This paper presents a method of investigating the dynamics of a biological population, using a technique of simulation with a digital electronic computer. Its purpose is to show an analysis of a simulated exploited population.

This paper presents an application of a technique of simulation with a digital computer in the analysis of the spatial distribution of populations. It is shown that this method is useful: 1) in the determination of the distributional pattern, 2) in testing the applicability of analytical models and indices of dispersion (aggregation), and 3) in the elaboration of the experimental design.

The population of goete, Cynoscion petranus (Ribeiro, 1915), commercial marine fish caught along the southern coast of Brazil (24ºS-26ºS) presented from 1959 to 1962: 1) One main spawning per year. 2) Absence of morphometric polymorphism according to the relationship "maximum-girth/total length". 3) Aggregated distribution. 4) Absence of migration parallel to the coast. 5) Recruitment rate ............................................................. 42% per year Natural mortality ............................................................. 57% per year Total mortality ................................................................ 44% per year 6) Mean size of the population ............................................ 5.10(6) individuals 7) Overfishing.

We determined the age of the commercial marine fish "pescada-foguete" (Macrodon ancylodon, Bloch 1801) caught by trawls along the southern coast of Brazil (28ºS-34ºS), from 1961 to 1963, by means of the annuli in otoliths (CHUGUNOVA, 1959). We correlated the mean total length (L) in centimetres with the age (t) in years by means of the BERTALANFFY expression adjusted by FORD-WALFORD method (BEVERTON & HOLT, 1957). The mean total length was correlated with the mean weight (W) in grams, by means of the expression W = aLb adjusted by least square method, after a logarithmic transformation. Results:

The "pescada-foguete" fish presented (1961-1964) migration along the southern coast of Brazil (from 28ºS to 34ºS), according to the following expression, adjusted by the least squares method: y = 30.2 + 1.7 cos 30 (x - 1.5) where: y - latitude with maximum production per unit effort (ºS) X = 1, % .... 12, months of the year

The correlation between the latitude where denser concentrations of the croaker (Micropogon furnieri) occurred and the month of the year were established in this paper. The unit effort production (kg/hour haul) was used as the concentration index and the hauls made within 30' were grouped in the immediate superior latitude. The croaker migrates along the Brazilian coast between 28º S and 33º S, according to the expression: y = 30.6 + 1.85 cos 30 (x - 2), where: y = latitude (ºS) x = 1, 2 .... 12 (months of the year)

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.

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.