It’s cool when somebody who knows fishing and knows science can tell you in detail about the critters you love. Alaska West’s own Jordan Sly dishes today on our leopard rainbow trout.
This is a good one!
What Makes Alaskan Trout Different
Living in Washington among a large population of steelhead anglers I often get questions from people about our rainbow fishing in Alaska.
A typical conversation:
“Are the rainbows up there searun?”
“No, they did a study in 2009 that showed they do migrate between the Kanektok and the Arolik a little, but that was on a rare occasion, and that isn’t really considered searun either. So for the most part they just stick to their home waters, in other words, no.”
“How come they get so big then?”
“A lot of it has to do with abundant food source during their growth period, and the morphological difference of leopard rainbow when compared to the average lower 48 rainbow that allows them to take advantage of that.”
“Never mind, they are just awesome fish and super aggressive during our fishing season because that’s when they get the majority of their nutrient intake for the year”
“Oh, that kind of makes sense.”
Well I plan on trying to clarify some things about our beautiful leopard rainbows we have at Alaska West. Will this information make you a better fisherman? Maybe, maybe not, but I hope it makes you appreciate fish and the environment they live in more.
The first thing I think that is important to discuss is feeding habits. There isn’t too much of a genetic difference between the different subspecies of rainbow trout Oncorhynchus mykiss, but the feeding habits can be drastically different. The majority of resident salmonids are all opportunistic feeders, meaning they feed on what’s available when it is available, the difference is that as they grow, their feeding habits often change.
Lower 48 rainbows for the most part tend to be the most opportunistic feeder among the resident salmonid populations through out their life cycle when compared to others – meaning they feed on small fish, aquatic insects, eggs, flesh, and really almost anything that comes by, when it comes by, they don’t seek certain food items, they just eat whatever. This is a lot different when compared to a brown trout – Salmo trutta, who mainly turn piscivorous (fish eaters) when they get larger. Cutthroat trout – Oncorhynchus clarki – are kind of the middle ground when compared to browns and bows, they are more piscivorous than bows, but less than browns.
I don’t want to waste your time explaining all the different feeding characteristics of resident salmonids, but I feel it’s important to understand this because a more piscivorous diet is much more beneficial to a fish if the food source is available. Fish need a certain amount of basic nutrients and proteins to grow, well the best food source of those nutrients with minimal waste is other fish, eggs, and even mammals because they are higher in the right proportions of nutrients, causing minimal amount of waste, the “perfect packet.”
The downside to this “perfect packet” feeding is often the increased amount of effort needed to catch other fish and mammals.
Second it is important to point out the differences in physical form, often referred to as morphological differences, between leopard rainbow trout, lower 48 rainbow trout, and other resident salmonids. Leopard rainbow trout develop a mouth pocket that is more similar to a brown trout, and cutthroat trout. This morphological difference allows leopard rainbows to utilize that “perfect packet” of nutrients. They can easily eat larger food sources with higher ratios of basic nutrients for growth, such as large sculpin, big hunks of flesh, and mice. It’s all about gaining as much nutrients as possible while exhibiting the least amount of energy.
I’m sure you see how these two differences go hand in hand with each other, larger food source, larger mouth…but why the change from a typical rainbow? The answer is because of seasonal availability. The leopard rainbow on the Kanektok are under ice the majority of the year, so they need to take advantage of the food while they can, and those “perfect packets” are the best option. Over the years, the fish that could utilize those “perfect packets” during the summer months had a better survival rate, created more offspring, thus causing their morphological difference to be passed on more often.
So what’s this mean for fishing at Alaska West you ask? The rainbow trout are extremely aggressive during our fishing season because that is their main feeding and growth season – they need to eat while they can. With this aggressive behavior, and this drive to eat large food items, the mouse fishing can be awesome, and they will hammer a well placed sculpin. Once the egg drop happens the focus of the rainbows changes towards eggs and flesh because they can get large amounts of nutrients without putting much effort into it.
Does this mean they won’t eat mice in August, no, they will, but if they had a choice between a hunk of flesh drifting towards them or a struggling mouse on the surface, they would probably go for the flesh first, but then gobble that mouse if it was not on shore yet.