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EXECUTIVE SUMMARY
This report combines up-to-date information on lobster biology and ecology with oceanographic and geological data in order to define Essential Lobster Habitats. The following preliminary report and maps update knowledge of the marine bottom sediments in the Gulf of Maine region and combine this with the distribution of lobsters found in NMFS trawl data. Additionally, surface temperatures, current patterns and water masses have been defined from satellite data and combined with lobster distribution patterns where possible.
While the physical tolerances of the American lobster have been studied for more than a century, the lobster's habitat preferences have only recently been explored. Modern experiments with state-of-the-art techniques have given us entirely new insights into the optimal conditions sought by the lobster. With this in mind, lobster life-stages are described in detail and inferences are made about shelter requirements and dependency during various growth phases. Known or suspected lobster habitats are reviewed and evaluated. Where possible, an estimate has been made of lobster density for each life stage.
The literature suggests that lobsters are highly dependent on natural shelters for some period during each stage of their life cycle. The young must find coarse sediments for settlement in order to avoid predators. They must continually find or create new shelters as they molt and grow. Mature lobsters continue to need shelter protection during molting and also to facilitate reproduction. Many large male lobsters apparently have difficulty finding a mate without suitable mating shelters. This places an extraordinary burden on lobsters to locate and defend shelter-providing habitats. Additionally, some large females are unable to reproduce without the availability of large males.
While inshore lobsters have been reported on nearly every substrate, they appear to be concentrated near cobble or rocky shorelines and around island margins and estuaries. Offshore lobsters tend to focus along relatively narrow bands at the edge of the shelf and possibly close to the transitions from one habitat to another.
Until such time as accurate maps can be generated of total lobster distribution, we can only approximate how lobsters utilize various habitats. However, given the definitions of Essential Fish Habitat (waters and substrate necessary to fish for spawning, breeding, feeding or growth to maturity) and the identification of the most vulnerable habitats of these habitats (where vulnerability is based on the extent to which the habitat is sensitive to human-induced environmental degradation; whether, and to what extent, development activities are, or will be, stressing the habitat type, and the rarity of the habitat type), we have identified the following habitats as those both utilized by lobsters, important to the completion of their life cycle, and sensitive to human activities:
Peat Reefs - All life stages have been reported, with shelter-restricted and emergent juveniles most common; thus may also be an important nursery ground when cobble is lacking. Since these reefs are part of wetlands, they have a great potential of being impacted by human activities and should be considered a vulnerable habitat.
Island Margins - All life stages seem to be present at these margins.
Kelp Beds - These habitats may represent important grounds for the more vagile adolescents.
Eelgrass Beds - The regional importance of eelgrass beds as a lobster habitat appears to be minor, but adequate studies are still lacking. Until more is known, and according to the conservative approach adopted by NMFS, they should probably be considered Essential Lobster Habitat. Futhermore, human activities have negatively impacted eelgrass beds in the past and can continue to do so, making them a particularly vulnerable habitat.
Intertidal Zone - Given the fact that shelter-restricted, emergent, and vagile juveniles have been found in this habitat in 5 New England states, NMFS should probably adopt a conservative approach here and declare it as a potential nursery ground and Essential Lobster Habitat. The intertidal zone also has one of the greatest potentials to be strongly impacted by human activities and should be considered vulnerable.
Bedrock Base with Rock and Boulder Overlay - An important and probable Essential Lobster Habitat for vagile juveniles, adolescents, and adults. May be vulnerable to certain fishing practices.
Offshore Sand Base with Rock - This substrate type is not very common offshore, but is almost certainly an Essential Lobster Habitat for all life stages. It too may be vulnerable to certain fishing practices.
Clay Base with Burrows and Depressions - Apparently this substrate is depth-restricted, but is a probable Essential Lobster Habitat for adolescents and adults.
Mud-Clay Base with Anemones - An extremely fragile environment which is also severely depth-restricted. It is a strong candidate for an Essential Lobster Habitat for adolescents and adults and is extremely vulnerable to fishing activities because of its fragility.
Clay Pipes - There have been numerous anecdotal reports of clay pipes serving as lobster habitat and until more is known, NMFS should adopt a conservative approach to their protection, particularly given their rarity.
Submarine Canyons - The offshore submarine canyons represent a particularly important habitat for abundant adolescent and adult lobsters, ovigerous females that may be hatching their eggs, and may be one source of larval supply. As such, they should be protected as an Essential Lobster Habitat.
Two other habitats which should be considered as potential Essential Lobster Habitat are Mud-shell/rock substrate and Mud base with burrows. However, these habitats are less important than those listed above, given the lower densities of lobsters found on them.
By protecting Essential Lobster Habitats which offer optimum conditions for growth and reproduction we can, perhaps, perpetuate a strong and viable lobster stock.