Predator-mediated recruitment and size of kelp-associated fishes (funded by National Undersea Research Program; National Science Foundation; SDSU Grant-in-Aid)

Predation is an important process in the post-settlement mortality of reef fishes. Todd Anderson and Andy Davenport investigated experimentally the role of a piscivore, the kelp bass, Paralabrax clathratus, in the recruitment success of fishes that settle to the giant kelp, Macrocystis pyrifera. For two successive years (2002-03) recruitment of young-of-year kelp bass (left photo; ~ 2 cm), giant kelpfish (Heterostichus rostratus; right photo; ~ 3.5 cm), and senorita (Oxyjulis californica) to plots of giant kelp were examined in three treatments: predator access, predator exclusion, and a cage control.

The species composition of recruits differed between years, but recruitment was significantly higher in each year within plots of kelp which excluded predators than in plots that allowed access to predators. Cage controls indicated that exclusion pens neither enhanced nor inhibited settlement of recruits. In addition, the size distribution of recruits of kelp bass differed among treatments; larger recruits occurred on plots in which predators were excluded than on plots open to predators, which could be caused by differences in consumption rates, growth rates, or size-selective predation.

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