Abstract
Oysters are keystone species and ecosystem engineers that play many important roles in shoreline ecosystems. Oysters can serve these same roles even when farmed. Further, oysters could play an increasing role in a sustainable blue economy in coastal communities. In some farm operations, a process called oyster tumbling is used. Farmed oysters are put through a machine that rotates, removing barnacles and unwanted organisms and breaking off the edges of the shell. This results in a detritus free oyster with a more desirable shape that is shorter in length with a deeper cup, also commanding in a higher market price. This process commonly involves removing oysters from the water and running them through a diesel powered ‘tumbler’. Alternatively, increasing numbers of wave and tidal powered tumbling processes are being developed that use the power of moving water to tumble oysters. These typically tumble the oysters less intensively by using specially designed tumble bags or cages that allow tides and waves to bump them into each other for their entire growing cycle, rather than moving the oysters in and out of a mechanical tumbler several times throughout the growing process. Existing designs for tide or wave powered tumbling equipment include floating bags, long line baskets, and flip bags. Conventional farming technology that does not involve a wave or tidal powered tumbling process are on-bottom or bed farming, bottom cage systems, floating cages, tray cultures, and lantern nets. Farming methods such as these most often employ diesel powered mechanical tumbling where oysters are removed from the water and run through the tumbling machine to clean and sort them and then are returned to their growing location. Other farmers use more laborious techniques of pressure washing and vigorously shaking instead of tumbling. Preliminary literature searches find that tide powered tumbling tends to make for a less expensive, less laborious oyster farming process compared to farming techniques that require mechanical or human powered tumbling. Issues raised with wave-powered equipment are that it requires too much storage space and deployment can be difficult, however these are common issues raised with conventional equipment as well. To assess the opportunity for integrating wave or tidal powered tumbling to farming operations, this study aims to understand the factors considered when deciding what technology to use for oyster farming. Major factors include geography, weather conditions, water characteristics such as depth and extent of tide, cost of equipment and labor and maintenance requirements. There are ocean powered techniques that are applicable in a wide range of environments, specifically flip bags may be used in tidal waters, long line baskets may be used in shallow waters (< 6ft), and floating bags may be used in shallow or deep waters (> 8ft) meaning marine energy powered techniques are likely scalable to a wide variety of environments and conditions. This presentation will highlight the range of conditions that tide powered tumbling operations can operate, anticipated cost, as well as the future opportunities for design and demonstration projects for oyster farmers.