Observations on living estuarine nematodes show that previous feeding type classifications do not accurately represent the trophic structure of an intertidal mudflat in the Westerschelde Estuary (Netherlands). A new scheme with six major nematode feeding guilds is proposed: (1) microvores; (2) ciliate feeders; and (3) deposit feeders sensu stricto are all nematodes without a distinct buccal armature. In the first two groups bacteria and protozoa, respectively are the major particulate food sources, while other items are included in the diet of the third. The three other categories are recognized among the nematodes with a buccal armature: (4) epigrowth feeders; (5) facultative predators; and (6) predators. Diatoms and other microalgae are an important particulate food for many epigrowth feeders. The importance of bacteria as a food source for these nematodes remains poorly documented. A strictly or mainly predatory behaviour has been described for only few species from the study area. Several nematodes, however, are facultative predators. The predatory strategy of Calyptronema maxweberi, as described in this paper, suggests the use of a paralysing or lethal secretion in prey capture, which, to our knowledge, is the first report for aquatic nematodes. Furthermore, the importance of sources other than particulate food in free-living aquatic nematodes is stressed. Our observations show that many aquatic nematodes are in fact opportunistic feeders, which may change feeding strategies in response to available food.

Side-scan sonar and underwater video were used to determine the impact of a trawl fishery on an epibenthic community associated with the horse mussel, Modiolus modiolus in a Northern Ireland sea lough. The presence of marks caused by trawl otter-boards on the sediments could be clearly seen using side-scan sonar and changes to the epibenthos are described from the video survey. It is apparent from the side-scan sonar survey that changes have occurred in the structure of the superficial sediments on heavily trawled areas. However, there was no clear indication of temporal changes. The utility of side-scan sonar coupled with GIS techniques to detect temporal and spatial effects is discussed.

The dominant planktonic calanoid copepods in inshore and estuarine habitats in northern European waters; the Acartiidae, Centropagidae and Temoridae, produce eggs which survive and can remain dormant in the sediments (Marcus, 1996). Eggs of Eurytemora survived passage through the guts of fish larvae, in contrast with eggs of Pseudocalanus (Conway et al., 1994). Eggs of Paracalanus do not survive in sediments (Marcus, 1991). Lindley (1992) suggested that families within the superfamily Centropagoidea, including Eurytemora but not Paracalanus and Pseudocalanus, produce eggs which remain viable in sediments. Previous work on these eggs has been from subtidal sediments, although Naess (1996) showed that calanoid eggs survived in sediments in seasonally drained fish ponds.

Diel vertical migration (DVM) and in situ feeding of Thalia democratica (Tunicata: Thaliacea) was studied in the field (Agulhas Bank, South Africa) over a 48 h period in March 1994. Thalia democratica did not display DVM, and both aggregates and solitaires were mostly confined to the upper layers of the water column throughout the study period. Thalia democratica did not display any discernible diel feeding rhythm, and pigment content increased with salp size. Individuals with greatest pigment content were found at the chlorophyll maximum. Estimates of grazing impact varied with salp abundance and gut passage time, ranging from less than 1% to greater than 100% of phytoplankton productivity.

The gametogenic and spat settlement patterns of two Mytihis edulis beds were studied in Dundrum Inner Bay, Northern Ireland. There was evidence of gonad development throughout the year with the main development period between November and March. Spawning was protracted, lasting from May to November. Slight inter-annual and inter-population differences in the riming of the phases were observed but the cycles at both beds were broadly similar to each other and to those of other British and Irish sites. Settlement occurred throughout the year and there was evidence of both primary and secondary spat settlement at both sites. Although the reproductive cycles were similar, distinct seasonal and inter-site differences in spatfall were apparent. At the Downshire Bridge bed, settlement peaked during summer and was dominated by spat in the 0·;5-1·0 mm size range. At Ballykinler, settlement levels were highest in the winter months and larger (>1 mm) spat dominated the samples. The orientation of spat collection pads also significantly affected numbers of the larger (>1 mm) spat. Collectors facing the flood tide attracted significantly more secondary settlers than ebb-facing collectors. This effect varied seasonally and was greater at the Ballykinler bed. It is suggested that hydrodynamic regimes may be an important factor in the differences in settlement patterns of M. edulis.

