Progress report for FNE24-097
Project Information
The objective of this project is to find the optimal tumbling schedule to achieve well-shaped, petite oysters. The amount of labor and equipment time will be weighed against size, shape and meat quality improvements, across treatments and compared to controls.
As many new oyster farms are started each year in the Northeast, the market competition increases. Many farms which have been in operation for decades, are challenged to keep up with market and consumer trends. On Martha’s Vineyard, a dozen oyster farms have been operating successfully in Katama Bay in Edgartown, for nearly 30 years. Katama Bay provides moderately high salinity water which is rich in phytoplankton food and favorable water temperatures. Farms in Katama Bay are able to achieve market size of 3”+ in about 18 months to 24 months. This has led to great success for most of the growers. However, more recently, many consumers prefer a “petite” oyster, or one that is closer to 2.5 inches. Growers in Katama struggle to produce a well-cupped, petite oyster because they grow so fast. The inability to produce a specific product is creating instability in some of the farms, as other farms in other growing areas, are in fact able to achieve a well-developed, smaller product. In order to maintain competitiveness, farms in Katama Bay and other highly productive growing areas, will need to adapt and create new methods for different results.
We propose a series of experiments to help growers in a similar position control the size and shape of the oyster they grow, through handling and tumbling. It is well-established that tumbling oysters, which chips away the thin, sharp new growth of an oyster, encourages the oyster to grow deeper and wider, instead of longer. Currently, the custom of most Katama Bay farms is to tumble the oysters just once before market, to round off the sharp growing edge. Additional tumbling sessions will cost labor and equipment time, and there for determining the optimal input needed for the desired output, is critical to the sustainability of the businesses.
Cooperators
- - Technical Advisor
Research
Starting in March of 2024 I began modifications to the oyster tumbler. The goal was to use mesh suitable for smaller oysters. I succeeded in modifying the mesh and works beautifully for our experiment at this time.
At the end of May every year we purchase oyster seed at 1.5 mm for our whole year's operation. This process takes only a few hours. I carried out this task and the oyster seed were on their way! Pictured below.
In October 2024 we put aside our experimental cage and aquaculture bags for experimentation. We reserved 12 bags of 200 oysters each for this experiment. They were cared for periodically by air drying, if needed, over the next winter and spring. In June of 2025, staff from the MV Shellfish Group came out to the Little Minnow farm and the experimental cage was retrieved. We removed the oysters lost to winter mortality and put the remaining oysters back into the bags at about 120 oysters each. This is the standard stocking density we use for sub-adults on our farm. Three treatments (1-3) were designed to measure the impact of increased tumbling frequency and control group was established to compare experimental treatments to standard tumbling practices for our farm. On the June sampling date, the oysters in all three treatments were tumbled in the water for 5 minutes and then put back into their respective bags. This gently cleaned and abraded the oysters. The control group was not tumbled at all, and would not be tumbled until the final sampling in October.
On the second tumbling session which was July 25, 2025, Treatments 2 and 3 were tumbled for 5 minutes, then returned to their respective bags.
On the third tumbling session on August 15th, Treatment 3 was tumbled again and returned to their bags.
Final tumbling was completed for Treatments 1-3 and Control Group 1 in late October, 2025. The Martha’s Vineyard Shellfish Group assisted in processing and gathered samples from all treatment groups for growth and condition testing. Fifty individuals from each of the four groups were sent to collaborators at the C-SALT lab of Virginia Institute of Marine Science, to be processed for quality assessment. The C-SALT lab specializes in benchmarking traits and marketability of different varieties of farmed oysters, using traditional measurements of oyster growth (shell height, width, length, fan ratio, etc.), along with measurements of wet versus dry meat weight, to calculate the condition index of each individual. The condition index is a standard used by researchers and industry professionals for determining the health and “quality” of individual oysters. This ratio is calculated by dividing the dry meat weight by dry shell weight, multiplied by 100. Additionally, “body condition” of oysters was assessed utilizing an adapted version of the Pacific Oyster Grading System created in 2009 by the Australian Seafood Cooperative Research Centre (see attachment). This qualitative method rates the body condition of an oyster based on their shell dimensions as well as the meat weight (wet vs. dry), quality, and visual proportions relative to its shell. A summary of quality assessments measured by the C-SALT lab is attached to this report.
