Journals 2003/2004

Margaret Brumsted
Dartmouth High School, Dartmouth, Massachusetts

I worked on some more data entry today and spent some time on the upweller. I hadn't really noticed before that some of the quahogs have a zigzag pattern on their shells. I think that as the quahogs grow it is easier to see this unique pattern.

The zigzag quahogs are actually a subspecies called Mercenaria mercenaria notada. The subspecies occurs naturally in two percent of the population. I wanted to know why are bins were loaded with the zigzagers.

Karin told me that hatcheries have been culturing quahog seed for 50 to 60 years. Shellfish constables or fish and wildlife officials traditionally buy quahog seed and reseed areas on a yearly basis. Over time the resource managers wanted to have a way of tracking the millions of seed that they had been dumping into the water year after year. If the seed could be marked in some way they might be able to determine if their yearly reseeding efforts were successful.

Because of the demand for hatchery reared quahog seed that would have markings that were different from the natural or wild population hatchery managers began selectively breeding the notada subspecies. The stripe becomes accentuated over time from selective breeding. With the distinctive markings resource managers are able to follow the hatchery reared stock into the fisherman's bushel basket.

If you can breed the quahogs for color patterns, why not breed for other characteristics, like fast growers? It seems pretty obvious that this would be a good thing, as it takes quahogs over three years to reach a marketable legal size. Apparently, fast growth in quahogs is not desirable and it has more to do with the method of harvest than anything else. Here in Rhode Island most of our quahogs are harvested using bullrakes. Fast growing quahogs lay down shell material quickly resulting in thin, brittle shells. These quahogs are more prone to breakage during harvest and have a shorter shelf life in markets.