Substrate Associated Recruitment Of Juvenile Sebastes In Artificial Reef And Natural Habitats In Puget Sound And The San Juan Archipelago Washington

Author : Gascon, Dominique
Publisher : National Library of Canada
ISBN 13 : 9780315123724
Total Pages : 0 pages
Book Rating : 4.1/5 (237 download)

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Download or read book Reef Fish Community Structure [microform] : an Experimental Study Using Small Artificial Reefs in Barkley Sound, British Columbia written by Gascon, Dominique and published by National Library of Canada. This book was released on 1982 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Using small artificial reefs made of cement blocks, a community of shallow water reef fishes was experimentally studied in Barkley Sound (British Columbia) to examine the structuring mechanisms in this assemblage The community under study inhabited a shallow reef made of rock boulders. The abundance of fish fluctuated with the seasons The species diversity of this fish community was low (H' = 0.3-10), one species (Coryphopterus nicho/si) comprising more than 80% of the individuals present Four species of rockfishes ( Sebastes caurinus, S. ma/iger, S. me/anops, and S. pinniger) and three species of benthic fishes (Hexagrammos decagrammus, Jordania zonope, and Artedius spp.) were also common. Experimental communities were established on ten identical artificial reefs made of cement blocks. Two series of reefs, built six months apart on sand 10 m away from the natural reef, tested the effects of seasons on community development. A third series, built in direct contact with the natural reef, examined the effects of distance and isolation on community development In each series a species equilibrium (approximately 6 species) was reached within six months The specific composition of the artificial reefs was similar to that of the natural reef, although species other than Coryphopterus nicho/si were more abundant Both juveniles and adults of all species were present, except for the rockfishes, which were represented only by young individuals. Tagging indicated that the benthic species remained permanently on the reefs, whereas a yearly turnover in rockfishes occurred The intensity of interactions between species was estimated by measuring shifts in habitat use on the artificial reefs. Only Sebastes me/anops showed consistent shifts in its space use in response to changes in the density of other species Only two of these shifts appeared to be the result of interspecific competition. Interactions between species, with the exception of S. me/anops had little effect on the spatial distribution of fish within the reefs. I examined the significance of the patterns of similarity between communities inhabiting identical habitats. High similarity values are usually interpreted as indicating the equilibrium status -- that is communities structured primarily by interspecific competition -- of a community, whereas low values are usually interpreted in the opposite direction -- i.e non-equilibrium communities structured by mechanisms other than interspecific competition (mostly stochastic events). This was tested using a randomization test. The null hypothesis of the test was that random colonization from the surrounding habitats was sufficient to explain the community structure on the artificial reefs. Six additional reefs (one third the original size) were built to test the effects of habitat size on community structure. The observed values on the reefs did not differ significantly from the null values, indicating that mechanisms, such as competition, were not required to explain the structure of the community. Habitat size had a strong effect, and the interpretations of previous studies were re-examined in light of this finding.