Friday, September 28, 2007

Blue crabs in trouble in the Chesapeake Bay

Is another sad story coming? Blue crabs are in trouble in the Chesapeake Bay. Blue crabs are a big deal, millions of pounds caught and hundreds of millions of dollars in revenue. Oh yeah, they're interesting and important creatures too.

There are fewer blue crabs than we want. Lots of problems afflict blue crabs, but here's an interesting question.

Is it ok to catch half of the crabs or more each year? That's the fishery management goal, around half of the crabs get pulled out of the bay for people. Is that reasonable? Fishery science says it's reasonable.

Now that crabs are in trouble, people are asking what's wrong. Is it pollution harming the crabs?

An interesting statement came out...blue crabs aren't reproducing fast enough to recover from the pressure they're under, according to the Department of Natural Resources. So the problem is the crabs? They're not reproducing fast enough to satisfy our wants?

I'm sorry, I like sustainable fishing, but there has to be common sense applied. I don't think catching half the crabs is reasonable. The fishery models may say it's ok, but I have doubts. It just seems like taking too many crabs. It might work when we're lucky, but it doesn't seem like a good long-term strategy.

Sustainability is about more than using a model to allow maximum take. Sustainability also means being prudent and cautious and allowing the crabs to thrive so we don't have trouble when conditions are bad for crabs. When we're killing half of the crabs each year, there's no reserve if they fail to have a good year for reproduction. Two years of poor reproduction and they're gone. Bye bye crabs.

This is the biggest problem with most fishery management, we're reckless and aggressive and the needs of fishing are viewed as the baseline. And those damn crabs just have to reproduce fast enough to make everything ok.

This isn't the first time that I've seen the bizarre statement that a problem was caused by fish or crabs that didn't reproduce as fast as they were caught. What a nutty way to look at a problem.

5 comments:

thomas said...

I used to live near the Chesapeake, and as a kid really looked forward to the crab feasts in August. Outside, around picnic tables with red and white checked linens and lots of Old Bay. Those are fond memories.

Back in reality, 50% seems like a lot to me!!!

Anonymous said...

Hello, I would like to comment on this issue if I may.

I realize that what I am about to say possibly has nothing to do with blue crabs, but, her in California we have Dungeness Crab and approximately 85 to 90 percent of all the legal males are harvested each season.

The fishery is considered to be robust and aside from the fact that much of that 85 to 90 percent is harvested in the first few weeks, the fishery has proven sustainable.

We do not harvest Dungeness during their softshell stage because the practice would be detrimental to the crab population and the meat content is very near zero.

Furthermore, only the males of the species are harvested that are 6 1/4" and have performed several seedings.

The female molts at a different time than the males and during that time the males "clutch" the females and deposit their sperm sacks. The female is able to fertilize two years of eggs with the one seeding event.

It should be noted that Dungeness Crab seem to follow an 11 year cycle. There has been some debate as to the occurence of the numartian worm that feeds on the ripening eggs. During years of high freshwater outflow, the worm seems to abate its presence.

Just some food for thought.

Mark Powell said...

But wait, all may not be well with the Dungeness crab fishery...the fishery is overcapitalized with too many pots in the water, stock abundance is unknown, and cycles of low abundance can not be explained adequately. It's a fishery that's riding good luck, IMO. Remember, groundfish in the same area were thought to be well-managed right up until the late 1990s crash.
See
http://links.jstor.org/sici?sici=0030-1299(199110)62%3A1%3C106%3ACEFCEC%3E2.0.CO%3B2-K
and
http://www.sfgate.com/cgi-bin/article.cgi?file=/chronicle/archive/2000/01/24/MN56859.DTL
and
http://www-comm.pac.dfo-mpo.gc.ca/publications/speciesbook/invertebrates/dungeness.html(Canadian Dungeness fishery problems, managed similarly)
and
http://www.sf.adfg.state.ak.us/FedAidPDFs/sp06-09.pdf (Alaskan Dungeness crash, it is possible!)
There's a pattern of people feeling good about fisheries only to find problems later, so the feeling that the fishery is robust is no guarantee of long-term success. I'd worry about taking 85-90% of the males if I were involved.

natlaquarium said...

Hi Mark - you have our support! We run a program called AquaPartners that "educates students on how to preserve the bay and participants have the opportunity to catch, hold, and release a crab." We also hold volunteer clean-ups and educational events designed to teach people how to help restore the bay. If you would like more info, check out our blog post on the issue: http://nationalaquarium.wordpress.com/2008/06/25/can-we-have-our-crabs-and-eat-them-too/

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