The shrimp, Crangon crangon (L.) (Crustacea: Crangonidae), is a significant predator of the smallest sizes of plaice, Pleuronectes platessa L. (Teleostei: Pleuronectidae), during and immediately after the fish settle on sandy beaches when predation rate is strongly dependent on the size of both the predator and the prey. Laboratory experiments showed that this size-dependency is caused principally by the superior escape capabilities of larger fish once captured rather than differences in the ability of different sizes of shrimps to capture their prey. Fish that escape after capture are often wounded and some of these wounds may subsequently be fatal. Many shrimps capture and eat fish that are larger than their stomach volume resulting in long handling times and low prey profitabilities. For all sizes of shrimps used (36–65 mm total length) prey profitability (mg prey ingested min−1) increases with decreasing fish length.

Between 1980 and 1985 ninety-seven stations were sampled by Smith-Mclntyre grab from the offshore northern section of the North Sea. Four hundred and nine infaunal species were identified from the 76 selected macrofaunal stations. The number of species per station varied from 25 to 80 with a maximum abundance of 9,600 individuals m−2. The biomass ranged from 0.13 to 18.86 g dry weight m−2. At most stations, however, biomass varied between 1 and 4 g dry weight m−2. Diversity and abundance were highest in the 120–140 m zone, characterised by fine sand containing variable amounts of silt. The highest biomasses were recorded in two areas; firstly where stronger currents predominate and the sediments are coarser (east of Shetland and west of the Norwegian Trough), and secondly in the fine sandy deposits of the centrally located area. In the silty sediments (Fladen Ground and smaller depressions) there was a predominantly subsurface deposit-feeding community, whereas in the coarser area east of the Shetlands carnivores predominated. Over the remaining area surface deposit feeders were dominant.

The introduction of non-indigenous marine plankton species can have a considerable ecological and economic effect on regional systems. Their presence, however, can go unnoticed until they reach nuisance status and as a consequence few case histories exist containing information on their initial appearance and their spatio–temporal patterns. Here we report on the occurrence of the non-indigenous diatom Coscinodiscus wailesii in 1977 in the English Channel, its subsequent geographical spread into European shelf seas, and its persistence as a significant member of the diatom community in the north-east Atlantic from 1977–1995.

Idotea feeds on large food masses. It is potentially an omnivorous scavenger, but each species may have a characteristic diet depending on the availability of food in its particular habitat.

The structure, topography and action of the mouthparts are described: spines on the maxillules and maxillipedes scrape the food material whilst the mandibles actually bite the food; toothed spines on the maxillules and mandibles push the food upwards to the molar processes of the mandibles; debris is brushed forwards between the lobes of the paragnath by setae on the inner endites of the maxillules, maxillae and maxillipedes; and spines on the maxillipedal palp, and on the first leg, comb the mouthparts.

The structure of the foregut resembles that of Asellus and Ligia.

The relation of the feeding mechanism to the functional evolution of the mouthparts of Peracarida as a whole is discussed.

The Galapagos Islands are among the most important nesting areas for the green sea turtle, Chelonia mydas, in the eastern Pacific Ocean. In addition, the coastal waters of this oceanic archipelago host many important feeding areas for this species, although little is known about green turtle feeding ecology at these sites. The goal of this study was to identify and quantify the most important items in the diet of the green turtle at the foraging grounds of Bahia Elizabeth, Caleta Derek and Punta Nuñez. Our analysis was based on 65 oesophageal samples from turtles captured in 2006 and 2007. We compared spatial and seasonal composition of diet using non-metric multidimensional scaling analysis (MDS) and analysis of similarity (ANOSIM). Green turtle diet was composed mainly of the algae species Ulva lactuca, Polysiphonia sp., Hypnea sp. and Dictyota sp., and the red mangrove Rhizophora mangle. Turtles also consumed animal matter, mainly cnidarians, albeit to a lesser extent. Content of turtle diets was different among feeding grounds and seasons. The ANOSIM showed that diet composition can differ between foraging grounds using presence/absence of diet items. Even though U. lactuca was the most abundant algae consumed in both seasons, changes in species richness of algae were found between both sampling events, with diet during the warm season more varied than the cold season (χ2 = 16.84, df = 6; P < 0.05).

Monthly samples of the Laminariaceae, L. saccharina and L. cloustoni, from three localities on the Argyllshire coast have been taken from March 1948 to March 1949, and analysed for dry matter, ash, mannitol, laminarin, crude proteins, inorganic nitrogen and alginic acid, and the seasonal variation in these constituents correlated with the changes in composition of the sea water.

The results show that a correlation does exist and that a period of rapid photosynthesis occurs from March to June/July, but is restricted in July/August when nitrate is undetectable in the water and phosphate is as low as 0·16–0–20 mg. atom/m.3. The replenishment of the photosynthetic layer with nutrients is retarded in July/August, apparently due to the warming of the inshore waters, which may set up a thermocline restricting vertical mixing.

