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Wildlife spy: Mysteries of the deep: Do you know where your halibut has been?

Tip: A fishing trip gives you a window into the hidden depths of the ocean

Posted: August 24, 2012 - 12:00am
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A close-up of a halibut head.  Patty Wing
Patty Wing
A close-up of a halibut head.

We’re heading out into Prince William Sound on a new adventure for this Wildlife Spy — searching for Pacific halibut. The boat is the Tango out of Valdez, a charter run by Mike and Patty Wing. They’ve been plying these waters since 1995, and put their experience to good use.

It’s an astonishingly clear, calm day, but it wouldn’t matter to the halibut if it was a raging storm — they mostly lurk in the depths. There’s even a word for their habit of hanging out on or near the sea floor: “demersal.” Unlike spotting the flamboyant silver salmon leaping out of the water, finding halibut takes a combination of knowledge of the fish and technology in the form of a depth-finder.

In North America, pacific halibut range from Nome all the way to Santa Barbara, Calif. A parallel population plumbs the deeps from Hokkaido, Japan to the Gulf of Anadyr in Russia, with fish occasionally wandering to this side. Halibut prefer cold waters. They can also survive to depths of 3,600 feet. Halibut don’t have a swim bladder, an air sack that some fish have to control buoyancy, so they can take advantage of a wide range of depths without the danger of rising too quickly and causing injury.

Where we stop to fish is basically the kiddie pool depth to the fish we’re searching for, registering a bit more than 200 feet deep. Our guides’ experience soon pays off. Someone’s fishing rod tip starts bobbing. In short order, Mike and Patty are lifting our first prize of the day on board.

At first glance, a halibut looks like it would be clumsy and slow. A flattened form with bulbous eyes crowded onto one side of the head like Picasso’s idea of a fish, the halibut’s mouth is the first clue it is anything but bumbling. Halibut have plenty of teeth — a single row on the bottom and double row on top, all the better to eat you with, if you’re anything smaller than a halibut.

The orientation of the mouth, symmetrical on both sides of the fish’s head and at the front of the face shows the halibut is a versatile hunter, able to grab fish along the bottom or chase them above the sea floor. Another clue to the hunting style is in the colors the fish sports. The drab, dull olive with splotches of darker and lighter tones on its upper side help it blend into the background when it lies in wait on the ocean floor. When prey approaches, with a quick lunge the halibut snaps up the unsuspecting critter, sometimes swallowing it whole.

One of the halibut we pull up has a crab the size of my palm in its mouth. Patty and Mike have seen 100-pound halibut with whole salmon or rockfish inside. These voracious fish eat anything that fits, and sometimes things that don’t. Patty recalls seeing a halibut with a fish too large to swallow wedged into its mouth like a cork in a bottle. Halibut start out life dining on plankton. As they grow, they add creatures to their diet, small fish or the shrimp-like krill whales enjoy, expanding the menu to include shrimp, cod, sculpins, rockfish, turbot, crabs, octopus, squid and even mobile fish such as sand lance, herring and salmon.

This snatch-and-grab method of capturing food means places where a halibut can camp out near a current that will bring food drifting past draw the fish like a lodestone. Underwater cliffs or pinnacles where upwellings flow, places where the tides cause currents, or places where larger ocean currents sweep past all are potential halibut buffets.

With nearly everything that swims as a potential meal, it’s no wonder Pacific halibut can grow to be one of the largest of the bony fishes. Some leviathans edge up toward 500 pounds, reaching more than eight feet long. Females grow much larger than males, most likely because the larger the female, the more resources she can put into producing more eggs. A fifty-pound female can generate 500,000 eggs, but a female over 250 pounds can produce up to 4 million. Males are featherweights, comparatively speaking, often less than 100 pounds. The most common size caught commercially is in the thirty-to-forty pound range. The fish we catch are “chickens” (about ten to fifteen pounds) and “turkeys” (up to about thirty pounds). They all start out, however, smaller than a dime.

Even though they are bottom-dwellers, halibut are strong swimmers, on the move throughout their lives. During the winter months, sometime between November and March, mature halibut migrate from feeding grounds toward the continental shelf, a massive undersea cliff. They mate in the dim depths anywhere from 600 to 1,500 feet below the surface, setting the next generation adrift in the currents.

The fertilized eggs hatch after about 15 days. The newborn halibut, called a larva at this stage, looks, well, wormlike. Its eyes start out on either side of its head and its mouth isn’t quite developed. A yolk sac bulging below its head provides a food source for a while as it grows. Its body is slightly heavier than seawater, so it floats in mid-water, taking advantage of strong ocean currents. It develops jaws to start gobbling plankton. At about an inch long, one of its eyes starts shifting toward the other side. The vast majority of halibut are right-sided: the right side becomes the upward side with color and both eyes. The bottom side fades to white.

At about six months, the halibut looks like a tiny copy of an adult. Up until then, a fish that hatched in Alaska has drifted on ocean currents that carried it north and west. At six months it settles in a shallow area near shore to start the serious business of eating and growing.

After a couple years, the young halibut moves to deeper waters. It starts swimming east and south, retracing the direction it drifted before it was big enough to buck the currents. It may wander for years: if it’s a male, it won’t reach maturity until about eight years old, and a female takes until twelve years old. The larger they grow, the deeper the water they seek. They can cover long distances: one fish biologists tagged near Atka Island in the Aleutians was found in Oregon 2,500 miles away a few years later.

As we fished, we hit a hot spot. At several points, four of the six guests on board were reeling up fish. Younger, smaller halibut, like the ones we pulled up, sometimes congregate in groups. Larger fish tend to be more solitary, perhaps because they need more food. Researchers have found there is not a specific age-to-size ratio. Rather, it seems to fluctuate over the course of years; in some decades fish grow faster than others. Although this isn’t entirely understood, the conjecture is that it’s a mix of environmental conditions and the pressure of halibut and other fish populations.

It’s one thing to understand halibut like deep waters and sea cliffs, and quite another to know where those places are, and when to check. As we head back toward the harbor with the sun still flashing off the jumping salmon, I find myself grateful for the experience of Mike and Patty for giving me the chance to examine these creatures of the deep.

• Beth Peluso is a freelance writer, illustrator, and avid birder. She enjoys spying on wildlife around Alaska.

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