Isles of Scilly Fish and Fisheries - Cornwall Wildlife Trust

in total length) were found in upper shore rockpools on St Mary’s and St Agnes, and
also on Gugh and St Martin’s (B. Cowburn pers. comm., 2010), some were readily
identified as G. paganellus by a pale or bright orange band along the upper edge of
the first dorsal fin, but other apparently similar specimens lacked this (Fig. 3). These
fish lacked the “pepper and salt” colouration of a typical British G. cobitis. They were
closely and carefully examined in the hand and photographed, but it was found
virtually impossible to distinguish these gobies from G. paganellus. The tentacles of
the anterior nostrils, the free rays of the pectoral fin and the membrane of the pelvic
disc are similar in these two species; and they are even reported to hybridise in the
Black Sea. Until an observer is familiar with both species it seems they are best
separated by minor differences of the lateral line system of the head, and the number
of scales in the lateral series 59–67 in G. cobitis and 46-59 in G. paganellus. While G.
cobitis can grow to 270 mm, size is not a good indicator as G. paganellus can reach
120 to 140 mm, and most of the G. cobitis found by Wheeler (1993) were small (13-80
mm) and only a few larger ones of 120-180 mm. A detailed study of the distribution
and status of this enigmatic species in the islands is highly recommended, however it
would require a licence from Natural England. Such a project would unfortunately not
be directly comparable with previous studies as these largely involved emptying the
rockpools, or the addition of anaesthetic or toxic substances to the pools, neither of
which would be acceptable with a protected species today.
Figure 2. Gobius cobitis, Marazion, January 2010.
© David Fenwick snr
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