Muestreo de desembarque de caballa (Scomber japonicus) en el puerto de Mar del Plata (38° S) y determinación de niveles de captura en el área El Rincón; período 1989-2003
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Chub mackerel caught by the commercial fleet in El Rincón (39°-41° 30’ S) and Mar del Plata (38° S) areas was analyzed. In 2001 and 2002 samples from El Rincón were obtained from landings or collected by scientific observers on board the commercial ships. Samples from Mar del Plata were acquired during the 2001-2002 and 2002-2003 fishing seasons, on board two vessels of the small purse-seine fleet. Landings were mostly adults and only a small fraction of juveniles was observed (< 5%). Length growth parameters from El Rincón samples were estimated, and length-weight and length-age relationships were fitted by Least Squares. The results were as follows: L(mm) = 538.4; k (years-1) = 0.122; t0 (years) = -4.92; Pt = 4*10-7 * Lt 3.536. Natural mortality was estimated at 0.30 and age limit at 10 years. The standardized catch per unit effort (CPUE) annual mean (kg h-1) for the 1990-2002 period was calculated by means of a General Linear Model which justified 41% of total variance. The most significant variables resulted to be the seasonal pattern of exploitation of the resource (month), and its pronounced concentration in the exploitation area (fishing position). Values of the standardized CPUE annual mean fluctuated with trends that were similar to those registered between 1993 and 2002. Due to fluctuations in the Chub mackerel abundance and the possible negative effect caused by the activity of large ships in El Rincón, a maximum annual catch of 13,000 t for 2003 is suggested for this area as a precautionary measure.