Littleneck Clam and American Oyster Polyculture: Economic Viability and Nursery Technique

View the project final report

Commodities

• Animals: shellfish

Practices

• Animal Production: aquaculture, stocking rate
• Crop Production: double cropping, intercropping, multiple cropping
• Farm Business Management: market study

This project aims to continue and expand work begun in SARE project FNE17-877; testing crop diversification on a subtidal oyster farm through the introduction of littleneck clams (Mercenaria mercenaria) as a secondary crop species. The original project demonstrated that littleneck clams could be grown in the same footprint as eastern oysters- providing an additional crop without added disturbance of wildlife, recreation, or traditional wild-harvest fisheries. The small seed-clams (1mm) used in the project presented some unforeseen challenges that warrant further investigation. Despite excellent growth rates (up to 17-fold growth in some individuals), the clams did not reach a size that allowed for testing the effects of density on growth or for a realistic economic analysis as proposed in the original project. This proposal would give the the clams planted in 2017 an additional season of growth to allow for the completion of the intended protocol and an additional analysis of overwintering mortality.

This proposal also includes a re-visitation of the nursery phase of clam-rearing, using lessons learned from the prior experiment and newly available large seed-clams (2.5mm and 4mm) to test if the early-season losses seen in 2017 could be mitigated.

Outreach for this project will focus on a website and digital pamphlet targeted towards farmers and aspiring farmers and promoted through region-wide aquaculture industry list-serves. A digital focus on outreach would allow information to persist beyond in-person presentations and would allow the target audience of small farmers to see project outcomes without necessitating costly travel to a conference.

This project will continue testing the viability of growing clams in contained-culture in the sediments below a floating oyster farm. This iteration will focus on obtaining a realistic view of the economic viability of the technique and aims to reduce reduce nursery-stage loss seen in the 2017 experiment.

1) Test the efficiency of floating nursery equipment using two different (and newly available) clam-seed sizes (2.5mm and 4mm) measured in seed-loss and percent of seed-clams reaching plant-able size

2) Measure the growth rates of bottom-planted clams under three different stocking densities

3) Note degree of mortality under different treatments

4) Record fouling and pest presence

5) Estimate projected value of crop (if best stocking densities were applied across the entire farm)

6) Perform a cost/benefit analysis to determine if this method could supply a viable supplemental farm income given equipment costs and labor

7) Determine actual value of crop if market-size within the study period.