is more visible from April to August. From March on, the curves show two clear modes; they also show a class of small fish, with low modal values. By examining the values of Table V it can be seen that small fish included in "mistura" appear in the catches in great quantity at that period. The monthly mean lengths (Table VI and Fig. 4) fluctuate from month to month, in the period from the end of winter, spring and almost all summer (Southern Hemisphere), but there is an overall trend towards a lower mean length during this period. It is suggested that this period is a period of reduced growth. In the period which includes all autumn and part of the winter months the mean lengths show, at the beginning of the period, a sharp fall followed by rapid increase, and this is the period of growth. This, together with the results from the modal values, suggests that in March small fish are recruited to the fishery. The modal values in Table V show that the period of growth is from the end of summer through autumn and part of winter, or from the end of March until August, a similar result is obtained using mean length values. The examination of scales showed rings (Fig. 6) which, it was thought, could be used for age determination. After two independent readings of the scales of the corvina samples and the corvina included in "mistura", the mean length per group of rings and the standard error of the mean for each group was calculated (Tables VII and VIII). The standard error was low for all groups with 0 to 5 rings. The method of back calculation was used and the assumption made that the relation between scale size and total length was linear. No correaction factor was applied. Using these data a growth curve (Fig. 9, curve A) was constructed and von Bertalanffy's formula was used to express the results. Lt = 50.7 (1 - e -0.25 t - 0.14) It can be seen that there is rapid growth until the 3rd ring after which growth is less marked. Using the mean length per ring group (Tables VIII and IXb) and the modal values from the length distribution of all fish (p. 74) growth curves were also drawn (Fig. 9, curve B) and the equation of von Bertalanffy applied. In this manner two sets of curves were obtained. Curve A is based on the size of the fish at the formation of the ring (without correction for non linearity in the scale/length relationship) and curve B based on the total length for each ring group. The modal lengths are similar to the mean lengths per ring group and it can therefore be assumed that the modes represent ring groups or age groups. The mean lengths per ring group (Table X) for each month are shown in Figure 8 for the 2, 3 and 4 ring groups. It can be seen that there appears to be only one maximum and minimum during the period August to October of the following year, and the maximum in one group approximates to the minimum in the following group. The minimum occurs in April. The rings are therefore assumed to be formed annually sometime before April, in summer or beginning of autumn. Using the age sampling in the form of an age?length key, together with the total number of fish of each length landed, the number of fish at each age was calculated (Tables X and XI, and Fig. 10). It can be seen that the fish landed as "mistura" belong to the 0 ring group. The dominant ring group are the 2 and 3 ring group and after these the fish with 1 or 4 rings on the scales. The monthly age distribution (Fig. 11) shows one period when the 2 and 3 ring group predominate, either one or the other being dominant. This lasts from August 1958 to March 1959. The other period from April to August 1959 has a higher frequency of fish with 0 and 1 ring on the scale. This later period is the period of recruitment into the fishery. The same can be seen from the data taken from "mistura" (Table XI). The equations used to express the relation between age and weight, age and girth of the fish, length and weight, length and girth, and girth and weight are as follows: Age/weight: W = 3,304.8 (1 - e -0.12 t - 0.37) 3.12 (Fig. 12) Age/girth: P = 39.28 (1 - e -0.12 t - 0.37) - 1.00 (Fig. 13) Length/weight: W = 0.008 L 3.12 (Fig. 14) Length/girth: P = 0.62 L - 1.00 (Fig. 15) Girth/weight: W = 0.008 <img width=32 height=32 id="_x0000_i1027" src="../../../../../../img/revistas/bioce/v12n1/a04form01.jpg" align=absmiddle> (Fig. 16)