The size of fish and squid prey of Loligo forbesi was investigated using otoliths, beaks and statoliths collected from stomach contents analysis of samples obtained from Scottish and Irish waters between 1990 and 1993. Loligo forbesi was found to consume a large range of prey sizes, but prey size was always less than the predator size. Season was shown to significantly influence the predator size-prey size relationship for sprat and sandeel prey, but this itself could be influenced by seasonal changes in the size of prey. Fish prey size increased with increased predator size up to a mantle length (ML) of 200 mm. Loligo forbesi of mantle length >200 mm consumed a range of prey sizes, with no clear increase in the size of prey. For most prey taxa the relationship between prey size and squid size was similar, the exceptions being dragonets and silvery pout. Cannibalism by L. forbesi was mostly limited to larger L. forbesi (>150 mm ML) feeding on smaller (20–50 mm ML) conspecifics.

INTRODUCTION

The deep-sea eel, Synaphobranchus kaupi, is widely distributed on the continental slopes of the North Atlantic (Saldanha & Bauchot, 1986; Haedrich & Merrett, 1988). It was a dominant fish species in epibenthic sledge and semi-balloon otter trawl (OTSB) hauls on the West African slope (Merrett & Marshall, 1981; Merrett & Domanski, 1985). Also in the eastern North Atlantic, it was the most abundant species on the slopes of the Porcupine Sea Bight off south-west Ireland (Merrett et al., 1991; Priede et al., 1994). In the western North Atlantic, it was the dominant species on the middle and lower slopes of the Middle Atlantic States of the USA and on the upper slopes of the Grand Banks off Newfoundland (Sedberry & Musick, 1978; Houston & Haedrich, 1986).

The ecology of the sepiolid Sepiola atlantica in Firemore Bay, Loch Ewe, on the west coast of Scotland was investigated by beam trawling surveys. Low densities of this species were present in the shallow sublittoral zone of the sandy bay. A size range of 4–21 mm dorsal mantle length (DML) was obtained, with no significant differences detected between the mean sizes of males and females. Males reached gonadal maturity slightly earlier and at a slightly smaller size than females. Sepiola atlantica was present in the bay in each of the months in which sampling took place suggesting a resident population, the structure of which varied considerably. Juveniles were found over a prolonged period of the year but peak recruitment (animals of 4–10 mm DML) was in May and July. Animals <4 mm DML were not caught and no egg masses were found in the trawls. In aquarium conditions, S. atlantica fed on live crustaceans such as mysids, Crangon crangon and Palaemon serratus, although Corophium volutator, an estuarine crustacean not normally found in the marine sandy bay, was the most accepted food.

Marine mussels are widely distributed and have been used extensively as environmental biomonitors. Communities associated with mussel patches have a high species richness but are typically dominated by a few very abundant species. These communities exhibit significant temporal and small-scale spatial variations in abundance and diversity which should be recognized when considering global patterns of marine biodiversity. Many of the species associated with tropical mussel beds are also represented by taxonomically and functionally equivalent species in mussel communities from temperate waters. The phenomenon of ‘parallel communities’ on rocky shores is thus apparently replicated on a finer spatial scale within mussel patches.

The aims of the present study were to investigate food consumption, growth and the dynamics of feeding hierarchies in the same groups of juvenile greenback flounder (Rhombosolea tapirina: Teleostei) fed either high or low rations. Differential food consumption by individual greenback flounder held in groups of 20 showed the presence of feeding hierarchies in which individuals consumed between 0 and 22% of the available food. Inter-individual differences in food consumption resulted in different growth rates leading to growth depensation (measured as an increase in the coefficient of variation for weight). Intra-individual differences in food consumption tended to be larger for flounder which consumed a lower share of the available food. When the group ration was reduced the inter-individual and intra-individual variations in food consumption increased. Consequently, the relationship between inter-individual and intra-individual variation in food consumption tended to become stronger at lower food availability and indicated an increase in the strength of the feeding hierarchies. This study suggests that individual differences in food consumption, mediated through exploitation competition, contribute to growth depensation in this species of flatfish.

