The management of a marine fishery is a difficult task and in tropical island nations, where ecologically complex ecosystems are under heavy pressure from rapidly increasing anthropogenic stress, the problem is exacerbated. In recent years, there has been increasing interest in conserving fish habitats. Identification of what habitats are important for marine fishes is difficult, because their habitat requirements are poorly understood. In particular, little is known about habitat utilization patterns of coral reef fishes.

Among the most commercially valuable and most vulnerable nearshore reef fishes are the larger species such as groupers (Epinephelidae). These species are generally slow growing and long lived, often with delayed reproductive development.  Spawning occurring in aggregations and low replenishment rates. These life-history traits render them particularly susceptible to overexploitation. Groupers are subject to intense fishing pressure and catches have declined dramatically over the past few decades. In addition to their fishery value, large reef fishes are important to divers and have high tourism value. Determining nursery habitat for groupers may be problematic in that many large reef fishes undergo stage-dependent, ontogenetic habitat shifts. For example, juveniles are known to settle on small patch reefs, in seagrasses, among mangrove prop roots, or in algal-dominated clumps of coral. As juvenile fish grow, their risk of predation likely decreases, while their foraging capacity and probability of survival likely increase. Larger size also initiates higher metabolic demands, and juveniles may need to find a more suitable habitat to meet these requirements.

In order to better manage these species, especially in terms of spatial management via marine protected areas, we require detailed information on their habitat utilization patterns. Simply identifying the habitats that fish use is inadequate, as such a broad approach to determining essential habitat does not allow for prioritization of habitats for conservation and management. A better approach would be to concentrate conservation and restoration efforts on habitats or sites that are most important for the replenishment of adult populations. The most obvious examples are spawning aggregation sites and nursery habitats. Many countries have now enacted legislation to protect grouper spawning aggregations, but to date there are no policies in place to identify or protect nursery habitats.

A true nursery is a juvenile habitat that provides disproportionately greater biomass per unit area to adult populations. In order to determine if a particular habitat or habitats is truly a nursery, a suite of important ecological processes must be measured within all available habitat types. These include density, growth, survival, and movement to adult (or intermediate) habitats. All of these processes may contribute to a higher production of biomass recruiting to the adult population.