A commercial fisherman brought me a shore rockling, Gaidropsarus mediterraneus, and a three bearded rockling, Gaidropsarus vulgaris, last night for a school class I am teaching.  The Gaidropsarus rocklings, and possibly others, have a low first dorsal fin that constantly oscillates rapidly in a wave along its length.  The first dorsal fin is so low that it is difficult to see so the fin gives the impression that it is a pulsing 'light' travelling down the back of a fish.  Has someone studied this phenomenon? Does this fin serve a useful function for the fish?  Do other subfamilies of fishes also display this characteristic?

The fisherman told me that at certain times of year he noticed that some three bearded rocklings have a bright orange spot on their body. He wonders if this is a sexual character and whether the species can be sexed using this character.

Yours sincerely,
Richard
Richard Lord
Guernsey GY1 1BQ
Great Britain

Email:  [log in to unmask]
Tel: +44 (0)1481 700688
Fax: +44 (0)1481 700699

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