Miniature acoustic transponders wrapped in bait were deployed on the sea floor in the continental rise and slope regions of the Porcupine Seabight during August 1992. These were ingested by Centroscymnus coelolepis (Chondrichthyes, Selachii) at 1517–1650 m depth, Antimora rostrata (Osteichthyes, Moridae) at 2020–2501 m depth, and Coryphaenoides (Nematonurus) armatus (Osteichthyes, Macrouridae) at 2501–4050 m depth. Fish with baits in their stomachs were tracked using a scanning sonar deployed on the sea floor. All fish had moved out of range of the sonar (500 m) within 3–9 h of the bait reaching the sea floor, indicating no site fidelity. Swimming speed of C. (N.) armatus increased with depth from 0056 m s-1 at 2500 m to 0·109 m s-1 at 4000 m. This is partially explained by a bigger-deeper trend in fish size.

Demersal fishes on the continental rise and slope were sampled by trawl, baited trap and a baited camera. Seventy-one different species were trawled, but only 18 species approached baits. At rise soundings (4100 m to 2250 m) Coryphaenoides (Nematonurus) armatus was dominant at baits and comprised 41·5% of the trawl catch. On the slope (<2250 m) Synaphobranchus kaupi was dominant at baits and comprised 32·7% of the trawl catch. At 1500–2501 m Antimora rostrata competed at baits and comprised 5–10% of trawl catches. At 1500–1650 m Centroscymnus coelolepis also consumed baits but was not captured by trawl. For C. (N.) armatus abundance was proportional to tarr2 (where tarr= arrival time), demonstrating that arrival time of the first fish at baits provides an estimate of population density. Maximum estimated abundance at 2897 m was 877 km-2, more than five times the abundance on the abyssal plain. Halosauropsis macrochir, Lepidion eques, Coryphaenoides guentheri, Gadiculus argenteus and Coryphaenoides rupestris were important in trawl samples but absent or rare at baits.

The analysis of 35 bottom trawls taken on the slope in the Catalan Sea (western Mediterranean) has shown the existence of two different demersal fish assemblages occurring on the upper (350–650 m) and middle (1150–1300 m) slope. The middle slope assemblage is characterized by much higher values in some ecological parameters such biomass and mean fish weight, resulting from the dominance of middle to large size species (e.g. Alepocephalus rostratus, Trachyrhynchus trachyrhynchus, Mora mom). On the upper slope two different stations were considered, one inside and the other outside a submarine canyon. Only slight differences were found in species composition, and hence sample and species were not clearly separated by a correspondence analysis. However, some interesting ecological differences exist between these two stations. Much higher values in abundance and biomass inside the canyon were indicative of higher food availability there. Moreover, a drop in mean fish weight was also noted inside the canyon. The analysis of size distributions in the commonest species along the upper slope showed that the submarine canyon acts as a recruiting ground for some of them.

A Galway Bay population of the dragonet Callionymus lyra (L.) was investigated between March 1978 and November 1979. Monthly collections were made on board commercial fishing vessels. A total of 3302 fish was examined. The male to female sex ratio in the catch was 1·14:1 and it departed significantly from a 1:1 ratio. Males grew significantly faster than females, when measured by length and by weight, and attained a greater maximum length, but females had a longer life span. Females were significantly heavier than males for any body length. The spawning season was protracted, lasting from January to August and peaking during February-April. Callionymus lyra is a carnivore, feeding mainly on polychaetes and crustaceans, but molluscs and echinoderms were also eaten in abundance. A yearly cycle in feeding intensity was observed, showing reduced feeding during the colder months. The feeding index expressed as gut weight / body weight was significantly higher for females.

Atlantic salmon smolts were sampled from the intake screens of the Oldbury power station in the inner Severn Estuary at weekly intervals between July 1972 and June 1977. These catches, and those taken over nearly three years from the nearby Berkeley power station, demonstrated that the abundance of smolts in the estuary peaked in autumn (October) and, to a far greater extent, in spring (April and May). However, small numbers of smolts were occasionally found in all other months of the year except July. Standard length-frequency distributions of smolts remained unimodal throughout the year. Lengths ranged from 76 to 187 mm, mean 130·2 ±1·87 mm (95% CL), and wet weights ranged from 5·4 to 68·0 g, mean 26·9 ±1·17 g. The mean monthly standard length of smolts increased slightly between the autumn of one year and the spring/early summer of the next year, suggesting that, on average, the former were six months younger than the latter. The condition factor was significantly greater in autumn (1·40) than in spring (1·23). It is estimated that the total number of salmon smolts entrained annually on the screens at Oldbury during the five years ranged from 92 to 791, with a mean of 405. Total estimated numbers at Berkeley ranged from 196 to 788 per annum. The numbers at Oldbury are lower than those estimated for the downstream migrants of the Twaite shad, another anadromous species, and far lower than those of the most abundant of the marine fish species that use the Severn Estuary as a nursery area.

