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Habitat use and trophic position determine mercury concentration in the straight fin barb Barbus paludinosus , a small fish species in Lake Awassa, Ethiopia
Author(s) -
Desta Z.,
Borgstrøm R.,
Gebremariam Z.,
Rosseland B. O.
Publication year - 2008
Publication title -
journal of fish biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.672
H-Index - 115
eISSN - 1095-8649
pISSN - 0022-1112
DOI - 10.1111/j.1095-8649.2008.01920.x
Subject(s) - biology , profundal zone , mercury (programming language) , trophic level , littoral zone , barbus , benthic zone , ecology , cyprinidae , fishery , fish <actinopterygii> , computer science , programming language
The diet, habitat use and mercury concentration of the small fish species, the straight fin barb Barbus paludinosus , were studied in Lake Awassa, Ethiopia, for a period of 1 year from February 2003 to January 2004. Stable isotope signatures of nitrogen and carbon in different total length ( L T ) classes were used to determine trophic positions and organic carbon sources, respectively. Barbus paludinosus mainly occupied the protected benthic habitats (littoral and profundal) of the lake. The δ 13 C values were in the range from −24 to −19‰, indicating that the carbon source for B. paludinosus was benthic, as well. Small individuals (≤ 60 mm L T ) mainly preyed upon ostracods, intermediate sizes (60–100 mm) on aquatic insects and gastropods, while a tiny cyprinodont fish Aplocheilichthys antinorii dominated the diet of large individuals (100–160 mm). The progressively increase in δ 15 N with increasing L T also indicated a diet shift towards piscivory in larger individuals. The mercury concentration ranging from 0·02 to 0·74 mg kg −1 wet mass (wm), was unexpectedly high in this small species, and was significantly positively related to L T , as well as to δ 15 N. Some large individuals had mercury concentrations < 0·1 mg kg −1 wm, and low δ 15 N, indicating substantial variations in diet between individuals of same size. The study suggests that other piscivorous species which include B. paludinosus in their diet may have a high mercury intake risk.