Año 2001, Número 14: 37-56.

Año 2001, Número 14: 37-56.

Wöhler, O.C.; Cordo, H.D.; Hansen, J.E.; Cassia, M.C. 2001. Análisis secuencial de la población de polaca (Micromesistius australis) en el período 1987-1997, ajustado con valores de rendimiento por unidad de esfuerzo de pesqueros comerciales.
Rev. Invest. Desarr. Pesq., 14: 37-56.
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The current status of southern blue whiting stock is described. A single, closed fish population is assumed to inhabit the SW Atlantic. Based on catch data corresponding to years 1987-1997, a sequential analysis on the stock is carried out (Cohort Analysis). Within an adaptative conceptual framework, catch per unit of effort data from commercial vessels are used to fit the model. Two commercial fleets are used in the fitting, i.e. polish vessels (1987-1994) and argentine surimi factory vessels (1991-1997). Results indicate that both total stock biomass and spawning stock biomass would have declined. Total biomass would have decreased from a maximum close to 1.4 million tons in 1990 down to 0.5 million tons in 1997 whereas the current spawning stock biomass would be 30% below the virgin spawning stock biomass. Recruitment also showed a decreasing trend to become extremely poor by the last part of the period. That seems to be the main cause of the stock biomass decrease although the exploitation rate is relatively high (0.60) and the current fishing mortality (0.22) is above the biological reference points (F30%=0.20) and much higher than the one considered as management objective (F0.1= 0.14). Simulation trials were performed to project the future evolution of stock and catches under three different exploitation levels (no fishing; fishing under F0.1; fishing under F1997). Whatever the exploitation level, if recruitment maintained its current status, the stock would suffer a sharp decrease to stabilize at very low abundance levels. In the short term, projections forecast a remarkable decrease of catches for 1998 that, even at the effort level exerted at present, would be over 73 thousand tons. Considering the current status of the stock, a series of measures to be applied in the short term are suggested. Such measures include a 35% reduction of the effort exerted in 1997 to limit fishing mortality to the F0.1= 0.14 reference point and promotion of parallel actions by Argentina and the United Kingdom to achieve the recovery of the resource.