For the third time since the season opened on Nov. 4, the California Department of Fish and Wildlife has implemented a partial recreational crab trap restriction and delayed the commercial Dungeness crab fishery due to the entanglement risk for humpback whales. The Dungeness crab fishery is one of California’s largest, and the season co-occurring with the whale’s migration is causing entanglements.
Traditionally, the Dungeness crab season has had minimal overlap with the migration of gray whales, but due to the species beginning to recover and the number of whales increasing, results indicate that more whales are being caught in the traps.
“The whales are typically leaving this time of year,” said Rayn Bartling, senior environmental scientist supervisor for CDFW. So, historically, the fishery has occurred when the whales are not typically present. There is a little more overlap now because the whale population has begun to recover, and there have been some season changes.”
Changes began when the fishery saw delays begin to occur in 2016 and 2017 as the fishery and the migration patterns began to overlap with the returning whales; an anomaly, according to Bartling.
Humpback whales are currently migrating south from Alaska to Central America and the lagoons of Mexico to breed in warmer waters. The migration routes form a loop, with whales traveling from their feeding grounds in polar or subpolar regions, such as the Antarctic Peninsula for the Southern Hemisphere population and places like the Gulf of Alaska for the Northern Hemisphere population, to breeding and calving regions, such as Hawaii, Mexico, and the Caribbean and back.
Typically, the fall and early winter months have slightly overlapped between the whales’ migration and the Dungeness fishery season, but it’s traditionally been short-lived.
One solution is to modify the opening and closing dates of the season.
“With our risk assessment mitigation program, that’s what we’re doing with the season delays, and we’ve also done early season closures,” explained Bartling. “For example, south of the Sonoma/Mendocino county line, the season can run as late as June 30. It has been closed several instances as early as April in recent history.”
According to Bartling, there has also been a discussion about potential longer-term solutions with a permanent season curtailment, but that would require a legislative change outside of CDFW’s control.
Similar to spiny lobster traps, the traps used for catching Dungeness crabs are called crab pot/trap and are 36-40 inches on average, made of heavy rebar and mesh. When fishermen set the trap, they deploy it to the desired location and each trap has a vertical line attached that goes to the surface with a buoy so the fisherman can locate the trap. Whales passing by the traps become entangled in several different ways. Often, it can be through their mouth, their baleen or around their tail fluke. The act of foraging and having those vertical lines in the water, especially if there is a loose line or slack line at the surface, runs the risk of a whale becoming entangled.
“For the commercial fishery, on average, we probably see over 100,000 vertical lines when the fishery opens,” said Bartling. “It can actually be much more than that. They have a lot of gear; it’s a high likelihood that [the whale] would become entangled.”
In California, there is no restriction that limits the number of lines that can be dropped within a specific vicinity at one time. The only requirement is that anglers use best practices to minimize the amount of line and scope and the number of splices and weights.
Dungeness crabs are prominently a soft-bottom species, so that is where they have to be caught. Soft-bottom species inhabit areas with a soft or muddy substrate on the ocean or estuarine floor. Soft bottom refers to the sediment type composed of mud, silt, sand or a combination of these materials. Soft-bottom habitats contrast with hard-bottom habitats, which may consist of rocks, coral reefs or other hard structures where you would find the California spiny lobster. Bartling says the commercial fishery fishes in depths as deep as 300 feet on average.
Recreational anglers can catch crabs inshore with hoop nets and possibly with snares, but that’s not sufficient at the commercial production level.
The most recent delay only applies to commercial fishermen. In the recreational fishery, CDFW will restrict traps when the entanglement risk is high, but recreational fishermen can still use hoop nets, snares or secure their take by hand.
The Sonoma and Mendocino county line is the central management area and has been delayed three times this season compared to the Northern locations, which have been delayed twice. There are other delays in the North due to crab quality, which impacts the season.
While a sea turtle was recently reported becoming entangled, this is a rare event, and the CDFW has only two turtle entanglements on record. As for the humpback whales – entanglement statistics vary. California can see as few as one or two entanglements a year. This calendar year has seen four. There have been years where it’s been much higher.
“The grey whales will be starting their northern migration soon,” Bartling said. “But the good news is we don’t see many entanglements [with grey whales]. Their migrating and feeding behavior are slightly different, so it keeps them away from the lines. Entanglements do occur but definitely much, much less.”
Director Charlton H. Bonham will re-evaluate available data to inform the potential for a commercial fishery opener and modification of the recreational trap restriction, which has yet to be announced. For more information on the risk assessment process, please visit CDFW’s Whale Safe Fisheries page. For more information on the Dungeness crab fishery, please visit wildlife.ca.gov/crab.
