MEPS 235:195-203 (2002)  -  doi:10.3354/meps235195

A simple method for estimating larval supply in reef fishes and a preliminary test of population limitation by larval delivery in the kelp bass Paralabrax clathratus

Mark A. Steele1,*, John C. Malone2, Amy M. Findlay3,**, Mark H. Carr4, Graham E. Forrester1

1Department of Biological Sciences, Biological Sciences Center, 100 Flagg Road, University of Rhode Island, Kingston, Rhode Island 02881-0816, USA
2Department of Organismic Biology, Ecology and Evolution, University of California Los Angeles, 621 Charles E. Young Drive South, Los Angeles, California 90095-1606, USA
3Department of Biology, California State University, Northridge, 18111 Nordhoff Street, Northridge, California 91330-8303, USA
4Department of Biology, University of California, Santa Cruz, California 95064, USA
*E-mail: **Present address: Community Environmental Council, Watershed Resource Center, 2981 Cliff Drive, Santa Barbara, California 93109, USA

ABSTRACT: This paper describes a method for estimating larval supply of a temperate reef fish, the kelp bass Paralabrax clathratus, that is simple, inexpensive, requires relatively low effort, and integrates larval supply over time. Using this method, we sampled larval supply concurrently at 4 sites spread over about 35 km for nearly an entire settlement season. With these data and visual estimates of recruitment (the density of young-of-the-year after the end of the settlement season), we tested the hypothesis that spatial patterns in recruitment were set by larval supply. This hypothesis was rejected: kelp bass recruitment to the 4 sites was not related to patterns of larval supply. Furthermore, in contrast to the findings of an earlier study, recruitment was not related to the density of the macroalga Macrocystis pyrifera. Recruitment was, however, strongly correlated with the density of 1 yr old kelp bass, suggesting that spatial patterns of recruitment were consistent between the 2 cohorts. Recruitment, however, was not correlated with the density of bass 2+ yr old. We also measured larval supply in a second year and found that spatial patterns of supply were strongly correlated between years at a relatively small scale of 10s to 100s m, but not at a larger scale of several km. This finding suggests that some deterministic process (or set of processes) sets spatial patterns of larval supply at small, but not large scales. At large scales, consistent patterns of recruitment between 2 cohorts in the face of variable larval supply suggest that deterministic, postsettlement processes may generate predictable patterns of recruitment even when the supply of larvae is variable. In addition to demonstrating that spatial patterns in the abundance of demersal fish are not always well predicted by larval supply, this study introduces a technique that may facilitate more thorough exploration of the role of larval supply in determining the dynamics of populations of reef fishes.

KEY WORDS: Larval supply·Settlement·Recruitment·Reef fish·Population dynamics·Paralabrax clathratus

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