PARENT SESSION
Oral Session #26: Aquatic Ecology: Fish - Populations, life history, autecology. Presiding: M. Fox.
Tuesday, August 7, 2001. 8:00 AM to 12:00 PM. Hall of Ideas H.
Density-dependence in reef fish: a meta-analysis.
Osenberg, Craig1, St. Mary, Colette1, Holbrook, Sally2, Schmitt, Russell2, Chesson, Peter3, Byrne, Barbara3, 1 2 3
ABSTRACT- Density-dependent survival can play an important role in population dynamics. The strength of density-dependence in marine fishes, however, continues to engender considerable debate. Density-dependence may play a critical role by homogenizing the variation introduced through variable larval supply. Using a quantitative framework based on a continuous time version of the Berverton-Holt recruitment (and presented at last year's ESA meeting), we conducted a meta-analysis based on a literature search of papers published in 20 journals over the past 30 years. The approach assumes age-independent parameters. We evaluated this assumption using studies that permitted estimates of parameters at different times during a single experiment. Only a few studies with time series were available, and results were inconclusive. We therefore cautiously applied the model to the remaining studies and examined the possible influence of several factors on the strength of density-dependence (e.g., region of study, age of fish, size of fish, duration of study, presence or absence of predators). Overall, effects of density on survival were strong but heterogeneous (i.e., varied among studies), and were not strongly linked to other factors. Studies that showed the strongest effects of density-dependence were those conducted at high overall densities. Interestingly, these studies showed the weakest per capita effects, suggesting that systems with stronger effects of density-dependence incur disproportionately greater settlement which more than compensates for less intense within-cohort interactions.
KEY WORDS: density-dependence, fish, meta-analysis, mortality