Grad student wins grant to study fish-counting method

Posted: Monday, May 22, 2000

JUNEAU (AP) -- A University of Alaska graduate student has won a $96,000 fellowship to study a novel way of estimating fish populations.

Dana Hanselman, a fisheries biology doctoral candidate at the University of Alaska Fairbanks center at Auke Bay, will continue his research on how to apply adaptive sampling to rockfish populations.

The long-lived fish cluster in schools. That makes it hard for the usual random sampling to provide biologists with reliable population estimates. They need those estimates to know how many fish, which are mostly sold to the Japanese market, can be commercially harvested.

''If you're wrong, it's bad because they're so old,'' said Hanselman, 25. ''If you overharvest them you can really knock them down for a long time.''

Under adaptive sampling, scientists change where they survey as they sample fish, reacting to clusters. Instead of sampling at random, they take samples around schools of fish until they don't see that density anymore.

Why is that better? ''The first obvious reason is you're getting more samplings, and you're gauging more of the population,'' Hanselman said.

The technique seemed to work well for some species of rockfish in the Gulf of Alaska, said Jon Heifetz, a fishery research biologist at the National Marine Fisheries Service.

''We ended up with more certain estimates of abundance, but we're not sure how to apply this in a larger survey area,'' said Heifetz, who is Hanselman's mentor for the fellowship.

The technique has been used in other fields, including forestry and studying clusters of diseases. But it's rarely been used for ocean fish populations, said Terry Quinn, professor of fish population dynamics at UAF.

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