Derelict Crab Trap Removal Program
Louisiana Blue Crab
The blue crab (Callinectes sapidus) is a mainstay of local cuisine and an important commercial fishery in Louisiana. According to Louisiana Department of Wildlife and Fisheries, an average of 45 million pounds of blue crab are harvested in Louisiana each year. The fishery is typically open year-round with no commercial catch limits or limit on the number of commercial traps. Size limit for blue crab is 5 inches from point to point of upper shell, unless premolt and held in a separate container. Additionally, there is a ban on the commercial harvest of immature female blue crabs, unless they are pre-molt being held for the making of softshell crab (through 2019). No more than 2% of random sample of 50 crabs in possession may be either egg bearing crabs, or immature female crabs. Currently, blue crabs can be legally harvested using a crab drop net, trawl, skimmer net, and most commonly, crab traps. For more on commercial fishery regulations, see LDWF.
Derelict Crab Traps
Derelict crab traps are any crab traps that have become discarded, lost, or abandoned in the marine environment. In Louisiana, they are a widespread form of marine debris. Derelict traps are a hazard to navigation, a source of habitat degradation, and a nuisance. They disrupt fishing by becoming tangled in shrimpers’ nets, and can damage boat propellers, particularly when they are cut from their float line. They also continue to catch fish, crabs, and even birds or small mammals when washed ashore. The exact number of derelict crab traps in coastal Louisiana is unknown, but one estimate for the entire Gulf of Mexico was more than 600,000 with an additional 250,000 becoming derelict every year. Applying the Gulf-wide rate estimate (25%) and the most recent average number of traps per license holder (460) to the number of commercial crab fisherman reporting landings (1,458), approximately 167,670 crab traps become derelict every year in coastal Louisiana.
Derelict traps can also get caught in and cause damage to boat propellers.
Redfish captured by a derelict crab trap. In addition to crabs, many species of fish and even birds can be captured by derelict traps.
Not just blue crab! Stone crabs are frequently found in derelict traps in more brackish parts of the estuary.
A major effect of derelict traps is “ghost fishing” or continued capture of crabs and fish without fishers maintaining or baiting of traps. Ghost fishing can be a long-term problem because crab traps take years to degrade. Fish and crabs that are caught in the derelict traps die and continue to "re-bait" the traps, attracting more animals. Millions of dollars in crab harvest are likely lost to abandoned traps every year. Blue crab mortality might be as high as 25 crabs per trap per year left in the environment. The pictures below show the three step process that cause derelict crab traps to ghost fish.
How Derelict Crab Traps Ghost Fish - A 3-Step Process
Step 1: The derelict crab trap trap grows barnacles
Step 2: The barnacles attract a sheepshead to feed and it becomes trapped.
Step 3: The sheepshead dies and re-baits the trap, catching more crabs which may eventually die.
Derelict Crab Trap Rodeo Program
The Derelict Crab Trap Rodeo Program was initiated in 2004 by the Louisiana Department of Wildlife and Fisheries (LDWF) to remediate the ecological, environmental, and economic costs of derelict crab traps. The Louisiana Wildlife and Fisheries Commission dictates a closure area for derelict crab trap removal within Louisiana state water bottoms. During these closures, crabs can’t be taken by commercial fishers in the designated areas and crab fishers are asked to remove their traps. During the closure, LDWF and its designees may collect and dispose of derelict traps. Typically, volunteer days allow the public to collect traps within specific locations. For each trap, bycatch and location information is recorded and organisms released. Traps are transported by boats to a designated marina where they are crushed and placed in a dumpster for offsite disposal.
Sequence of derelict crab trap removal process, clockwise from upper left: Abandoned traps are retrieved, from marsh or water (top left), Bycatch and location are recorded and traps are transported to the marina (top right), traps are unloaded from boats by volunteers (bottom right, and crushed using a modified wood-splitter before being placed in dumpsters (bottom left).
Derelict Crab Trap Removal in the Pontchartrain Basin: 2016 - 2018
Since 2016, Pontchartrain Conservancy (PC) has worked with the Louisiana Department of Wildlife and Fisheries (LDWF) to accelerate the retrieval of derelict crab traps from Louisiana waters. So far, PC has helped remove 8,305 derelict traps from the Pontchartrain Basin. Our project focus is to streamline removal efforts by hiring boats well-suited to picking up derelict crab traps, allowing us to maximize efficiency during the limited closure periods.
