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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 loss rate estimate (25%) and the average number of traps per license holder (257) to the number of license holders in 2015, approximately 109,000 crab traps become derelict every year in coastal Louisiana.

Redfish captured by a derelict crab trap.  In addition to crabs, many species of fish and even birds can be captured by derelict traps.

Derelict traps can also get caught in and cause damage to boat propellers.

Artistic sculpture made from litter and a derelict crab trap by local artist Jacqueline Ehle Inglefield. Art was on display at LPBF’s New Canal Lighthouse and Education Center for several months.

Ghost fishing

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.

2017 Derelict Crab Trap Rodeo pictures showing sequence of 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 Louisiana: 2016 & 2017

2016

The 2016 closure in Lake Pontchartrain lasted nine days, from February 12 through February 21.  A total of 1,386 crab traps were removed from the eastern Lake Pontchartrain closure area.  Over 600 traps were collected by LPBF staff or contractors, and 554 were collected by volunteers.  LPBF staff and contractors used LPBFs <20’ center console boats and were able to retrieve between 20-30 traps per trip.  Typically, LPBF staffed boats made 2 to 3 trips a day, resulting in a removal cost of $19.77 per trap.  This method was similar to other rodeos in that the boats used for crab trap collection are typically small passenger boats, not designed for commercial fishing (i.e vessels are 16 to 24 ft in length, often with a center console and without a fantail or large workspace).  These boats are not ideal for transporting traps and are limited in how many traps they can carry.

2017

One of LPBF’s main goals in 2017 was to improve efficiency by increasing the number of traps retrieved and decreasing the cost of collection from $19.77/trap. To this end, LPBF contracted a 35’ x 19’ aluminum open deck shallow draft boat, better suited to collecting crab traps. Before the start of the 2017 closure, LPBF met periodically with LDWF, LA Sea Grant, St. Bernard Parish, and fishermen, to identify the areas of high derelict crab trap densities. This information was used to target areas with high densities of visible crab traps.

The 2017 closure occurred from February 20 through March 6.  A total of 3,822 crab traps were removed from the Pontchartrain Basin; 2,096 were collected by LPBF staff or contractors, and over 1,500 were collected by volunteers.  Overall, the 2017 DCTR was more efficient than 2016, resulting in removal of nearly 4,000 traps from a small geographic area. The 35’ aluminum boat proved to have a capacity of 100-175 traps per trip and made 2 trips per day.  Calculated removal costs subsequently decreased from $19.77/trap in 2016 to $8.84/trap in 2017.

More derelict crab traps were collected over a smaller area in 2017 (yellow) vs. 2016 (pink). Relative to the Coastal Zone within the Pontchartrain Basin, little area was cleaned of derelict crab traps.

LPBF v-hull center console boat loaded with crab traps in 2016 (left) vs. a commercial flat boat rigged to collect and transport crab traps in 2017 (right). The larger commercial boat reduced average cost to remove, smash, and place a trap in a dumpster from $19.77 to $8.84 per trap.

Estimated # of Visible Derelict Crab Traps Remaining in the Pontchartrain Basin

Data collected from 2016 and 2017 were used to estimate the number of visible derelict crab traps (i.e., traps with floats) within the Pontchartrain Basin and coast-wide in Louisiana. A visible derelict trap density was calculated based on the traps retrieved (1,384) from Lake Pontchartrain in 2016 from the area of actual water surveyed (129 sq. miles), and the assumption that 100% of the visible traps were retrieved. This produced a derelict trap density of 11 traps per square mile. A density was also calculated for the 2017 area. Based on the traps retrieved (3,664) from the area of actual water surveyed (42 sq. miles), and the assumption that 100% of the visible traps were retrieved, a derelict trap density of 87 traps per square mile was calculated. These numbers were then used to estimate how many derelict traps remain within Pontchartrain basin and the Louisiana coast.  Our estimates indicate the Pontchartrain Basin may have from 39,000 to 125,000 visible derelict crab traps remaining. The Louisiana Coastal Zone may have from 121,000 to 390,000 visible derelict crab traps remaining.

Estimates of Impacts and Cost

Based on the published estimated mortality of 25.8 crabs per year in Louisiana, the range of possible mortality from derelict traps can be calculated.  To calculate value of wasted crab, derelict traps are assumed to fish for 3 years and crab is priced at $1.55/crab (LDWF reported price in 2015).  For the Louisiana Coastal Zone, the economic value of lost blue crab ranges from $15 M to $47 M over a three year period. Assuming rodeo techniques utilized in 2017 with a cost of retrieval of $12/trap, then the cost to retrieve all derelict traps coast-wide ranges from $1.4 M to $4.6M, which indicates a positive return on investment of 10 to 1. Furthermore, the economic value does not include other impacts, such as those to recreational fishing, shrimp fishing, and navigational incidents.

Future Removal Efforts

In 2018 (and beyond) LPBF plans to capitalize on cost saving strategies learned in 2016 and 2017 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. Information about LDWF 2018 closure areas for Derelict Crab Trap Removal can be found here.

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.

Dr. John Lopez, Director, Coastal Sustainability Program (left) and LPBF staff/contractors after unloading a boat full of muddy crab traps.