The spatial distribution and temporal variations of the Abra alba-Pectinaria koreni community from the eastern part of the Bay of Seine were investigated through four winter surveys (1986, 1987, 1988 and 1991). A grid of 40–67 stations was sampled each year using a Hamon grab (0·25 m-2) for macrofauna collection and sediment analysis. The fauna was dominated by polychaetes and in a lower part by molluscs and echinoderms. Although species richness with ~100 species collected during each survey was high, total density and biomass (±SE) resulted principally from about ten dominant species, and varied between 846·9 ±163·5 and 1135·3 ±186·7 ind m-2 and 23·52 ±4·41 and 27·48 ±4·45 g m-2respectively. The dominant species were patchily distributed and exhibited weak spatio-temporal fluctuations except the two bivalves A. alba and Cultellus pellucidus. Factorial correspondence analysis (FCA) of the distribution of main species among stations and automatic hierarchical classification identified five faunal assemblages which were relatively stable in space and time. The temporal stability of the community could be generated by processes of larval retention near parental population, and sediment stabilization induced by the low abundance of deposit feeders and the high densities of the tube-dwelling polychaete Owenia fusiformis. While the sediment variables were a poor indicator of the spatial structure of the community, the salinity gradient off the Seine Estuary and post-settlement processes (e.g. food limitation and postlarval drifting) have been proposed to explain it. Comparison with an earlier survey (i.e. 1971) suggested a degree of long-term persistence of the community structure in qualitative and quantitative terms.

This study constitutes a first approach of the use of a stereological method for estimating potential fecundity in cephalopods. Squid samples were taken in two regions from the south coast of Portugal. In Olhäo, commercial trawlers provided mainly immature squid during winter. In Quarteira, a summertime traditional jigg fishery provided maturing and mature squid, which were used in the fecundity estimates. A total of 38 female squid, Loligo vulgaris (Cephalopoda: Loliginidae), from all maturity stages were analysed. The results revealed that: (1) the development of the ovaries is monocyclic and the oocyte growth and development is asynchronous; (2) oogenesis proceeds in six histological stages, showing statistically different oocyte maximum diameters; and (3) the best estimate of potential fecundity seems to be obtained by counting all oocytes in the ovaries of the mature females in maturity stage IV

Monthly samples of fish from the intake screens of power stations at Oldbury and Berkeley in the inner Severn Estuary and Hinkley Point in the inner Bristol Channel, were used to analyse the community structures of the ichthyofauna in these regions. Marine species that use the estuary as a nursery area (marine estuarine-opportunists) were very abundant in the shallow inshore waters at Oldbury. Diadromous species were more abundant in the offshore and deeper waters at Berkeley than at Oldbury. Only one of the two species that complete their life cycles in the estuary was even moderately abundant in the inner estuary and the 15 freshwater species were relatively rare. Bass and particularly the sand goby complex were more numerous in the protected, inshore waters than the more offshore waters of the estuary. With the yellow and silver stages of the European eel, the reverse situation pertained. Seasonal changes in faunal composition were more pronounced in the inshore shallow than in more offshore deeper waters of the estuary. This largely reflected the sequential immigration of large numbers of the juveniles of marine estuarine-opportunist species into the former area for relatively short periods. Although the ichthyofaunal composition in the shallows at Oldbury underwent the same pattern of cyclical variation in each of five consecutive years, the degree of intra-annual variability differed, reflecting interannual differences in the recruitment strengths of the 0+ age classes of the different marine estuarine-opportunists. These cyclical changes were not correlated strongly with either salinity or water temperature. The faunal composition of the protected inshore, more marine waters of the inner Bristol Channel differed from those in both inshore and offshore regions of the inner estuary. The species which typified the fauna of the Channel were bib, poor cod, five-bearded rockling, sole and conger eel. Although the first four of these species were relatively more abundant in these waters than in the estuary, their juveniles often made extensive use of the shallows at Oldbury. This study emphasizes that, for some marine species, the protected inshore, and more marine, waters in the Bristol Channel can act as alternative nursery areas to those provided by the inshore shallows of the Severn Estuary.

