Theories abound, and there is much anecdotal evidence as to why clams are plentiful for a few years and in down times so scarce that 80 percent are imported from Maryland and Maine, said Whitten. Some say severe winters with lots of ice improve clamming, suggesting the ice has a scouring effect on the flats. Or, maybe hard winters kill off predators. No one knows for sure, he said. The biggest problem is that not a consistent seeding takes place in nature.
Conditions vary from year to year.
Spawning puts larvae into the water column. Larvae settle to the bottom in about two weeks, but for varied reasons, don't always take hold. Shellfishing has one of the highest economic multipliers in the local economy said Whitten. That is, every dollar earned by clammers, who receive a direct economic benefit, gets turned over numerous times for indirect economic benefit, to the dealer and wholesaler, to local restaurants and staffs, and all the other businesses that support the industry, including supplies, food and clothing. Water quality was measured in the Merrimack River, and successful shellfish acquaculture methods in Maine and on the Cape were investigated and tested.