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Dietary map of Nile tilapia using stable isotopes in three tropical lakes, Ethiopia
Author(s) -
Fetahi Tadesse,
Rothhaupt KarlOtto,
Peeters Frank
Publication year - 2018
Publication title -
ecology of freshwater fish
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 55
eISSN - 1600-0633
pISSN - 0906-6691
DOI - 10.1111/eff.12361
Subject(s) - nile tilapia , zooplankton , oreochromis , food web , food chain , macrophyte , tilapia , isotope analysis , biology , ecology , environmental science , fishery , trophic level , fish <actinopterygii>
Comprehensive analysis of food webs requires identifying dietary sources that support the production of all major organisms within the food web/food chain. Here, we use stable isotope ratios (δ 13 C, δ 34 S and δ 15 N) to assess the relative contribution of different basal carbon sources to the diet of Nile tilapia ( Oreochromis niloticus L.) in three tropical lakes Hawassa (also Awasa in literature), Ziway and Koka (Ethiopia). Computations were carried out with Stable Isotope Analysis in R (SIAR) model to quantify the dietary proportion of each prey for the tilapia fish. Basal food sources were distinguishable based on their δ 13 C, δ 34 S and δ 15 N values. In Lake Ziway, macrophytes (64%) were the dominant assimilated diet of tilapia while particulate organic matter (POM) and zooplankton contributed only 20% and 16%, respectively. In parallel, Nile tilapia in Lake Hawassa assimilated macrophytes (35%), POM (33%) and zooplankton (32%) at comparatively equal proportion. The dietary sources of the fish in Lake Koka were POM (49%) and zooplankton (51%). In contrast with earlier studies based on gut content analysis, the present results reveal that macrophytes contributed more and phytoplankton less than previously reported especially in macrophyte‐dominated lakes Ziway and Hawassa. The ecological condition of the lakes might have been predominantly accountable for the diet change of the tilapia. As dietary data are prerequisite for food web/food chain analysis and aquaculture industry, re‐evaluating the diet of aquatic organisms appear relevant.