Thirteen species of Amphipoda have been recorded from the stomachs of plaice and 11 species from dabs, with Perioculodes longimanus the most notable prey oedicerotid in both flatfish species sampled from the shallow sublittoral zone (<-6 m depth) at Kames Bay, Millport. Plaice took mostly bivalve siphon tips (Angulus sp.). Polychaetes were more numerous in larger plaice. Sand gobies specialized on small crustaceans, taking 13 amphipod species inter alia (with P. longimanus again the most notable oedicerotid). Amphipod numbers in sand goby stomachs increased with the length of the fish. Neither dabs nor sand gobies consumed bivalve siphon tips and only rarely consumed polychaetes. Although amphipods formed only a minor part of the diet of plaice, at the population density known for this species in this bay, its depredations would still constitute an important selective agency governing patterns of activity in epibenthic oedicerotids.

The feeding habits of Trigla lucerna L. (1758) and Aspitrigla obscura L. (1764) (Pisces: Triglidae), off the coast of the Gulf of Valencia (Spain), were investigated between October 1989 and January 1991. The two species examined in this study appear to have distinct feeding types, based on the species composition of prey and the frequency of occurrence of major food items. Tub gurnard had a more diverse diet and fed mainly on crustaceans (mysids and decapods), teleosts and molluscs, whilst long fin gurnard were less piscivorous and fed mainly on mysids and natantids. No significant differences were found in the annual variation of vacuity coefficient for either species. Diet composition in these species did not show great changes with either season and size of fish. There was little dietary overlap between these two species.

The known geographical distribution of the sea anemone Actinothoe sphyrodeta (Gosse) (Cnidaria, Actiniaria), hitherto generally believed to occur in the north-eastern Atlantic Ocean from the Shetland Islands to the Bay of Biscay, has been extended with new records from the Iberian Peninsula. These records comprise three from the west coast of Portugal and one from the Mediterranean coast of Spain.

The sea anemones (Actiniaria) of the north-eastern Atlantic Ocean have been closely studied for at least a century and a half, and along with those of the Mediterranean Sea, constitute perhaps the best known actiniarian fauna in the world. Furthermore, there has long been discussion of the endemicity of Mediterranean sea anemones, and of apparent overlaps between the distributions of some Atlantic and Mediterranean species. It is, therefore, of particular interest when a species thought to have a solely Atlantic or solely Mediterranean distribution is discovered on the ‘wrong’ side of the Strait of Gibraltar. The anemone Actinothoe sphyrodeta (Gosse) was hitherto generally believed to occur only in north-western Europe, with a range from the Shetland Islands to the Bay of Biscay (e.g. Fischer, 1890; Manuel, 1981). It is reported here for the first time from Portugal and from the Mediterranean coast of Spain.

Cadmium was rapidly concentrated by Mytilus galloprovincialis (Mollusca: Bivalvia) during one week's exposure to 0–5 ug Cd ml-1 sea-water. Cadmium accumulation was determined in the gills, adductor muscle and viscera. The amount of cadmium bound to metallothionein (MT) provided a specific index of exposure to this metal. Maximum values were reached in viscera; this observation is consistent with the presence, in the viscera, of the hepatopancreas which is commonly regarded as a major site for MT synthesis. In tissues of M. galloprovincialis exposed to Cd different energy charge (AEC) responses were observed. Adenylate energy charge (AEC) values appeared to be more affected by Cd exposure in adductor muscle than in the gills and viscera. These variations could be related to an impairment of oxidative metabolism leading to a partial switch from aerobic to anaerobic metabolism. The data obtained from anoxic incubation did not show significant differences in AEC values between pre-exposed and untreated animals, with the sole exception of adductor muscle of exposed mussels.