Our experiment aimed to find how the tumbling of juvenile one year old oysters effect their final fully grown shell shape and any side effects of the tumbling. Using a tumbler if a common practice for oyster aquaculturists to clean the oysters for marketing purposes. The reason that that the tumbler can affect the shape of the oyster is that it abrades the shell. Oysters are very good at repairing shell when its damaged and we take advantage of that with this technique. The shell that is chipped off is generally an imperfect non rounded part of the shell with that part chipped away it guides the oyster to grow rounder. My worry was that sometimes the oyster doesn’t survive the chipped shell or isn’t able to repair. By examining the effects of tumbling once, twice, and three times over the grow-out season, this project will show if it is worth using this method and how many times to tumble to be optimal.
In the fall of 2024 I set up the experiment and excitedly waited for the weather to warm up so that we can continue and get some results. I have modified the tumbler to handle the size of the oyster seed. After the final tumbles to clean the treatments and control group in late October of 2025, measurements and assessments of each group was done.
Average length of individuals within each group decreased with increasing tumbling frequency (see figure). Of the three experimental groups, treatments 2 and 3 exhibited the most significant difference from the control group, with average shell length approximately 10 mm less than that of the control. There was no significant difference in shell width between all groups. However, all treatments resulted in a more substantial fan ratio (length/width) compared to the control group. This is primarily due to the difference in average length. While there is no significant difference in cup ratio (depth/length) between groups, treatment groups 2 and 3 did tend to have deeper cups than the others.
Average dry tissue weight between groups did not follow the same pattern as shell length. Treatment group 1 retained the highest average weight overall, closely followed by group 2. Treatment group 3 and the control group were effectively the same. This suggests that changes in shell directional growth do not necessarily alter tissue growth. Average condition index for all groups was high (5-7 or greater is considered healthy), with treatment group 2 displaying the highest average score, and group 1 the next highest. Treatment group 3 had the best body condition score using the adapted qualitative Pacific Oyster Grading System.
The results of this study show that more frequent tumbling of oysters does result in more rounded oysters of equal condition and tissue quality. Of the three experimental treatments, groups 2 and 3 displayed the most significant change compared to the control. While group 3 retained the highest average fan ratio and shortest average length, the difference between group 2 (tumbled 3 times) and group 3 (tumbled 4 times) was minimal. These results help to demonstrate that more frequent tumbling of stock can lead to a more marketable product, without sacrificing the condition and quality of the meat. This helps to offset the high growth rates of farmed oysters in Katama Bay, and may make products from this area, and highly productive areas like it, more competitive. Additionally, average cleaning time (amount of time to shuck one oyster) was shortest with groups 2 and 3, suggesting a cleaner, more proportional shell. These characteristics can also increase demand with second or third party suppliers, who may value a visually pleasing oyster that can be shucked and served efficiently in large quantities.
While increasing tumbling frequency can provide a more valuable product, it also represents an increase in effort on the part of the farmer. A standard tumbling process (for Little Minnow Farm) involves pulling cages, unloading oyster bags into the tumbler, tumbling, counting out individuals for market, and re-loading/deploying of remaining stock. Average time required for each full tumble is between 1.5-2.0 hours depending on the number of assistants present. Approximately 10 cages can be tumbled within this timeframe. Our farm has capacity to manage 300 cages of oysters. Depending on the size of the farm, tumbling the full stock at increased intervals may or may not be feasible. However, applying this treatment on a select stock of oysters for special events, direct sale, or other like purposes may help to boost overall marketability and branding for that farm.
I sought out to improve the tumbler to handle the size oyster seed for the experiment. Additionally I sought out to receive the oyster seed and grow them to the point that the experiment can be conducted. Finally I sought to set up the experiment by labeling aquaculture bags with the experimental oysters and putting them away for winter. I succeeded in completing all of these tasks.
