Document: CRA-3-79-3

Density-dependence in reef fish: A quantitative synthesis.

OSENBERG, C.W.* ¹, S.J.HOLBROOK ², R.J.SCHMITT ², C.M.STMARY ¹ and J.A.WILSON ¹

University of Florida Gainesville FL 32611 USA ¹
University of California Santa Barbara CA USA ²

Abstract:
Density-dependent processes play important roles in population dynamics and in determining the efficacy of management strategies. This is especially true in marine systems where recent interest in marine reserves has spawned new applications of population dynamic models. The strength of density-dependence in marine fishes, however, continues to engender considerable debate. Some investigators argue that density-dependence plays a critical role, essentially homogenizing the variation introduced through variable larval supply, while others argue that larval supply drives patterns of local abundance with little subsequent modification by density-dependent processes. We took two approaches to help resolve this issue using field results compiled through a literature search of papers published in 20 journals over the past 30 years. Data were subjected to meta-analytic techniques to assess the effect of conspecific density on settlement, and post-settlement survival, growth, and reproduction. Results demonstrated strong effects of density on settlement and survival. Data on growth and reproduction were too sparse for analysis, perhaps because they are considered less important in driving local dynamics in open systems. We also used a conceptual approach developed by Schmitt to estimate the simultaneous effects of limited larval supply, density-independent mortality, and density-dependent mortality on local abundance. The available results revealed comparable effects of density-dependence and supply limitation. We could not, however, estimate the relative importance of density-dependence in most studies. Studies frequently lacked concurrent estimates of natural settlement rates and density-dependence, or relied upon natural variation in settlement to assess the strength of density-dependence (and thus overlooked any covariance between settlement and habitat quality).

Keywords: reef fish, marine, density dependence, meta-analysis, recruitment

This abstract is being presented at: 11:30 AM in session:
Oral Session #57: Ocean-Going Fish and Mammals.