Graduate Thesis Or Dissertation
 

Distribution and abundance of coastal fish and macro-invertebrates in the Galapagos Islands

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  • The Galapagos Islands, located off the coast of Ecuador, have a spatially diverse marine environment suitable for a variety of species with different climatic requirements. A year-long inventory program was carried out in 2000-2001 to provide baseline data on the abundances and distribution of coastal fish and macro-invertebrates. The purposes of this analysis are to use these data to describe the major trends in the community composition of coastal fish and macro-invertebrates and to relate the observed community structure to environmental parameters. A series of Non-metric Multidimensional Scaling (NIMS) ordinations, Multi-Response Permutation Procedures (MRPP) and Indicator Species Analyses (ISA) were performed on the community data. The results are analyzed with respect to major climate zones, upwelling regimes, prevalent benthic community, regional distribution of species, and habitat preferences. The results show that the community of coastal fish and macro-invertebrates in the Galapagos has a considerable degree of structure. Although most environmental variables do not show a strong relationship with individual ordination axes, a clear pattern can be discerned. The species composition of the communities in the warm tropical zone to the north is different from that of the coldest zone of the islands in the west. The community composition of the central and southern zones do not separate as clearly in the ordination space, but the communities belonging to the cool southern region are more similar to those of the tropical zone than to those of the coldest western region. Weaker patterns of community structure are observed when analyzing the data with respect to upwelling regime and community type (algal or coral). When groups of sites are defined with respect to environmental attributes, MRPP shows that there are small differences in species composition between groups, while Indicator Species Analysis yields several strong indicators for each group. The results of the ordination, MRPP tests, and Indicator Species Analysis suggest that the majority of fish and macro-invertebrate species of Galapagos are generalists, found across all environmental gradients; but that there are also significant numbers of more specialized species that occur in only limited regions. In order to properly protect these specialized species, fully protected zones should be established in each of these different regions. This study provides a baseline for future studies of nearshore marine faunistics in Galapagos. Future studies of the community structure of fish and macro-invertebrates in the Galapagos Islands will be able to document changes by comparing their results to those presented here. This information can then be used to help identify causes for changes, whether they are natural or anthropogenic.
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