Statolith microstructure was studied in 162 specimens of Illex coindetii (mantle length ranging from 48 to 300 mm) captured on the shelves of Sierra Leone and Western Sahara between May and November 1987. Growth increments were revealed in all statoliths studied, but they were not well-resolved as in other congeneric species Illex illecebrosus and Illex argentinus. Age and growth rates were estimated assuming that growth increments within statoliths were produced. In both regions, differences in growth rates between sexes (females become larger than males) occurred first in length and then in weight. Geographical differences in sex-specific growth (Western Sahara squid grow faster and attain larger sizes than Sierra Leone squid) was apparent after 150 d in females and 120 d in males. Illex coindetii in Sierra Leone started maturing at smaller sizes but at approximately the same age as the Western Sahara squid. Small sized early maturing groups of I. coindetii with a life span of ~0.5 y occurred in both regions. However, large sized late maturing squid with a life span of ~1 y were encountered only in the Western Sahara. In waters of the west African shelf, I. coindetii spawn throughout the year.

There is a greater diversity of spectrally distinct chlorophyll(ide) pigments in individuals of many of the large number of higher taxa of marine oxygen-evolvers which contain only small organisms than in those few higher taxa which also (or only) have large-sized organisms. The occurrence of more types of pigment in smaller organisms can be mechanistically related to the lesser degree of self-shading in smaller organisms, thus allowing spectral diversity to be reflected in enhanced photon absorption from a given light field as a result of multiple spectral forms of chlorophyll(ide)s. This provides a mechanistic basis with ecological significance for the greater chlorophyll(ide) diversity in small marine O2-evolvers which show greater biodiversity at the level of higher taxa than do classes or divisions which are comprised only, or predominantly, of macrophytes (Ulvophyceae, Rhodophyta, Phaetophyta, seagrasses).

The astropectinid asteroid Plutonaster bifrons (Wyville Thomson) occurs on the continental slope of the north-east Atlantic between 1000 and 2500 m depths. As in most deepsea animals, the factors limiting bathymetric distribution of this species are unknown. Eggs were fertilized in vitro and incubated through the early embryonic cleavage stages at pressures that correspond to depths from 0 to 3000 m. The highest percentage of normal development occurred near the peak of the species distribution (2000 m), and virtually no normal development occurred at a pressure corresponding to 3000 m depth. Develop-mental rate was retarded at pressures higher and lower than those found near 2000 m. These experiments indicate that embryonic pressure tolerances could determine both the upper and lower bathymetric limits of distribution for this species.

The spatial and temporal patterns of variation of a tropical soft-bottom fish community sampled by a shrimp trawl and a fish trawl were compared at two sites, North and South Bay, of St Vincent Bay, New Caledonia. Results indicated that the species richness and particularly the species composition were related to the type of trawl. However, the overall density and biomass, species diversity, and evenness did not vary significantly as a function of gear type. The same species dominated the catches of the two trawl types, but differences appeared between density, biomass and mean weight of particular species, calculated from the shrimp and the fish trawl catches. The spatial variations of the community structure were comparable between the two gear types, though the composition of the species assemblages were not the same. Differences appeared for the temporal structures. These differences were insignificant in one of the sampled sites (North Bay), but more important in the other site (South Bay), where species diversity, size range of the individuals, and shape diversity of fishes were more important. However, the major differences between the community structures remained the same, independent of sampling gear type. These results validate studies comparing spatial and temporal patterns of variations in general characteristics (i.e. number of species per haul, density, biomass, species diversity and evenness) of tropical soft-bottom fish communities determined by shrimp and fish demersal otter trawls. This also validates the determination of species assemblages especially spatial assemblages. However, important problems may arise when more particular points are studied, such as species composition of the communities, determination of the characteristic species of the assemblages, or study of a particular species.

A hydraulic dredge survey was conducted during January – June 1994 in north-west, north and east Iceland, to provide a first assessment of ocean quahog, Arctica islandica (Mollusca: Pelecypoda) resources in these areas. Ocean quahog was found in significant concentrations and high density. The combined high-density areas were 91.7 km2 with a minimum biomass (live weight) of 304.80 tonnes. Information on population structure and meat yield were also provided. The population in the areas was characterized by unimodal size distributions comprised of mostly larger-sized individuals. Most quahogs were between 70 and 90 mm with no individuals <17 mm which might be due to the selectivity of the dredge or because of poor recruitment in the population. Little difference was observed when comparing the mean shell length for the quahogs from the three areas. The mean shell length in the north-west area was 75.4 mm and 74.8 mm in the north and east areas. The shell length frequency distribution for the north-west area was different in shape from the two others which were not significantly different from each other. Mean quahog meat yields in the areas were from 30.1 to 33%. The meat yield was highest in the 50.55 mm size class in all areas.

