Damselfish ID

[b1gcountry]

So, I have a really hard time ID'ing some of the Damselfish. Especially the Longfin vs. Dusky. What characteristics are you looking for to differentiate between adult:

Cocoa vs Longfin vs Beaugregory vs Dusky Damselfish?

I think I have the three-spot damsel down because it seems to always have a gold rim around the eye, and they seem to prefer to form loose colonies. I have an awfully difficult time with the other ones though.

Tom

 

[b1gcountry]

PS, I'm talking Carribean here, BTW.

 

[drdiver1952]

They are difficult. I still occasionally have trouble after all my years of fish work.

Longfin Damsel have a blue border on their anal fin. The fins (especially their lower fin) should extend well past their caudal peduncle (narrow part of the tail)

Duskies don't have the blue border and often have a dark border in its place. Their fins do not extend past their caudal penduncle.

Cocoa damsels usually a dark spot (mnemonic chocolate chip) on their upper caudal peduncle and the base of their pectoral fin. They also have long fins like the longfin, but their scales form lines on their sides and they tend to be yellowish in color along with the dark brown. Their snouts are also blunter than the other two. The spots are not always there and they are easy to confuse with the beaugregory that can also have the spot. However, beaugregories do not have the distinctive lines formed by the scales on their sides and have a more humped snout. Beaugregories usually are very common and when I see a beaugregory that doesn't look quite right, I think cocoa.

Hope this helps.

 

[b1gcountry]

Thanks for the response, this helps.

I always have trouble deciding whether the fins actually extend past the caudal peduncle or not. I usually decide that the fin looks rounded, but also extends past the base of the tail. Problem is I usually come to this conclusion with most of the Damselfish I find on the reef

Tom