The dry weights, carbon and nitrogen content of fresh dried Calanus spp. Pseudocalanus elongatus, Acartia clausi, Temora longicornis, Mesocalanus teniricornis, Metridia lucens and Candacia armata were determined from samples taken in the southern North Sea, the English Channel, the Irish Sea and the Celtic Sea in December 1984 and February 1987. Usually adult females were picked out but some data were obtained for adult males and copepodites of Calanus spp. and T. longicornis and male M. tenuicornis. Significant differences were found between stations on the same cruise in the results for adult females of the same species. The weights of Calanus spp. females in February 1987 were found to be inversely related to temperature.

Scats (N=200) of harbour seals (Phoca vitulina) were collected from haul-out sites on the Island of Mousa, south-east Shetland, during July, August and September 1994. A total of 5,531 fish otoliths were identified in scats and measured to reconstruct fish lengths and weight. Gadid fishes dominated the diet of harbour seals on Mousa during the study period, both in terms of weight and the frequency with which they occurred. There was evidence for the existence of temporal trends. Over the period July–September the importance of gadids in the diet increased while that of sandeels declined. These temporal trends are probably associated with changes in prey availability. Comparisons of the size of sandeels, herring and whiting eaten by seals with trawl catches suggest that seals were probably not size-selective, but a corollary of this is that, while otolith size is reduced during passage through seal guts, application of correction factors derived from captive feeding experiments led to over-estimates of fish size.

Growth of the echinoid Sphaerechinus granularis from the Gleiian Islands (Brittany, France) was studied by analysis of growth zones in longitudinal cross-sections of interambulacral oral plates. The diameter-at-age data pairs were increased using a back-calculation technique, which allows for a more efficient estimation of von Bertalanffy growth curve parameters. The annual value of the skeletal growth marks agreed with the analysis of the population's size-frequency distributions taken from a previous study. Significant differences in growth and morphological parameters were observed between two populations of the archipelago in close geographical proximity and inhabiting the same type of substratum. These differences, which appear as population phenotypic responses to different hydrodynamic conditions, confirms growth plasticity in S. granularis.

Eight individuals of Mullus surmuletus (Teleostei: Mullidae) ≤80 mm total length were captured in shallow water in the Firth of Lorn, western Scotland in August and September 1995. The species is rare on the west coast of Scotland and the occurrence of juveniles is a new record for the area.

The red mullet (Mullus surmuletus L.) is a species whose distribution is centred on the Mediterranean where it forms the basis of a commercial fishery (e.g. Renoñes et al., 1995). Outside the Mediterranean it is found on eastern Atlantic coasts from the Canaries northwards to the English Channel and the southern North Sea where it is ‘moderately common’ (Wheeler, 1969). Further north it is regarded as rare (Wheeler, 1969; Hureau, 1986) and the northern limit is variously given as Scotland (Lythgoe & Lythgoe, 1992) or southern Norway (Wheeler, 1978). Most northern records are from the North Sea (Rae & Wilson, 1954; Rae & Lamont, 1964), presumably reflecting the intensive fishing effort in this area. Records to the west of the British Isles are few and have been summarized by Gordon (1981) and subsequently by Henderson (1986, personal communication), including one from the Faeroes (Blacker, 1977). All recorded occurrences in western Scotland are of adult fish (26–31 cm) caught by commercial fishing vessels and juveniles have never been reported from this area. This note documents (Table 1) the capture of small individuals (N=8) in shallow water off the west coast of Scotland in an area where they had never been recorded previously, despite intensive studies of the local fish fauna since 1970 (R.N.G., personal observation; Gibson, 1973; Gibson et al., 1993). The eight fish were caught on Tralee beach, Ardmucknish Bay, Firth of Lorn, Argyll (56°31′N 5°29′W). The sea bed in this area consists of fine sand (Gibson et al., 1993). It is possible that their occurrence is linked with the unusually warm summer of 1995 allowing juveniles to penetrate further north than usual. Water temperatures at 2–5 m on 29 August, 1995 were 14.3°C compared with a maximum of 13.6°C recorded over the period 1986–1989 (Gibson et al., 1993).

