A simple alteration to recreational crab pots could save thousands of crabs from going to waste each year, all because crabs are unable to escape from lost crab pots that keep on working, according to a new study.
The Crab Pot Escapement Study, commissioned by the Northwest Straits Foundation, is the first to measure how well crabs use the escape routes provided in the design of every crab pot sold in Washington state.
The findings were somewhat of a surprise, according to Jason Morgan of the Northwest Straits Foundation. Jason told me that he is eager to get the information out to recreational crabbers, who could voluntarily take steps to reduce crab mortality. The findings might even lead to revised regulations for crab pots.
Of course, the best thing that crabbers can do is to avoid losing their pots in the first place. For tips, check out the brochure from the Washington Department of Fish and Wildlife (PDF 2.9 mb) or the Northwest Straits website. About 12,000 crab pots are lost each year in Puget Sound, representing the wasteful deaths of nearly 200,000 crabs, according to a revised estimate derived from the new study.
The study, in partnership with Natural Resources Consultants, placed live Dungeness crabs into six common types of crab pots, using 13 various configurations. After the seventh day, the biodegradable escape cord (“rot cord”) was severed to provide an opening through which the crabs could escape — at least in theory. The researchers then measured the time it took for the crabs to get out, if they could.
One thing the researchers learned was that crab pots with hinged doors tended to keep the crabs trapped, especially when the door was located away from the edge of the pot. The doors simply stayed closed after the escape cord broke free.
A modification of the doors with a bungee cord significantly increased the number of crabs that could escape. The doors were modified to spring open when the escape cord broke.
The best configuration of all involved the use of escape rings — a circular opening at least 4.25 inches across. These rings are required by law in all crab pots to allow females and under-sized males to get away before the pot is brought to the surface or in the event that it becomes derelict.
Many crab pots sold today tie the rings into the crab pot with escape cord. When the cord breaks, the ring falls away to provide a larger opening for the crabs to get out.
“It’s still a small opening for the crab to crawl out,” Jason said. “We did not expect it to be effective at all, but it works very well.”
In some crab pots, the required rings are welded into place on the iron cage. It would be easy enough for people to cut the rings out with a strong pair of wire cutters and then tie them back in with escape cord, Jason said.
Manufacturers of crab pots have become interested in the study, Jason told me, and he expects some will quickly convert to tying the rings in place rather than welding them. The difference in cost, if any, should be small, he said, and drawbacks seem minimal.
Requiring this method of escape for future crab pots sold in Washington could be another result of the study, but nothing is proposed at this time, Jason said. The next round of studies is likely to look at commercial crab pots, which are generally larger but still require an escape route in case they become lost.
A related issue that needs attention is the escape cord, which is made of cotton and designed to deteriorate in a reasonable period of time when left in saltwater. Cords that last longer are likely to cause more crabs to die. Studies have shown that approved escape cord takes between 30 and 148 days to disintegrate, with most people selecting larger cord that can last toward the longer end of that range.
“That is certainly something that we are not happy with,” Jason said. “We would like to see regulations that would require escape cord to be smaller.”
A smaller cord would break sooner and allow more crabs to survive when a crab pot is lost, though it would require crabbers to change the cord more often. That would seem to be a small inconvenience to avoid the kind of waste often seen in photos of derelict crab pots filled with dead and dying crabs. Even longtime experienced crabbers can lose a pot now and then, Jason said.
Northwest Straits Foundation is working on one or more videos to help people see the benefits of providing escape for crabs and to demonstrate how to modify their crab pots.
According to the study, the right modifications to crab pots could allow 99 percent of the crabs to get free when a crab pot is lost in the depths of Puget Sound.