Downeast Institute’s goal is to increase the supply, quality, and species diversity of U.S. seafood through pilot and commercial-scale culture of Arctic surf clams. Expanding upon DEI’s research findings from phase 1 (2013-2015), this second phase of research focused on:
1) Determining the interactive effects of transplant time of year, size of cultured seed, and type/orientation of predator exclusion netting on the growth and survival of cultured juveniles in pilot and commercial-scale field trials in eastern Maine.
2) Determining the interactive effects of geographic location and sampling date on bioaccumulation of paralytic shellfish toxins (PSTs), and to determine the rate of biotoxin depuration in the lab of animals challenged with bloom levels of the toxic dinoflagellate, Alexandrium fundyense.
3) Demonstrating aquaculture technologies, and provide training for fishermen and other entrepreneurs in aquaculture production methods focused on culturing Arctic surf clams.
Process:
In 2016, this phase began with experimental trials to examine growth and survival of cultured juveniles at fifteen selected sites along the Maine coast with a concentration of sites in eastern Maine, where aquaculture development of the species has occurred over the past five years, and an assessment of human health and product safety by examining the interaction of this species with biotoxin uptake both in the field and laboratory.
In 2017, additional comparative experiments were established at five lower intertidal locations in eastern Maine from Trenton to Lubec in September/October and removed in April/May 2018. Animals were seeded in 10 different field treatments to examine the efficacy of different types of predator-exclusion and predator-deterrent netting and determine which type performed the best.
In addition to the small-scale experiments (Fall 2017-Spring 2018), a series of larger-scale trials were deployed at each of the five sites during April, May, and June 2018. In those trials, the interactive effects of stocking density and predator exclusion were examined in terms of survival and growth parameters.
From April – October 2019, pilot studies using 2 sq. ft. grow-out boxes were conducted in Beals and Cutler. Surfclams (10-15 mm SL) were stocked at densities of 25, 50, or 100 individuals sq. ft.
From April- October 2020, grow-out trials were continued using 2-sq. ft. and 4-sq. ft. grow-out boxes placed in a lower intertidal area in Beals. Sixty boxes (thirty @ 2-sq. ft. and thirty @ 4-sq. ft.) were deployed with two rigid pieces of netting (one panel of 6.4 mm VEXAR, and another made from 14-gauge, vinyl- coated lobster trap wire [12.8 mm aperture]) added to the top of the frame to protect the clams from predators while they grew.
Results
The research hit a major breakthrough in 2019. During the April – October 2019 trials, both the Beals & Cutler sites experienced over > 95% survival of surfclam juveniles. Animals initially averaged (± 95% CI) 10.9 ± 0.5 mm (size range = 8-13 mm SL), and grew an average of 17.7 ± 0.5 mm in length (size range = 21.7-36.9 mm). Neither survival nor growth rates were density-independent at either site. Similar results were observed at one site (Beals) in 2020 using both sizes of boxes (2-sq. ft. and 4-sq. ft.).
Read more about the results of this phase of the work here.
Funding
In 2016 this research was supported by National Sea Grant National Strategic Initiative Funds.
From October 2017 through September 2019 this research was funded by the National Marine Fisheries Service (NMFS) Saltonstall-Kennedy grant program.
Below, Dr. Brian Beal explains DEI’s research on the culture and grow-out of Arctic surf clams.
