Hatchery Trout Coloration and Diet

[Dave_W]

The topic of the coloration of hatchery trout based on diet has come up (again). In the past, the matter of adding paprika or other supplements has been shown (I think) to affect the coloration of hatchery brown trout in a positive way: deeper reds and stronger yellow flanks etc.

Private clubs have long stocked fish that were "better" in large part due to the aesthetically pleasing coloration of their fish, BTs in particular.

If you have experience, links, or opinions on this, by all means comment. It's an interesting topic for those of us who appreciate the beauty of trout.

 

[troutbert]

This is what is used in commercial salmon aquaculture to boost flesh coloration.

http://www.dsm.com/markets/anh/en_US/products/products-solutions/products_solutions_tools/Products_solutions_tools_salmon.html

The better coloration of many trout produced in coop hatchery is probably due to the fish getting more natural food in their diet.

Many of the coop hatcheries are diversions off of streams, so aquatic invertebrates get carried into the raceways by the current.

Also, many of the coop hatcheries are small facilities, often with earthen raceways, with natural vegetation nearby, so they probably also get to eat more terrestrial insects than in the large hatcheries which have large expanses of concrete.

Both insects and crustaceans have naturally occurring pigments which lead to more colorful fish flesh and skin pigmentation.

 

[troutbert]

Technical stuff on trout and salmon color:

https://en.wikipedia.org/wiki/Astaxanthin#Natural_sources

 

[Wild_Trouter]

I have caught stocked trout that originated from hatcheries based on limestone spring streams. I haven't formally researched the matter but can say that rainbow and brook trout from these facilities looked every bit wild as far as coloration, with the fin condition being the giveaway. I am guessing the alkaline rich water/higher Ph has a lot to do with it and not just the scuds/cressbugs etc. found in that type of habitat.

 

[dsmith1427]

I'm a firm believer you are what you eat and what you eat eats. Also, I believe you are a product of your environment... Feed the fish a poor diet they respond with poor appearance. Raise them in unhealthy conditions and you will have unhealthy looking fish.

Regarding feeding supplements, I wonder what research was done to choose the supplements? Was it a nutrient the fish were missing in their diet or merely something to improve their appearance. If I read the above links right, the salmon fan was based on "consumer preference" and makes no reference to the fish health or nutritional value to the consumer. I skimmed the Wikipedia article about Astaxanthin and it talks about using this as a colorant in salmon farms. I did not see any mention about nutritional value for either the fish.

When I buy fish, I usually buy wild caught, buts that just me.

Don

 

[JackM]

dsmith1427 wrote:
I wonder what research was done to choose the supplements? Was it a nutrient the fish were missing in their diet or merely something to improve their appearance.

I am going with the latter.

 

[pcray1231]

The pigments which cause the brighter coloration are actually pretty lean in mayfly and caddis diets. Fish that subsist on them tend to be paler in color.

And baitfish eaters tend to be more silvery.

Freshwater shrimp, cressbugs, sowbugs, and crayfish, though, are very rich in pigments. Anything with a shell, basically. These foods give that bright red stripe on rainbows and the reds and butter colors on browns. I believe stoneflies also have quite a bit.

 

[salmonoid]

I have no idea what the flesh in the new-diet stockers looks like, but would astaxanthin be the reason that the skin color of the new-diet stockers is improved? The colors are definitely a bit more vibrant -more yellows on the browns (but orange, and not red spots and nothing on the adipose), and more vibrant spots on the brookies.

Since arthropods fix oxygen to copper proteins (hemocyanins) for circulation, and trout eat insects and crayfish and shrimp, I wonder if some of the blue colorations (eyespots on browns, or the blue halos on brookies) comes from that copper?

 

[Hook_Jaw]

pcray I think your right on with baitfish eaters are more silvery and crayfish eaters more reds and butters

 

[troutbert]

There's plenty of info on pigments of plants and animals here:

http://www.webexhibits.org/causesofcolor/7H.html

 

[troutbert]

Brook trout in infertile freestone streams often have very vivid colors.

Those streams do not have scuds or sowbugs.

In some cases quite infertile freestone streams do have crayfish. How common that is though, I'm not sure.

