Guest Blogger: Gabrielle Renchen, Biological Scientist with the Florida Fish and Wildlife Conservation Commission
In an effort to understand regional derelict trap issues, two projects with recently published papers were funded by the NOAA Marine Debris Program.
Traps become marine debris as they are lost or abandoned, and are then usually referred to as ‘derelict’. The impacts of derelict fishing traps are three fold. (1) Derelict traps can continue to ensnare and kill fish and other organisms. Fish that die in derelict traps won’t be part of the harvestable catch for fishermen, and won’t reproduce in the future. (2) Derelict traps are lost to the fishermen, who will need to replace every lost trap. (3) Derelict traps damage the habitat, which can negatively impact where the fish live and eat.
Florida Keys’ Derelict Lobster Traps
What typically comes to mind when you think of the Florida Keys? Beautiful blue waters, coral reefs, fish, and other amazing marine life… but there’s something else lurking below: marine debris! In addition to metal cans, glass bottles, and monofilament fishing line, lobster traps are the Florida Keys’ prominent type of marine debris. A team of scientists from NOAA’s Center for Coastal Fisheries and Habitat Research (Amy Uhrin), the Florida Fish and Wildlife Conservation Commission (Tom Matthews) and the Keys Marine Laboratory (Cindy Lewis), conducted surveys to identify and count lobster trap debris and other types of marine debris. These surveys consisted of two divers who were towed behind a boat to study underwater habitats throughout the Florida Keys.
Lobster trap debris included wood slats, rope, and the cement weights used to sink the traps. The scientists counted ghost fishing traps which are lost but still able to catch and kill lobsters and other animals as well as non-fishing traps which were found in various stages of breakdown. They estimated that over 85,000 ghost traps and over 1 million non-fishing traps were in the waters of the Florida Keys. To put these numbers into perspective, about 483,000 lobster traps are actively fished annually.
Trap debris was found in a variety of environments; seagrass, algae, sand, with the highest density of trap debris observed in coral habitats. The accumulation of lobster trap debris in coral habitats, a rarely targeted lobster fishing area, suggests that wind plays a role in moving traps, harming corals, sponges, or sea fans. Other research has indicated that many traps move continuously until finally becoming lodged in the shallow water areas where corals reside.
Trap loss is both an economic issue for fishermen and a source of damage to the environment. Harvest losses due to lobster mortality in ghost traps and missing gear are substantial sources of lost income for fishermen. Although trap debris removal efforts exist, they are expensive and cannot remove the debris as fast it accumulates. And in the Florida Keys the causes of trap loss include boat propeller cut offs, hurricanes, and theft.
Here’s how you can help: be an alert boater by avoiding trap buoys and organize your own trap debris cleanup through the Florida Fish and Wildlife Conservation Commission’s Trap and Trap Debris Removal Program!
US Virgin Islands’ Derelict Fish Traps
Fish traps are a culturally and economically important fishing gear used to catch reef fish in the U.S. Virgin Islands (USVI) and throughout the Caribbean. Fish traps are placed in a variety of habitats that can include seagrass, sand, algae, and coral habitat. Given the USVI fishermen’s concerns regarding fish trap loss, our team of researchers from the University of the Virgin Islands, the NOAA Biogeography Branch, and the St. Thomas Fishermen’s Association worked together to investigate the impacts of derelict fish traps. Like in the Florida Keys, theft, vandalism, and buoy-marker severing, where a boat propeller cuts the line and renders the trap derelict, are common causes of trap loss in the USVI in addition to severe storms.
We deployed fish traps built by local fishermen in nearshore and offshore waters where trap fishing was known to occur. Between January and July of 2010, checking traps 2-3 times a week, divers recorded more than 1,100 fish in the derelict fish traps. Topping the list were surgeonfish, snapper, and porgy and hundreds of small juvenile fish and invertebrates. Overall, 34 fish were found with skin abrasions while 2% of the trapped fish died, with the cause of death attributed to ghost fishing. Using our accounts of the species that died and the local fish market prices, we estimated that each derelict trap was capable of causing an annual loss of $52.
Improving spatial planning can reduce the occurrence of severed trap buoy lines, while simple modifications to trap escape panels will significantly reduce mortality from ghost fishing, and the implementation of land-based trap disposal programs could reduce the impact of recoverable derelict traps. This project reveals the impact of derelict traps and their unintentional loss to both the fishing community and coral reef ecosystems. It also speaks to what can be accomplished when we work collaboratively to understand an environmental challenge!
Click for more information on our derelict fish trap project.
To read the full article: Impact of derelict fish traps in Caribbean waters: an experimental approach