Journal Article

Diel vertical behaviour, predator–prey relationships, and occupation of space by jack mackerel (<i>Trachurus murphyi</i>) off Chile

Arnaud Bertrand, Maria Angela Barbieri, Jose Córdova, Carola Hernández, Fabián Gómez and Francisco Leiva

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 61, issue 7, pages 1105-1112
Published in print January 2004 | ISSN: 1054-3139
Published online January 2004 | e-ISSN: 1095-9289 | DOI: http://dx.doi.org/10.1016/j.icesjms.2004.06.010
Diel vertical behaviour, predator–prey relationships, and occupation of space by jack mackerel (Trachurus murphyi) off Chile

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In the southeastern Pacific, jack mackerel (Trachurus murphyi, Carangidae) is a heavily exploited pelagic species, and its presence in Chilean waters in autumn and winter is assumed to be mainly due to an inshore feeding migration. Predator–prey relationships are known to depend on the spatial and temporal scale of observation, but they can also be strongly affected by factors such as diel vertical migration. In studying the case of jack mackerel in detail, we used data from three acoustic surveys carried out in central Chile in 1997, 1998, and 1999. In terms of spatial occupation, jack mackerel behaviour is “atypical” behaviour, i.e. more aggregated during the night than during the day. The patterns we observed can be related to their nocturnal active foraging behaviour. Diel feeding behaviour is therefore a key factor in the aggregating behaviour of jack mackerel and its vulnerability to the purse-seine fishery that targets these nocturnal aggregations. This particular fish diel feeding behaviour also affected predator–prey relationships in relation to the spatial scale. Positive correlations at a “small” spatial scale (<7–25 km) were observed during the night when jack mackerel foraged, but not during the day. Finally, we show that prey biomass was lower where jack mackerel were abundant, which could indicate a jack mackerel top–down control on prey communities.

Keywords: aggregating behaviour; jack mackerel; predator–prey relationships; spatial patterns; vertical diel behaviour

Journal Article.  4604 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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