42 MARCH 2022 • WORLD AQUACULTURE • WWW.WA S .ORG stocked into 37-L,3 2-mmmesh bags, and sequentially transferred with growth to 4-, 9-, and 14-mmmesh bags. Oysters grown in the ALS were initially stocked into 15-L,4 3-mmmesh baskets, then to 6-mm and 12-mm versions as oysters grew. Management of the farm involved routine desiccation of oysters and gear to minimize growth of algae, barnacles and other fouling organisms. In summer, oysters were desiccated weekly from 1600 h to 1000 h the following day to avoid excessive midday and early-afternoon heat. The desiccation period was increased to 24 h for all other seasons every 10-14 days, depending on the amount of biofouling observed. Biofouling on gear was also controlled by periodically removing oysters from biofouled gear to clean bags and baskets, followed by pressurewashing on land. Although time consuming and labor-intensive, cleaning of gear is required by Texas law to take place on land. To maintain appropriate stocking densities, oysters were divided in approximately half and restocked every two weeks from July to November 2020. Growth rate of oysters decreased during cooler months, resulting in less-frequent reductions in density, approximately every 4-6 weeks, from December 2020 to May 2021. Most oysters reached minimal market size (64 mm) by April 2021, indicating a less-than-one-year grow-out time from spawn to harvest. When oysters reached market size (Fig. 6), the majority were relocated to another part of the bay to aid in reef restoration efforts, while some were kept on the farm for use as broodstock for future research efforts. Managing through Challenges The HRI oyster farm faced several environmental challenges throughout its first year of operation. The 2020 hurricane season was highly active, resulting in several storms that threatened the Texas coast. A hurricane protocol was enacted three times during the 2020 season that involved lowering ALS lines to the lowest position on the riser posts. Floating cages were lowered to the bay bottom by removing the caps on the pontoon floats and filling them with water. After each storm, ALS lines were placed back in normal operating position and floating cages were re-floated using a boat with a davit. Fortunately, none of these storms caused any damage to the gear or loss of oysters. In mid-February 2021, extreme cold temperatures from a winter storm dropped water temperature to 1 C and was particularly problematic related to the strong north winds associated with the storm. This resulted in exceptionally low water levels (Fig. 7) on the farm site, potentially exposing the oysters to below-freezing air temperatures for several days. In an effort to protect the oysters from freezing, a temporary line was set up at the deepest portion of the lease using helix anchors and nylon rope. Oysters were placed on this rope and allowed to rest on the bay bottom in the hope that they would remain submerged during the worst of the cold. The emergency relocation was successful and no significant mortality was observed in the days or weeks following the freeze. A prolonged freshwater-inflow event occurred fromMay 2021 through August 2021 in which the area received over 130 cm of rain. The area received more rainfall in three months than the area typically experiences in an entire year, resulting in salinities below 5 ppt for almost three months. Farm salinity was below 1 ppt for days and sometimes weeks at a time. During this time, desiccation and any non-essential handling of the oysters was suspended in an attempt to minimize any further stress to the oysters. Mortality on the farm had been low (<2 percent) up to this point, and fortunately the majority of oysters had already reached market size and been relocated. The approximately 10,000 oysters remaining on the farm during the freshwater event survived these low salinity conditions with minimal mortality for approximately two months. Ultimately, by late July 2021, a large portion of these oysters had died. By late FIGURE 6. Market-size oysters grown at the HRI oyster farm (Photo: Bailey E. Schacht). NEED FIGURE 5. Eastern oyster (Crassostrea virginica) seed stocked at the HRI oyster farm (Photo: Bailey E. Schacht).
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