 

[Canoetripper]

I have been fishing at a private R&G club in the western Pocono Mountains since the 1960's. More and more members practice C&R.

A lot of these stocked trout survive because of the C&R. I think that they are very different fish after surviving. They have to figure out what to eat after the trout pellets aren't there any more.

There are also a lot of Ospreys and Otters preying on them. They have to figure out a way to avoid both of them. The stream looks like dark iced tea because of all of the tanic acid in there.

I am not a biologist. I just know that these holdover stock trout that can make it through the winter are very different from time spent in the creek from when they were stocked.

I have never seen any evidence of them naturally reproducing.

 

[LetortAngler]

Good point TroutB.
To add to your point, many of the trout that I've caught from the Letort (full of crustaceans) and other springs are actually quite pale compared to the freestone or tailwater (Savage comes to mind) counterparts where coloration seems more pronounced, even brighter. Not to say there isn't any buttery browns in the Letort, cause there are.

Perhaps there's more to play there than strictly diet. Limited sunlight being under cover constantly could give the paler appearance as well.?

 

[Dave_W]

salmonoid wrote:
I have no idea what the flesh in the new-diet stockers looks like, but would astaxanthin be the reason that the skin color of the new-diet stockers is improved? The colors are definitely a bit more vibrant -more yellows on the browns (but orange, and not red spots and nothing on the adipose), and more vibrant spots on the brookies.

This is mainly what I'm wondering.

Flesh color of salmonids is definitely a reuslt of these chemical processes and this produces a better looking fish when the fillets are laid out at the grocery store seafood bar.

But what about the aesthetic appearance - the beautiful yellows, oranges, and reds that we FFers like to see in BTs? Have studies been done with hatchery food supplements that show improvements here? (Sorry if I missed a link)

 

[JeffK]

I used to attend the big plastics show in Chicago as part of my job and as far back as the late 80's there were booths with pigments to color fish feed to get a desired flesh color. I was kind of freaked out to see "color fans" to dial in the proper color and for quality control.

 

[bearfisherman]

After a stocking a local stream this year, it was noticed by many how brightly colored the goldens were compared to previous years. The PFBC truck driver replied that the hatchery was trying a new feed this year with the goldens, and that they were probably going to expand its use in the future to other species.

 

[TJones]

Hook Jaw & PCray I agree with the crayfish and baitfish diet in relation to coloration as well. Fits my observations...

 

[Dave_W]

Regarding the changed coloration of stocked trout after acclimation to a natural diet....I think we have all noted (if we keep trout to eat) that stocked fish can develop not only brighter spots and skin coloration, but also a more natural looking flesh color.

In my experience, stocked trout caught in early spring have white flesh. By this time of year, they can start to exhibit darker flesh with more of an orange tone to it. It's not the bright orange one would expect to see in a wild fish, but moving in that direction.

The pic below shows a couple stocked trout I caught yesterday. Note the striking difference in flesh color. My guess would be that the orange fish was likely stocked in preseason whereas the light flesh fish was stocked later in in-season. I doubt the orange fish is a 2016 holdover as holdovers are rare in this stream (but possible).

These fish were caught in the same pool so probably had much the same diet. I think it can best be explained by time in the stream.

 

[mike_richardson]

Any input on the amount of light that the fish is exposed to as well? I caught a brown on a stream with a dense canopy and hemlocks surrounding it. That brown also appeared to be under a large boulder most of the time. The fish was almost black.

 

[gulfgreyhound]

Diet ,as I understand, determines the color of flesh in members of the trout and salmon families. Wild Sockeye Salmon owe the distinctive orange flesh to a diet of shrimp and other crustaceans while in salt water. Caretonids? are the agents of this coloration. Maybe Krill are the base of this food chain and the color in the flesh.
I know that there is a hatchery in Juneau Ak. that hatches and releases Chum Salmon that return and are processed into fish meal that goes to Chile for use as to feed pen reared Salmon. I visited it on a trip years back. Our local grocery stores now have "wild " Sockeye Salmon for sale. Good stuff with a little honey, citrus glaze,yum. GG