Histriobdella homari is a polychaete annelid belonging to the Order Eunicida and Family Histriobdellidae. Histriobdella homari is normally found in the gill chambers or among the eggs of the lobster Homarus vulgaris from the English Channel (Roscoff) and in the southwestern part of the North Sea (George & Hartmann-Schroder, 1985). Two independent sightings of H. homari living on the pleopods of Nephrops norvegicus from the Irish Sea and Clyde Sea area are reported.

A pilot study was conducted to follow condition and swimming performances over two months using three samples of 50 juveniles of white sea bream, Diplodus vulgaris. The initial result indicated that the weight-length relationship followed the model; W=5.2xl0-3L349. According to this relationship, condition indices were estimated for each individual as the observed weight related to the computed weight. Measures of swimming velocities realized in an artificial flume show variations through time with an increase and decrease directly correlated to condition indices. Maximum speed of an individual was measured at 12.3 cm s1. Analysis of environmental conditions indicated that the decrease of condition index and swimming performances was related to bad weather which induced turbid water in juvenile habitats.

Six colour varieties were recognized in an intertidal population of Amphipholis squamata from Normandy (France). Each variety exhibits its own capacity to produce light, the light emitted by the most luminous variety being 500 times more intense than that emitted by the least luminous one. Differences in luminescent capabilities observed between varieties do not seem to be due to differences in pigmentation or to be of exogenous origin. It was shown that the capability to produce light changes according to whether individuals are brooding or not, brooding individuals emitting a more intense light than non-brooding ones. This supports the defensive use of luminescence generally associated to ophiuroid production of light. However, light capabilities differ so much between A. squamata colour varieties that bioluminescence could also be associated with another role in the species.

Data are presented on the density of ten species of Amphipoda and two species of Isopoda from terrestrial to aquatic (freshwater through brackish water to marine) habitats, derived using a new modification of the displacement method involving batch testing of animals and subsequent Probit Analysis of data.

Surprisingly few data are available in the literature concerning the densities of marine organisms. Extensive work on this topic was published some half a century ago by A.G. Lowndes. He reported widely on crabs and lobsters (Lowndes, 1943a), echinoderms (Lowndes, 1953) and fishes (Lowndes, 1955). In his paper to the Linnean Society (Lowndes, 1938a) he included data on some of the smaller freshwater Crustacea. Gross & Raymont (1942) have published on the specific gravity of the marine copepod Calanus finmarchicus.

In espousing the displacement method for dealing with live individuals (Lowndes, 1938a,b, 1942, 1943b, 1955), he dismissed summarily earlier techniques that involved ascertaining whether killed or narcotized animals sank or floated in liquids of known density. While we recognize the limitations of the old methods, Lowndes’ displacement technique, although very accurate for individuals (he quoted figures to five decimal places), is very tedious to replicate [“elegant if somewhat exacting”, according to Hutchinson, 1967] and so reliance tends to be placed on figures obtained for very few individuals, typically only one or two. Even Lowndes himself was wary of attributing significance to the last two decimal places in his estimations, since individuals will vary in density according to sex, the contents of the gut etc. (Eyden, 1923; Lowndes, 1938b; but see Fox & Mitchell, 1953).