Note to readers, attached is the complete final report for FNE01-399.
The goal of this project was to evaluate growth, specifically shell shape and shell density, of oysters raised in a drum (cylinder) system against those grown in a traditional mesh bag system. Rulon wanted to determine if heavier, rounder oysters could be grown in less time.
Bags of oyster seed were split into equal densities, with half of each bag going into a drum, the other half remaining in the original mesh bag. Both the bag and drum were put onto the same rack and grown in the same location for the season. Several experiments were conducted, including using drums for first year seed, using drums with and without flotation, placement of drums both intertidal and subtidal, and evaluation of various densities in the drums.
Rulon reports that the results were impressive. Drums that were suspended in the water, allowing the tide to gently roll and tumble the oysters in the drum, consistently produced a rounder, fatter, deeper oyster, with a heavier shell. They produced salable oysters in less time and there was a slight improvement in shell cupping. Rulon also reports that the oysters produced in drums did not grow as well if the drum was simply set out on the bottom. The drums caught sand and silt and water circulation through the bottom of the drum was prevented, resulting in mediocre growth.
The advantages of drums included improved oyster shape, ease of handling, reduced labor, and reduced fouling. The drums provided a more marketable, consistent product, produced with less labor. Rulon calculated that the direct break-even point for drum use is 5% improved marketability during one growing cycle. He observed between 8% and 20% increased salability of oysters grown in the drums. The main value of the drums is primarily due to the effect on the “marginal” size class. Those oysters grown in drums that were of a marginal size class were heavy enough, and of high enough quality, to sell, as opposed to those grown in mesh bags that were not.
Rulon is excited about the results because of several factors and is planning to expand the use of the drums. Product quality was improved and time to market reduced for a proportion of the total crop. They had an immediate improvement of at least 5-10% marketable product as well as higher meat quality. The drums allow use of upper intertidal areas that are too high for the use of racks, and can also be set out subtidally, as well as floated. The drums also produced larger, fatter, higher quality seed.