Experience and thoughts on stocked vs wild trout…
There are a number of things, obvious and/or contextual. I’d add images but most are not digitized. Will try to describe…
Mark mentions warped fins, and that is the most recognizable, longest lasting, feature of stocked trout –at least those that were in hatchery conditions beyond the fingerling stage. Most trout, esp for put-n-take purposes, and in streams, are stocked as yearlings –long enough for the crowded conditions in hatchery raceways and pools to result in warped fin rays. The leading edge of the dorsal fin shows it most, the pectorals next, and occasionally the pelvics. When trout are stocked as fry or fingerlings (usually large volume stocking of lakes) the fins may not show much warping. Streambred fish tend to have a straight (unwarped) leading edge of the dorsal fin. If your fish has even a slight dorsal warp, it’s a prime candidate for factory origin.
Pecs and pelvics are also the targets for fin-clipping, where that’s done. Fin clipping is often done on fingerlings released into lakes. As adults such fish would be difficult to recognize as stockies otherwise. Fin clipping is not easy to do –somewhat of a skill you need to get used to. You have to clip right at the joint at the pelvic girdle –too shallow and the fin will regenerate (although distorted), too deep and the little fish is at risk of infection.
Tails are not as good an indicator of origin bc they can commonly become distorted naturally, from either:
-Redd digging when spawning showing up on at the bottom edge, and lower lobe of the caudal fin. These heal after a month or so depending on fish health.
-Habitual holding at foraging or hiding sites from repetitive abrasion against substrate. These are more common on browns and brookies bc they are more cover oriented, and also commonly use the calm water just ahead of rocks, deadwood, and tailouts as key drift-feeding sites (I call these spots 'cushions'). This abrasion shows up usually on the lower lobe of the caudal fin and are still inflamed during summer (compared to spawning abrasions).
Truly large browns from small streams often have abraded tails, often the top lobe of the caudal fin, from stuffing themselves under cover during daylight hours, often undercuts and logjams that result in the upper lobe being abraded. I‘ve also seen this type of tail distortion in larger resident (non-migratory) Finger Lakes rainbows –a certain small segment of those populations remain stream resident and use wood cover.
As Mark’s image of a super-nice holdover brown shows, coloration isn’t always a good determinate. But, in recently stocked trout coloration it is. And in many holdovers too, bc, in the streams I’ve fished, trout do not recover colors well or maybe it just takes more time (years). Small stream fish tend to have shorter lives than river or lake fish. Possibly, the ability to adapt to stream life –become effective residents –enters in.
Trout are almost chameleon-like in their ability to adjust color, associated with water and sky conditions, life history periods, and behavioral requirements. Their colors are a combination of camouflage and communication requirements.
Recently stocked trout tend to be duller in coloration. In hatchery raceways they are so bc of the concrete lined raceways. But I’ve seen some fairly pretty browns in hatchery “finishing ponds” that offer more natural backdrops. Stocked trout seem to hold this dull gunmetal (in brookies), olive in browns, for at least a year, often showing up the same way, but with stronger spotting, as holdovers. I’ve caught some pretty ones, like the one Mark shows, but these are rarer, possibly older, fish. The following tries to account for their existence in spite of the challenges stockies face:
Behavior/Life History “Strategy”:
The fact is, most stocked trout die, esp when dumped into streams, since they are not accustomed to (downright ill-equipped for) the energetic rigors of drift feeding. Many are stocked too large for smaller streams to support, at least in such numbers. One thing they do know is that they are not getting enough food so they tend to drop downstream, further and further, until they get into too warm water down the watershed as summer comes on. I’ve seen such fish (by direct observation, hook-n-line fishing, and electro-fishing) in 80degree water and these fish tend to be emaciated. An interesting study compared hatchery and long-established streambred (Catskill) browns “stocked” into a trout stream. The stockies dropped downstream (into more food but potential heat trouble), and the wild fish moved upstream –presumably toward cooler headwaters as many small stream trout that know their schtick do come summer heat up.
It appears that a very few “drop-outs” survive. If they remain in “trout water” they become “holdovers” and live by drift feeding and/or aggressive pursuit feeding of larger prey items. Pursuit feeders, btw, have the opportunity to outgrow strict drift feeders. Hatchery trout, raised in crowded raceways, and fed tossed pelleted food, develop aggressive feeding behavior, and those that are the best at it, grow fastest. And that’s just what a hatchery manager wants, to meet stocking size range requiremsnts. Some drop-outs may find pockets of cool water down the watershed, where there is often larger habitat and more food, and such fish can grow LARGE. Some wild fish find their way to these places too, either by having the penchant to migrate, swept from flooding, or possibly as descendants of successful holdovers.
This “penchant for migrating” is interesting. Our brown trout are all from Europe and being indigenous salmonids several strains/morphs/flavors developed -often within populations- and these were introduced and mixed in hatchery stocks. Some brown trout, in streams attached to lakes or the ocean, have a segment of their populations that “go migratory”. Studies have shown that they can come from the same redd as non-migratory individuals. What sends them to the sea appears to be either a genetic switch that turns on, environmental conditions, or rapid growth that results in those individuals outstripping their food supply. Sounds a lot like hatchery trout grown fast and large (and aggressive) in a hatchery to meet stocking size quotas, and then dumped into a wild stream where the rules are completely different. Thus, when I catch outsized trout, notably browns, from smaller streams, they are apt to be holdovers (with warped dorsals) for, I believe, the above reasons.