Shana Thesis

Understanding whether artificial reefs yield significant fish production relative to natural reefs is important if we wish to continue using them for habitat enhancement and mitigation purposes. In addition, how fish production may vary with the type and amount of habitat is also valuable in designing reefs, in assessing the production potential of natural reefs, or in evaluating the quality of habitats. Because of the inherent difficulties in estimating fish production, the focus of Shana Sharfi's research was to determine fish production methods that are meaningful and to determine whether fish production differs with habitat structure how such differences are manifested.

San Clemente Artificial Reef (SCAR) has been deployed as partial mitigation for negative impacts on kelp-bed resources from the operation of the San Onofre Nuclear Generating Station. This reef is unprecedented in spatial scale, covering over 22 acres of hard substratum along > 2 km of coastline. Moreover, the reef has been constructed with experimental design in mind, using a series of 0.16-ha modules that vary in combinations of substrate type (recycled concrete or quarry rock) and levels of substratum coverage (percentage cover of hard substratum).

Shana took advantage of this reef as an ideal system with which to estimate fish production experimentally with habitat structure and potentially in comparison to natural reefs at a regional scale. Juvenile black surfperch (Embiotoca jacksoni) were collected from the artificial reef to validate daily growth increments in otoliths of this fish and to obtain basic data (e.g., length, weight) which will be used in hindcasting somatic production from the size of otoliths. The black surfperch provided an excellent model with which to examine production. It is a live-bearer that produces young that appear to have high site fidelity and are not likely to move from modules in which they are born, and this species feeds on the benthos associated with the rocky substratum. Shana also examined gut fullness and food resources on the reef to determine if either metric differed among treatments of substratum coverage. Densities of black surfperch on the artificial reef modules were used to estimate total production on a module and to examine whether per capita production and total production was a result of compensatory processes or differences in habitat. Shana and Todd Anderson worked with UCSB research biologists Dan Reed and Steve Schroeter in obtaining data and estimating fish production.

Fish production and habitat structure on a large-scale experimental artificial reef (funded by California Sea Grant)