We assessed the abundance and distribution of derelict spiny lobster trap debris in the Florida Keys National Marine Sanctuary using towed-diver surveys. We found that most trap debris aggregates in and around coral habitats. This accumulation suggests wind has a role in redistributing traps and trap debris in the sanctuary. Removal of trap debris from these areas would mitigate habitat impacts but not address future trap loss, ghost fishing, or the cost of lost gear.
Why We Care
The commercial spiny lobster fishery in the Florida Keys National Marine Sanctuary is well documented, but little information is available on the prevalence of lost or abandoned lobster traps. As of 2013, there are over 450,000 permitted traps in this fishery. The law requires that all lobster traps have an attached surface buoy. Buoy lines are a navigational challenge in this region of high boat traffic and often are severed by boat propellers. The resulting absence of surface demarcation leads to impaired trap relocation and gear loss. Other causes of loss include vandalism, theft, and entanglement of gear on the bottom, inability to relocate traps, and gear degradation. Although Florida fishermen are required by law to retrieve their traps before the close of the season, some abandonment of traps occurs. Strong winter storms, tropical storms, and hurricanes greatly exacerbate gear loss. Fishermen reported 63.4 percent trap loss in 2005 when four hurricanes (Dennis, Katrina, Rita, and Wilma) battered the Florida Keys between July and October. If this loss rate is applied to the 479,536 active traps for that season, close to 300,000 traps may have been lost as a result of those storms.
Spiny lobster trap debris is a common feature along shorelines and in nearshore waters of the Florida Keys. Derelict gear presents a hazard to navigation and public health and safety, and derelict traps continue to actively fish lobsters (ghost fishing) as well as a number of other commercially and ecologically important species, including some endangered species, leading to mortality due to confinement. Derelict traps can move hundreds of meters during storm events, which results in tissue abrasion, breakage, and often complete removal of Essential Fish Habitat including seagrass, sponges, and hard and soft corals.
Efforts to address the accumulation of derelict fishing gear have included debris recovery and programs designed to reduce overall fishing effort. Retrieval programs, however, are prohibitively expensive, and experience suggests that such programs cannot remove debris as fast as it is accumulating. Understanding the sources and processes that drive the spatial distribution of marine debris is crucial to remediation efforts.
What We Did
In 2007, we conducted 151 towed-diver marine debris surveys covering 120.8 hectares in the area primarily targeted by the commercial lobster fishery across all benthic habitats in the Florida Keys National Marine Sanctuary. We recorded all observed pieces of trap debris and any other marine debris items encountered. We estimated trap debris density (debris incidences/hectare) in historic trap-use zones and in representative benthic habitats.
We collaborated with the Florida Fish and Wildlife Conservation Commission and the Keys Marine Laboratory to conduct this work with funding from the NOAA Marine Debris Program.
Outcomes and Benefits of Our Work
- To our knowledge, this is the first study to estimate the number of derelict spiny lobster traps that may exist on the seafloor of the Florida Keys National Marine Sanctuary.
- We estimated that 85,548 ghost traps and 1,056,127 non-fishing traps or remnants of traps were present in the study area.
- Surprisingly, more trap debris was observed in regions of the sanctuary where fishing effort is not as pronounced.
- Coral habitats had the greatest density of trap debris despite trap fishermen’s reported avoidance of coral reefs while fishing.
- The accumulation of trap debris on coral emphasizes the role of wind in redistributing traps and trap debris in the sanctuary.
- Removal of submerged trap debris from especially vulnerable coral-dominated habitats could reduce debris from areas in which it accumulates thus preventing potentially negative impacts to sensitive habitats.