Derelict Traps and Casita Debris in the Florida Keys National Marine Sanctuary: Distribution, Habitat Impacts, and Bycatch Mortality
Spiny lobster and stone crab trap debris and casitas (artificial structures illegally deployed by divers to attract lobsters for subsequent harvest) are common features along shorelines and in nearshore waters of the Florida Keys National Marine Sanctuary (FKNMS). Tens of thousands of traps are lost annually during routine fishing and hundreds of thousands of traps are lost during hurricanes. The number of casitas is unknown but a recent cleanup effort removed 66 tons of debris. In addition to presenting a hazard to navigation and public health and safety, derelict traps and casitas may both impact Sanctuary resources. Essential Fish Habitat (EFH) may be threatened as derelict gear rests directly on top of habitat features and moves during storms (Figure 1 and 2). Commercially and ecologically important species, including some endangered species, may also be threatened as derelict traps continue to actively fish, causing mortality of confined animals.This project uses towed-diver surveys throughout the FKNMS to document the distribution of derelict trap debris and casita structures and the extent of habitat damage from both (Figure 2 and 4). We specifically identify debris in sand, seagrass meadows, algae beds, hardbottom, and low-relief coral habitats (Figure 3). Additionally, we estimate mortality of lobsters and other confined animals due to derelict traps. In combination, these key pieces of information will help more effectively manage the trap fisheries in the FKNMS by providing quantitative information on the existence and extent of the debris problem and identification of specific targets for remedial action.
Fulfills FKNMS habitat management requirements
Facilitates revision of Essential Fish Habitat (EFH) provisions in regional fishery management plans
Promotes informed industry decision-making with respect to trap placement, the need for gear removal at the end of the season or at the onset of severe storms, and the effect of derelict gear on EFH
Encourages a more effective and ongoing debris removal program in the FKNMS
Research on Derelict Traps and Casita Debris in the Florida Keys
In 2007, NOAA and the Florida Fish and Wildlife Conservation Commission began a project in the Florida Keys National Marine Sanctuary (FKNMS) to provide critical data on the distribution of trap and casita debris, the impact of this debris on Essential Fish Habitat, and lobster and bycatch mortality. Marine debris surveys were completed, covering over 750,000 square meters of the seafloor in FKNMS. More trap-related debris (68.3 percent of total) was found per survey area on Atlantic Ocean habitats (7.4 sightings per hectare) versus Florida Bay (4.1 sightings / ha). The highest amount of trap debris was recorded from the Middle Keys on the Atlantic Ocean side (9.4 sightings / ha) while the least amount of trap debris occurred in the Middle Keys of Florida Bay (1.4 sightings / ha). Marine debris estimates from this study identify spiny lobster trap debris as the primary form of marine debris in FKNMS. The high abundance of trap debris on coral habitat, relative to the actual amount of coral habitat found in FKNMS, suggests that this habitat may act as a sink for trap debris. Derelict traps continue to catch and kill lobster. Additional research is needed to determine lobster mortality estimates due to confinement in derelict traps. Non-lobster bycatch in derelict traps is minimal, with some fauna utilizing the traps as refuge.
Figure 1. A derelict spiny lobster trap rests on colonized hard bottom. Notice the bare “halo” in the foreground where shifting of the trap during a storm event has scoured the seafloor. Photo courtesy of Cindy Lewis (FWC).
Figure 2. A deteriorated spiny lobster trap (a) and a stone crab trap (b) resting on coral habitat. Photo courtesy of Amy V. Uhrin (NOAA/CCFHR).
Figure 3. Project diver, Stopher Slade, is shown actively towing across mixed seagrass/low-relief coral habitat. Photo courtesy of Amy V. Uhrin (NOAA/CCFHR).
Figure 4. Project divers Tom Matthews (foreground) and Jenny Vander Pluym assess the extent of habitat impact from a derelict spiny lobster trap observed during a tow.
This video depicts a portion of a 1 km marine debris survey-tow conducted on Tennessee Reef, Florida Keys National Marine Sanctuary on July 13, 2007. Video courtesy of A. Uhrin, NOAA/CCFHR.
Download the 1-pager handout (pdf 1.12MB) on this project here.
This program is funded through NOAA's Ocean Service, Office of Response & Restoration, Marine Debris Program.