Chilean jack mackerel (Trachurus murphyi) is a highly migratory pelagic species that inhabits the Southern Pacific Ocean, constituting the most important fishery for Chile. This species exhibits an onshore migration during the summer related to coastal food availability, and an offshore migration towards reproductive oceanic areas (beyond Chilean EEZ) in early spring. During the spawning peaks (November) of 1998, 1999, 2000 and 2001, jack mackerel eggs were collected from four systematic surveys using 8-10 fishing vessels, deployed in the spawning area (76-92 W) off central Chile. Spatial distribution of eggs was modeled by geostatistical techniques. Environmental information including SST, wind, sea level anomalies and chlorophyll-a, as well as SST gradients, turbulence and currents were calculated. Exploratory results suggest a higher egg density related to warmer waters (16-19 C), moderate winds (4-8 m s-1) and low currents (< 15 cm s-1) as well as SST gradients (< 0.3 C 10 km-1). Statistical analysis developed with the purpose of providing evidence of habitat-species association, reveal a significant relationship (p<0.05) between egg density and both SST and wind magnitude. The spatial coupling between eggs and environmental data was accomplished by using the spatial Empirical Orthogonal Functions method (EOF), showing that high amplitudes of the first mode were spatially coherent with high density of eggs, warm waters and low magnitudes of wind, suggesting a bio-physical coupling among these variables in the jack mackerel spawning area

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-2year-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-2year-1 (17% of the primary production) and 207 gCm-2year-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

Se analiza la sustentabilidad de los niveles de desembarque actuales de peces pelágicos en Chile (sobre 7 millones de ton en 1994 y 1995), utilizando como enfoque la capacidad productiva del sistema de surgencia costera de Chile en relación con el desembarque anual promedio de peces pelágicos durante el período 1989-96. Se estima la producción primaria requerida (PPR) por los principales recursos de peces pelágicos explotados sobre la base de las capturas promedio, el nivel trófico de las especies y la eficiencia de transferencia ecotrófica. Además, se analizan indicadores globales del excedente de producción de estas pesquerías a través de la relación existente entre las capturas totales y el esfuerzo de pesca de la flota nacional. Se consideran tres zonas geográficas: norte (18°20'S-29°15'S), centro-norte (29°15'S-32°10'S), y centro-sur (32°10'S-39°23'S). Se asume que el área productiva de la zona costera se extiende hasta 60 millas náuticas fuera de la costa en cada región. La PPR alcanza valores de 137, 34 y 614 gCm-2año-1 para las zonas norte, centro-norte y centro-sur, respectivamente. El alto valor para la zona centro-sur se debe a los desembarques de Trachurus symmetricus murphyi que, por su naturaleza oceánica y comportamiento migratorio, puede acceder a la producción de otros ecosistemas. Al eliminar este recurso del análisis, la PPR para los restantes recursos pelágicos alcanza a 55 gCm-2año-1 a nivel nacional (17% de la producción primaria) y a 207 gCm-2año-1 si se considera que T. s. murphyi accede parcialmente a la productividad del ecosistema de surgencia. Un análisis de la relación entre las capturas totales y el esfuerzo de pesca indica que la pesquería nacional de peces pelágicos parece haber llegado a un nivel muy cercano al máximo sustentable. En su conjunto, estos análisis sugieren que la capacidad productiva del ecosistema de surgencia costera frente a Chile limita el desembarque nacional de peces pelágicos costeros. El nivel de desembarque promedio observado en el período 1989-96 es sustentable solamente si los excedentes productivos de T. s. murphyi son compatibles con la intensidad de su explotación actual por parte de la flota industrial de cerco de la zona centro-sur

The hydrographical conditions founded in Port Foster (Deception Island) and Chile Bay (Greenwich Island) both belong to the South Shetlands Islands group, Antarctic Peninsula, has been described. This survey has been carried out from the Chilean Navy Oceanographic vessel "YELCHO" in January 1978. An stratification in the area closed with the Antarctic surface waters has been observed. The temperature ranged between -1,60 º C to 1,30º C in Port Foster and 0,46ºC to 1,70ºC in Chile Bay; the salinity ranged between 33.80 ‰ to 34,24‰ in Port Foster and 33,61‰ to 34 ‰ in Chile Bay; the dissolved oxygen varied between 3,47 to 7,02 ml O2/l in both area. The characteristic density (Sigma t) of Antarctic Surface waters in the area, i.e., 26,92 and 27,58 has been observed.