The ciliate Cryptocaryon irritans Brown, 1951 is a parasite of tropical marine fishes, being recorded chiefly from coral reef species (Laird, 1956; Burgess, 1978; Colorni, 1985). The disease, cryptocaryosis, accounts for fish mortalities in aquaria (De Graaf, 1973) and mariculture systems (Huff & Burns, 1981; Colorni, 1985; Kaige & Miyazaki, 1985; Rasheed, 1989); however, relatively few studies have been undertaken on the biology of C. irritans, as highlighted by Lorn & Dykova (1992). Sikama (1937) described the major features of the life cycle, infection of the fish epidermis alternating with a free-living phase of reproduction within a protective cyst. Most other investigations of C. irritans have been concerned with morphology (Sikama, 1937, 1938; Brown, 1951, 1963; Nigrelli & Ruggieri, 1966; Cheung et al., 1981; Colorni, 1988) with a recent work on the ultrastructure of the pellicle (Matthews et al., 1993). Little is known regarding the behaviour of free-living stages and the possible influence of environmental factors on transmission. Nigrelli & Ruggieri (1966) noted photopositive responses in theronts. The establishment and maintenance of C. irritans in mullet under controlled conditions (Burgess & Matthews, 1994) provided an opportunity further to investigate light in the survival strategy of this fish pathogen.

A first quantitative description of the suprabenthic fauna in a coarse sand community from the western English Channel is provided. One hundred and twenty species of Crustacea were collected in 22 suprabenthic sledge hauls collected throughout the year (1988–1989). Mysids and Amphipods dominated the fauna, among them Anchialina agilis (Sars), Gastrosaccus spp., Apherusa spp., Eusirus longipes Boeck, and Stenothoe marina (Bate) were the dominant species. Although most dominant species showed a vertically decreasing gradient of density from the lower net to the upper level of the sledge, the most abundant species, Apherusa spp., showed similar density at all four levels. The mean density at the four levels of the sledge did not differ significantly with the distance above the sediment. Species performed nocturnal vertical migrations: the densities of mysids were higher during the day than at night; conversely, the densities of amphipods and decapods were higher at night than during the day. The density and species richness showed high seasonal variation, from low values at the end of autumn and winter to high values in summer and the beginning of autumn. The results are compared with the available data on suprabenthic communities from the North Atlantic; this highlights (1) the lack of concentration of suprabenthic fauna towards the sediment on coarse sand, and (2) the highest abundance of the suprabenthic fauna from muddy substrata.

The recruitment and succession of fouling organisms was examined on four substrata (concrete, plywood, fibreglass and aluminium) in Quibray Bay of Botany Bay in New South Wales, Australia. Eighteen 10×10 cm panels of each substratum were submersed in each of four seasons: January (summer), March (autumn), May (winter) and October (spring) 1992. Six of each substratum were retrieved after 1 month, 2 months and 4–5 months. Thus in this study, as a methodological improvement over many other studies of succession, samples were taken independently with regard to time.

Seasonal recruitment was important in determining the pattern of succession and the composition of the assemblage. Sydney Rock oysters, Saccostrea commercialis (Iredale & Roughley), recruited in large numbers on panels submersed in January and, by their rapid growth, dominated the available space after 4–5 months. The greatest recruitment of the barnacle Hexaminius sp. and the greatest percentage cover of algae (six species) occurred on panels submersed from October to March. While panels submersed in January for a period of 4–5 months resulted in a single outcome, an oyster-dominated assemblage, panels submersed in October for the same period of time resulted in a set of alternative outcomes depending on the relative abundance of barnacles and algae.

The summer vertical distribution of appendicularian species was analysed at 22 stations in the central Cantabrian Sea by means of vertical tows covering the surface, thermocline and deep layers. According to their preference for shallower waters, the appendicularian species could be arranged on the series Oikopleura longicauda (Vogt), Oikopleura fusiformis (Fol), Fritillaria pellucida (Quoy & Gaimard) and Oikopleura rufescens (Fol), with Oikopleura dioica (Miiller) in an uncertain position, probably closer to the end of this series. Principal components and correlation analyses suggest that a temperature gradient causes this pattern, which agrees with previous findings made at very different temporal and spatial scales. By means of particle-size spectra, it is shown that those oikopleurids that prefer cold, deep waters, O. fusiformis and O. rufescens, co-vary with a coefficient of particle-size quality. The lower the temperature, the lower the proportion of small, ingestible particles to large inlet-filter-clogging particles. This is proposed as an important reason for the presence of inlet filters in oikopleurids.

