RECRUITMENT DYNAMICS OF REEF FISHES: PLANKTONIC PROCESSES, SETTLEMENT AND DEMERSAL ECOLOGIES, AND FISHERY ANALYSIS William J. Richards and Kenyon

Factors influencing variability of recruitment in coral reef fishes are of great theoretical and applied interest for population dynamics, oceanography, and fishery management. Due to the complexities of evaluating the many factors influencing recruitment processes throughout the life history of mcroplanktonic organisms, recruitment is often an umbrella-term encompassing interrelated problems in a management sense, but largely distinct biological processes or events. Research primarily addresscs factors determining: (I) survivorship of cohorts of planktonic larvae; (2) temporal and spatial patterns of demersal settlement from the plankton; and (3) natural and fishing mortality of adult and juvenile cohorts. Current and early research representing a varicty of approaches to the recruitment dynamics of reef-associated fishes is examined. Absolute survivorship during planktonic life stages is a function of parental abundance and fecundity, and highly complex interactions among predation, oceanographic processes, growth and starvation. A matrix outlining the relative effects of important biotic and abiotic factors upon the survivorship of egg through adult life history stages is developed. Larval maneuvering behaviors which utilize specific physical features (e.g., fronts, internal waves) may be exceedingly important mechanisms for influencing transport and reducing mortality. Variability in numbers oflarvae surviving through settlement can be the ultimate determinant of adult population sizes. In long-lived commercially exploited species, mortality on juvenile life stages also may significantly impact stock sizes. Variations in recruitment may also contribute to significant species composition shifts within both virgin and exploited reef fish communities. Reef fishes are often a major component of tropical and subtropical ichthyofaunas and support important commercial and recreational fisheries in many regions. Sound management policies are needed, but the multispecies nature of these fisheries, the complicated community ecologies of coral reef fishes, and the nearly universal pelagic dispersal of early life history stages, makes the task of understanding and modelling such systems a formidable task. Reef fishes are here considered as fishes associating with coralline or similar hard bottom environments in tropical, and to a lesser degree, temperate regions. Most reef fishes spawn externally in the water column above hard bottom structures. Fertilized zygotes subsequently undergo oceanic advection and diffusion. Even in species which guard nests of eggs or are live bearers, newly hatched larvae usually enter the pelagic realm. At the end of planktonic life, surviving larvae settle onto reefs or associated inshore environments where they mature and may eventually enter local fisheries. The importance of variable early survival of larvae upon fluctuations in adult population sizes has been recognized for many temperate marine fishes since the work of Hjort (1914; 1926). Workers in low latitudes have recently focused progressively greater attention on early life history studies, particularly processes influencing recruitment (Sale, 1980; Rothschild and Roath, 1982). Recruitment (in modern usage from the French "recruite" = "fresh growth" and synonymized in most dictionaries with "reinforce" or "replenish") is often an umbrella-term for a variety of fundamental processes controlling stock maintenance. Recruitment encompasses interrelated resource management problems but highly distinct biological processes and life history stages. For example, the