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Diet and feeding habits of Economidichthys pygmaeus (Perciformes: Gobiidae) in Lake Pamvotis, NW Greece

Authors


Author’s address: Ioannis Leonardos, Department of Biological Applications and Technology, University of Ioannina, Ioannina, PC, GR-45 110, Greece.
E-mail: ileonard@uoi.gr

Summary

The purpose of the study was to define the diet composition, feeding preferences, seasonal, size and sex related changes in diet, feeding strategy and diel cycle of Economidichthys pygmaeus. Important features of the overall feeding patterns of the goby include (i) feeding activity, (ii) bottom habits and (iii) consumption of food items to identify the dietary breadth. Stomach contents of 533 specimens, 13.42–48.65 mm total length (TL), collected by hand net (2 mm mesh size) from October 2006 to September 2007 were analyzed. The percentage of 76 empty stomachs (14.26%) did not vary significantly with season. The food composition suggested that the goby is a carnivorous fish. Prey items identified in the stomachs belonged to four major groups: Crustaceans, Insects, Mollusca and Plants. Copepods were the most important (%IRI = 57.51), especially in fish larger than 23 mm TL. Chironomids (%IRI = 43.23) constituted the main prey for fish <23 mm TL. Diet composition showed little seasonal variation. Copepoda dominated the diet in autumn and winter (43.4%; 82.4%) and were replaced by Chironomidae larvae in spring (39.7%) and summer (47.7%). During the reproductive season, large males show a narrow food spectrum as opposed to large females, reflecting the different activity pattern exhibited by males and females during the breeding season, since the former supports parental care. According to the modified Costello graphical method, specialist individuals form the goby population that feeds on two preferential prey types (e.g. Copepods, Chironomids). Nevertheless, they consume some occasional prey (e.g. Cladocera, Insects, Gastropods). The species foraged chiefly at night and early morning, during lower light intensity. The highest feeding activity recorded at night (02.00 hours) and during early morning (08.00 hours) could be related to the cryptic behaviour displayed by the species.

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