Two small demersal fishes, the sand goby Pomatoschistus minutus and the common goby Pomatoschistus microps, were quantified on soft bottoms at 20-40 m depth in the Baltic Sea, using a camera placed above the bottom. The largest numbers of gobies were seen following the settlement of young in late summer and autumn. Most recorded fishes were sand gobies. An annual average of 4Á7 individuals m À2 (0Á24 g dry mass m À2 ) was recorded in 1983-1985 and 2Á5 individuals m À2 (0Á13 g m À2 ) in 1997-1998. Using these densities, the annual goby food consumption was estimated to 100 kJ m À2 in 1983-1985 and 50 kJ m À2 in 1997-1998, corresponding to most of the annual macrobenthos production available to the gobies. The resulting goby production, assumed equal to 25% of the food consumed, must have been an important food source for the larger fishes occasionally recorded in the photographs. # 2005 The Fisheries Society of the British Isles

In autumn and winter, the sand goby (Pomatoschistus minutus) in the Baltic Sea is to a large extent found on soft bottoms deeper than the summer thermocline. Although P. minutus are numerous during a large part of the year in these areas, most studies on this species have been performed on very shallow bottoms. Here we study the activity of P. minutus in autumn using video recordings in the laboratory, under light (1.5-2 lux) and temperature conditions prevailing at ca. 30 m depth. We propose that the results can be used to evaluate in situ abundance censuses. P. minutus had the same nocturnal activity pattern in low light intensity as described for light intensities found in shallow water. The fish swim significantly more in darkness than in light, and bury in the sediment mainly at day. These behaviours, recorded in the absence of predators, are suggested to be adaptations to avoid predators.