Six months after seed oysters (average 25 mm in shell height) to be stocked right into 14 mm mesh Vexar bags (October 2016), they were harvested in April 2017 (12 month from spawn). Replicated field trials were performed at the UF speculative lease within the Dog Island Aquaculture use Area off Cedar crucial to paper the results of ploidy (diploid matches triploid), stocking thickness (125, 150, 175 oysters/bag), and also float architecture (square matches bullet) on oyster production. To identify growth, a sample the 35 oysters from each of the 42 bags (six replicate bags every treatment) to be measured for covering height, length, and width and weighed (see number 1). Five oysters per bag to be shucked and meats weighed. Images of meats and shells (external and also internal) to be taken to file appearance. In addition, a sample of 5 oysters per bag were shipped come Dr. Susan Laramore because that assessment of health and wellness (presence that parasites). An additional five oysters per bag were maintained for confirmation of ploidy, and also 10 every bag were frozen to analyze later for dried meat weight, condition index, and also biofouling. Survival was identified by counting the variety of live oysters per bag and dividing by the number of oysters originally stocked. This data were statistically analyzed to determine the definition of ploidy, stocking density, and float architecture on oyster growth and also survival. Transparent the six-month trials, the lot of time forced to finish various work was recorded. This information, which will be provided to approximate labor costs, together with seed and gear expenses will aid to calculation profitability based on production data obtained in these trials.

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Figure 1. From left to right, top: measure up shell elevation (SH), shell length (SL), and also shell width (SW) with calipers. Native left to right, bottom: measure up oysters for total weight (TW) and meat (wet) load (MW) through an digital scale.






Results: Ploidy Comparison, Diploid (2N) versus Triploid (3N)

After 6 months in growout, distinctions in ploidy form were determined. Measurements were averaged by ploidy type across all stocking densities tested. The shell height of triploid oysters average 83 mm (3.3”), which was significantly greater than the average elevation of diploid oysters (76 mm, 3”). Total weights were likewise significantly different with triploid oysters averaging 143 grams (3.2/lb) and also diploid oysters averaging 109 grams (4.2/lb). Likewise, meat weights differed with triploid oysters averaging 13 grams and also diploid oysters averaging 9 grams. In contrast, survival was higher in diploid oyster bags v an mean survival of 97%; triploid oyster bags had actually an median survival the 90%. Nonetheless, results obtained for both ploidy species over a “winter” growing duration (October through April) are considered commercially acceptable.

Figure 2. The distinctions in growth and survival that diploid and triploid oysters cultured in 14 mm mesh bags supported by square floats are portrayed below. These data to be averaged throughout stocking densities tested; the number of replicate bags to be 18 every ploidy type. White lines in ~ the optimal of every bar represent the typical deviation, which is the variation among replicate bags.


Results: Stocking thickness Comparison

There to be no significant differences in shell height, total weight, meat weight, or survive of diploid oysters cultured at three stocking densities (125, 150, and 175/bag). Likewise, stocking density did not have a far-reaching effect ~ above growth and also survival the triploid oysters. Averages of development (SH, TW, MW) for each density were consistently greater in the triploid oysters than the diploid oysters at the moment of harvest, whereas typical survival the each density treatment was higher for diploid oysters. These results imply that autumn densities as high together 175 every bag over a “winter” growing duration can result in commercially viable production. However, these results may differ during a “summer” growout period, as thickness may have much more of an effect on oysters reaching harvestable size when water temperatures room warmer.

Figure 3. Median shell height, full weight, meat weight, and also survival among three autumn densities (low, medium, high) are displayed for diploid (2N) and also triploid (3N) oysters. The number of replicate bags were 6 per density. White lines at the peak of every bar stand for the standard deviation, i m sorry is the variation among replicate bags.

