[OANNES Foro] Schooling behaviour and environmental forcing in relation to anchoveta distribution: An analysis across multiple spatial scales

[raul sanchez]

Progress In Oceanography
Volume 79, Issues 2-4, October-December 2008, Pages 264-277 
The Northern Humboldt Current System: Ocean Dynamics, Ecosystem Processes, and Fisheries 
doi:10.1016/j.pocean.2008.10.018    

Schooling behaviour and environmental forcing in relation to anchoveta distribution: An analysis across multiple spatial scales 

Arnaud Bertranda, b, , , François Gerlottoa, b, Sophie Bertranda, b, c, Mariano Gutiérrezb, 1, Luis Alzab, Andres Chipollinib, Erich Díazb, Pepe Espinozab, Jesús Ledesmab, Roberto Quesquénb, Salvador Peraltillab and Francisco Chavezd

aIRD, CRH, Avenue Jean Monnet, BP 171, 34203 Sète Cedex, France

bInstituto del Mar del Perú, Esquina Gamarra y Gral. Valle s/n, Apartado 22, Callao, Lima, Peru

cUniversity of Washington, School of Fisheries, Box 355640, Seattle, WA 98195, USA

dMonterey Bay Aquarium Research Institute, 7700 Sandholdt Rd., Moss Landing, CA 95039, USA

Abstract
The Peruvian anchovy or anchoveta (Engraulis ringens) supports the highest worldwide fishery landings and varies in space and time over many scales. Here we present the first comprehensive sub-mesocale study of anchoveta distribution in relation to the environment. During November 2004, we conducted a behavioural ecology survey off central Peru and used a series of observational and sampling tools including SST and CO2 sensors, Niskin bottles, CTD probes, zooplankton sampling, stomach content analysis, echo-sounder, multibeam sonar, and bird observations. The sub-mesoscale survey areas were chosen from mesoscale acoustic surveys. A routine coast-wide (2000 km) acoustic survey performed just after the sub-mesoscale surveys, provided information at an even larger population scale. The availability of nearly concurrent sub-mesoscale, mesoscale and coast-wide information on anchoveta distribution allowed for a unique multi-scale synthesis. At the
 sub-mesoscale (100s m to km) physical processes (internal waves and frontogenesis) concentrated plankton into patches and determined anchoveta spatial distribution. At the mesoscale (10s km) location relative to the zone of active upwelling (and age of the upwelled water) and the depth of the oxycline had strong impacts on the anchoveta. Finally, over 100s km the size of the productive area, as defined by the upwelled cold coastal waters, was the determining factor. We propose a conceptual view of the relative importance of social behaviour and environmental (biotic and abiotic) processes on the spatial distribution of anchoveta. Our ecological space has two y-axis; one based on self-organization (social behaviour), and the other based on the environmental processes. At scales from the individual (10s cm), to the nucleus (m), social behaviour (e.g. the need to school) drives spatial organization. At scales larger than the school, environmental forces
 are the main driver of fish distribution. The conceptual ecosystem models presented in this paper may provide the final links needed to develop accurate forecasts of the spatial distribution of anchoveta over multiple scales.

Keywords: Fish schooling behaviour; Habitat suitability; Peruvian anchovy Engraulis ringens; Spatiotemporal distribution; Predator–prey relationships; Peru Humboldt Current system; Dissolved oxygen and partial pressure of CO2; Basin model framework

Saludos,

Raúl E. Sánchez Scaglioni