Fish Communities and Conservation of Aquatic Landscapes in Northeastern Mesoamerica.

Abstract

Tropical river conservation is a global priority because these rivers support high biodiversity and rural livelihoods, and contribute to maintenance of marine ecosystems. A challenge to river conservation in tropical developing countries is the paucity of scientific information to assist with conservation planning at appropriate spatial scales. This research attempted to alleviate some of the information scarcity impeding conservation of rivers draining to the coast of Belize in northeastern Mesoamerica. This work drew on field and museum collections of freshwater fishes to: (1) investigate the influences of reach- and catchment-scale environmental conditions on fish communities; (2) document spatial and temporal patterns of spread of an invasive fish, African tilapia (Oreochromis spp.), and make recommendations for its control; and (3) design a freshwater protected areas network in a riverine context. Environmental characteristics across scales described a large portion of total fish assemblage variation (64%), and catchment-scale factors explained a greater percentage of total variance (25%) than reach-scale environment (14%). The high correlation between assemblage patterns and catchment-scale factors suggests that fish conservation efforts are most appropriately conceptualized at this scale. A reconstructed spatial chronology of tilapia spread suggested that the invading population experienced an initial lag period before advancing from its initial home range, and that Nile tilapia (O. niloticus) is now widely distributed in the coastal plain rivers of at least 9 of 29 drainage basins. The study revealed unintentional releases from aquaculture and flooding as the two most likely dispersal mechanisms, leading to recommendations focused on (1) prevention of tilapia spread to un-invaded systems, and (2) control of aquaculture activities. Riverine conservation areas comprising 11% of the study area that had high fish biodiversity and low human influence were identified using conservation planning software and species distribution models for 63 fishes. Management zones were specified to mitigate threats to conservation areas, protect fish movement corridors, and target basin management. Despite chronic information limitations, this work demonstrates how limited field data, interviews with resource users, and modeling can be used to create biologically realistic hypotheses about ecological reality that can serve as a starting point for conservation planning in rivers.Ph.D.Natural Resources and EnvironmentUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/62271/1/esselman_1.pd