In 2013, Freeport's Town Council approved a total of $170,000 to be used to help its Municipal Shellfish Program gather information about green crabs and declining clam stocks. A portion of those funds was used to conduct two field studies - green crab trapping, and green crab fencing. The effort began in April with a proposal to the Army Corps of Engineers (ACE) to install traditional "green crab fences" along the mouth of Recompence Cove to deter crabs with the goal of encouraging settlement/recruitment and increasing survival of wild clam spat behind the fencing. The ACE proposal also included a description of a field experiment at nearby Little River flat that would establish six 30-ft x 30-ft x 18-inches tall fences (with 1/2-inch mesh) to closely examine the effect of crab deterrence on clam spat. In addition, a green crab trapping study was initiated during the last week of May 2013 that continued through early November. Information collected from the trapping studies included the effect of "soak time" (length of time the traps were fished) on catch mass, whether differences in crab abundance occurred between traps fished in the intertidal vs. subtidal, and how sex ratios, and size frequencies varied spatially and temporally.
The following photos document the effort through early November 2013.
See the video from the Portland Press Herald
To read from other sources about the trapping studies conducted in 2013 in Freeport, see:
On 26-27 July 2013, we began to deploy fencing at Recompence flat and Little River flat. The wooden fences were pre-fabricated in lengths of 8-, 10-, and 12-feet, and then taken by airboat to both flats. The goal of the fencing at Recompence flat was to completely close off the mouth of a cove to green crabs in hopes that deterring these predators would result in an enhancement of wild seed clams that could be seen/measured/documented in the fall. (Soft-shell clams spawn in the spring/early summer; swimming/planktonic larvae develop for 3-4 weeks, then settle to the bottom; by October/November, clams that have survived [called spat] are typically 2-8 mm in shell length and are easily seen from bottom samples that are washed through fine mesh screens.)
To determine the interactive effects of clam size and predator netting, we devised and set out a field experiment at both Little River and Recompence flats on 18 August 2013. Shown above are the three different methods used to deter crabs and other predators from clams seeded within 6-inch diameter plant pots that were filled with ambient sediments. a) open pot - the rim of netting around the periphery ensures that clams remain enclosed in the six-inch diameter area - the netting does nothing to deter predators; b) a pot that is covered in two types of netting - a piece of 6.4 mm extruded (hard) plastic netting is closest to the pot and this is held in place with a piece of 4.2 mm flexible netting, similar to the type used in the larger experiment (see above); c) a pot that is covered with a piece of 4.2 mm flexible netting. Not shown are the clams originally planted at 12 per pot. Three sizes of cultured clams were used: 8.2 mm, 14.2 mm, and 19.4 mm. Every combination of clam size (a = 3) and predator exclusion (b = 3) were used to form nine treatments. Five replicates of each treatment were used at each site. Pots were removed from Little River flat on 16 November, and from Recompence flat the following day.
To review the results of the green crab trapping, fencing, and small-scale predation/clam size experiment, see the Final Report to the Freeport Town Council that was completed in early January 2014.