Tuesday, May 27, 2008
353

Generalists vs. specialists: Who inhabits a tropical urban river fish community?

Diana M. Martinó-Cardona, Noraida Martinez-Rivera, and Alonso Ramírez. Institute for Tropical Ecosystem Studies, University of Puerto Rico-Río Piedras, PO Box 21910, San Juan, PR 00931

Urbanization has multiple negative impacts on fish communities.  Among them, there is a clear trend for dominance by non-native species in urban streams.  Humans living in close proximity to the streams facilitate the introduction and establishment of non-native species by directly introducing them and changing habitat availability and physicochemical characteristics.  As a result native species are replaced by taxa better adapted to the particular conditions of the urbanized stream.  Successful invaders are generally omnivores, a strategy that facilitates survival on a changing environment. Here we assessed the food web structure of the Río Piedras Watershed, one of the most urbanized in Puerto Rico.  Eight streams were sampled using backpack electrofishing.  All individuals were counted and identified and at least ten individuals per species were dissected for stomach content and stable isotope analysis.  Of the ten species found in the watershed, five were native.  In addition, 6 species were specialists, predators and algivorous, and 4 omnivorous.  Therefore, the fish community in the Río Piedras Watershed does not show the typical urban river characteristic of a higher number of omnivorous fishes.  In the Río Piedras, non-native species have been added to the already existing fish assemblage and no species replacement was detected.


Web Page: urban streams, food webs, tropical streams

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