Oysters that were tumbled once showed a clear deference to our control in shell shape. The oysters were more rounded and consistent size to those who were not tumbled. The single tumbling successfully reduced irregular growth patterns and promoted a high value appearance that could improve marketability. Importantly morality rates remained low showing that tumbling once has a good effect on shape without stressing the oysters.
Oysters that were tumbled twice- once at the beginning of the experiment then for a second time showed clearly better shapes and uniformity than the one-time tumbled and the control. Also showing smaller sizes in which many of the oyster eating population enjoys. The improvements to the shell shape were minimal but also noticeable. The second tumble increased the stress on the oysters resulting in more mortality a pattern of diminishing returns is apparent after the second tumble takes place.
Oysters That were tumbled three times during the grow-out season showed the best shape and marketability of all the other groups of oysters. Additionally, this group of oysters showed the highest rate of mortality of all the groups. The small improvement in shell shape coupled with the increased mortality rate shows diminishing returns more apparent after the third tumble. These finding indicate that too much tumbling is counterproductive showing lower yield.
In summary, the outcomes demonstrate that tumbling oysters one time at one year of age at the beginning of the grow-out season shows the most significant gain in oyster quality and marketability. One tumble promotes the oysters to be uniform size rounded shape with a desirable cup without increasing stress and mortality risk. Therefore, from a farmer's perspective one tumble is the most optimal practice for producing high-quality oysters efficiently and sustainably. This experiment has changed the way I think about tumbling my oysters, and I think it will be interesting to farmers who use a similar approach. Using the tumbler to clean the oysters has been a method to clean oysters for market since we built our first tumbler in 2010. I suspected that tumbling chipped of edges of oysters and the result of that could be a more marketable oyster. I now have taken the steps to prove my hypothesis and confirm my beliefs in this experiment. I will now use my tumbler to shape my oysters every spring now knowing the value of this practice. For my size farm I will only be able to logistically tumble once in the spring and once in the fall but I feel as though this should be more than adequate to see a big difference in oyster marketability and shape. For a smaller farmer though I would and will recommend two rounds of tumbling for optimal results in producing gorgeous oysters to their customers. This practice of tumbling market size oysters I could see a farmers oysters fetching a higher price over time resulting in a higher profit margin. This could be a catalyst to help the farm be a success and compete with other farms.
The results of this study have demonstrated that more tumbling of oyster stock can help to develop favorable growth characteristics in Katama Bay. Future study could look at the feasibility of up-scaling these methods, to integrate extra tumbling into normal commercial processes. Simultaneously, further experimentation of the timing of additional tumbling could help to maximize favorable results. For example, an updated tumbling schedule might combine growth stage thresholds with seasonal considerations, avoiding tumbling during the hottest part of the summer (Late August to mid September), when animals are more stressed.
Education & outreach activities and participation summary
Participation summary:
I plan to post on social media about this project @littleminnowoyster and @mvshellfishgroup on instagram. We plan to present either orally or with a poster to the Vineyard aquaculture community and the regional community. We planned to present at the recent Northeast Aquaculture Conference and Expo, but results were not in in time to submit an abstract unfortunately.
Learning Outcomes
Farmers that I have talked to about this my finding include Jeremy Scheffer , Dan Gilkes, And Ryan Smith all farmers from Martha's Vineyard they were all very interested in the results and said they will put some thought into implementing practices from this experiment. I will report if i hear of anyone else using this technique in the future.
Project Outcomes
I will be using methods from this experiment this coming growing season and am happy to report how it went when finished in the fall. I will report of others using this method in the future as well.
This projects success stems from the ability to be patent and carefully plan the day in which the experiment took place. The commitment of all those involved taking time out of our busy days to learn how this experiment can help oyster farmers all over the globe. I definitively answered the question that I set out to answer. I will use and am happy to report findings in the future that are related to this experiment. My use will be applied to a much bigger scale and am excited to report on future thoughts and successes pertaining to this experiment. I do not feel anymore investigation on this particular topic is not needed at this time. I feel that anyone who is growing oysters in highly productive waters (fast growing oysters) and is having trouble with oyster shape and quality should consider using the methods laid out in this experiment.