Date:March 1, 1996
Special for the Kodiak Daily Mirror ComFish '96 issue
KODIAK, Alaska--Every summer you see them--halibut nearly as big as a Volkswagen--hauled in from the fishing grounds off Kodiak Island. But those monster halibut weren't always so big. In fact, they started out no bigger than a dime, in local waters that are crucial nurseries for twelve species of flatfish.
Brenda Norcross is a fisheries oceanographer at the University of Alaska Fairbanks. She studies Alaska's flatfish species when they are still quite young, to learn more about where they live on the bottom of the sea. Using underwater cameras, sonar, and scuba divers, she has discovered that juvenile flatfish are very particular about where they grow up.
"The type of ocean floor matters a lot to flatfish. Little flatfish can't bury themselves in sediments that are too big, like really heavy sand or large gravel. At the same time, if they bury themselves in something with a silt fraction it's going to be very difficult for them to breathe because their gills would fill up with mud."
Norcross says young flatfish prefer to hang out in places scientists call nurseries. Kodiak's numerous shallow bays and fjords make good nurseries because they offer advantages that increase the fishes' odds of survival.
"The feeding is good and the bays around the island offer important protection from predation because in these shallow areas you're less likely to find the bigger fish are going to feed on them. It's safer because the small fish aren't not getting munched on."
Juvenile flatfish also are able to change color, which helps them hide from predators and it also helps scientists like Norcross figure out what the sea floor is like without having to actually send down cameras or a diver to take a look.
"I can learn a lot about the bottom by pulling the fish up because the fish aren't the same color on all bottoms. Fish change color patterns to go with the bottom they're on. They get really brilliant colors and very mottled when they're on a bottom that has tiny broken pieces of shell. They're beautiful."
Norcross believes her studies on juvenile flatfish are crucial to protect these flatfish nurseries from development that in turn could harm Alaska's thriving commercial and sport fisheries.
"The Gulf of Alaska is unique because it supports 12 species of flatfishes. There has to be something very special about it. I'm trying to find out what makes it unique."
In the future, Norcross wants to learn how habitat preferences might change as flatfish get older and move to deeper waters in the Gulf of Alaska and Bering Sea. Ultimately, she hopes to unlock the mysteries of why flatfishes are so abundant in Alaska.
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