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What is the meaning of the fatty-fin of the salmonoids2007-11-24 23:41:48

The fatty-fin is the fin on the back just before the tail of the salmonoids. What is the purpose of this fin?

Answers:

I assume you mean the adipose fin between the dorsal and caudal fin of salmonoids, characins and catfish. From every resource I've found, including an undergrad degree in zoology, there is no real purpose for the fin.

Like the appendix in humans, it doesn't serve a purpose, but is more than likely a vestige from a past fin. You can see on all other fins a fleshy area at the base before the rays start -- the adipose fin is probably this area from a fin in fishes of old. To confirm this, you'd have to look at the fossil record, and I'm not sure anyone has.

In some areas, sport fishing officials clip the fin (without ill effect on the fish) to indicate which ones can be kept -- usually over a certain size to prevent juveniles from being taken.

Hope it helps!

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This fin is called the adipose fin. It's a small, single fin located behind the dorsal fin and in front of the caudal fin on the dorsal side of the fish. It's somewhat fleshy and is sometimes called a "fat fin". The adipose fin only occurs in some groups of fishes, including salmon, trout, characins and catfishes. The purpose of the adipose fin is not clear but it is believed to aid the effectiveness of the dorsal fin.