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Forty-three species of fishes and 16 species of larger crustaceans were caught by trawl and seine during a 4 yr study on a sandy beach on the west coast of Scotland. There were considerable differences in the species composition of the trawl and seine catches such that neither alone provided an adequate description of the sampled cornnlunity. Approximately monthly s a m p h g demonstrated a clear seasonal cycle in abundance and species composition. A few species were resident on the beach all year round; the majority were only present from spring to autumn. Increases in both numbers and species were caused mainly by the recruitment of young of the year individuals whose numbers subsequently declined rapidly probably due to a combination of predation and emigration. There were marked differences in both species composition and abundance between years. Annual cycles in species richness and abundance closely paralleled those of temperature and sahnity. It is suggested that the cycles result mainly from recruitment and mortality rather than from immigration and emigration in response to physical factors.

ABSTRACT. Fishes were sampled by seine and beam trawl over tidal and diel cycles on a sandy beach on the west coast of Scotland in J u n e and August Species composition of the catches of the 2 gear types differed. There was a signif~cant pos~tive relationsh~p between depth (0 to 5 m ) and species richness but a few specles were restricted to depths of < S m Although s~gnif~cantly more species and individuals were caught at night and at low tide there was no evidence for the existence of d~stinct 'day' and 'night' communities. D~fferences between catches at hlgh and low water were caused by the movement of a few species into the ~ntertidal zone on the rising tide. Diel differences In abundance were pnnc~pally d u e to an inshore migration of several species of gadoids at dusk and movement offshore at dawn. Longer term changes in abundance and distr~bution were attributed to predation and movement ~n t o deeper water

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Swimming activity of the Antarctic scallop at a temperature of c. -1.4" C was analysed using in situ video recordings obtained from a remotely operated vehicle (ROV) in Terra Nova Bay, Ross Sea. Data are presented on swimming trajectories, distance travelled and velocity during a swimming bout, adduction frequency, shell gape angle, and the angular opening and closing velocities of shell. This scallop is an effective swimmer although swimming bouts in response to the ROV were generally short, consisting of 2-5 adduction cycles in the take-off phase followed by 1-4 (exceptionally 14) adductions during level swimming. The maximum velocity during each adduction cycle ranged from 19.443.1 cm s-' and the mean velocity during a swimming bout from 12.0-23.5 cm s-I. Each adduction cycle consists of opening, closing and glide phases of approximately equal duration. Adduction frequency during swimming averaged 1.5 adductions s-I .

The functional morphology of twelve British species of the Veneridae is described. The systematic position of Mysia undata and evolution within the Veneracea are discussed.Structurally, the members of the family Veneridae show a lack of special adaptations. The ability to move horizontally as well as ventrally in soft substrata is retained; the pedal gape is large and the foot well developed. The siphons are relatively short and fused. The food-collecting mechanisms of the mantle cavity are largely unspecialized and function in maintaining a considerable flow of water, and retaining as much as possible of the suspended material. Members of the Veneridae show a considerable uniformity of structure, but trends of evolutionary change may be distinguished. The genera Gafrarium and Callista are least specialized. The genus Dosinia has evolved along an independent line and is specialized by the possession of a stream-lined, circular shell, deep lunule, and greatly elongated siphons, for a relatively deep-burrowing habit. Within the superfamily Veneracea major lines of adaptive evolution have given rise to the rock-boring Petricolidae and the deep-burrowing Glaucomyidae, and the genera Venerupis and Irus show affinities with both these families.