More derelict traps were retrieved during the complete fishery closure in 2017 (orange) than in 2016 (pink) or 2018 (yellow).
PC v-hull center console boat loaded with crab traps (left) vs. a commercial flat boat rigged to collect and transport crab traps (right). The larger commercial boat reduced average cost to remove traps.
Estimated # of Visible Derelict Crab Traps Remaining in the Pontchartrain Basin
Data collected in 2018 were used to update the estimated number of visible derelict crab traps (i.e., traps with floats) within the Pontchartrain Basin and Louisiana coast-wide. These calculations do not include what could be a very large number of derelict traps on water-bottoms without a float line and, therefore, not visible from the surface. Using a range of visible trap densities that we have encountered over the three years of removing traps, we were able to estimate how many visible traps remain in our basin. Our estimates indicate the Pontchartrain Basin may have from 42,600 to 60,600 visible derelict crab traps remaining. The Louisiana Coastal Zone may have from 93,300 to 133,000 visible derelict crab traps remaining.
Impacts of Derelict Crab Traps
Based on a published estimated mortality of 25.8 crabs per year in Louisiana, the range of possible mortality from derelict traps can be calculated. Assuming that derelict traps ghost fish for three years (may be as great as nine years), and that the average retail price for a crab is $1.55 (LDWF reported price in 2015), an indication of the economic value of the wasted blue crab resource can be calculated. For the Louisiana Coastal Zone, the economic value of lost blue crabs to derelict crab trap ghost fishing ranges from $11M to $15M over the three-year period that the trap continues to fish. Using our higher cost of removal ($18.00/trap), and the economic value of the crabs saved when the traps are removed, the return on investment is about 650%. The economic value estimate of the wasted crabs does not include many other economic impacts, such as those to recreational fishing, shrimp fishers, or due to navigational incidents. It also doesn’t include the longer-term impact of un-retrieved traps that have lost their float line.
Ghost Fishing Impacts
During PC’s 2018 derelict crab trap removal, 4,000 crabs were released. Of these 4,000, 6% were dead. Using the average of 25.8 dead crabs per trap/year and a derelict trap life of 3 years, PC prevented 83,979 crabs from being wasted in derelict traps.
Unlike previous years, PC observed live and dead diamondback terrapin turtles (Malaclemys terrapin) caught in derelict crab traps. Diamondback terrapin turtles are native to brackish marsh, and considered a species of concern in most states within their range. Blue crab habitat overlaps with that of diamondback terrapin and derelict crab traps are considered a major threat to their survival in some areas. When found in derelict crab traps, diamondback terrapin are often observed in large numbers; PC observed as many as 16 dead turtles in one trap.
Blue crabs in a derelict crab trap, 2018.
Derelict crab trap full of drowned diamondback terrapin turtles from retrieval in 2018.
Two diamondback terrapin turtles that were released from derelict crab traps during 2018 removal.
Future Removal Efforts
In 2019, PC plans to capitalize on lessons learned 2016-218 to ramp up the number of traps removed from Lake Pontchartrain Basin and the Louisiana Coastal Zone as a whole. Our objective is to remove more than the number of traps that are lost every year, so that the existing inventory of traps lost in past years can start to be reduced.
With their negative ecological and environmental impacts, “ghost traps” are clearly a detriment to the Louisiana coastal zone and removing them should be a priority for coastal stakeholders. In the future, the crab trap removal program looks to incorporate improvements to sustainability, such as reduction of lost gear and recycling or reuse of derelict traps.
Volunteer reaching to retrieve a derelict trap with a boat hook.
Gar caught in a derelict crab trap.
Bird caught in a derelict crab trap retrieved from the edge of a waterway. The bird was rescued.
The Derelict Crab Trap Program is funded through donations from:
Colonial Pipeline Company
Stantec Consulting Services
Louisiana Department of Wildlife and Fisheries
Louisiana Crab Task Force
Larry Garvey Foundation
Common Ground Collective
Tyler J. Kelley
St. Bernard Parish Government