The Oregon Coast Aquarium’s "Passages of the Deep" exhibit boasts an underwater world of fish accessible to visitors thanks to acrylic tunnels surrounded by several feet of sea water.

Oregon Coast Aquarium photo

Passages of the Deep at the Oregon Coast Aquarium.

Each 8-foot long tunnel section weighs approximately 4,119 pounds, or just over two tons and each tunnel is 10 feet wide. The tunnel lengths and water capacity varies, however.

Passages of the Deep Habitat Statistics

The Orford Reef tunnel is 22 feet long and holds 200,000 gallons of water. It offers a lot of shelter for the fish and the exhibit’s other water-loving creatures.

The Halibut Flats tunnel is 32 feet long and holds 275,000 gallons. The seafloor in that tunnel is home to animals that are adapted to concealing themselves in an open environment, including flatfish, skates, burrowing fishes and invertebrates. Larger fish pass through in search of prey. Any source of cover at all, such as a sunken ship, attracts large numbers of fish and animals that do not bury or burrow and need some other kind of shelter. Expect to see rockfishes hanging out near the shipwreck.

The Open Sea tunnel is by far the largest at 64 feet long. It holds a whopping 850,000 gallons of water. Like a desert, the open sea has no shelter save darkness and what an organism can provide for itself, like countershading, disruptive coloration or bioluminescence. In both habitats, finding food can require traveling long distances, so open sea dwellers either float on the currents (plankton) or have strong swimming abilities (sharks, tuna and jack mackerel).

Many residents of this habitat must have other ways to navigate and find food besides vision, since the vast majority of the open sea has no light at all. Skates, rays and ratfish can find their food by smell; sharks can sense vibrations, sound waves and electromagnetic fields—and of course they have an incredibly sensitive sense of smell.

Sharks of the open sea include spiny dogfish, smoothhound, brown, leopard, soupfin and sevengill sharks. Rays, bats, yellowtail jack, salmon, pacific mackerel, and jack mackerels also dwell in the Open Sea tunnel.

Feeding Info

Orford Reef

•60 pounds of food, three times per week

•Feed days are Sunday, Wednesday and Friday

•Most food is broadcast (flung over the water surface)

•Exceptions: fish-eating anemones are hand fed small pieces of fish; other anemones get krill shakes (a mixture of pacific krill and water, blended and poured into a water bottle)

Halibut Flats

•100 pounds of food, three times per week

•Feed days are Sunday, Wednesday and Friday

•30 pounds of food are broadcast, mainly to distract the sablefish. The other 70 pounds are dumped into the tank in large quantities, in hopes that most of it will make it to the bottom for the halibut and skates.

Open Sea

•180 pounds of food three times per week (Sunday, Wednesday and Friday), and 60 pounds of food twice per week (Monday and Thursday)

The animals are fed mostly fish -- anchovies, herring, salmon, mackerel and silversides. Some are chopped into various sizes, some are fed out whole. Aquarium staff also also feed squid, krill (for the anemones) and clam (for the rockfish and leopard sharks).

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The most aggressive feeders in “Passages of the Deep” are the sablefish, which out-compete the sharks, aquarium officials said.