Black estuarine fish which looks like a tadpole.

[Jessicajil]

I was watching all the fry in the water at high tide in the Adur estuary, when a jet black fish came by swimming past just below the surface of the water. Most of time it wriggled so that it looked just like a tadpole. Every so often it put relatively large pectoral fins.
It was so small (about 3cm?) that I would never have seen it again if I had run in to get the camera.
My grandson and I had been out in the dinghy the day before and he said he'd seen a tadpole, and I had been rather dismissive, but I guess he saw the same kind of fish.
I have lived here for fifteen months and never seen one of these before.
Does anyone know what it is?

[Dogghound]

Could be anything, sounds like a juvenile of some description most likely a species of goby, blenny, scorpion fish, sculpin or rockling. We do have a tadpole fish Raniceps raninus which is another good possibility although they tend to live over rocky ground rather than estuaries.

[GCN lova]

tadpoles live in freshwater and common frog tadpoles are up to 4 cm long and marsh frogs tadpoles up to 8 cm long.

[Jessicajil]

Originally Posted by Dogghound

Could be anything, sounds like a juvenile of some description most likely a species of goby, blenny, scorpion fish, sculpin or rockling. We do have a tadpole fish Raniceps raninus which is another good possibility although they tend to live over rocky ground rather than estuaries.

It certainly looked similar in shape to the Raniceps raninus except that it hard large pectoral fins. The most striking thing about it was how very black it was, looking like black velvet. It's behaviour was quite different to all the other fish fry, partly because it was on it's own and swimming very determinedly in one direction, whereas the fry tend to dart about and be in shoals. The other difference was that it was staying very close to the surface, rather than changing heights. As this is a river estuary there tends to be a very thin layer of fresh water on top of the sea water, and it almost looked as if it was swimming in that?
I found one picture of a sculpin (adult as a fisherman had caught it!) which looks quite like what I saw, but the sculpin is a bottom living fish, where the thing I saw clearly wasn't! and they don't seem to be jet black, but they do have the large pectoral fins. According to what I have read they are not usually intertidal, but they have been caught of Shoreham where I live.