Christopher J. Petrone, Virginia Sea Grant, Virginia Institute of Marine Science
Carried from land to the ocean by wind, streams, and rivers, debris can then be transported by ocean currents around the globe. During the 2016 International Coastal Cleanup, 800,000 volunteers picked up more than 18 million pounds of marine debris. Though this is a very impressive haul, there are still millions of pounds of trash and debris that plague our ocean and coasts.
Commercial Crabbing in Virginia
The extraordinarily popular blue crab, Callinectes sapidus, has been a staple in Chesapeake Bay’s long fishing history. In Virginia, all crabbing (commercial and recreational) is regulated by the Virginia Marine Resources Commission (VMRC). As in most states where blue crabs are found, commercial crabbing requires a limited-quantity license. The license dictates how many crab traps, or pots, the waterman is allowed to put into the water, the type of pot, and the time of year he or she is allowed to set out pots.
Two different types of pots are used in the blue crab fishery, depending on which life stage of crab the watermen are targeting. The typical hard crab pot is very familiar to coastal residents and tourists in the Mid-Atlantic. The peeler pot is used to catch crabs preparing to molt, or peel out of, their existing shell (exoskeleton) as they grow in size. This pot has the same shape, but it has smaller openings and a slightly different architecture, due to the bait that is used. In one version of the peeler pot, instead of using food to lure molting females, watermen will place between one and three adult male crabs in the trap to attract females. Shedding females are in search of a mate and respond to chemical cues released by the males. Once peelers are removed from the pot, they are transferred to land-based shedding tanks and left to shed their exoskeletons. The resulting soft-crab is then processed, packaged, and sold.
Crab pots are set out on the Bay floor and have a tethered buoy so that the watermen can find and retrieve them again. These buoy lines are occasionally cut if other boaters accidentally run over the buoys, or the lines can disintegrate with age. The result is an unmarked, and often irretrievable, pot. Pots can also be lost due to strong storms. Rough seas may push the pots out of the waterman’s usual work area, or roll the pots, which causes the buoy lines to tangle and results in the buoy floating below the water’s surface, where it cannot be seen by watermen. On average, watermen may lose approximately 20% of their crab traps in a single season. In 2009, Virginia issued 1,867 commercial crab pot licenses. Those 1,867 licenses accounted for 392,175 pots (both hard crab and peeler pots; Havens et al., 2010). When these pots are lost or abandoned, they continue to catch animals, and because the derelict pots (also known as ghost pots) can no longer be found by the watermen, they are not emptied, and in most cases, the animals caught inside die, until the pot can no longer fish.
Ghost pots have a varying life expectancy depending on their construction. On average, a galvanized wire pot can continue to ghost fish for about two years before it is too broken down. However, vinyl-coated wire pots can continue to ghost fish for roughly four years.
Despite all of the negatives, there is some good that may come from a ghost crab or eel pot (used to catch American eels, which are mostly exported to Europe and Asia). The wire of these pots has been found to be a very good place for oyster larvae to set and aggregate. This map shows areas where ghost pots were removed that had attracted substantial oyster settlement.
A Problem and A Solution
As a result of a drastically low blue crab population, the VMRC decided to close the winter crab dredge fishery in 2008. In this fishery practice, watermen drag a heavy iron frame with teeth across the sea floor, dislodging buried crabs, which are then deposited into a bag behind the toothed frame. Most often, these dislodged crabs, which bury in the sediment in winter to escape cold Bay waters, are gravid, or pregnant, females. Removing gravid females further hurts the failing population.
In order to supplement the income lost due to the winter dredge season closure, a new program, funded by the National Ocean and Atmospheric Administration (NOAA) and the VMRC, was begun at the Virginia Institute of Marine Science’s Center for Coastal Resources Management in 2008. Fifty-eight watermen, who were affected by the seasonal closure, were employed in Year One of the Virginia Marine Debris Location and Removal Program. Eight additional watermen were added in Year Two. All project participants received training and specialized gear, including a side-scan sonar imager, waterproof digital camera, maps, and data sheets. Most watermen used their usual crab-dredging vessel for the project. Training included NOAA marine mammal avoidance protocols, side scan sonar use, proper crab pot retrieval techniques (to reduce the amount of Bay floor disturbance) and proper data collection methods.
The watermen were restricted to 49 days of on-the-water work between December and March, and were paid $15,000 each, plus fuel and incidentals. This compensation equaled, or even exceeded the average watermen’s earnings from dredging blue crabs during the winter season (Havens et al., 2010).
Upon retrieving ghost pots and nets, watermen recorded their contents, photographed the gear, and emptied it. The watermen were then free to reuse viable components, recycle the gear, or dispose of it at the dump.
A PowerPoint slideshow is available and includes images of, and from, the side scan sonar, the grappling devices used to retrieve the ghost pots, and transect maps of the area.
A video explaining the program, showing the gear, and featuring interviews with some of the scientists and watermen involved in the project is available here.
The Virginia Marine Debris Location and Removal Program is one of several derelict-fishing gear removal projects on the East Coast and Gulf of Mexico. Similar programs can be found in:
The NOAA Marine Debris Program also awarded funding for programs in Alabama and Delaware in September of 2016.
Applying the information you have learned above, you can now explore catch data reported by watermen involved in the derelict crab pot project from 2008 through 2012. All data used below are available for your own investigation in this Excel spreadsheet.
Download the Student Worksheet and complete the following analyses.
Using Figure 1, a column graph of removed fishing gear, answer the following questions. (Note: If your students need additional work creating their own graphs, please see Table A in the above Excel workbook for these data, which can be graphed by hand or in Excel.)
Using Figure 2, pie charts of major bycatch categories, answer the following questions. (Note: If your students need additional work creating their own graphs, please see Table A in the above Excel workbook for these data, which can be graphed by hand or in Excel.)
Catch per Unit Effort (CPUE) Data
1. Fill in (a) and (b) in the table to calculate the average number of pots recovered per waterman during the four project-years.
Bilkovic et al. 2016. Ecological and Economic Effects of derelict Fishing Gear in Chesapeake Bay: 2015/2016 Final Assessment Report. Download Full Report
Havens, K.J., Bilkovic, D., Stanhope, D, and Angstadt, K., 2010. Fishery Failure, Uemployed Commerical Fishers, and Lost Blue Crab Pots: An Unexpected Success Story. Environmental Science & Policy.