© 2006 International Council for the Exploration of the Sea
The effect of coastal topography on the spatial structure of anchovy and sardine
a Hellenic Centre of Marine Research, PO Box 2214, 710 03 Iraklion, Crete, Greece
b University of Patras, Department of Biology, 26500 Patra, Greece
*Correspondence to M. Giannoulaki: tel: +30 810 337831; fax: +30 810 337820. e-mail: marianna{at}her.hcmr.gr.
Acoustic-survey data from 1995 to 2004 (six acoustic surveys in summer and two in winter) in the Aegean and Ionian Seas (eastern Mediterranean Sea) were analysed to investigate the spatial organization of European anchovy and European sardine populations. The potential effect of certain topographic characteristics (e.g. area, bottom depth, and the degree of land enclosure) on the spatial structure of the fish was studied in different geographic subareas (i.e. how topography affects the organization of fish into clusters of schools). Parameters calculated by geostatistical techniques were used as descriptors of the spatial organization. The results indicate the significant effect of area and land enclosure on the spatial structures of both species, suggesting that environmental spatial heterogeneity attributable to coastal topography affected the way fish schools were organized into aggregations. In summer, the spatial structure of sardine was more heterogeneous in subareas with increased land enclosure, whereas the spatial structure of anchovy was not significantly related to any of the area characteristics examined. In winter, the spatial structure of both species was more heterogeneous in subareas with increased enclosure and in small rather than larger subareas. The findings are discussed in terms of the species' response to their environment.
Keywords: anchovy, coastal topography, exhaustive variograms, geostatistics, land enclosure, sardine
Received 31 May 2005; accepted 11 October 2005.