Nursery Habitat - Determination

Determination

In order to determine the nursery habitat for a species, all habitats used by juveniles must be surveyed. This may include kelp forest, seagrass, mangroves, tidal flat, mudflat, wetland, salt marsh and oyster reef. While density may be an indicator of productivity, it is suggested that alone, density does not adequately provide evidence of the role of a habitat as a nursery. Recruitment biomass from juvenile to adult population is the best measure of movement between the two habitats.

Consider also biotic, abiotic and landscape variability in the value of nursery habitats. This may be an important consideration when looking at which sites to manage and protect. Biotic factors include: structural complexity, food availability, larval settlement cues, competition, and predation. Abiotic: temperature, salinity, depth, dissolved oxygen, freshwater inflow, retention zone and disturbance. Landscape factors involve: proximity of juvenile and adult habitats, access to larvae, number of adjacent habitats, patch shape, area and fragmentation. The effects of these factors may be positive or negative depending on species and broader environmental conditions at any given time.

It may be more holistic to consider temporal variation in habitats used as nurseries, and incorporating temporal scales into any testing is important. Also consider assemblages of species. Single species approaches may not be able to be used to adequately manage systems appropriately.

Acosta and Butler conducted experimental observation of spiny lobster to determine which habitats are used as nurseries. Mangroves are used as preferred nursery habitat when coral density is low. Predation on newly settled larvae was lower in mangrove than in seagrass beds and coral crevices. In comparison, Pipefish prefer seagrass over algae and sand habitats. King George Whiting have a more complex pattern of development. Settlement is preferred in seagrass and algae. Growth stages are primarily preferred in reef algae. 4 months post settlement, they move into unvegetated habitats (Jenkins and Wheatley, 1998).