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Feature Articles
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Measuring lobster blood protein levels
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This article is reprinted with permission of Commercial Fisheries News, the Northeast's fishing newspaper for over 30 years, ©2003 Compass Publications Inc. Commercial Fisheries News is published monthly; annual subscriptions are $21.95. To subscribe or request a sample issue: call (877) 263-4496; fax (207) 367-2490; e-mail (cfoster@fish-news.com); or click on the hot link.
By Sandra Dinsmore
STONINGTON, ME - An eastern Maine dealer reported sending product into Boston on a truck with lobsters from Nova Scotia. The Maine product serum protein levels were 4-5, the Nova Scotia product 12-13. Which lobsters will end up supplying holiday markets in Europe?
The level of serum protein in the blood of a lobster indicates its molt status, nutritional condition, general health, and vigor. This knowledge is of immense importance to those who ship or hold the animals in tubes or pounds.
When dealers speak of shippability, they're referring to the muscle mass or quantity of lobster meat filling the shell. They can make an objective determination of the meat by taking a sample of lobster blood, placing it on an instrument called a refractometer, holding the refractometer to the light, and reading the number. It's rather like putting a drop of blood on a slide and then, instead of looking at the slice under a microscope, reading it as if it were a thermometer.
It's easy to do. There are several places where the blood can be drawn, but most people choose the tail. Once bent down, a slightly darker line sort of like a vein on top of the tail becomes apparent. From there, it' s just a matter of inserting a hypodermic needle and drawing the necessary drop of blood. A refractometer costs about $200.
Protein levels are measured by number, depending on the refractometer scale.
The higher the number, the stronger the lobster. After it sheds, the animal's serum protein level is low. As the lobster's shell hardens, the reading increases, an indication to a buyer that the lobster could survive the stresses of shipping.
Although this method of determining serum protein levels was developed 25 years ago, it took about 20 years to catch on. Now, its an important tool in assessing shipping quality as well as feeding programs for holding facilities.
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