Muestreo bioestadístico de pescado en el puerto de Mar del Plata. Anchoíta (Engraulis anchoita). Período 1986-1990.
Autor: Jorge E. Hansen.
Contribución INIDEP 996
Hansen, J.E. 1997. Muestreo bioestadístico de pescado en el puerto de Mar del Plata. Anchoíta (Engraulis anchoita). Período 1986-1990. INIDEP Informe Técnico 15, 1-24. Disponible en: http://hdl.handle.net/1834/5794.
Biostatistical fish sampling at the Mar del Plata port. Anchovy (Engraulis anchoita). 1986-1990 period. This paper deals with the commercial landings of bonaerensis anchovy at the Port of Mar del Plata (Buenos Aires province,Argentina), during the years 1986 to 1990. The mean catch was 15,501t per year. A total of 59 fish samples were taken for total length distributions (N=20164), and 24 sub-samples (N=2370) were analyzed to record individual data (length, weight, sex, sexual stage, age fromotoliths reading). The numer of fish per kg ranged between 28 and 53(mean=34.6). The mean size was 156.63 mm, and the most abundant fish in the landings were those being 3 and 2 years old, as it was also recorded during the period 1980-1985. Ordinary length-weight relationships by season were fitted, and the results were as follows:1) Autumn-Winter: W=8.5* 10-7* L3.392; 2) Spring-Summer: W=7.6* 10-6* L2.972. The von Bertalanffy Growth Function in length was fitted by using the methods of Allen (1966 and 1969) and Gaschütz et al.(1980). The last method was also used to fit the VBGF in weight. The number of ‘young of the year’ fish, as estimated by cohort analysis,has shown two levels: the first one (years 1980 to 1984) was three times the later. There is no sure explanation for the recruitment decreasing occurring since 1985. Predictive Virtual Population Analysis (VPA) (Thompson Bell, 1934) was used to explore the possibilities for the fishery yields to raise significativelly. The most reasonable way would be get by increasing the explotation rate over the 1 and 2 year old fish, which are assumed to be underfished at present, and also slightly over the eldest ones. The highest yield forecasted, under the assumption of at least 80 percent marketable catches,was 170,000t/year. Of course, that change in the present fishing pattern should not be made suddenly, in order to avoid the risk of failures in recruitment. The mortality rate M, as estimated by the method of Pauly (1980) ranged between 1.06 and 1.14 (T°C=14-16°C).The estimates for the total mortality rate Z by plotting logarithms of numbers against are age ranged between 0.94 and 1.80; it issuggested that a value of Z=1.47 could be a good approximation. No significant differences were detected insize-at-50 percent maturity between males and females. The between join value was estimated at 102.9 mm of total length (C.I.95 percent between 98.2and 107.7 mm). Over a half of the fish are mature when they are one year old.