5 Interesting Facts About Steelhead Trout

Ramseyderschal/ Fishing in Western Washington/ 0 comments

The steelhead trout are native to the North American continent and are found in its freshwater and ocean environments. In recent times, they’ve been introduced to every other continent, the only exception being Antartica. The name ‘Steelhead Trout’ has been given to the anadromous form of the coastal rainbow trout. It is also known as the redband trout.

The steelhead migrate to the ocean and return to its freshwater tributaries for spawning. On the other hand, the rainbow trout don’t leave freshwater. The steelhead are larger and less colorful than the rainbow trout. These are the major differences between these two forms of the species. Now, let’s take a look at the most interesting facts about steelhead:

1. The two distinct runs of steelhead

In the world of steelhead fishing, the two distinct runs of this fish species is well-known. Owing to these runs, the steelhead are termed as ‘summer-run steelhead’ and ‘winter-run steelhead’. The summer-run steelhead begin migrating during the spring and summer seasons.

The winter-run steelhead move to freshwater during the winter months. They enter the freshwater system at a relatively developed stage of maturity. This begins around November and continues through May. At this point, their bellies are robust and their attention concentrated. They have a limited amount of time to spawn after transitioning from saltwater to freshwater.

The summer-run steelhead begin entering into freshwater as early as April. They enter in large numbers during the warmer months. Their numbers begin to decrease by November. Sexual maturity in the summer-run steelhead greatly differs from the winter-run steelhead. The reproductive organs in summer-run steelhead begin to mature only after they make their transition from saltwater to freshwater.

The comfortable water temperatures and mild weather play an important role in increasing the metabolism of the summer-run steelhead. Despite the differences in their timing of migration, both these types typically spawn during spring or early summer.

2. Time taken for migration

Upon reaching the stage of maturity, both summer-run and winter-run steelhead follow a certain migration pattern. The winter-run steelhead is always up against the clock of Mother Nature. They mainly dominate the tributaries that are located within 100 miles of the ocean. On the other hand, the summer-run steelhead can remain in freshwater up to a year. They travel hundreds of miles away from saltwater.

Both the types of steelhead can survive up to a year in freshwater without feeding in large quantities. The summer-run steelhead require more time as they make long journeys and encounter major obstacles on the way. The summer-run steelhead must ensure that they make it to their spawning beds on time.

3. The presence of otoliths

The otoliths in steelhead are also known as ‘earstones’. They are located on their head at the back of the fleshy part of their brain between the ears. An otolith is a part of the hearing and balance system in the steelhead. It is solidified calcium carbonate that mainly comes from water.

As the steelhead grow older, new crystals of calcium carbonate begin forming. They allow the binding of trace elements with the otolith, which causes the development of layers. For the biologist, this composition and build-up is extremely important. Scientists can determine the steelhead’s age and the properties of water bodies they have occupied earlier from the otolith.

They can also know from the otolith how long each steelhead has been in freshwater as well as saltwater. It can also identify the fish that have returned to freshwater for spawning more than once. The biologists can also identify the specifics about the age of the fish with the help of their scales.

Despite this, the biologists consider the scales unreliable because they can become misconfigured or damaged during migration for spawning.

4. The role of body fat reserves in migration

There are many similarities between the spawning habits of the steelhead and rainbow trout. One of the unique facts that many don’t know is that the rainbow trout can fertilize steelhead eggs. Similarly, the steelhead also have the ability to fertilize the eggs of the rainbow trout. There have been studies in recent times based on such data.

In this process, the amount of lipid body fat within a steelhead is specifically noted. The healthy fish that don’t have the desperation to gain body mass may possibly remain in freshwater. This can avoid the dangers associated with ocean travel entirely. A fish seeks saltwater if it’s low in body fat. Once it enters the saltwater, it feeds heavily until it attains a substantial size.

High amount of body fat is often because of water temperatures as fish found in cold water have greater lipid reserves. As one travels further down a river system, the water gets warmer. This prompts the fish to move to the ocean owing to their lower reserves of body fat.

According to the latest research, the male juvenile steelhead show a higher inclination to be in freshwater. This is due to the fact that they don’t need to gain more mass than the egg-bearing females. Besides, they have the ability to spawn with multiple females many times.

5. Adaptability of the steelhead

The steelhead have showed a greater degree of adaptability over the years, which is beyond what anyone can comprehend. It is, perhaps, the result of the choices that they have made historically. In some parts of Russia, the steelhead have reportedly spawned almost ten times. Despite having such features, their survival rate is decreasing drastically.

The smolt-to-adult return (SAR) rates of the steelhead have varied historically between 10 to 20 percent. Biologists use the SAR rates to calculate the percentage of fish returning as adults. The SAR required to maintain the existing population levels of steelhead is 2 percent. Currently, the data shows a significant decrease, as the SAR rate is as low as 1 to 2 percent.

There’s another worrying aspect with regards to their population levels. It is the misconception that they return to spawn again during their life cycle. The belief that the steelhead do not decay is a faulty assumption. Most of the steelhead do perish after spawning while attempting to return to the ocean. The male fish tend to eject their sperm multiple times while spawning. This results in a severe fatigue in them.

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