Studies of the interplay of immigration, emigration and extinction in shaping the fauna of islands (McArthur & Wilson, 1967) have influenced the terrestrial ecologists view of the creation and maintenance of diversity. Although in the deep ocean, hydrothermal vents have been the subject of a number of biogeographic studies (Tunnicliffe, 1991), there have been few attempts to validate theories of island biogeography in the shallow marine environment. To rectify this situation, a study comparing the fauna of the mainland of Cornwall, with that of the Isles of Scilly, which lie 45 km from the mainland and were separated from it ~0·3 my BP has been undertaken.

Evidence for some comparative impoverishment of the Isles of Scilly fauna was provided by Crisp & Southward (1958) who noted that a small number of cirripedes and molluscs with planktonic larvae, living close to their geographic limits of distribution in Cornwall, were unable to bridge the gap to the islands. They suggested that although species with long-lived planktonic larvae can be widely dispersed, excessive dispersal can lead to their loss from the fauna of small islands. This is clearly demonstrated on the remote island of Rockall where both Crisp (1956) and Moore (1977) noted that only animals with direct development occur. On the Island of Lundy, four species of gastropod were estimated to be less abundant than on the mainland which lies only 18 km away (Hawkins & Hiscock, 1983). However, such studies only deal with a small number of conspicuous intertidal species, and there is a requirement to expand observations to the community level. The present study attempts to question the following hypotheses: (1) α - diversity (that of single samples) is lower on the islands than the mainland; (2) the diversity of species with planktotrophic larvae is lower on the islands than on the mainland.

The glandular epithelium of both escae and caruncles originates from a solid, branched ingrowth of epidermal cells from the distal surface of the bulb-shaped light gland primordia in the larva. The lumina within the glandular epithelium appear to originate by the breakdown of the central cells within the solid mass of epithelial cells. An epithelium-lined duct connecting the central glandular lumina with the distal surface of the bulb-shaped primordium was seen only in sections of the posterior esca. This suggests that the intraglandular lumina are formed before the duct to the surface, which then develops within an initially solid strand of cells.

Patterns of variation in the assemblage structure of butterflyfishes (Chaetodontidae) of the Red Sea and western Indian Ocean have been compared. There is a lower number of species in the Red Sea, a high proportion of which are endemic to the region, both features that have been attributed to the relatively recent origin of the Red Sea. In the Red Sea overall mean abundance of butterflyfish is greatest in the central part, decreasing both to north and south. Several species present in the southern Red Sea are absent from the north. By contrast, most western Indian Ocean species are widely distributed within the Indo-West Pacific. Comparative field studies in the northern Red Sea (Egypt) and western Indian Ocean (Kenya) showed that mean number of species was higher in the western Indian Ocean, but mean density of butterflyfishes was higher in the Red Sea. In both areas diversity of butterflyfish was related to mean substrate diversity (the number of coral growth forms). Mean spatial niche breadth of butterflyfish species was much higher in the Red Sea than in the western Indian Ocean, whereas the extent of microhabitat use was higher in the western Indian Ocean. It is suggested that these differences may be related to the more recent evolution of the Red Sea fauna.

The dogfish eggcase protects the developing embryo for up to a year against predation and fouling. The mechanical protection is provided by the strength and resilience of the case. The aim of this study was to determine the mechanisms underlying the case's antifouling proficiency. The eggcase is constructed of oxidatively cross-linked proteins, which are primarily collagen. Two main hypotheses were examined, firstly that the egg case scavenges heavy metals and these act as deterrents. Secondly, the tanning agents, particularly dihydroxyquinones, through reaction with Fe2+, produce hydroxy radicals that act as deterrents. This process is called the Fenton reaction. Using ten different species of marine bacteria, Semibalanus cyprids and Enteromorpha zoospores, a variety of experiments were conducted to examine the effect of surface chelation, iron loading, changing the surface roughness, different collagen types and quinones, and the presence of antioxidants. The results suggest that the photoactivated generation of free radicals is partially responsible for the antifouling mechanism of the eggcase. Collagen and quinone chemistry and surface integrity are also considered to be important in the antifouling process.

