Thesis

The cryptic fish fauna of a shallow rock reef habitat, Santa Catalina Island, California

The rock reef/kelp forest habitat of southern California is among the most productive and well-studied marine habitats. The importance of the cryptic fish fauna, however, has not been studied. This study was undertaken to assess this particular element of the fauna in a rock reef habitat, and to relate the findings to past studies conducted on the conspicuous fishes. Among the aspects of the fauna studied were species compositions, numerical abundance, seasonal and temporal variations, depth distribution, size distribution, biomass density and diversity. The fishes were collected using an ichthyocide (rotenone) and a specially designed net. Bimonthly collections were taken, five samples from each of three depth strata: 2.2 to 3.0m, 4.2 to 5.1m, 6.4 to 7.6m. The collected fishes were weighed and standard length was measured. Conspicuous fishes were censused by visual diver transect at two six-month intervals. Ninety percent of the cryptic fish fauna was made up of five species, Lythrypnus dalli, Paraclinus integripinnis, Gibbonsia elegans, Alloclinus holder and Lythryonus zebra. Water temperature correlated significantly with the numbers of individuals (r = 0.433, p (0.05) and the H (Shannon-Weiner) diversity (r = 0.459, p (0.05). Distribution by depth correlated significantly with greater numbers of L. dalli in deeper water. L. dalli while G. elegans recruited in May and June. Comparisons between this study and previous investigations indicated that the inclusion of the cryptic fishes may have enhanced total density of individuals by an average of 80% and as much as 83%; diversity an average of 44% and as much as 60%; and biomass density by an average of 10% and as much as 15%.

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