Evaluation of Oyster Aquaculture as a New Texas Coastal Industry
A demonstration project evaluating oyster aquaculture cages from an environmental, biological, and economic perspective
Oyster populations in Texas bays and estuaries have been declining over recent years due to over-fishing and a series of environmental disasters ranging from extreme freshwater inflow to hurricanes. At present all U.S. coastal states with the exception of Texas, practice oyster aquaculture.
We have developed a small research site in Copano Bay at which cages containing oysters have been located. These cages are representative of various common methods used to grow oysters in natural waters. These methods include: off-bottom culture (trays supported off the bottom), mid-water column (adjustable long-line), and floating cages. The purpose of the project is to evaluate various types of oyster aquaculture cages from an environmental (impact), biological (growth survival of oysters), and economic perspective. The oyster cages are being periodically evaluated for growth and survival and the site, as a whole, is being monitored for various environmental/water quality criteria (e.g., temperature, salinity, dissolved oxygen, plankton counts, total dissolved solids, total suspended solids, total settleable solids, etc.).
With the advent of warmer water temperature, cage biofouling (both hard and soft) is becoming an issue that requires periodic inspection for cleaning in order to improve flow of water. The major increase in biofouling appears to be associated with “soft” vegetative growth in which the cage, itself, is being used as a substrate. Level of biofouling also appears to increase with proximity of cages to the benthic surface of the bay.
Other issues are associated with high wind velocity and increased wave action, largely affecting floating cages. Increased wave action through vertical mixing has caused some of the bottom cages to settle into the sediment, creating challenges for routine assessments. Adjustable long-line cages (ALS) that are situated in the middle of the water column have proven to be the most successful for this particular location, but have required additional maintenance to reduce the accumulation of biofouling. Overall, the shallow waters, increased wave activity associated with cold fronts, and general location of the project are presenting unique challenges to each type of cage and although all were successful for the project, the mid-water cages proved to be the most suitable for Copano Bay. For commercialization of oyster aquaculture, site selection will be critical with respect to ease of management as well as suitability of cage type.