Seeking didemnum on Georges Bank
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Seeking didemnum on Georges Bank
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    Purpose: To test the efficacy of an acoustic sensor in identifying the distribution of an aggressive sea squirt on Georges Bank that is threatening scallop and groundfish fisheries. Introduction: The presence of Didemnum vexillum (formerly referred to as Didemnum sp. A), an introduced and invasive sea squirt in New England was first highlighted with the MIT Sea Grant College Program's funded Rapid Assessment Survey of Marine Invaders in August 2000. By 2003 the sea squirt was observed from Long Island Sound to Damariscotta, Maine (the earliest verified record in 1993) and in Georges Bank. This aggressive sea squirt has invaded hard surfaces in subtidal areas and marinas where it overgrows most species and may be the dominant biomass in the community. Its presence in Georges Bank has the potential to impact the valuable groundfish and scallop fisheries that are already suffering from environmental change and fishing pressure. Documenting the risk Didemnum poses as one more threat to the economically important fisheries, was identified as a major regional marine invasion issue by the Northeast Aquatic Nuisance Panel. Surprisingly, the spatial coverage and abundance of D. vexillum in Georges Bank is not known, and what information exists is based on optical images (SEABOSS and HabCam) that have covered only a small portion of the potential sea squirt habitat. The MIT Sea Grant College Program is committed to addressing timely regional projects in support of fisheries management 1. After extensive consultation with researchers who are surveying the presence of Didemnum and its impacts to the community, we proposed to test the efficacy of new technologies to improve surveying for Didemnum that achieve two goals: 1. achieving greater spatial coverage per unit time that meets the current standard of optical imaging and 2. initiating studies to document areas suitable for Didemnum in support of efforts to predict its spread. The specific purpose was to evaluate an acoustic sensor, the Sound Metrics DIDSON.
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