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Baker L.L.,8 West Hemming St | Baker L.L.,Dalhousie University | Wiff R.,University of Concepcion | Quiroz J.C.,Institute Fomento Pesquero IFOP | And 5 more authors.
Environmental Biology of Fishes | Year: 2014

The pink cusk-eel (Genypterus blacodes), a benthic-demersal fish confined to the southern hemisphere, supports an important commercial fishery in Chile where it is exploited over an extensive geographic area. Although the fishery was originally divided into a northern (41o28′-47o00′S) and southern (47o00′-57o00′S) zone for the purposes of fisheries management, recent studies have reported significant differences in life history parameters between these zones. Individuals from the southern zone reached larger asymptotic sizes and possessed higher survival rates compared to the northern zone. We estimate and compare the gonadosomatic index (GSI), shape of the maturity ogive, and length at 50 % maturity (L 50%) of female G. blacodes between management zones and across time using biological data collected from the industrial fleet between 1985 and 2009. Females in the northern zone had higher monthly mean GSI than females in the southern zone. Our analyses also revealed L 50% to be significantly higher in the southern zone than in the northern zone from 1985 to 2009. The significant differences in life-history traits between fishery management zones agree with the trade-offs predicted by Charnov's life history theory. Together these results provide additional support for the hypothesis that two separate stocks exist and suggest that females from the northern zone have developed a life-history strategy, which favours early maturation and a proportionally greater investment in reproduction than females from the southern zone. © 2013 Springer Science+Business Media Dordrecht. Source

Claramunt G.,Arturo Prat University | Cubillos L.A.,University of Concepcion | Castro L.,University of Concepcion | Hernandez C.,Institute Fomento Pesquero | Arteaga M.,Institute Investigacion Pesquera
Fisheries Research | Year: 2014

In Chile, anchovy (Engraulis ringens) and common sardine (Strangomera bentincki) are two commercially important small pelagic fish. In southern Chile (32-41° S), both species coexist and inhabit the coastal zone. In northern Chile (18-25°. S), only anchovy is present in the coastal zone. The determine onset, peak, end, and duration of the spawning periods in these small pelagic fish are key factors in population studies and of great interest for fisheries management. The objective of this study is to determine the temporal trends of spawning in these two species. A quantitative method was developed to obtain objective indicators of the spawning periods and the method is a useful tool for comparative studies between populations as well as to study the relationship of spawning periods with other demographic variables affected by fishing or environmental variability. Peak spawning in the three populations was consistent through time but showed changes in the duration of the maximum reproductive period. Anchovy and common sardine of the southern zone show synchrony and a shortening of the duration of spawning periods, probably in response to environmental fluctuations. Anchovy in northern Chile have shown an increase in duration from 1986 that is coincidental with the regime shift reported for the Humboldt Current Ecosystem in the mid-1980s. © 2013 Elsevier B.V. Source

Garces-Vargas J.,Austral University of Chile | Ruiz M.,Austral University of Chile | Pardo L.M.,Austral University of Chile | Nunez S.,Institute Investigacion Pesquera | Perez-Santos I.,University of Concepcion
Latin American Journal of Aquatic Research | Year: 2013

The area between 37° and 41°S of the southeastern Pacific coast, have a great number of microtidal (tidal range less than 2 m) estuaries. One of the most important estuaries in these latitudes is the Valdivia River estuary, whose thermal and haline structure is poorly known. Thus, this work, through hydrographic measurements of temperature and salinity taken during an annual seasonal cycle and the analysis of the main forcings (tide, river flow, wind and solar radiation) explain the variability and its changes in vertical stratification. The analysis of the the thermohaline structure of the water column revealed that the estuary varied seasonally behaving like a salt-wedge estuary in winter and spring due to a higher flow of tributaries. However, in summer and autumn behaved as partially mixed due the lower river flow. In winter and spring the water column showed a temperature inversion which was associated with a large surface heat loss and subsurface advection of warm waters from the adjacent ocean to into the estuary that is not mixed with the surface due to intense stratification by salinity. The change in the estuarine salt-wedge regime to partially mixed according to the season and the presence of thermal inversion seasonal are necessary hydrographic features to implement conservation efforts of vulnerable habitat into the zone (nursery areas of juvenile species), and use of this system for aquaculture activities and marine resources management. Source

Wiff R.,Institute Fomento Pesquero | Quiroz J.C.,Institute Fomento Pesquero | Gatica C.,Institute Investigacion Pesquera | Contreras F.,Institute Fomento Pesquero | And 2 more authors.
Latin American Journal of Aquatic Research | Year: 2012

Alfonsino (Beryx splendens) is a species associated with seamounts, with an important fishery in Juan Fernandez archipelago, Chile (33°40′S, 79°00′W). Since 2004, this resource has been managed by catch quotas estimated from stock assessment models. The alfonsino model involves high levels of uncertainty for several reasons including a lack of knowledge of aspects of the population dynamics and poorly informative time-series that feed the proposed evaluation models. This work evaluated three hypotheses regarding population dynamics and their influence on the main state variables (biomass, recruitment) of the model using age-structured and dynamic biomass models. The hypotheses corresponded to de-recruitment of older individuals, non-linearity between standardized catch per unit effort, and population abundance as well as variations of the relative importance of length structures. According to the results, the depletion of the spawning biomass between 1998 and 2008 varied between 9 and 56%, depending on the combination of hypotheses used in the model. This indicates that state variables in alfonsino are not robust to the available information; rather, they depend strongly on the hypothesis of population dynamics. The discussion is focused on interpreting the causes of the changes in the state variables in light of a conceptual model for population dynamics in alfonsino and which pieces of information would be necessary to reduce the associated uncertainty. Source

Porobic J.,University of Concepcion | Parada C.,Institute Investigacion Pesquera | Parada C.,University of Concepcion | Ernst B.,University of Concepcion | And 2 more authors.
Latin American Journal of Aquatic Research | Year: 2012

Located approximately 360 nm off the coast of Chile there is a disjoint realm of two small oceanic islands systems, the Juan Fernández and the Desventuradas archipelago. Currently the local economy of the islands is almost exclusively supported by the harvest and trade of marine resources, focusing mainly on the exploitation of the rock lobster (Jasus frontalis). This endemic species is distributed in both archipelagos, forming a metapopulation, whose population structure and dynamic is modulated by oceanographic forcing, especially during its extended planktonic larval phase. The population structure and the conection-retention within and between islands was assessed, based on the use of coupled biophysical model (the hidrodynamics model OFES and an individual-based model of J. frontalis). The analysis of the hydrodynamic model predictions showed the presence of mesoscale structures associated with the islands systems. The simulation results indicated significant levels of connectivity-retention within and between island systems showing also a strong interannual variation of these. Biophysical modeling results indicated that recruitment varibility associated with the Juan Fernández archipelago depends mainly on larvae originated within this system, which as well will contribute with recruits to the Desventuradas archipelago. The sensitivity analysis of the biophysical model to identify the potential biophysical forcing of the dependent variables of the model (e.g. connectivity-retention index), resulted in that temporal and spatial patterns reproductive larval stage duration and season (year) are highly significant factors. Finally, a metapopulation structure for J. frontalis, with a high level of connectivity in the archipelago of Juan Fernandez and a considerable amount of larvae in the Desventuradas islands is proposed. These fluxes are determined mainly by the coupling between prevailing biological and oceanographic factors. Source

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