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Accession Number 5004032

Title Effects of some commercial fishing activities on eelgrass, Zostera marina, in New

England: characterization of impacts and measurement of regrowth potential

Project Description Eelgrass (Zostera marina L.) is the dominant seagrass species of northern temperate coastal

waters. In New England it forms extensive meadows in low intertidal and shallow subtidal areas of

relatively low wave energy, where it contributes vital functions to the ecological integrity and

economic value of coastal ecosystems. Various human-induced disturbances have contributed to

declines in distribution and abundance of eelgrass in New England and elsewhere, with the direct

effects of human activities emerging as a significant source of local habitat loss with the potential

for large-scale cumulative impacts. Interest in effects of commercial fishing on eelgrass has

intensified recently, due in large part to new federal and state policies acknowledging the critical

dependence of healthy fish stocks on sustainable fish habitat. Implementation of policies to

protect eelgrass from adverse affects of fishing is hampered by the paucity of scientific information

on the extent of disturbance from commercial harvest operations and the recovery potential within

impacted areas. The goals of this study are to characterize impacts of commercial fishing

activities on eelgrass in New England and determine revegetation potential following disturbance.

Our approach is to evaluate ongoing impacts within a representative estuary, Maquoit Bay, which

is the northwestern boundary of Casco Bay, Maine. Hand digging of soft shell clams and bait

worms occurs throughout the intertidal eelgrass beds, and mechanical dragging for blue mussels

occurs in subtidal grass beds. Preliminary aerial and field observations reveal patches that have

been denuded by fishing activities, ranging in size from a few square meters to up to 70 acres.

Our specific objectives involve landscape- and population-level measures of harvest effects and

revegetation patterns. We will (1) measure the extent of impacts of harvesting activites in Maquoit

Bay with metric quality aerial photography and bottom profiling equipment, and use a geographic

information system to compare eelgrass distribution to historic records; 2) determine the local

intensity of impacts of harvesting activities on eelgrass by comparing plant and sediment

characteristics between impacted and undisturbed sites; (3) document patterns of revegetation

using low altitude aerial photography; (4) quantify rate of eelgrass regrowth from edges of

disturbed patches by measuring rate of eelgrass rhizome elongation, and use this information to

predict recovery time; and (5) compare eelgrass characteristics within patches along temporal

gradients of disturbance to provide additional estimates of bed recovery time. Finally, we will

compare predicted recovery rates from Maquoit Bay with concurrent measurements of

revegetation at eelgrass restoration sites in the Piscataqua River, Maine-New Hampshire border,

to ensure broad geographic applicability, as these sites have previously been related to other

eelgrass beds in New England.

Keywords commercial fishing, disturbance, eelgrass, seagrass, zostera marina,

Principal Hilary A Neckles, USGS Patuxent Wildlife Research Center: hilary_neckles@usgs.gov; Seth

Investigators Barker, Maine Department of Marine Resources: seth.barker@state.me.us; Frederick T Short,

University of New Hampshire: fred.short@unh.edu;

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