By: Kirk Havens, Guest Blogger
Wire trap fisheries such as blue crab, lobster, Dungeness crab, and stone crab experience around a 20% annual loss rate of traps globally, creating a significant marine debris issue. Traps are frequently lost when their lines are tangled and moved during storms, or cut from boat traffic. New synthetic materials have extended the life of traps which now, when lost, can last for several years. This amounts to potentially millions of derelict traps worldwide that can continue to capture and kill hundreds of thousands of marine animals every year for multiple years. In many situations, animals captured in derelict traps serve as attractants for other animals resulting in a self-baiting ‘ghost’ fishing cycle.
In the Virginia portion of the Chesapeake Bay, USA, over 32,000 lost and abandoned blue crab traps were removed by commercial fishers over four winters in a program funded through NOAA with federal commercial fishery failure funds. Over 30 species numbering over 30,000 animals were captured in the traps during the low-activity winter months. During warmer months, when more species move into the Bay and animals are more active, those numbers are expected to be much higher. While this was a successful program that partnered commercial fishers, regulatory personnel, and scientists, removal of lost traps is expensive and mostly prohibitive at large scales so a mechanism to render the traps ineffective at capturing animals once the trap is lost is needed.
To reduce the impacts of lost traps, researchers at the Virginia Institute of Marine Science, College of William & Mary have developed an escape panel made of a naturally occurring polymer that biodegrades completely in the marine environment. The polymer, which is produced naturally by bacteria in marine systems and is biodegraded by microorganisms into carbon dioxide, methane, water, and other organic and inorganic compounds, is certified by the American Society of Testing and Materials as biodegradable in the marine environment. The polymer can be designed to biodegrade at different time intervals and if regularly removed from the water while a trap is actively fished the life of the panel can be extended for the fishing season. Once lost and no longer exposed to the atmosphere, the biodegradation process is accelerated.
Escape mechanisms on traps that rely on hinges or degradable attachment points fail because of encrustation by bio-fouling organisms such as barnacles, mussels, and sponges which hold or weight the non-degradable panel in place once the trap is lost. The biodegradable escape panel is sized to mimic the entrance funnel of the trap so that once the panel dissolves anything that can enter the trap can also escape. In addition, since the panel biodegrades due to microbial activity, encrustation of marine fouling organisms is not an issue.
The biodegradable panel can be effective in most trap fisheries and has been shown to have potential as a practical and inexpensive solution to the worldwide problem of lost or abandoned traps. For more information visit: http://ccrm.vims.edu/marine_debris_removal/index.html