When Do Rainbow Trout Spawn? Expert Guide

Rainbow trout are some of the best fish to target. They’re aggressive and eager to take whatever you throw at them. They are hearty fish with large populations worldwide, making them highly accessible for most anglers.

In the spring, rainbow trout spawn, so anglers must be careful not to target spawning fish. The spawn is vital for the survival of the rainbow trout population, and anglers need to do their best to protect the fish in the spring as they’re spawning.

What Time of Year Will Rainbow Trout Spawn?

Generally, rainbow trout spawn throughout the spring. If you’re targeting spawning fish in the northern hemisphere, they’ll spawn sometime between February and June. In the Southern Hemisphere, rainbow trout spawn from September to December.

The brook trout and cutthroat trout spawn in the spring, and brown trout in the fall.

Factors That Affect Rainbow Trout Spawning

The rainbow trout spawn is heavily dependent on the environment. While they will always spawn in the spring, it doesn’t mean it happens all simultaneously. Temperature, stream flow, and oxygen level are all significant factors in determining when the trout spawn officially happens. Spawning trout are sensitive fish, and the process takes a lot out of them, so abnormal conditions can harm the overall rainbow trout populations.

Temperature

As temperatures begin to warm in the spring, the pre-spawn can begin. Rainbow trout wait until water temperatures are above 40 degrees before moving to the gravel bars and making final preparations for the spawn.

The ideal temperatures for the spawn are somewhere between 40-55 degrees. They’re warm enough that the trout’s metabolism isn’t too low, but it’s not too warm that they’re sluggish. Too warm temperatures can cause significant damage to trout and potentially kill them.

Water temperatures will hit 40 degrees earlier than usual in some years, but trout can adapt and get ready despite the sooner-than-normal warmth.

The general rule of thumb for the spawn is that trout in lower elevations will start the spawn far sooner than trout in upper elevations.

Stream Flow

The following important factor for the spawn is the stream flow. In the spring, runoff starts in lower elevations as soon as temperatures get above freezing, so consistent flows aren’t always easy to find. If runoff starts right as water temperatures reach above 40, trout will wait for more consistent flows later in the spring.

However, the entire spawn can occur before runoff starts if it’s a frigid year.

Trout need consistent and clear stream flows for the spawn to start. These consistent flows generally mean highly oxygenated water, essential for the spawn.

There isn’t a consistent CFS (cubic feet per second) rate that trout need before the spawn can happen because each river and stream is different. They don’t want extremely high CFS because it can force them to exert too much energy and wash all of their eggs downstream. Generally, a 200-500 CFS flow rate is ideal for a spawning rainbow trout.

River Bottom

Rainbow trout will look for a gravel river bottom in water 1-4 feet deep. The gravel is the perfect place to set up their spawning grounds. They’ll dig into the gravel so the eggs have a safe place to incubate once fertilized. These spawning grounds are known as Redds.

The eggs would wash downstream if they weren’t stored somewhere safe from the current. The hole in the river bottom allows the current to pass over the eggs and minimize the amount washed downstream.

All trout species create Redds. Females will lay the eggs, and the male trout fertilize and protect them.

Oxygen Level

One final factor that needs to be in place before the spawn can occur is the oxygen level. As mentioned earlier, all trout will spawn in a highly oxygenated water section. Wild trout, native trout, and stocked trout need it.

Trout choose areas with gravel and rocky bottoms because flows will be consistent and strong. The higher the oxygen level, the more chance eggs have of surviving.

Ideally, the oxygen level is somewhere around 7 mg/L. This level occurs when the water temperatures get to around 50 degrees.

Trout eggs are extremely volatile, so trout seek out consistent levels. Without them, eggs will die, and rainbow trout populations will suffer.

How to Fish for Rainbow Trout During the Spawning Season

Fishing for rainbow trout during the spawn can be a challenge. Since the fish are fully focused on spawning and not feeding, you must use different techniques to get the fish to strike. Plus, you have to be careful about where you’re fishing. Make sure you pay close attention to the location of the Redds and do not disturb spawning fish.

Before the Spawn

Generally, anglers have more success fishing before the spawn. During the pre-spawn, fish are aggressive in their movements and feeding. Most rainbow trout are fattening up because as soon as the spawn starts, the fish won’t eat. They’re only worried about laying eggs and keeping them safe.

If you’re fly fishing for trout, throw eggs and streamers. These are larger and more appetizing patterns that look like easy meals. Trout want as much food quickly as possible, so streamers are a good choice. Swinging the streamers during the pre-spawn is the most effective method. Cast your streamers upstream, let them across your body, and begin stripping as soon as you see the line get tight below you. Feel free to strip hard because the fish are more aggressive than usual.

Egg patterns make trout think that the spawn has already started, so if you drift these near gravel bars, you’ll get some of the non-spawning fish to eat. Rainbow trout are happy to eat trout eggs, so find a gravel bar near a pool, and you’ll be in business. High-stick them through the riffles and let them float naturally in the pools.

During the Spawn

During the spawn, fish are only going to strike out of aggression. If you cast near a Redd or find an active fish, they’ll likely strike your fly. If it’s an exciting-looking pattern, you shouldn’t have any trouble landing fish.

When fishing the spawn, ensure you’re fishing downstream of the Redds. Eggs will move downstream.

Should You Target Spawning Rainbow Trout?

Spawning rainbow trout are not technically off limits or illegal to target, but anglers should avoid targeting spawning fish. The spawn is a highly exhausting process for these fish, and a few hard fights could permanently damage or kill them.

Also, a rainbow trout amid the spawn is more than likely protecting or laying eggs, so interrupting that process can be detrimental to future rainbow trout populations.

Wait for the spawn to conclude or target non-spawning fish. Not every rainbow trout is sexually mature enough to spawn, so there is plenty of fish in the river to catch.

What Is a Redd, and What’s It Look Like?

Rainbow trout spawning areas are known as Redds. Redds are found in a relatively shallow river with constant currents and a gravel bottom. The gravel bottom is easy for the trout to dig into to create a safe place for the eggs to incubate.

Some of these Redds are up to 15 inches deep and can be the size of a bathtub. As you’re walking up or downstream, look for sections of water that have a deep red color. The red color is a dead giveaway of eggs. Steer clear of these sections of water. You don’t want to step on a Redd and kill rainbow trout eggs.

Will Rainbow Trout Die After Spawning?

No, rainbow trout do not die after they spawn. Even though it’s exhausting, they’ll recover from it after a few weeks. If you happen to catch a spawning rainbow trout or a larger predator attacking them, they can die.

Otherwise, they’ll be weak for some time after the spawn and eventually recover by mid-summer.

Frequently Ask Questions About Rainbow Trout Spawning