Yonathan Zohar

Q&A --

Helping To Save The Crab

UM scientist says the population of the Chesapeake Bay's trademark crustacean can be brought back - if money for `very aggressive' research can be found again

May 11, 2008|By Rona Kobell | Rona Kobell,Sun Reporter

Eight years ago, a chance question at a Maryland General Assembly hearing put Yonathan Zohar on a path to unlocking the secrets of the Chesapeake Bay blue crab.

The Jerusalem-born, Paris-educated endocrinologist answered questions about techniques he used at his Inner Harbor lab to enhance the breeding stock of certain fish. Today, Zohar is using the same techniques to help reinvigorate the once-robust crustacean. He and his team have spent more than $12 million - most of it courtesy of a federal earmark from Sen. Barbara A. Mikulski - mapping out the blue crab's life cycle in their hatchery and placing the crabs in the bay to watch how they lived.

The director of the Center for Marine Biotechnology at the University of Maryland Biotechnology Institute said researchers are ready for the next stage - creating millions of baby crabs in the hatchery, then releasing them into the bay to enhance breeding stocks. But their funding was not renewed this year, so the researchers are figuring out how to continue their project.

Meanwhile, the bay's blue crab population continues to slide. Last month, officials in Maryland and Virginia announced crabbing restrictions in hopes of reducing the harvest by a third.

The Sun sat down with Zohar to discuss what he's learned about the blue crab and how to best manage the species in the current crisis. What have we learned in the past six years about the blue crab in the Chesapeake Bay that we didn't know when you started your work?

We learned how long it takes for a blue crab to grow to maturity, which we didn't know before. ... It's five months from hatch. From egg to adult female. It has huge implications to managing them.

Another striking example was the reproduction. The dogma was that a female crab only produces one sponge in her lifetime in the Chesapeake Bay. Here, all of a sudden, we demonstrated that a female crab can produce up to five successive sponges in the same season, in the same summer, in two- to three-week intervals. So it has a huge impacts in terms of their life cycle and to management. So if you think about it, now when you harvest a mated female, you harvest up to four to five times her potential to produce offspring compared to what was believed to be the case before.

We learned a lot about their migration routes. We mapped the location of those routes, and we also know the exact timing. We know that a baby we released into the Chesapeake Bay can, in the same year, make it down to the spawning grounds in Virginia as a mated female. What are the things that we still don't know in terms of the blue crab? Are there secrets that remain?

We think we can develop a soft-shell blue crab industry based on aquaculture, hatchery-based babies we can produce every day of the year. But here we have a few secrets left to understand.

The main bottleneck is to be able to control molting, when the crab sheds its shell and becomes soft. Cannibalism is one of our main issues. If we are able to control molting, there will be no cannibalism. We know what hormones control molting, and the idea is maybe to find natural sources of those, mimics of those hormones so maybe we can feed it to the crab, and then get those crabs to molt whenever we want them to. What were the main objectives of your research program? What did you set out to accomplish?

There were four main issues. The first was to understand the basic biology of the blue crab, because very little was known about it. How they reproduce, how they molt, how they migrate, what type of food they eat, what type of habitats they prefer, what are their main predators.

The second goal was to see if we could develop hatchery and nursery technologies to mass-produce blue crab juveniles in captivity, which was thought to be something that could not be done.

The third goal is to very clearly test the feasibility of using hatchery-produced juvenile crabs to replenish the spawning stocks of the blue crab in the Chesapeake Bay. The abundance of the breeding stocks has dropped about 85 percent in the last 15 years.

And No. 4, if it was going to work, to scale it up and transfer the technology to the industry. How much of that do you feel you were able to accomplish?

We know that the concept of using hatchery-raised crabs does work. What we were unable to do so far is to scale it up, to produce millions of crabs annually, to make a difference. Right now, we are doing hundreds of thousands, and while it is very good for the study, it is not enough to make a difference. Are you still searching for funding to finish the work, and where might that come from?

We as scientists at the Center for Marine Biotechnology live and die by research grants from federal and state agencies. But they are very small grants. They do not allow the scope of work that needs to be done here. And I kept saying that, in order to make a difference, to quickly reach solutions to reverse the declines, we need a very aggressive type of a research program. ...

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