School typology and 3d dynamics: Study of the behavioural mechanisms allowing adaptations of collective structure to environmental changes

• Francois Gerlotto ^[2] ; Mariano Gutierrez ^[1] ; Sophie Bertrand ^[2]
  1. [1] Marine Research Institute

     Marine Research Institute

     Islandia

     
  2. [2] IRD (Research Institute for the Development)
• Localización: Gayana, ISSN-e 0717-6538, ISSN 0717-652X, Vol. 68, Nº. 2, 2004, págs. 224-233
• Idioma: inglés
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• Resumen

  • Being the collective interface with the environment and the exploitation, schools and their typology represent an important life history trait of gregarious fish. Changes in the characteristics of the environment sensu largo induce changes in the school typology, which can be used as indicator of stock adaptive patterns. In order to understand the interactions between school structure and environment patterns, a first step consists in studying the school internal structure and the functioning of fish aggregation inside it and in its surroundings. The paper describes the spatial morphology and dynamics changes in Peruvian Anchovy (Engraulis ringens) schools in Peru using multibeam sonar observation on a station. Different cases of school types are extracted from a data base of around 200 recordings: from small circular well individualized schools to large aggregation surrounded by scattered targets. The internal structure of the aggregations is described at a 10 cm definition scale. The shape and dynamics of internal structures (nuclei) are described. The school edges are measured in shape and dynamics, and the relationship between the school and the fish surrounding the school are measured, using geostatistics and fractal dimensions approaches