Spatial patterns in abundance of a damselfish reflect availability of suitable habitat

Abstract

For species with metapopulation structures, variation in abundance among patches can arise from variation in the input rate of colonists. For reef fishes, variability in larval supply frequently is invoked as a major determinant of spatial patterns. We examined the extent to which spatial variation in the amount of suitable habitat predicted variation in the abundance of the damselfish Dascyllus aruanus, an abundant planktivore that occupies live, branched coral throughout the Indo-Pacific. Reef surveys established that size, branching structure and location (proximity to sand) of the coral colonies together determined the "suitability" of microhabitats for different ontogenetic stages of D. aruanus. Once these criteria were known, patterns of habitat use were quantified within lagoons of five Pacific islands. Availability of suitable habitat generally was an excellent predictor of density, and patterns were qualitatively consistent at several spatial scales, including among different lagoons on the same island, among different islands and between the central (French Polynesia and Rarotonga) and western (Great Barrier Reef, Australia) South Pacific. A field experiment that varied the amount of suitable coral among local plots indicated that habitat for settlers accounted for almost all of the spatial variation in the number of D. aruanus that settled at that location, suggesting that spatial patterns of abundance can be established at settlement without spatial variation in larval supply. Surveys of four other species of reef-associated fish revealed that a substantial fraction of their spatial variation in density also was explained by availability of suitable reef habitat, suggesting that habitat may be a prevalent determinant of spatial patterns. The results underscore the critical need to identify accurately the resource requirements of different species and life stages when evaluating causes of spatial variation in abundance of reef fishes.

Fitness consequences of habitat variability, trophic position, and energy allocation across the depth distribution of a coral-reef fish

“…Habitat suitability for demersal reef fishes is dependent on processes that affect growth, reproduction, and condition, such as shelter and food availability (Forrester 1990;Holbrook et al 2000), with diverse consequences that range from behavioral adaptations to mortality. For example, predation pressure and competition affect resource accessibility, thus influencing survival and fitness of individuals (Hixon and Jones 2005;Figueira and Lyman 2007).…”

Red snapper management in the Gulf of Mexico: science- or faith-based?

“…Some believe that the availability of interstices (i.e., small hiding spots) for newly settled post-larvae and juveniles can be limiting; those individuals not finding refuge suffer higher predation rates. In this case, mortality is thought to be density-dependent (Forrester 1990;Holbrook et al 2000;Forrester andSteele 2000, 2004). It should be noted, however, that age-0 red snapper rarely recruit directly to high-relief natural or artificial reefs, rather they settle on sand/mud substrates and transition to more structured habitat with size and age (Patterson 1999;Patterson et al 2005;Wells et al 2008a, b;Gallaway et al 2009).…”

Availability, usage and expected contribution of potential nursery habitats for the California halibut

“…despite the consequences of local density (Holbrook et al, 2000). Subsequently, there are growth or mortality costs following high settlement that reduce interannual variation in recruitment via density-dependent mechanisms during the juvenile phase (Van der Veer et al, 1991;Modin and Pihl, 1994).…”