This field study examined competition for space among encrusting bryozoans on artificial panel substrata used to simulate the habitat found on the undersides of boulders. In all 1761 interactions were analysed, involving 16 species of cheilostomes (genera Callopora, Celleporella, Cribrilina, Electra, Escharella, Escharoides, Haplopoma, Membraniporella, Microporella, Phaeostachys, Schizomavella, Schizoporella and Umbonula) and two ctenostome genera (Alcyonidium and Flustrellidra). Neither absolutely transitive nor intransitive arrangements of competitive outcome occurred among the species. Instead, the high incidence of ‘ties’ and reversals of outcome produced a network-like arrangement. In terms of outcome alone Escharoides coccinea (Abildgaard), Membraniporella nitida (Johnston) and Schizoporella unicornis (Johnston in Wood) were apparently ‘overgrowth dominants’, Alcyonidium spp. and Cribrilina cryptooecium Norman were ‘intermediate dominants’ and Callopora lineata (L.), Callopora craticula (Alder), Celleporella hyalina (L.) and Electra pilosa (L.) were ‘inferior competitors’ for space. The effects of four variables on the outcome of specific competitive encounters were assessed in detail and included (i) the identity of the colony encountered, (ii) the angle of contact between the competing colonies, (iii) the location (two sites, on both the east and west coasts of Scotland) and (iv) the year (1983, 1984). Models incorporating these variables were developed, using the Generalized Linear Interactive Modelling System (GLIM), to examine their influence on the outcome of bryozoan encounters. All of these factors contributed to explaining the considerable variability in the outcome of competitive interactions. The species were not, however, affected equally by all the variables, although encounter angle and year were significant for dominants and encounter angle, site and year all were significant for intermediate species.

Samples of the mud shrimp Callianassa subterranea (Montagu) were taken at irregular intervals (September and October 1989, April and July 1990, August 1991) from a depth of 47 m at a fixed station in the North Sea (54°35′N 04°50′E). At this site, mud shrimps appear to have a contagious distribution, the mean density varied between 38 and 59 individuals m-2 and the sex ratio was biased significantly to males (mean male: female ratio, 1·9), except for shrimps of ≥8 mm carapace length (CL) which had an equal sex ratio. The combined samples for the full sampling period showed a bimodal distribution for males and females, with a possible third mode for males, suggesting a life cycle of between 2 and 3 years. Only females ≥7 mm CL carried eggs. Lack of samples over winter prevent any conclusive description of seasonal population patterns; however, reproduction (based on the presence of ovigerous females) extended from April to September with a peak in July and post-larval shrimps (<3 mm CL) were present each month. The allometric growth of the primary chela identified male (6·5 mm CL) and female (7·5 mm CL) size at maturity. Differences in allometric growth after maturity result in males having larger and more massive primary chelae than females of equal carapace length. The parasitic isopod Ione thoracica (Montagu) infected between 20% (October) and 10–8% (August) of mud shrimps, with males having a significantly higher level of infestation than females.

Expected lifetime investment in eggs and related parameters are described for a lagoonal population of Hydrobia ventrosa (Mollusca: Gastropoda) in East Anglia, UK, and these are compared with those of East Anglian lagoonal populations of H. neglecta and both lagoonal and intertidal-marine populations of H. ulvae. In contrast to an earlier study on Danish populations, which suggested that H. neglecta and H. ventrosa are at opposite ends of the hydrobiid spectrum of investment in reproduction, the order of increasing relative allocation of resources to egg production runs H. neglecta = H. ventrosa → lagoonal H. ulvae → intertidal-marine H. ulvae. That is, from the two small, short-lived, specialist lagoonal species producing few, large, directly-developing eggs, to the larger, potentially longer-lived H. ulvae that produces many small eggs which develop into veliger larvae. The lagoonal populations of all three Hydrobia species, however, are very similar to each other in terms of reproductive investment. When like cohorts are compared, in each, the annual egg weight is equal to the annual adult growth increment, and the weight of eggs produced per expected lifetime is half the adult growth increment at the time of death. These lagoonal populations are markedly dissimilar to intertidal-marine populations of H. ulvae, which produce an annual weight of eggs some 15 times the annual adult growth increment, and an expected lifetime egg weight some two-and-a-half times the adult growth increment at the time of death.

Rates of occurrence and degrees of imposex, and tissue concentrations of organotin compounds (tributyltin, TBT; dibutyltin, DBT; butyltin, MBT; triphenyltin, TPT; diphenyltin, DPT; and phenyltin, MPT) in the rock shell, Thais clavigera and T. bronni (Mollusca: Gastropoda) were investigated at 32 sites in Japan from May 1990 to October 1992. The rate of occurrence of imposex was 100% in both species, at almost all sites surveyed. Degrees of imposex indicated by relative penis length (RPL) index reflected the pollution levels not only of TBT, but also TPT. In heavily polluted areas, many individuals were found with oviducts which were blocked by vas deferens development, and capsule glands which were filled with aborted egg masses. These organisms were thought to be sterile.