In this paper we present evidence for female mimicry in a population of Salaria pavo (Pisces: Blenniidae). Parental males differ markedly from females by the presence of a large crest on the head and anal glands on the two spiny rays of the anal fin. We found a proportion of smaller and younger males that are almost identical to females both in morphology and behaviour. These ‘female-like’ males lack secondary sexual characters and actively court parental males, displaying the female's colour pattern and courting behaviour. These males are sexually mature and their gonadosomatic indices are higher than those of parental males. Female mimicry is considered to be a functional way to achieve sneak fertilizations.

The effect of artisanal fishing on the abundance and diversity of coral reef fish assemblages was investigated in the Kisite Marine National Park and Mpunguti Marine National Reserve at Shimoni, Kenya. Fishing is prohibited within the Park whereas in the Reserve artisanal fishing using traditional methods is practised. Visual censuses of six representative reef fish families (Chaetodontidae, Lethrinidae, Lutjanidae and Serranidae in 1992 and 1994, and Labridae and Pomacentridae in 1994 only) were undertaken along 250×10 m band transects on two similar pairs of reefs subject to differing fishing pressure. The abundance of commercial species (Lethrinidae, Lutjanidae and Serranidae) was depressed in the Reserve. The unfished butterflyfishes (Chaetodontidae) and damselfishes (Pomacentridae) also showed a greater abundance in the Park than in the Reserve. However, neither species number nor Shannon diversity (H′) of any of these families was affected by fishing pressure. Possible reasons for these findings are discussed. The abundance of commercial species, though not of non-commercial unfished species, increased significantly in the Reserve between 1992 and 1994, suggesting that the unfished Park may be acting as a source of larvae or supply of emigrating adults for the depleted Reserve. The results are comparable with other recent studies describing the effects of fishing pressure and also with those studies detailing the effects of habitat refugia in coral reef areas.

Penis size and morphology of an oviparous species of rough winkle Littorina arcana Hannaford Ellis (Gastropoda: Prosobranchia) was studied at Robin Hoods Bay on the English east coast. Monthly collections were made over a two year period from August 1987 to August 1989 and again from May to December 1993. Number of penial glands was recorded and a six point scale was used to quantify penis maturity. Results indicate that male L. arcana shed their penes in summer and regenerate a new one during the following 12–20 weeks. Male L. arcana in captivity shed penes in July but not in November. The significance of penis shedding and the differences in reproductive seasonality between L. arcana and its ovoviviparous sibling species L. saxatilis is discussed.

Mosshead sculpins, Clinocottus globiceps, of the North American Pacific coast commonly feed upon sea anemones and in doing so make frequent body contact with the anemone tentacles. An attempt was made to determine if some sort of acclimation process, as seen in certain pomacentrid anemone fishes, is necessary for C. globiceps to engage in such repeated contacts. The laboratory experiments with C. globiceps and three species of anemones (Anthopleura xanthogrammica, A. elegantissima, Urticina crassicornis) revealed no obvious and consistent acclimatory behaviours by the fish toward anemones following a period of enforced isolation from anemones. Actions by C. globiceps toward anemones included frequent bites to tentacles, touches to tentacles without biting (whether intentional or not), and bites to the anemone's base or column. Tentacle bites occurred, on average, significantly earlier than tentacle touches in trials with Anthopleura elegantissima. There was no evidence that either tentacle bites or tentacle touches occurred earlier than the other in trials with A xanthogrammica and U. crassicornis. In paired trials where individual

C. globiceps were tested first with A. xanthogrammica and then with U. crassicornis, the fish showed no significant difference in response to the two anemone species, either in the frequencies of different types of actions (bites or touches) or in the average order in which tentacle bites or tentacle touches occurred. Experiments were also conducted to compare the degree to which different sculpin species avoided contact with anemone (A. elegantissima) tentacles. Clinocottus globiceps seemed more tolerant of contact with tentacles than were the other sculpins, and only C. globiceps appeared intentionally to touch tentacles, sometimes leaning against or biting them.