What goes down will come back up…
By Michael A. Moore
Puget Sound Dungeness crab harvests have been at record levels for the last four seasons, fluctuating between 8 and 11 million pounds total harvest. The 2011-12 season holds the record of close to 11 million pounds, with 2012-13 down to 9 million pounds.
The 2013-14 season may be lower than that. “My friends who crab on Whidbey Island tell me this year’s catch is off from last year,” said David Armstrong, Director of the School of Aquatic and Fisheries Sciences at UW. “We don’t have any good explanation for the drop-off, but the trend seems to be that adult crab harvests fluctuate in four year cycles. The good news is that I have been getting photos sent to me from people along the coast showing beaches covered with young crabs, so four years from now may be another record harvest.”
While the scientists may not know why the crab harvests seem to fluctuate in four-year cycles, they do know that the overall trend of the Puget Sounds harvest has been steadily upward for the last twenty years. A timeline which closely coincides with the famous “Rafeedi decision”, in which federal judge Edward Rafeedi ruled that Puget Sound tribes were entitled to one half of the harvestable shellfish and crabs in any given year. Previous to Rafeedi, the tribes’ average allotment from the state was a little more than a third of the harvestable amount.
“The harvest for the 1992-93 year was about 3.5 million pounds,” a crab biologist who requested anonymity told Fishermen’s News. “ The next year it was a little closer to 4 million pounds, two years after Rafeedi it was over six million pounds and has been going up ever since.”
The biologist said it is his personal theory that the reason for the upward jump in the Puget Sound harvest after Rafeedi was decreased pressure on the crab population due to the fact that the tribes were not equipped to harvest all of their allotment for a number of years. This allowed the populations to build up to the present 8 to 11 million pound range.
“There are a number of factors that have affected the Puget Sound crab population,” said Don Velasquez, a crab biologist with the state Department of Fish and Wildlife. “One of the main factors is the reduced pressure on the juvenile crab from the decreased salmon population in the Sound. Another is that there are more baited pots out during the year than ever. Those pots act as feeding stations for the pregnant females and juveniles.”
Velasquez laughed when told that his description almost made it sound like Puget Sound is a giant crab ranch. He went on to mention several things all crab harvesters should be doing to help keep the crab harvest high and perhaps grow even more.
“It’s extremely important to be careful how you release crab that are too small or you don’t want to keep,” he said. “Don’t throw them like a Frisbee. That will hurt the crab and make it easy prey for the seagulls. The best technique for releasing a crab is to be as close to the water as safely possible, maybe a foot or two, and drop it in sideways, like a coin.
“Remember that the same crab may be caught several times and if it gets beat up repeatedly there is a good chance it will not survive to adulthood. And make sure to release the females immediately.”
Derelict traps are one of the main dangers to the crab population according to Velasquez.
“All fisheries have their share of traps that were either lost or the line got wrapped around a log,” he said. “Those traps ghost fish, crabs become caught in them and act as bait for even more crabs. It’s really important to make sure your trap has a biodegradable device to disable it.”
A couple of other bad habits to avoid in handling crab are letting the crab dry out before releasing it and to make sure they don’t get crushed between the pot and the sorting table.
One of the most important things to help the state manage the crab harvest is to accurately fill out the catch card, Velasquez emphasized. “We use those numbers to help us calculate how the harvest is going.” He said it is possible to raise the harvest amount during the season if the catch cards are accurate and the data show the harvest taken so the fisheries scientists are working with real numbers.
Another important action that harvesters can take is to report anyone violating the regulations, including harvesters in their own user group. “It’s easy to point the finger at someone in the other user groups,” Velasquez said. “But it’s important to keep an eye on and report violators in your own group. They hurt the fishery for everybody.”
One of the greatest threats to the mid to long term crab and shell fish population is the increasing acidification of the ocean. The first indicators that the lowering of the ocean’s pH can affect shellfish came from the ongoing investigation Hood Canal shellfish growers have been having with getting their seedlings to grow into mature individuals.
CO2 dissolved in seawater became a prime suspect when the NOAA reported research that showed there is a seasonal upwelling of deep ocean currents that brings absorbed CO2 to the surface. The CO2 levels of the upwelling currents are believed to be indicators of carbon dioxide absorbed fifty years’ previously.
Ocean acidification’s effects on Washington’s crab and shellfish populations is recognized as important enough that Governor Inslee announced on August 8 the funding of a hub at the University of Washington to coordinate research and monitoring of ocean acidification and its effects on local sea life such as oysters, clams and fish.
“Based on what is learned, the center will marshal efforts to improve the ability to forecast when and where corrosive waters might occur and suggest adaptive strategies to mitigate the effects,” according to a UW press statement.
“I don’t know of any other place in the nation where the state legislature has had the foresight to allocate funding to address these questions,” said Terrie Klinger, UW associate professor of marine and environmental affairs, and co-director of the new center with Jan Newton, principal oceanographer at the UW Applied Physics Laboratory.
The UW, which received $1.8 million in state funding for the center’s first two years, will work with investigators from other universities such as Western Washington University and with agencies, tribes, the shellfish industry and other organizations to address the needs specified by the legislature.
When the ocean absorbs excess carbon dioxide from the atmosphere it becomes slightly more acidic and can deprive animals such as oysters, clams and crabs of the building materials for their shells. When such animals encounter carbon dioxide-rich waters, particularly in their earliest stages as larvae and juveniles, it can cause poor development or death.
Washington’s shellfish industry is the nation’s top provider of farmed oysters, clams and mussels and generates $270 million each year while supporting 3,200 direct and indirect jobs. Marine resources in Washington produce additional jobs and income through recreation, tourism and fisheries. Providing information to help sustain these sources of revenue and to maintain healthy ecosystems is an overarching goal of the new center, Klinger said, and the knowledge generated will be made available to scientists, resource managers, decision-makers, industry representatives and the public.
NOAA scientists are also working on a more thorough understanding of the effects of ocean acidification on crabs and shellfish.
Jason Miller of NOAA’s Northwest Fisheries Science Center is working specifically in the effect of absorbed carbon dioxide in open ocean water on crab megalopa, the larval stage before they transition to small juvenile crabs.
“I have yet to fully complete a study based on the effects of two different levels of absorbed carbon dioxide in open ocean water on crab larvae in the megalopal stage,” Miller said. He used ocean water in the lab that simulated today’s level of 400 parts per million of absorbed carbon dioxide and a future predicted level of 1000 ppm of absorbed CO2. Both of those figures are well above the pre-Industrial Era baseline of 280 ppm.
“The evidence so far suggests there is a difference in the survival rates of crab megalopae when the CO2 rates are at 1000 ppm.” Miller stated. He emphasized that his results are preliminary, and that he needs further replication of the study to verify the results.Meanwhile, the Puget Sound crab harvest continues at record levels, fluctuations and all.
