Arctic Science Journeys
Kachemak Bay Flatfish Nurseries
It's late February on Alaska's Kachemak Bay, but it feels a lot like summer. The weather is warm and the sea is calm, perfect for fishing as Alisa Abookire and the crew of the research vessel Munson Boat lower their small trawl net into the bay. Heavy lead weights pull it to the ocean floor 300 feet below.
"Lock! Slack! Fishin!"
Monster halibut and feisty salmon have made this bay famous among sport fishermen the world over. But the trophies Abookire seeks would fit in the palm of your hand. Abookire, a graduate student at the University of Alaska Fairbanks, is after juvenile flatfishes. Rock sole as big as a quarter and halibut the size of an omelet pan. She's studying the bay to identify flatfish nurseries, their habitat preferences, and prey species.
"There's a lot of knowledge about adults, but we don't know much about juveniles. And if we can get a handle on what their habitat is, and their abundance, and then if you could monitor that and see a change, that would directly benefit management."
Abookire and graduate students Liz Chilton and Brenda Holladay, have been on Kachemak Bay for a week. They've taken samples at the outer bay, from McDonald's Spit down to Bluff Point. Today they're sampling near Homer Spit, a four mile sliver of land that juts like a bent finger into the bay. They'll scoop up a sample of the bottom to see whether it's mud or sand or some combination of the two. They'll also take the ocean's temperature and note its salinity at various depths. Finally, they'll send a trawl net down to catch some of the flatfishes that might be living there.
Lab technician Pat Lovely spills the catch into a large galvanized tub on deck. Hidden in the twisted blades of green kelp is a slice of the bay's abundant marine life. Sculpins, shrimp, and other species wiggle about. Tanner crabs claw their way onto the deck, while a large hermit crab tries desperately to cram itself into an undersized seashell. The scientists take note of the bycatch. Jonathan Geagel, who's 12, and nine-year-old Mikey are playing hooky from school to help.
"Pretty small catch huh? Flathead. Big sea star. Are those halibut? These, most of these are rock sole, but we might find a halibut in here. Lots of shrimp, not the pink ones though huh? Oh. Ah, look at that. That's an alligator fish. Oh, no, no. It might be a tube nose. We've gotten a couple of those in Kachemak Bay before."
Abookire began her study of Kachemak Bay last summer. From that work, she learned when flatfishes spawn and when they transform from fingernail- size larvae adrift on the ocean into something resembling a flatfish. During the transformation, both eyes migrate to the top side of the fish's head, and the fish sinks to the sea floor. Scientists call it "settling-out."
"I mean we don't even know time of spawning or time of settlement. Like when we came out in May, we didn't catch any age zero rock sole or flathead sole, and that was something new, that nobody had known, we didn't know in the past when they settle out, and we were able to find out by the fact that we didn't catch any in May because they hadn't settled out yet in May. That's significant right there for management."
On this cruise, Abookire hopes to find out whether flatfishes migrate to new habitats during winter, and what species predominate on the bay's muddy bottom. Brenda Holladay is curious about that too. Her studies of flatfishes off Kodiak Island found halibut and rock sole to be most common on that region's sandy and rocky bottom, and she wonders if it will be any different here, where the bottom is mostly mud.
"Different species settle in different types of physical environments. So you get a lot of Dover sole and rex sole here and we get very few in Chiniak, very few around Kodiak generally."
From the mud, scientists also find out what's available for young flatfishes to eat. Pat Lovely pushes and swirls the mud through a screen, as if panning for gold, to get the answer.
"What we're doing is sifting all the sediment and mud out so we can get the small organisms that live in the mud called benthos out so we can see what's available for the flatfish to eat. A lot of them are bi-valves different types of worms, small crustaceans, crabs and stuff, and we'll get a lot of fragments when we're done with it that will be in the sample too.
Abookire's study is expected to continue for another year, after that her findings will be combined with similar research off Kodiak Island and in Cook Inlet. Ultimately, the discoveries will help protect critical flatfish nurseries and help fishery managers know what to expect as stocks mature.
For Arctic Science Journeys, this is Debra Damron.
Arctic Science Journeys is a radio service highlighting science, culture, and the environment of the circumpolar north. Produced by the Alaska Sea Grant College Program and the University of Alaska Fairbanks.
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