A procedure for accurately determining age and growth of the sea urchin Sphaerechinus granularis (Lamarck) (Echinodermata: Echinoidea) in the Bay of Brest (France) is described. Readings of growth lines were made from the longitudinal cross-section of interambulacral oral plates of sea urchins collected in February 1993. These results agree with age estimates calculated using the ELEFAN I programme based on diameter-frequency distributions of sea urchins collected from February 1992 to March 1993. A non-linear regression (monomolecular equation) best describes the relationship between test diameter and plate thickness. The diameter-at-age data can be increased by back-calculation, assuming a constant proportional deviation from the mean size of the test. Although von Bertalanffy growth curves fitted to actual observations were similar to those fitted to back-calculated diameter-at-age data, the latter produced a more adequate curve and increased the quality of the growth parameter estimators. The von Bertalanffy growth curve estimated by ELEFAN I shows a pattern similar to the back-calculated von Bertalanffy growth curve.

The capacity for oxygen uptake of a respiratory organ can be estimated using morpho-metric techniques, the two essential measurements being respiratory surface-area and thickness of the tissue barrier across which oxygen diffuses. In cephalopods, the gills are the main site of respiratory exchange and this study was designed to estimate oxygen uptake capacity of the gills of four different genera of cephalopods. A preliminary study was required to determine the form and structure of the gills. Light microscopy showed the surface of the gills to be highly folded, particularly in Octopus. A level of microscopy was chosen at which the outline of the smallest folds of the epithelium and the blood vessels of the gills could be easily resolved. Stereological techniques were then employed to obtain values for the respiratory surface-area related to body weight (cm2 g-1), tissue barrier thickness (μm) and oxygen-diffusing capacity (ml O2 min1 Torr·1 kg1). Values for these three variables obtained for the different species were as follows: Octopus vulgaris 2·9 cm2 g-1, 10 μm, 0·05 ml O2 min-1 Torr-1 kg1; Alloteuthis subulata 10·6 cm2 g1,6 μm, 0·27 ml O2 min-1 Torr-1 kg-1; Nautilus sp. 4·9 cm2 g-1,15 μm, 0·05 ml O2 min-1 Torr1 kg-1; Sepia hatchlings 13·3 cm2 g-1, 4 μm, 0·52 ml O2 min-1 Torr-1 kg-1.

A combination of photography and subsequent image analysis of the photographs has been used to measure maximum length, perimeter length and total area of fronds of tagged Fucus serratus L. as part of a study of the growth of this species on the Yorkshire coast. Maximum mean growth rate of 0·26 cm d-1 was observed during June–July. Minimum mean growth rate of 0·01 cm d-1 was observed during October-March. The method is relatively quick and convenient, and has the advantage that in addition to apical growth of the longest and/or other branches, lateral growth and total growth in surface area can all be recorded, while loss of tissue can also be determined. A further advantage is that a photographic record is obtained of the history of each individual plant.

The microhabitat and morphology of Grubea cochlear (Monogenea), a rare gill parasite of Atlantic mackerel (Scomber scombrus), were investigated for a sample of fourteen parasite individuals obtained from Lyme Bay, southern England. Grubea cochlear showed a preference for the inner hemibranch of the fourth gill arch, this localization contrasting with that of the related and sympatric species Kuhnia scombri. The morphology of G. cochlear in this sample differed slightly from some of the previously documented specimens, especially with regard to the number of small genital hooks and the relative size of the haptor. It is suggested that geographical morphological variation may occur in this species.

Columbus crabs, Planes minutus (L.) (Crustacea: Brachyura) are often found on the postero-ventral surfaces of sea turtles, particularly the loggerhead Caretta caretta (L.) (Testudines: Cheloniidae). There has been a general acceptance of a hypothesis that the crabs feed upon turtle faeces. However, evidence is presented here to demonstrate that Planes has a ‘cleaning’ role, feeding on other epibionts (e.g. barnacle cyprids, parasitic amphipods) during daylight hours. At night it is likely that the crabs feed on neustonic animals (e.g. euphausids). The species is also cannibalistic.

Long-term surface wave records from various parts of the English Channel are used to determine the percentage of time during a year for which waves disturb the sea-bed. Most of the bottom sediments are rarely disturbed by waves (<1% of the time), due to water depth and sediment grain size. The coastal zones (<30 m), including the embayments, experience significant wave disturbance at the sea-bed (i.e. >5–10%). The general distribution of surficial sediments can be explained in terms of tidally-induced processes alone. Even in areas where wave activity is high, fine-grained sediment transport is controlled by the same mechanisms.