The autumn cooling of the uppermost waters facilitates vertical mixing, regenerating the nutrients in the photosynthetic region, and a second burst of photosynthesis at a reduced rate from the spring ‘outburst’ occurs in October/November.

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.

A 5-year study of the population biology of the common shrimp Crangon crangon (L.) in the Bristol Channel is reported. Samples were collected from three commercial fishermen and from the filter screens of five power stations taking water from the estuary.

The Severn Estuary and Bristol Channel were found to contain a single shrimp population which undertook regular seasonal migrations in order to avoid low salinities and to reproduce. Previous studies had assumed that the regions held separate populations which migrated to avoid low winter temperatures.

It is suggested that the cumulative view of growth in which some index of biomass is plotted against time tends to obscure temporal variations in the growth process that might provide evidence of how it is controlled. Experiments with the colonial hydroid Campanularia flexuosa show that the action of a growth control mechanism can be demonstrated by considering changes in specific rates of growth determined at frequent intervals in time. However, it is also necessary to disturb the growth process slightly in order to initiate the action of the control mechanism, and having done so, to isolate the effect of the disturbance on growth and thus the action of the control mechanism. This is done by expressing the specific growth rate of organisms whose growth is disturbed as a percentage of that of control organisms of the same age.

Gut content and stable isotope analyses were used to investigate the feeding habits of loggerhead sea turtles (Caretta caretta) inhabiting the Balearic archipelago. Turtles caught in the pelagic realm (δ13C: -16.0±0.6‰ and δ15N: 8.5±0.9‰) and turtles caught on the continental shelf (δ13C: -16.7±0.6‰ and δ15N: 8.4±1.3‰) did not differ in their isotopic signatures, suggesting that their diets include the same prey types. A mixing model revealed that for the turtles here analysed, squid and the jellyfish Cotylorhiza tuberculata were the most relevant prey, although stomach contents analysis revealed that carnivorous jellyplankton, neuston, fish and other cephalopods were also consumed. Gut content analysis also indicated that most of the prey identified, including all fish and most cephalopods, were of pelagic origin. Thus, loggerhead sea turtles inhabiting central regions of the western Mediterranean appear to seldom exploit benthic prey, even while on the continental shelf.

For routine sampling of the infauna of the sea bottom an apparatus is required which is simple, easily handled, and which can give samples of consistent volume from different types of bottom and in varying weather conditions.

The Petersen sampler and its modification, the van Veen, are simple and easily handled and give reasonably consistent samples from some types of soil. But on hard ground they are less satisfactory, and in rough weather they tend either to land unevenly on the bottom, thereby taking smaller samples of variable volume, or to release in mid-water with the rolling of the ship, so that no sample is taken.

Data on tag recoveries of 31 adult female and two juvenile loggerhead turtles (Caretta caretta) along the eastern Adriatic coast were analysed. All adult females originated from Mediterranean nesting areas: 29 from Greece, one from Cyprus and one from Turkey. This is the largest aggregation of long-distance tag recoveries in the Mediterranean for the loggerhead population nesting in Greece. The short period elapsed between the last observation of some turtles on the nesting beach and their recovery suggests the existence of a migratory pathway from the Ionian Sea into the Adriatic. Recoveries of some turtles within a period of a year indicate that loggerheads reside in the Adriatic for some time, suggesting that some individuals may demonstrate a level of site fidelity for these marine habitats. The high concentration of tag returns in the shallow northern Adriatic highlights this region as an important feeding habitat, for the population nesting in Greece in particular. The Ionian–Adriatic loggerheads form an important management sub-unit for this nesting population.

Spray-dried Nannochloris sp. and Tetraselmis suecica were fed to larvae of the Manila clam (Tapes philippinarum).

These dried diets supported growth equal to, or greater than, their live algal counter-parts, but less than a control diet, a mixture of two algae species of known high nutritional value (Chaetocems calcitrans and T-ISO).

Larvae were grown through to metamorphosis on the dried Nannochloris sp. diet in 21 days, compared with 8–11 days with the control diet. Using dried Nannochloris, it was shown that T. philippinarum larvae do not have an essential requirement for long-chain (20 and 22C) polyunsaturated fatty acids, but are able to synthesize them from shorter chain (18C) fatty acids present in the diet. The higher total carbohydrate content of the dried algae was reflected in the larvae feeding on this diet.

