🐟 OnlyFins - Live Underwater Trout Cam

Looking up from underwater, the whole sky is squeezed into a cone about 97 degrees wide. Outside it, the surface acts like a mirror. The glowing patch at the top of the frame is the same view a trout has of the world above: every bird, angler and falling insect appears inside that window.

Trout hold nose-into-the-current so water flows over their gills and food drifts straight to them. Watch the fish on the cam: they line up like weathervanes.

The slow pocket behind a boulder lets a trout hold position with very little effort, then dart into the fast seam to grab food and slip back. Anglers call these spots pocket water.

Most of a stream trout's diet is drift: mayfly, caddis and stonefly nymphs knocked loose and carried downstream. A quick sideways flick of a fish on camera is usually a feeding strike.

Juvenile trout carry dark vertical ovals called parr marks. In dappled stream light they break up the fish's outline. Look for small, barred fish holding close to the bottom.

Rainbows have a pink-to-red band along the side, a rosy cheek and black spots that run onto the tail. Native to Pacific-draining rivers, they have been stocked in cold waters all over the world.

The Bonneville cutthroat trout became Utah's state fish in 1997. Look for the red-orange slash under the jaw that gives cutthroats their name.

A trout's lateral line, the faint line down each side, senses pressure and vibration in the water. Heavy footsteps on a bank can send fish into hiding.

Trout need cold, oxygen-rich water. The churning white water at the top of the frame mixes air into the stream, which is part of why fish gather just downstream of it.

Trout cannot close their eyes. They manage bright light by moving into shade and deeper water, which is why activity on the cam often picks up at dawn, dusk and on cloudy days.

Most trout in small mountain streams live about 3 to 6 years, and few make it past 7. Bonneville cutthroat in streams usually mature at 2 (males) or 3 (females) and spawn every spring after that. Age can be read like a tree: each winter of slow growth leaves a tight ring on the fish's scales.

A trout keeps growing its whole life, but only as fast as its stream allows. In a cold mountain creek, adults typically reach 8 to 12 inches. The same species in a big lake or reservoir can pass 20 inches. The difference is the stream's budget: cold water, a short growing season and a limited supply of drifting insects.

Four things cap a trout's size. Temperature: they grow fastest in roughly 50 to 60 degree water, and much of the year a mountain stream is colder. Food: small streams carry mostly tiny insects, and a fish must win more calories than it burns fighting current. Space: the best feeding spots behind rocks are limited, so bigger fish chase smaller ones away. Winter: months of near-freezing water bring growth almost to a stop.

Leeches live in streams too, mostly in the slower, softer water along the edges and in pools, hiding under rocks and in debris. Most freshwater leeches never bite people; many hunt small insects and snails or scavenge. When one lets go and swims, it ripples through the water in a slow, wavy undulation, and trout find that motion irresistible. A leech is a big, soft, high-protein meal that's worth far more energy than dozens of tiny nymphs, so even a cautious trout will move to grab one. They are most active at dawn, dusk and night, which is part of why the cam gets busier in low light.

Thin aquatic worms, relatives of earthworms, live in the silt and gravel of the streambed, and high water washes them loose into the drift where trout pick them off. Those bright red 'bloodworms' anglers talk about aren't worms at all: they're midge larvae, colored red by the same oxygen-carrying hemoglobin in our blood, which helps them breathe in low-oxygen mud. Both are a big part of a trout's diet, and both show up most after rain, when the current stirs up the bottom.

Growth comes from winning better real estate. As a trout grows it can hold a faster seam, where more food drifts past, and defend it. Bigger trout also switch to bigger prey: stonefly nymphs, crayfish, sculpins and even smaller fish. That calorie jump is what turns a 10-inch fish into a 16-inch one.

Young trout carry dark vertical ovals called parr marks. They usually fade over the first year or two, as the fish passes about 5 to 7 inches and moves out of the shallow edges into open water. In small, shaded mountain streams some adults keep faint parr marks for life. The black spots are different: those stay forever and get more defined with age.

Rainbows and cutthroats spawn in spring and early summer as snowmelt eases; stream cutthroat in Utah spawn around May and June. The female sweeps out a nest, called a redd, in clean gravel. The eggs hatch weeks later, and the tiny alevins stay hidden in the gravel living off their yolk sacs before emerging as fry by mid-to-late summer. Most never reach their first birthday.

Trout are cold-blooded, so as the stream cools their metabolism slows and they need very little food. Small fish go quiet first, in the 40s Fahrenheit; bigger fish stay active a bit longer. By late fall they move out of summer feeding spots into deep, slow pools and the gaps between boulders, then barely move until spring.

Surface ice is actually helpful: water keeps flowing underneath and the ice hides fish from herons and other predators. The danger is anchor ice, slush that freezes onto the streambed on the coldest nights and fills the spaces between rocks where young trout hide. Groundwater seeps that stay a few degrees warmer are winter lifesavers, and fish crowd into them.

Winter is a diet, not a fast. The stream's insects don't disappear: midge larvae and pupae, tiny mayfly and stonefly nymphs, and caddis larvae keep living among the rocks and still get knocked loose into the current, so a slow trickle of food drifts under the ice all winter. Midges even hatch on mild winter days, and small winter stoneflies crawl out onto the snow. Where they live, scuds (tiny freshwater shrimp) and sculpins are a richer meal. Trout eat only a fraction of their summer intake and stop growing, but a slowed-down body needs so little that they can go days between meals, living partly off fat stored in fall.

Cold trout won't chase. Instead of darting into fast seams, they hold in slow, deep water and take only what drifts within a few inches of their nose. Feeding picks up during the warmest hours of the day, when the water creeps up a degree or two and the midges get moving. On the cam, winter fish look almost motionless; watch for a small sideways tilt or a white flash of the mouth opening. That's a meal.

Snowmelt turns a calm creek into a torrent for weeks. Trout ride it out tucked behind boulders and in slack water along the edges, where the current barely moves. The flood also scrubs silt out of the gravel, which keeps it clean for spawning.

A heavy rain or fast snowmelt can turn clear water dark brown in an hour. Trout don't leave; they hunker down. They slide out of the main current into slack water along the edges, behind boulders, under undercut banks and into side pockets, where the flow is gentle and less silt is suspended. If the cam suddenly looks like chocolate milk, the fish are almost certainly still there, a few feet away, waiting it out.

When they can't see, trout switch senses. The lateral line along each side feels the vibrations of moving prey, and a keen sense of smell picks up food in the water. Muddy rises also bring a feast: worms washed out of the banks and land insects swept into the stream. Many trout feed hard along the edges as the water rises, which is why anglers love the first hours of a 'fishing the dirty water' day.

Adult trout usually ride out a muddy flood with little harm, but fine silt is tough on them in two ways. Heavy sediment irritates and clogs gills, so fish breathe harder. Worse, when the silt settles it fills the gaps in the gravel where trout eggs incubate, cutting off the oxygen that flows to them. A big muddy flood in spring, right after spawning, can wipe out much of that year's young.

Rain on a recent burn scar is the most dangerous kind of muddy water in the West. With no plants to hold the soil, a summer storm can send ash, mud and debris flows into a stream, dropping oxygen and choking gills. These events can kill fish for miles. Streams do recover: as the slopes heal, trout recolonize from tributaries and unaffected reaches upstream and downstream, usually within a few years.

Most mountain streams clear within a day or a few days after the rain stops, and the flood does some good on the way down: it scours fine silt out of the gravel and rearranges rocks into fresh pockets and pools. Smaller, younger trout are the most likely to be swept downstream, and they work their way back up over the following weeks.

Warm water holds less oxygen, and trout get stressed as water climbs toward 70 degrees. In summer they shift toward shade, springs and fast, bubbly water below falls like this one, where churning water keeps oxygen high.

Herons, kingfishers, ospreys, mink and otters all eat trout, and bigger trout eat smaller ones. That's why fish on the cam stay close to rock cover and dart away from sudden shadows overhead.