9322618 Radtke A pressing problem for conservation and restoration of freshwater resources is the lack of sound biological and population information. To approach this problem it is proposed to utilize amphidromous fishes (gobies and eleotrids) which are predominant elements of the freshwater fauna on tropical and subtropical oceanic islands worldwide. Information gathered for one species will have implications for amphidromous fishes and freshwater habitats elsewhere. The proposed research relates to such topics as island colonization, life cycles, reproduction cycles, amphidromy, and recruitment. %%% A plan of research is proposed which applies novel analytical techniques to evaluate the critical periods in the life history of fishes that may be affected by altercation, reduction or fragmentation of habitats. Recruitment from a planktonic larval stage to a more sedentary adult stage is a common life-history pattern in many fishes and invertebrates. Because of the disparate nature of environmental conditions in planktonic and benthic systems, the interplay of these two modes of existence strongly influences population structure of species with this life-history pattern; as well as communities in which such species are common. It is essential to identify which life-history stages and environmental events are significant to recruitment into adult population. %%% Otolith techniques have the potential to provide such life-history information. Both micro structure and chemical composition of otoliths will be investigated, to determine the causative agents involved in otolith formation. It will then be possible to interpret past environmental histories of field-captured gobies. Otolith increment analyses and elemental composition techniques will be applied to investigations of recruits, juveniles and adult fishes collected from their natural habitats. Age, growth rate and environmental perturbations will be determined from otolith analyses. Otolith analyses will provide a chronologic ally fixed history of each individual study. Otolith techniques are particularly appropriate where large numbers of individuals can't be used. Also it will be possible to use any specimens stored in alcohol, thus extending the technique to museum material. These data sequences will be of great importance to the management of endangered species since specimens that are in existing collections could be examined to evaluate past life histories. As a result, the proposed research will contribute to the development of effective strategies for the preservation and restoration of populations and thus biodiversity.