Male fiddler crabs, Uca pugilator (Crustacea: Decapoda), respond to conspecifics by claw waving, and to predators by freezing or escape. In field experiments it was found that this distinction was not made on the basis of angular size and speed, nor was shape important. The remaining possibilities were either the absolute size of the stimulus, determined from angular size and distance, or the position of the stimulus relative to the horizon. To distinguish between these, a crab was placed in a glass dish, and moved black stimuli on a white background, at a distance of 22 cm. Stimuli below the crab's horizon hardly ever evoked escape. However, identical stimuli partially or wholly above the crab's horizon produced escape responses whose frequency varied with the angular size of the stimulus. Halving the distance of the stimulus showed that it was angular and not absolute size that determines escape frequency; and experiments with a tilted horizon showed that it is the position of the stimulus relative to the eye equator that is important, rather than the geographical horizon itself. It has been concluded that crabs categorize stimuli as dangerous or otherwise by their position relative to the crabs’ visual horizon.

In 1883 Romanes first demonstrated the capacity of starfish to detect the presence of food. He claimed to be able to lead them in any direction by holding a piece of crab an inch or two from the end of one of the arms. He concluded that if the food was not more than a few inches away the starfish could smell it and move towards it. Milligan (1915 a-c) observed that Asterias rubens moved towards a dead pipefish from distances of 1½ in to 2 ft., and emphasized that the determined movement left no doubt that the starfish could smell the fish. Regnart (1928) found that A. rubens could locate food hidden in a bait chamber, moving away from the aerator in the centre of the tank.

The activity of lactate dehydrogenase was measured in the livers of 36 species of fish. These species could be divided into two groups, those with liver activities of more than 1000 mU/mg protein and those with activities of less than 100 mU/ mg protein. The lactate and pyruvate of samples of blood, muscle and liver from cod, plaice, bass and mackerel were determined. Samples were taken from ‘rested’ and trawled fish and from fish allowed to recover for 3 h after trawling. The rate of removal of lactate from the white muscle after capture in the trawl was not related to high blood and liver activities of lactate dehydrogenase. There was no relationship between the activities of nine of the glycolytic enzymes in the white muscle of cod and plaice and the liver lactate dehydrogenase activity. Little blood lactate appears to be taken up by the liver. It is concluded that the liver of cod, plaice and bass has a negligible role in metabolizing blood lactate.

In marine organisms the fresh-weight concentrations of the trace metals zinc and iron are 102–105 times the concentrations in sea water. Study of the transfer of these metals along marine food chains is of interest because of the possibility of their being pollutants of the marine environment. Also65Zn and 65Fe are released to the marine environment and have been found, in many instances, to be the predominant radionuclides in food chains leading to man (Lowman, Palumbo & South, 1957; Lowman, 1960; Osterberg, Pearcy & Curl, 1964; Preston, 1967). The transfer of these metals along marine food chains is thus of interest also in the context of human radiation exposure.

The aim of this study was to characterize the daily shell growth of Pecten maximus from early 1998 to late spring 1999 in the Bay of Brest with a careful qualitative and quantitative description of the pelagic primary production. Our results, in accordance with previous studies, demonstrate that there are episodic declines in the growth rate. Concurrent events of low growth rate and large bottom-concentrations of algae following diatom blooms (Cerataulina pelagica or Rhizosolenia delicatula), suggests that this high concentration of phytoplankton on the bottom layer may affect food intake or respiratory activity of the scallops by gill clogging or oxygen depletion. In this study, silicic acid or phosphorus are inferred to be limiting factors responsible for the collapse of the spring bloom. Further, we suggest that, in an N-enriched ecosystem, Si or P-limitation and the changing sinking velocities of phytoplankton, could affect the biology of benthic suspension-feeders.

The Saltash tuck-net is used in the estuaries of the Tamar and Lynher for seine netting on soft mud. The fishery is carried on during autumn and winter, from open boats with crews of two men.

Hauls were made with a tuck-net in every month between November 1935 and December 1937.

The fish population of the estuaries is essentially marine: its composition changes from month to month with the arrival from, or departure to, the sea of different species of fish. With the exceptions of salmon (Salmo salar), sea trout (Salmo trutta) and some of the Gobiidae, all the fishes of the estuaries go down to the sea to spawn.

Benthic assemblages of two Mediterranean submarine caves were compared. Species coverage and number of species were lower in internal (dark) communities than external. This feature was specially marked in the less illuminated cave. Ordination analyses performed on species coverage per community for each cave separately, distinguished several benthic communities from the outermost to the innermost zone of each cave. Cluster analyses on species coverage, taking into account all communities in both the caves, established similarities among communities: algal-dominated communities clustered according to the level of light received independently of the cave they inhabited, while animal-dominated communities were more similar within each cave than between the caves. Moreover, among the abiotic parameters measured irradiance was the only factor that clearly diminished from the entrance to the innermost zone in both the caves. In contrast, water movement and particulate organic matter varied differently in each cave. Results indicate that the different topography, depth and geographic location of the two caves determine water movement, light penetration and nutrient availability along the caves. These factors are responsible for determining species abundance and diversity, as well as species growth habit in each community.