Results: Float architecture Comparison

At harvest, triploid oysters get an impression in bags with bullet floats attached to the sides (n=6, average 88 mm SH) were considerably larger than triploid oysters get an impressive in bags with square floats attached come the bottom (n=6, typical 81 mm SH) (Figure 4). However, survival of oysters differed substantially in bags supported with square floats (91%) when compared to oysters in bags supported with bullet floats (84%). The square floats were 4.5” x 4.5” x 35” in length; vice versa, the cartridge floats were 3.25” in diameter and also 32” in length. As the oysters grew and also bags ended up being heavier, the cartridge floats did no have sufficient buoyancy to assistance the weight. Throughout the last month of the culture period, all bullet float-supported bags were uncovered vertical in the water column, which led to oysters being crowded at one finish of the bag. This most likely contributed to boosted mortality.

Figure 5. This graph summarizes expansion (shell height, total weight, meat weight) and survival the triploid oysters cultured in 14 mm mesh bags sustained by two float types (square and bullet). White lines at the optimal of every bar stand for the typical deviation, i m sorry is the variation among replicate bags.


Results: appearance

External shell Appearance and also Meats Shell dimensions (height, length, width) are supplied to calculation fan and also cup ratios to identify if outside shell appearance is appealing for the fifty percent shell market. This has not however been figured out for data acquired in the UF trials. Pictures in figure 6 below show a unique difference in between the two ploidy types, through triploids preserving their characteristic black “strike” on optimal of the shells. At the moment of harvest, there to be a high pervasiveness of maturation gametes (reproductive cells) in the meat of diploid oysters together they started to “ripen up”. This advancement is common in the spring when waters start to warm and oysters prepare to spawn. The presence of gametes gives oysters a various taste. Further, diploid oysters come to be deflated after ~ spawning, rendering them unappetizing and potentially less an important until they increase glycogen (“fat”) reserves in the complying with months. Triploid oysters, i beg your pardon are successfully sterile, should maintain a consistent kind and flavor throughout the year, an added benefit come increased development rates typically associated with them. It to be observed the over 90% that the diploid oyster meat sampled had partially occurred gonads. In May, diploid and also triploid oysters from this trials will certainly be rated because that appearance, texture, flavor, and overall acceptability by panelists at the UF/ Aquatic Food manufacturing Pilot Plant.

 Figure 6. Appearance of shells and also meats the diploid (2N, top pictures) and also triploid (3N, bottom pictures) oysters.

Internal shell Appearance After oysters to be shucked to achieve meats because that weighing, the shells were photographed and the existence or lack of parasites and also biofouling noted. The burrowing mudworm (Polydora websteri) is a typical pest found in oysters. Major infestations an outcome in blisters on the internal shell, which pipeline the covering brittle and prone to breaking (Figure 7). In addition, that detracts from the appearance of the product. Fragile and unattractive shells minimize the value of oysters that space harvested because that the fifty percent shell market. There to be no indicators of mudworms in either the diploid or triploids oysters (Figure 7). Every shells had actually a creamy white and yellowish coloration and were devoid of blisters connected with mudworm infestations.

 Figure 7. Shells that triploid oysters native this study (left and middle) and also shells with significant mudworm damage (right). The photo on the best was obtained from a study performed by Auburn university researchers (Gamble et al. 2016).

Biofouling The warm water temperatures in Florida allow for accelerated and year-round development of oysters; however, these conditions can additionally increase the existence of biofouling organisms, such as barnacles or sea squirts. In these field trials, oyster spat naturally recruited native “wild” oysters were the primary fouling organism discovered on diploid and triploid oysters. At harvest, spat to be counted on oysters from each bag to determine the percent fouling. Oysters v zero to 2 (0-2) spat were thought about marketable. Regardless of ploidy or density, oysters had an mean of 67-73% 0-2 spat every shell. Triploid oysters in bags supported by bullet floats were much less fouled through an average of 76% 0-2 spat per shell. The is amazing to keep in mind that a processing plant in Cedar vital efficiently culled oysters indigenous this examine that were greatly spatted (3-8 every shell) utilizing wire clippers, making them saleable as solitary oysters.

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Figure 8. The graph listed below shows the mean proportion that oysters through zero to two (0-2) spat per shell for every ploidy and also stocking thickness combination. White lines at the top of every bar represent the conventional deviation, which is the variation amongst replicate bags.