Producción primaria requerida para sustentar el desembarque de peces pelágicos en Chile

Abstract

The sustainability of the current landing of pelagic fish in Chile (over 7 millions tons in 1994 and 1995) is analyzed using as a focus the productive capacity of the Chilean coastal upwelling ecosystem in relation to the mean annual catch of pelagic fish during the period 1989-96. The primary production required (PPR) by the main pelagic species is estimated on the basis of the average catch, the trophic level of the resources and the ecotrophic efficiency of transfer. Furthermore, global indicators of the surplus production of these pelagic fisheries are analyzed using the relationship between the total catches and the fishing effort of the national fleet. Three geographic zones are considered: northern (18°20' S-29°15' S), central-northern (29°15' S-32°10' S) and central-southern (32°10' S-39°23' S). The assumption is made that the productive area of the upwelling system extends to 60 nautical miles from the coast in each region. The PPR reaches values of 137, 34 and 614 gCm-2 year-1 , respectively for the northern, central-northern and central-southern zones. The high PPR value in the central-southern zone is due to the landings of Trachurus symmetricus murphyi, which given its oceanic nature and highly migratory behaviour can feed in different kinds of ecosystems. Eliminating this species from the analysis, the total PPR for the remaining pelagic resources reaches 55 gCm-2 year-1 (17% of the primary production) and 207 gCm-2 year-1 by considering that T. s. murphyi has a partial access to the productivity of the coastal upwelling. The relationship between total catches and fishing effort indicates that the Chilean pelagic fishery has arrived near to the maximum sustainable level. Overall, these analysis suggest that the productive capacity of the Chilean coastal upwelling ecosystem limits the national catch of coastal pelagic fish. The average landing level observed during the period 1989-96 is sustainable only if the surplus production of T. s. murphyi is compatible with the intensity of their current exploitation by the industrial purse seine fleet of the central-southern zone.