01/06/2011

Bar Harbor’s Bugs

Underside of egg-bearing female Homarus americanus.

No, I’m not talking about the latest infestation, I’m talking about the one to four pound underwater variety which just about every visitor likes to see on his or her plate. The Maine lobster, Homarus americanus, leads a fascinating life. It starts with the female excreting her egg mass into her rows of abdominal flippers, “swimmeretes”, and gluing them there with a bio-adhesive, which she happens to also excrete. At this point a pretty weird fertilization occurs. A few weeks or more back the male lobster gave her a few packets of sperm which she stashed in a pouch and plugged. Now she pulls them out (older females can hold more and can fertilize several broods with one mating). The eggs stay glued under mom for 9 to 12 months. During this time the embryonic lobsters shed about 35 times.  Shedding is what lobsters do in order to grow, otherwise their shells become prisons. During this time the mother lobster must not shed, or the eggs will be lost. Her important job is safeguarded by Maine lobster fishers. Not only will they not take an egg-bearing female, they will mark her with a notch so that no one else takes her after she’s released her eggs.

Each time they shed, the tiny lobsters take a more developed form. When they finally hatch they are free swimming, propelling themselves with paddlelike appendages to the surface, where the wind moves them with the top layer of water, dispersing them like dandelion fluff. After a few more molts the free swimmers sink to the bottom in search of a safe home. By now they resemble tiny lobster, with tiny claws, antennae and legs. They are now “post larvae”. At this time it is important that the correct habitat is available on the sea floor–not sand, not clay, not ledge, but cobbles—medium sized stones. This is one of the big surprises of recent research, and perhaps the limiting factor to Maine’s lobster population.

If they survive they will continue to shed and grow. At first the shedding rate is blistering, but after a few years they settle into one or two sheds per year. It is at this time they enter adolescence, ready to mate and have eggs of their own. If they survive to over five inches in carapace length–male or female–they are considered “breeders” and can live long, productive lives, free from the dinner table. The egg bearing capability of a female is geometrically related to her size, so older females can really crank out the babies.

Over the course of the year, lobster migrate back and forth between deep and shallow water. The deep water stays warmer in the winter. Lobster move slowly in the cold, deep water and so don’t eat much. When things warm up they’re ready to move inshore and shed. It is at this time they also mate. Both deep and shallow places require housing, not only for safety from predators, but also from each other. They like to back into dark places and stick their antennae out. The perfect apartment even has a back door to escape through. Bigger males pick frequent fights to establish dominance and become alpha males, mating with multiple females. Both sexes require a safe place to shed. For a while their new body is like jelly and they can’t even stand.

So housing is important. Different bottoms offer different housing types to different age groups. One big concern of lobster fishers is that well-meaning government scientists may increase the size limit on lobster so that they may need bigger apartments. This may mean a lack of proper housing, resulting in greater mortality or migration to different areas. The end result could be a lower lobster population and smaller catches. File this in the unintended consequences section.

A lot of work, science and conservation goes into Maine’s sustainable lobster industry. Celebrate these efforts by having a lobster dinner tonight. Better yet, come to Maine and see what it’s all about.

Thanks to: The Secret Life Of Lobsters by Trevor Corson, Dr. Alistair M. Dove, U. of  N.H. and Maine Department of Natural Resources for photos.

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Comments on Bar Harbor’s Bugs »

01/09/2011

Pat @ 10:56 pm

Gee, who’s that cute kid on the left?

01/20/2011

Registered nurse @ 9:30 am

Great site. A lot of useful information here. I’m sending it to some friends!

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