Thursday, 14 October 2010

Wots that fish?

It happens to everyone... your cruising along at 18 meters through the pea soup that passes for ocean water in the North Atlantic when suddenly you spot a few colorful fish in your beam, darting in and out of the sea weed...

... or maybe its just a single fish, examining you from the security of a rock cleft....

... or possibly its a discoloration of the sand, that swims away as you pass over (after a bit of prodding with your torch, anyway)

You reach for your handy guide to the fish of the northern Atlantic waters (in my case a 40 year old copy of Collins Guide to Sea Fishes) and ignoring the difficult interactions of paper with water at depth, you flip to the appropriate page and quickly realize that you are seeing....

... well, no, actually, its not that clear... The difficulty of many of these fish guides is that they make a few assumptions about your situation, namely that you are viewing the fish from the side, in good light, on the surface, while the fish in question sits perfectly still with its fins outstretched. The pictures in the guides vary from  black and white sketches (not good if the obvious difference between species is color pattern), paintings (often taken from dead and slightly faded fish) or pictures of pickled specimens. It gets worse if you go to the technical literature... Handbook of the Marine Fauna of North-West Europe is one of the best books for identifying UK sea life, but unless you regularly take a dissecting microscope and a jug of formaldehyde on your dive trips its not going to be much use (who can count fin rays at depth, anyway?)  I have a personal rule about collecting live specimens (that is, I won't) so I'm limited to either a photograph or a short movie clip taken under what I would politely call less than ideal conditions.

 Fortunately, there seems to be more sea life publications written by divers for divers in recent years, with photos taken from life rather than illustrations or images of dead specimens. Without such aids, I would have been hard-pressed to identify either of these fish, as they belong to the Gobies, one of the more difficult fish groups.

  The species, incidentally, are female Two-Spotted Gobies and a lone Common Goby.

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