SRC size, growth rate, food source, genetics?

With regard to SRC living in the salt... is their growth rate and growth limit genetic? Is it limited to food source? Seems like there is plenty of food in the salt especially. Is their size affected by the fact that they move around allot? I ask, because some of the Cutt's I've caught in other waters, especially rivers, seem to get rather huge compared to SW Cutts! So is it mainly the genetic strain of the fish that calls for the average size?
I've always wondered about that. Why don't they get big like every other species that goes to the salt. Rainbows go to the salt, come back steelhead. Browns go to the salt, the grow huge. Bulls/dollies/artic char grow big in salt. Sea run brookies get pretty big on the opposite coast. SRCs go to the salt and stay small. Even their inland cousins the westslope get bigger without salt.


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my 2 cents worth is that searuns do not venture very far offshore so that limits them to what food they find in close. as where salmon/steelhead go very far out and they eat bait fish that puts the pounds on. Herring, shrimp, etc. so after 2-3 years of that you get a bigger faster predator.
ok, but doesn't the puget sound at least have a good source of squid, shrimp, marine worms, baitfish...what else do they eat? Does anyone in this forum ever do a throat sample on salty SRC? I'm guessing that most of what you'll see will just reflect seasonal food availability. Either way, compared to trout restricted to rivers you'd think they the anadromous fish in the salt have a shot at bigger meals and a larger abundance of food... then again, maybe not? Admittedly I'm unlearned on this subject, so forgive my ignorance...trying to learn/understand here. Maybe less predators in the river vs salt... so maybe river fish grow older?


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Sea-run cutthroat are just one a 4 life histories of coastal cutthroat (resident, fluvial, adfluvial and anadromous). As with most of our salmonids it is common to see considerable differences in growth rates between the various life strategies or history. With most species including he coastal cutthroat the adfluvial fish are the fastest growing. The largest I have seen was over 14#s and only 7+ years old (on the whole coastal cutthroat seem to be relatively short lived species few surviving beyond age 8 or 9.

The following is base on what has been observed with north Puget Sound rivers anadromous form of coastal cutthroat. It is generally the case in our anadromous waters that there is a partitioning of the habitat use by the various species with each thriving in the habitat that they are best suited to. For the coastal cutthroat that habitat is the smallest of the anadromous streams (many of which can be crossed without getting ones feet wet). As the stream gets larger the over-all cutthroat use declines as they share that habitat with coho and to some degree steelhead. In those headwater areas the resident cutthroat rarely reach size any larger than 10 inches. In those anadromous water many of the juvenile cutthroat "smolt" at age 2 to 4 at a size of 5 to 8 inches.

Those smolts upon reaching the salt experience some pretty decent growth rates for the first few spring and early summer months. It is not uncommon to see growth of 1 to 1.25 inches/month. By the early summer grow rates slow and many of the fish begin staging and returning to the rivers. I have wondered if it maybe that coastal cutthroat may still mainly a freshwater fish who is not entirely suited to the marine environment. Suspect that it requires a lot of energy on the fish's part to maintain hydrostatic balance requiring that much of their food intact is diverted from growth. Once the small juvenile bait fish and salmon fry move off shore as the year progress the foraging opportunities for the cutthroat also declines; they seem to be closely tied to the shorelines and don't move into deeper water to forage. While the fish continue to feed once they are in the rivers there seems to be only slow growth (measured in just fractions of an inch/month). Once they reach adulthood the spawning process results in loss of body condition and a significant portion of the following spring feeding is required to recover condition. As a result it is typically to see only a couple inches of growth between spawnings.

I doubt the slow grow has little to do with genetics (it is common to see lakes that support both adfluvial and anadromous individuals that have very different growth rates) and everything to do with life history choices. It is common to see the various life histories actively spawning together demonstrating a single population.

my 2 cents worth is that searuns do not venture very far offshore so that limits them to what food they find in close. as where salmon/steelhead go very far out and they eat bait fish that puts the pounds on. Herring, shrimp, etc. so after 2-3 years of that you get a bigger faster predator.
Sorry, they've been netted 35 miles off shore.

The studies, which are limited, indicate pretty much the same genetics among clarki clarki. There are theories about the size parameters, but one that appeals to me is that there is a cost to the metabolism going back and forth from salt to fresh, plus a lot of energy burned moving in currents and tides, and spent chasing down food.

Joe Jaucquet has a study going in the south sound to find out what they really do eat besides flies and poppers, (don't try this without a sampling permit) but somebody could try for a grant to see why they usually top out at 19 or 20 inches.


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I've also read that it is thought that the difference in growth rates between adfluvial and anadromous cutts may be due to the biochemical mechanisms needed for the fish to adapt to a saltwater environment. While it is true that there is plentiful food in puget sound, it is rare to find SRC over 20", while it is not surprising to find cutts over 5lbs in Lake Washington. It seems that significant resources must be directed towards the metabolic shift into salt.

Bob Triggs

Stop Killing Wild Steelhead!
I seriously doubt that there is less forage for cutthroat in the nearshore environment or protected waters of Puget Sound, than there is in the offshore and coastal waters. If anything there is more forage available and for longer periods of time. If you have ever participated in the WDFW forage fish sampling along the shores of Puget Sound and Hood canal or Admiralty Inlet waters, using a scientific seine net to briefly live capture samples for counting and identification, you will quickly see that there is no lack of diversity and abundance of marine species for Cutthroat to gorge on. I have never worked on one of those sites when we did not get overwhelmed with all manner of fish etc. One thing that I think about these fish is that they are only out in the salt water for a few months at most each year, and not all of them are out at the exact same time. If they stayed in marine waters for years at a time, as do steelhead, I would expect to see some very similarly large cutthroat. In the course of a season I will see a few fish over 18-19 inches. Maybe one or two in the 20+- inch range. But in the last 14 years of fishing for sea-run Coastal Cutthroat trout I have only seen three fish that were easily over 23 inches, and one that was well into 26+ inches.

Chris Bellows

Your Preferred WFF Poster
the idea that the forage base inside puget sound is similar to offshore is laughable to anyone who has spent any time off our coast.
So far the main take away for me seems to be the fact that the fish move in and out of the differing systems ie salt and fresh and that this affects their growth. At least their sizes may fluctuate much based on that.


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I do find it interesting that the cutthroat of South Sound and Hood Canal are not significantly larger than the north Sound fish in spite of spending half again as much time in the salt. Makes me wonder in spite of the extra time in the salt they are not finding the groceries we expect them to in fall and early winter in the salt.



Active Member
I've wondered if there isn't perhaps some genetic pressure toward a limit on size determined by the cutthroat's marked preference for extremely small streams for spawning purposes. It seems to me that a fish capable of spawning repeatedly over its lifespan in a stream with a water depth of only a foot or so might find some advantage in evolving toward a limited maximum body size.