Nursery habitats
Encyclopedia
In marine environments, a nursery habitat
is a subset of all habitats where juveniles of a species
occur, having a greater level of productivity per unit area than other juvenile habitats (Beck et al. 2001). Mangroves, salt marshes and seagrass are typical nursery habitats for a range of marine species. Some species will use nonvegetated sites, such as Yellow Eyed Mullet, Blue Sprat and Flounder.
There are two general models for the location of juvenile habitats within the total range for a species which reflect life history strategies of the species. These are the Classic Concept: Juveniles and Adults in separate habitats. Juveniles migrate to adult habitat. General Concept: overlap of juvenile and adult habitats.
Some marine species do not have juvenile habitats, e.g. arthropods and scallops. Commonly fish, ells, some lobsters, blue crabs (and so forth) do have distinct juvenile habitats, whether with or without overlap with adult habitats.
In terms of management, use of the nursery role hypothesis
may be limiting as it excludes some potentially important nursery sites. In these cases the Effective Juvenile Habitat concept may be more useful. This defines a nursery as that which supplies a higher percentage of individuals to adult populations.
Identification and subsequent management of nursery habitats may be important in supporting off shore fisheries and ensuring species survival into the future. If we are unable to preserve nursery habitats, recruitment of juveniles into adult populations may decline, reducing population numbers and compromising the survival of species for biodiversity
and human harvesting.
, 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 larva
e, 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).
Habitat (ecology)
A habitat is an ecological or environmental area that is inhabited by a particular species of animal, plant or other type of organism...
is a subset of all habitats where juveniles of a species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
occur, having a greater level of productivity per unit area than other juvenile habitats (Beck et al. 2001). Mangroves, salt marshes and seagrass are typical nursery habitats for a range of marine species. Some species will use nonvegetated sites, such as Yellow Eyed Mullet, Blue Sprat and Flounder.
Overview
The nursery habitat hypothesis states that the contribution per unit area of a nursery habitat is greater than for other habitats used by juveniles for the species. Productivity may be measured by density, survival, growth and movement to adult habitat (Beck et al. 2001).There are two general models for the location of juvenile habitats within the total range for a species which reflect life history strategies of the species. These are the Classic Concept: Juveniles and Adults in separate habitats. Juveniles migrate to adult habitat. General Concept: overlap of juvenile and adult habitats.
Some marine species do not have juvenile habitats, e.g. arthropods and scallops. Commonly fish, ells, some lobsters, blue crabs (and so forth) do have distinct juvenile habitats, whether with or without overlap with adult habitats.
In terms of management, use of the nursery role hypothesis
Hypothesis
A hypothesis is a proposed explanation for a phenomenon. The term derives from the Greek, ὑποτιθέναι – hypotithenai meaning "to put under" or "to suppose". For a hypothesis to be put forward as a scientific hypothesis, the scientific method requires that one can test it...
may be limiting as it excludes some potentially important nursery sites. In these cases the Effective Juvenile Habitat concept may be more useful. This defines a nursery as that which supplies a higher percentage of individuals to adult populations.
Identification and subsequent management of nursery habitats may be important in supporting off shore fisheries and ensuring species survival into the future. If we are unable to preserve nursery habitats, recruitment of juveniles into adult populations may decline, reducing population numbers and compromising the survival of species for biodiversity
Biodiversity
Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...
and human harvesting.
Determination
In order to determine the nursery habitat for a species, all habitats used by juveniles must be surveyed. This may include kelp forestKelp forest
Kelp forests are underwater areas with a high density of kelp. They are recognized as one of the most productive and dynamic ecosystems on Earth. Smaller areas of anchored kelp are called kelp beds....
, 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 larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e, 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
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
. Growth stages are primarily preferred in reef algae. 4 months post settlement, they move into unvegetated habitats (Jenkins and Wheatley, 1998).