Journal
DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY
Volume 95, Issue -, Pages 103-112Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.dsr2.2013.04.003
Keywords
Food web modeling; Stock dynamics; Top-down and bottom-up forcing; Jumbo squid predation; Central Chile
Categories
Funding
- Chilean Agency of Research and Technology (CONICYT) [FONDECyT 11110545]
- COPAS-SA Program at Universidad de Concepcion
- Fisheries Research Fund (FIP) of Chile [FIP 2005-38, FIP 2009-22]
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We analyzed recent food web and fish stock changes in the central Chile marine ecosystem, comparing the roles of jumbo squid (Dosidicus gigas) as predator, the environment, and fishing. To accomplish this we used food web modeling and the Ecopath with Ecosim software (EWE). The principal fish stocks have experienced wide decadal fluctuations in the past 30 years, including stock collapses of horse mackerel (Trachurus murphyi) and hake (Merluccius gayi), and there was a large influx of jumbo squid during the mid-2000s. We used two EwE models representing the food web off central Chile to test the hypothesis that predation by jumbo squid has been significant in explaining the dynamics of the main fishing resources and other species in the study area. Results indicate that predation by jumbo squid on fish stocks is lower than that of other predators (e.g. hake) and the fishery. Long-term fluctuations (1978 2004) in the biomass of the main fish stocks (as well as other components of the food web) seem to be related to fishing and to variation in primary production, rather than to predation by jumbo squid alone. Jumbo squid seems to play a role as predator rather than prey in the system, but its impacts are low when compared with the impacts of other predators and fishing. Therefore, we conclude that jumbo squid predation on its prey was not the primary force behind the collapse of important fish stocks off central Chile. Future efforts should be directed to better understanding factors that trigger sudden increases in jumbo squid abundance off central Chile, as well as modeling its trophic impacts. (C) 2013 Elsevier Ltd. All rights reserved.
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