Progress 04/01/06 to 09/30/07
OUTPUTS: During the course of this study, we have tested the importance of seed dispersal by fruit-eating fish. To this end, we have: 1) assessed the abundance and diversity of seeds dispersed by fish; 2) compared the viability of seeds that have passed through the digestive system of fish; 3) established botanical transects to determine how many seeds are available to fish during lengthy flooded seasons; and 4) tracked the movement patterns of fruit-eating fish using radio telemetry to evaluate the distance and directionality of seed dispersal by fish. We conducted this research both in the field in Pacaya-Samiria National Reserve (Peru), and in controlled aquaculture settings at the Institute for the Study of the Peruvian Amazon (Iquitos, Peru). Our results indicate the fish consume and disperse massive quantities of seeds. We have found more than 800,000 intact seeds in the diets of 238 individual pacus (Colossoma macropomum) and 55 individual red pacus (Piaractus brachypomus).
These seeds represented 38 species, which is nearly half of the 72 species of trees and lianas that produced fruit during the 2006 flooded season. Furthermore, fish can carry seeds up to 5.5 km. Thus, these results indicate that fish are very effective seed dispersers. To date, we have presented the results of this study at national and international scientific conferences, including the annual meeting of the Ecological Society of America (Portland, 2005), and the Latin American Conference of Botany (Dominican Republic, 2006). Additionally, we have given seminars about this research at Cornell University, the University of Pittsburgh, Utah State University, and Sam Houston State University. This research has also been the foundation of the undergraduate theses of four Peruvian students. Additionally, we have trained five Peruvian biologists in experimental design, and research techniques such as radio telemetry.
PARTICIPANTS: Partner Organization: Instituto para Investigaciones de la Amazonia Peruana (Institute for the Study of the Peruvian Amazon, Iquitos, Peru) Collaborators: Joe Saldana Rojas, Institute for the Study of the Peruvian Amazon Dr. Timothy Nuttle, Assistant Professor, Indiana University of Pennsylvania Training or Professional Development: We have guided four Peruvian students through their honors theses. These students are Cahuide del Busto Rojas, Elmer Vela Morales, Percy Mejia Poquioma, and Roy Rosales Fatama. We have trained an additional five Peruvians in research methodologies.
This study illuminates the importance of fruit-eating fish as vectors of seed dispersal; very little was known about the seed dispersal activities of fruit-eating fish prior to this research. These fish are overexploited throughout their range, and this overexploitation could influence the dynamics of regeneration in floodplain forests. The conservation implications are clear: unless we begin to conserve these fish, the structure of floodplain forests may change dramatically.
- No publications reported this period
Progress 01/01/06 to 12/31/06
This project examines the seed dispersal activities of two species of fruit-eating fishes in Pacaya-Samiria, a two million hectare floodplain forest reserve in northeastern Peru. In 2006, research was organized around three objectives. First, the diets of Colossoma macropomum and Piaractus brachypomus (both large bodied fish in the family Characidae) were analyzed for three months during the flooded season within the reserve. Second, seeds were collected for germination trials, and these trials were begun in the reserve. Third, 11 Colossoma macropomum were selected for a radiotelemetry study to assess their movement patterns in relation to their activities as seed dispersers. Fourth, botanical transects were established to quantify the number of tree and vine species that fruit during the flooded season. Finally, gut retention time trials were conducted in aquaria during the dry season to determine the time necessary for seeds to travel through the digestive tracts of
Colossoma macropomum. Results from this year, and the two previous years of the study, indicate that fish disperse large quantities of seeds long distances. The results from this project indicate that these fishes play a crucial role in the seed dispersal ecology of floodplain forests.
Fish constitute the most important source of animal protein for human consumption in South America; historically frugivorous fishes have been a major component of the fisheries. For example, Colossoma macropomum comprised over 40 percent of the fish sold in markets in Manaus, Brazil, in the late 1970s. Overexploitation accounts for the current threatened status of this species. Despite the importance of fruit-eating fishes in the commercial market, we do not yet understand the depth of the interaction between these fishes and floodplain trees. The results from this study suggest that the primary role of fish is to disperse seeds long distances against the prevailing water current. This work is the first to elucidate the importance of fruit-eating fish in the reproductive biology of floodplain forest trees. A thorough understanding of this interaction will compel interest in the conservation of this fruit-eating fishes and floodplain forests.
- No publications reported this period