Scientia Marina, Vol 68, No 3 (2004)

Feeding ecology of the gobies Pomatoschistus minutes (Pallas, 1770) and Pomatoschistus microps (Krøyer, 1838) in the upper Tagus estuary, Portugal


https://doi.org/10.3989/scimar.2004.68n3425

Joao Pedro Salgado
Instituto de Oceanografia, Faculdade de Ciências da Universidade de Lisboa, Portugal

Henrique Nogueira Cabral
Instituto de Oceanografia, Faculdade de Ciências da Universidade de Lisboa, Portugal

María José Costa
Instituto de Oceanografia, Faculdade de Ciências da Universidade de Lisboa, Portugal

Abstract


The sand goby Pomatoschistus minutus (Pallas, 1770) and the common goby Pomatoschistusmicrops (Krøyer, 1838) are among the most abundant fish species in estuaries, lagoons and along the Atlantic shores of Europe. In the Tagus estuary these species are particularly important in the food web. Fish samples were taken monthly in the upper estuary, and the gut contents of a total of 431 P.minutus and 382 P. microps were analysed in order to study preferences and seasonal changes in their diets and to understand intra- and interspecific relations between these two congeneric gobies. The sand goby had no dominant prey, although mysids were particularly important in the diet of this species. Shrimps and polychaetes were also common prey. P.microps preferentially ingested polychaetes, with isopods, amphipods, bivalves and copepods as secondary prey items. Significant seasonal variations in the ingestion of the main prey groups of both species were obtained, which reflect variations in prey availability. During the reproductive season there were differences in the food consumed by males and females, mainly for P.minutus, reflecting the different activity pattern exhibited by males and females during the breeding season, since parental care is supported by the former. The smallest classes from P.minutus increased their niche widths as they grew. Due to the different length reached by each species, the degree of interspecific overlap decreased with increasing body size.

Keywords


Pomatoschistus; feeding ecology; niche overlap; Tagus estuary; Portugal

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