Habitat structure and predation in the distribution of an intertidal sculpin (funded by SDSU Department of Biology)

Andy Davenport, Dane Bowker, Carrie Jenkins, and Todd Anderson examined the demography of a local tide pool fish, the woolly sculpin, Clinocottus analis. The woolly sculpin is found in tide pools from Cape Mendocino, California to Punta Ascuncion, Baja California and it is the most common fish in southern California tidepools. This sculpin occupies a very small home range, generally just over a few meters, and much of their life appears to be spent in a small circuit of tide pools. Individuals were marked to effectively decouple losses due to mortality from those due to emigration. A network of tide pools at two sites in the San Diego area (Ocean Beach and La Jolla) were selected that are at least somewhat segregated from nearby suitable habitat for this species.

The tide pools at each site were mapped initially in winter 2002, and rugosity (an index of topography), surface area, and depth have been measured along with the percentage cover of 13 different variables. After these variables are measured, each pool was emptied of water and all sculpins are caught, measured, marked, and released. The sculpins were divided into three size classes based on recruit, older juvenile, and adult life history stages and marked with elastomer (colored silicone) indicating size class and a specific tide pool.

The tide pools were re-sampled during low-tide cycles every several months to record the location and size of marked fish and to follow mortality rates at these sites over time. Because habitat structure and predators likely play an interactive role in mortality, laboratory experiments were done to examine the distribution of young recruits relative to algal cover and predators (the presence of older conspecifics). Recruits showed an avoidance to predators and a preference for algal cover, both of which support patterns of distribution of recruits in the field.

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