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Reproduction: Secret Weapon of the Dogfish? |
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Spiny dogfish are one of the rare success stories in the management of
shark fisheries, with the U.S. Atlantic population representing one of
the few shark stocks ever to fully recover from overfishing.
At first glance this doesn’t seem to make any sense: spiny dogfish are
one of the longest-lived and slowest-growing of the sharks that
regularly interact with human beings, and with a 2-year pregnancy it
doesn’t seem as though they could replace their numbers in anything less
than the decades that have gone by without successful recovery from
several other heavily-fished sharks. So how have spiny dogfish been
able to succeed in recovering from overfishing where so many other
sharks struggle? The answer may very well be in adaptations related to
that seemingly long reproductive cycle of theirs.
The essential book Biology of Sharks and Their Relatives has a good overview of the reproductive systems found in elasmobranchs, and that’s where we’ll lay the groundwork for the potential reproductive edge of dogfish. Carrier et al. (2004) summarize that there are two different basic reproductive cycles found in sharks and rays. Both involve two different processes, the development of pups and the development of eggs. Where these cycles differ is the timing of egg development. In some sharks, including members of the large coastal shark complex like blacktip and sandbar sharks, pup development occurs, followed by the development of the eggs. Basically, only one reproductive stage happens at a time. The mother shark puts all her reproductive resources into developing the pups, then develops the eggs that will hopefully be fertilized to develop into the next pups. Factor in the “resting period” that usually immediately follows birth and you have a reproductive cycle that can be considerably longer than the length of pregancy. Read the complete story from the Ya Like Dags blog.
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MELISSA WOOD, NATIONAL FISHERMEN: Meting out the meager
May 22, 2012 - Listening to the New England Council's Groundfish Advisory Panel talk about how that industry is going to pay for monitoring costs is kind of like trying to figure out how to pay your bills when you've just lost your job. Though monitoring is important keeping costs down is critical. As Panel Member Gary Libby pointed out, "If we had 100 percent monitoring we probably wouldn't have an industry."
