Exploring Husbandry and Equipment Solutions to Infestations of Polydora sp. on a Maine Oyster Farm

Exploring Husbandry and Equipment Solutions to Infestations of Polydora sp. on a Maine Oyster Farm

Summary

Goals restated:

– To evaluate the effect of equipment type, air drying, and salt brine dips on reducing the presence of mud blister worms (Polydora sp.) in eastern oysters (Crassostrea virginica) on my farm.
– To evaluate the effects of the above treatments on growth and survival of oysters.
– To transmit the results of our project to relevant stakeholders.

Objectives/Performance Targets

FARM DETAIL

Update the information on your farm since your project started. Include acres farmed, your current crops or livestock, and other key background on your farm.
My farm on the Bagaduce River in eastern Maine covers 4.3 acres, and includes several hundred thousand eastern oysters, of various sizes. I use part of the site as a nursery area, and part is for grow out. Virtually all of my oysters are grown in containment, as opposed to sowing them directly to the seabed. Over the last several years, the presence of mud blister worms has had a strong negative effect on the income from my oyster farm, and I have to find a solution to this problem. I’ve operated the oyster farm for over 10 years now, and generally I have a very strong market for my product, both in terms of volume and price.

COOPERATORS

My collaborators include Eric Moran, who has been a long-time partner in the business, and Dana Morse, who acts as the Technical Advisor. Erick helps out with on-the-water activities of the farm, and Dana helps with the project design, data collection/analysis, and reporting.

ACTIVITIES AND REMAINING WORK

Tell us what you actually did on your project and what remains to be done.
In 2009, we completed the following tasks, in accordance with our project design:
– Purchase, set up and stock our treatment equipment.
– Conduct the treatment maintenance as specified in the research program.
– Collect data on growth, mortality and sampled for incidence of blister worms
– Host a local SARE Coordinator to the site, to inform him about project details and future activities with respect to the project.

ACCOMPLISHMENTS AND RESULTS

To date, we have accomplished most of our goals with respect to equipping the experiment, carrying out the field treatments, and making measurements and observations. Two difficulties were encountered. First: we had originally intended to use a dilute iodine solution as one of our treatments. We were unable to carry this out because we found that the permitting would have been prohibitive in time and money, even given the very limited application we intended. So, the animals we had set aside for this treatment have been used as an extra set of controls. Second: we were unable to source juvenile urchins this year, but we have the experimental group set aside, and we anticipate better success in getting small urchins from a hatchery. However, we did institute and unplanned sampling in October, to serve as a mid-project check on the effectiveness of the treatments.

During our June sampling, we recorded the initial stocking volume of each shellfish bag, and a sampling for shell heights. During August and October, we made notes of shell heights and mortality. As noted above, during the October sampling, we also took subsets of each bag (tilted towards the larger individuals, since they are more prone to blister worm infection) for examination of worm load and treatment effectiveness.

The data from all sampling has been saved to an Excel spreadsheet, though analysis is incomplete: a switch to a new computer has impacted our ability to use packaged statistical software, and we are searching for solutions to this situation.

A suite of photographs is also being compiled as the project moves forward.

SITE CONDITIONS

No unusual conditions were encountered during our field season, although there was a lot of precipitation in June and July. No problems were encountered during the overwintering phase of our operation.

ECONOMIC FINDINGS

Economic findings are unclear at this point. We appear to be observing a slower growth and increased mortality in the longer dip treatments, but the second-year fieldwork should improve our understanding.

NEW IDEAS AND NEXT STEPS

This project has found interest outside the state and the region, certainly. An inquiry through the East Coast Shellfish Growers Association list serve revealed that growers along the East Coast have encountered similar problems, and are just as interested in a solution. To that end, it stimulated a pre-proposal to the Northeast Regional Aquaculture Center, to study the problem further. We were asked to submit a full proposal, which has been completed, and it includes producers from ME, MA, RI, and NC, with collaboration from scientists and others in RI, NY, DE and NJ. We are hopeful for this follow-on funding, and the results from this current SARE project will inform the proposed NRAC work – they should be good, complimentary studies.

Respectfully Submitted,
Dana Morse
Maine Sea Grant
16 March, 2010

Accomplishments/Milestones

Impacts and Contributions/Outcomes

Collaborators: