Rainbow trout are both prey and predator
In general rainbow trout face predation from above the water from the likes of Herons, Cormorants, Grebes, and Osprey but also mammalian predators such as bears and otters. Under the water, competition is even more fierce with attacks from Bass, Pike, and even larger trout.
There are even sightings of Snakes predating on trout. Keep reading to find out more.
Many Fish Prey on Rainbow Trout
Stocker trout are a protein rich gift for hungry bass. In lakes and ponds that contain bass stock trout need to be of a reasonable size to avoid predation.
Large rainbow trout and Bass can seem to coexist but usually to the detriment of the trout population.
Trout are cannibals, if a large trout is hungry and a small fry gets too close chances are it will become an easy meal.
Sometimes at stocking time, large resident trout have learned to recognize the sound of the stocking trout discharging and they all rush in for an easy meal of dazed stockers.
In rivers and streams, brown trout also tend to outcompete and replace rainbow trout.
Pike are a top level predator in their natural freshwater habitat, and their diet is largely fished based. Juvenile, and smaller trout make for an easy meal while larger trout can suffer from bite injuries.
Where Pike have been introduced into Rainbow trout waters can spell disaster to the later. Especially when trout populations are already under stress from over angling and environmental degradation. Illegal introduction of Northern Pike has become a serious issue in parts of Southcentral Alaska.
Out in the sea is a real fish eat fish world, and the Steelheads need to be fast and agile to avoid becoming a snack. In the ocean, steelheads are predated upon by several species of Shark and other predatory fish.
Birds Are a Main Predator of Trout
Trout often fall victim to aerial attacks.
Herons come in many shapes, sizes and colorations. They generally stalk the shallows and margins hunting for small fish. A trout fry can make for an easy meal, but large Blue Herons will happily swallow a stocker rainbow whole
One study, which took place on an Arkansas tailwater estimated that stock trout made up 67% of the Heron’s daily energy demand.
Cormorants are effective underwater hunters, and any small, and some not so small species of fish can easily fall victim on their hunts. I have even heard of Cormorants catching Rainbow trout that are much too large for them to swallow.
Cormorants are also clever birds, they learn to recognize that the stocking truck means buffer time. Some even follow boats around to try and grab fish that get released.
Historically some fish and game departments even culled Cormorants populations to try and protect trout. That practice was found to be rather ineffective and is no longer being practiced. Although it does not stop fishermen from grumbling about the presence of Cormorants.
Eagles and Osprey
I suspect we have all seen photos and footage of an Osprey diving down and snatching up a trout in its talon. A rather impressive site.
It has been estimated by the Alaskan Department of Fish and Game that an Osprey only needs one 10cm (25inch) fish per day to meet its energy requirements.
Kingfisher’s diet mostly coexists of insects, lizards and small fish. So given the opportunity, they will dive into the water to grab a trout fry. Large trout and even stockers are generally quite safe from Kingfisher predation,
Grebes are very cute fish eating birds, they dive beneath the water and hunt their prey a bit like Cormorants. Grebes are cute because there young often hitch rides on the back of their parents.
Mammals That Predate on Rainbow Trout
Otters are skilled aquatic hunters, and the majority of their diet is fish. So they readily hunt and eat Rainbow trout. At times, they seem to hunt and kill them just for the sport of it.
Stock trout make particularly easy prey for a hungry Otter.
When Rainbow trout and Steelhead which high enough densities on their spawning runs bears at times fish for them like they do Salmon.
Under normal conditions, Rainbow trout are too dispersed and difficult to catch so bears do not usually hunt for them.
Bears do feed on Rainbow trout but they much prefer to catch the more numerous Salmon.
Seals are opportunistic feeders that predate on a large range of seafood that does include Steelhead trout.
In fact, the sense of smell of a Rainbow trout is so good that they can detect the scent of Seals down to parts per million which assist in them invading becoming the next meal.
Racoons are really a significant predator of rainbow trout, but they do scavenge upon dead, dying, or trapped fish.
Raccoons are opportunistic feeders and will eat just about anything they can get their paws around, but unlike some online sources claim, they do not typically target Rainbow trout because they are much too fast and agile for them to capture.
Cats of all shapes and sizes are capable of catching fish, from moggy to mountain lions given the right opportunity they will not turn down an easy meal.
In saying that, I do not believe trout will make up a significant portion of their diet and it is unlikely they will target healthy fish that are not trapped in the shallows.
The same opportunistic behavior also applies to wolves and wild dog
Reptiles That Eat Trout
This might sound hard to beleive, but there are snakes that can hunt and catch Trout. One of the prime candidates is the Aquatic Garter Snake which mostly predates on fry to fingerling size trout. Although larger snakes can grab even a sizeable trout.
Here is a video showing a Snake with a brown trout.