During the summer and fall of 2014 and 2015, area biologists from the Maine Department of Marine Resources and DEI staff teamed up to examine the efficacy of using predator-deterrent netting to protect wild soft-shell clam recruits at sites across the entire Maine coast .
A series of comparative, large-scale manipulative experiments were conducted at each of two intertidal mudflats in three geographically distinct coastal regions (southwestern, midcoast, and eastern Maine) to examine potential management tools for areas closed for conservation purposes.
The study was conducted at two flats in Jonesboro, two flats in Boothbay, a flat in St. George and one in South Thomaston.
Specifically, tests were conducted to determine the efficacy of using plastic predator-deterrent netting (4.2- or 6.4-mm aperture) to enhance: (1) recruitment of 0-class juveniles, (2) survival of greater than or equal to 1-y class wild juveniles, and (3) wild stocks using cultured juveniles.
The results of the 2014 experiments are in this Final Report .
The results of the 2015 experiments are here.
A presentation about the results given at the 2015 Maine Fishermen’s Forum on March 5, 2015 can be found here.
These results were published in the Journal of Shellfish Research in 2016.
4-ft x 14-ft flexible netting (aperture = 1/6th inch, or 4.2 mm) being deloyed at the Potato Patch in South Thomaston on 2 July 2014.
Spreading out the flexible netting (2 July 2014 – Potato Patch, South Thomaston).
Styrofoam floats are affixed to the bottom of each piece of flexible netting that raises the net off the sediments during tidal inundation so that the netting will not interfere with clam feeding.
Netting is secured in the sediments by walking along the periphery of the net. This pushes the net into the sediments about 6-8 inches. The furrow created by walking along the edge of the net is back-filled with sediments so that there is a seamless transition from the unnetted portion of the flat to the netting.
Sometimes, sedimentation rates are high, as in this photo taken on 2 September 2014 at the Potato Patch, South Thomaston. The rate of siltation/sedimentation was so high that the netting did not act to protect wild clam recruits and even smothered some of the year-old clams in the plot beneath. Additional flotation would reduce this build-up of sediment along with routinely scraping the top of the nets with a squeegee.
Although the netting is designed to deter green crabs, a large green crab was observed under this net located at Bob’s Cove, Jonesboro, in September 2014. Crabs can enter netted plots by small rips or tears in the nets, by crawling under an edge that has accidentally lifted, or by being in the sediments at the beginning of the study and getting trapped beneath.
The size of 0-year class soft-shell clams (“recruits”) that were found under netting at a site in the Jonesboro River on 27 October 2014. Clams ranged in size from 1.75 to 12 mm (about one-sixteenth of an inch to one-half inch).