Fish ID

[rudedawg]

Being colour-blind, I am not very confident in my rainbow vs cutthroat ID. Sometimes the red slash really stands out for me, sometimes not so sure.

I landed this beauty last night in a Bow Trib (for details, see South Alberta Fishing Reports and Chat >> SW Streams). I assumed it was a rainbow, because cutthroat don't get that big, do they? But then looking at the photo, I'm not sure. Is that slash below the jaw definitive of cutthroat?

[Birdo]

I’d have to say a cutbow, with those colours and the slash under the jaw!

[fishing4trophies]

Looks like a cuttbow, a rainbow and cutthroat cross. Do you have any pics of the anal fin? A strong identifier for a cuttbow includes both dominant traits of cutts (slash), and white mark on anal fin for rainbows. I've landed cuttbows in the mid 20's before, so they can definitely grow big. 

[hydroman]

I agree - cutbow. 

[rudedawg]

20 minutes ago, fishing4trophies said:

Do you have any pics of the anal fin?

Hard to get a good image of when the fish doesn't really fit into the net. Here's one that shows the anal fin, but I don't know what you mean by "white mark".

[fishing4trophies]

3 hours ago, rudedawg said:

Hard to get a good image of when the fish doesn't really fit into the net. Here's one that shows the anal fin, but I don't know what you mean by "white mark".

 

Should've said a white tip instead of mark. Cuttbows have a white tip on their anal fin.

[scel]

On 7/30/2019 at 8:50 AM, fishing4trophies said:

Looks like a cuttbow, a rainbow and cutthroat cross. Do you have any pics of the anal fin? A strong identifier for a cuttbow includes both dominant traits of cutts (slash), and white mark on anal fin for rainbows. I've landed cuttbows in the mid 20's before, so they can definitely grow big. 

These are technically non-dominant traits---they are recessive traits.  Furthermore, the slash is ironically a non-definitive for cutthroat trout.  The orange slash can pop up in rainbow trout populations with no contact with cutthroat trout  (the gene would have to be present in rainbow trout in order for them to produce viable offspring), but it does serve as a good indicator if coupled with any of the primary characteristics.

The primary physical taxonomic features that define a cutthroat trout are basibranchial teeth (little teeth-like protrusions on the tongue) and jaw that extends past the eye orbital.  The most reliable secondary characteristic is the spotting pattern---higher density near the tail.  Although, this characteristic can be easily washed out of cutthroat population (like those in the Oldman drainage).

In this case, the jaw clearly extends beyond the eye.  The secondary characteristic of increased spotting near the tail is also present.  And, of course, the orange slashes are present.  Spotting pattern extends to the head, but not a reliable marker.  If there were basibranchial teeth, you might have close to a pure cutthroat.  Almost all Alberta populations of cutthroat have been hybridized to some degree with rainbow trout, so technically almost every cutthroat is a cuttbow.  I think the only 'pure' populations are in a couple lakes in the Banff park.

source: wife is trained taxonomist and practicing biologist.

EDIT: It has been pointed out to me, and I was scolded by my wife, that there are several statistically genetically pure pockets of cutthroats.  Still it is estimated that approximately 70% of the known populations have been interbred with rainbow trout.

Edited August 1, 2019 by scel
I erred

[fishing4trophies]

18 hours ago, scel said:

These are technically non-dominant traits---they are recessive traits.  Furthermore, the slash is ironically a non-definitive for cutthroat trout.  The orange slash can pop up in rainbow trout populations with no contact with cutthroat trout  (the gene would have to be present in rainbow trout in order for them to produce viable offspring), but it does serve as a good indicator if coupled with any of the primary characteristics.

The primary physical taxonomic features that define a cutthroat trout are basibranchial teeth (little teeh-like protrusions on the tongue) and jaw that extends past the eye orbital.  The most reliable secondary characteristic is the spotting pattern---higher density near the tail.  Although, this characteristic can be easily washed out of cutthroat population (like those in the Oldman drainage).

In this case, the jaw clearly extends beyond the eye.  The secondary characteristic of increased spotting near the tail is also present.  And, of course, the orange slashes are present.  Spotting pattern extends to the head, but not a reliable marker.  If there were basibranchial teeth, you might have close to a pure cutthroat.  Almost all Alberta populations of cutthroat have been hybridized to some degree with rainbow trout, so technically almost every cutthroat is a cuttbow.  I think the only 'pure' populations are in a couple lakes in the Banff park.

source: wife is trained taxonomist and practicing biologist.

Thanks for the lesson! Learned a bit.