Duc, Dog, & Dan,

As best as I know, Salmonbelly has this correct. Let's try to keep this civil. I think there are clear explanations for the observations of dorsal fins we all make. State, federal, and tribal hatcheries mark steelhead by clipping the adipose fin, ventral fin, and very occasionally, the pectoral fin.

The Quinault Tribe marks only a percentage of their hatchery steelhead production, which is why many hatchery steelhead in the Quinault, Queets, Salmon have adipose fins.

Deformed dorsal fins are common to most hatchery steelhead, and are a good way to identify hatchery steelhead not intentionally marked. When tested against scale reading some years ago, it was about 85% accurate. Some hatchery steelhead do have "perfect" dorsals, like their wild brethren. Dorsal fins are deformed on hatchery fish due primarily to nipping by other steelhead in the close quarters of the hatchery rearing environment. The dorsal fins, and hearsay has suggested, that some pectoral fins are eroded by rubbing against concrete rearing pond walls. Personally, I've never witnessed the behavior. Further, the net pens used for rearing a lot of hatchery steelhead that end up with similarly deformed dorsal fins, do not have concrete walls.

Hatchery steelhead with deformed dorsals, often do have dorsal fins greater than 2 1/8". I released two last weekend. The "credit card" rule for dorsal fin height is not a very good indicator for hatchery fish, in my opinion. Small wild fish have smaller, but usually perfect dorsal fins. Large hatchery fish with obviously deformed dorsal fins may have dorsal greater than 2 1/8". The NPS has adopted a regulation that was discarded by the state about 20 years ago when they began adipose clipping all hatchery steelhead production.

TK,

Bacterial infection can often lead to fin erosion, but it isn't limited to dorsal fins. Do you have documentation for your statement? I'm not aware of pH being associated with the common occurance of deformed dorsal fins on hatchery steelhead. The pH is about the same in most steelhead streams that I've sampled (6.5 to 7.8), and that covers both hatchery and wild fish rearing environments. How do you associate it with the effect on hatchery steelhead?

Sincerely,

Salmo g.