Seven species of the amphipod genus Ericthonius are described and figured from the North-east Atlantic and associated seas and a key to their identification is provided. West Atlantic material is also considered where relevant to the taxonomy of East Atlantic species. Two species are re-established after a long period of submersion in synonymy, and one species new to science is described. The previous confusion in the literature of some of the species is discussed, and a synonymy of species described in key works is provided.

The buoyancy, lipid levels, and orientation of five species of myctophid from the Biscay area were examined, and it was found that two of the five were probably normally denser than the sea water in which they live. Analysis of the swimbladder gas of Myctophum punctatum collected at the surface at night indicated that this species has a less extensive vertical range in this area than elsewhere. A functional classification of myctophids is proposed, based upon density, lipid levels, and the presence or absence of a gas-filled swimbladder.

Archidistoma is a genus created for a species discovered and described briefly by Garstang in 1891 as A. aggregatum. It has been found at different times only in the Plymouth region, the original locality, attached to rock surfaces in a few feet of water. Recently, however, it has been found near Cape Hatteras on the eastern American coast (Van Name, 1945), suggesting either harbour to harbour transportation by ship bottom, or that its inconspicuous appearance has obscured a wide distribution.

This form is of considerable interest as it represents a type less specialized in zooid structure, nature of tadpole, and method of budding than any merosomatous ascidian except the diazonids. Diazonids are oviparous and have the simpler development and tadpole associated with small eggs, although there is a more elaborate branchial sac correlated with the relatively large size of the mature zooid.

Colony

The colony consists of a brownish tough matrix forming a thin encrustation on stones and shells, with individual zooids (a few millimetres long), partly embedded in the test but for the most part extending freely in clumps usually of three or four. Sand grains and round particles adhere to or become buried within the test, making this form the most inconspicuous of ascidians.

Structure of Zooid

The zooid is divisible into a thorax and a long slender abdomen (Fig. 1). There is no postabdomen, nor is there hypertrophy of the ventral test vessels, thereby segregating Archidistoma as a type from that of the synoicids (polyclinids) and the clavelinids respectively.

Reef fish community structures at three sites in the state of Rio de Janeiro (Pedra Vermelha (PV), Cabo Frio Island—Arraial do Cabo; Mãe Island (MI), Itaipu—Niterói; Comprida Island (CI), Cagarras Archipelago—Rio de Janeiro) were investigated to assess differences in fish species composition, density and distribution of trophic groups, between sites, correlating the observed patterns of fish distribution with environmental factors. Thirty-six visual strip-transects yielded 67 species of 34 families. Studied locations shared at least 40% of all species, mostly of western Atlantic distribution. The three sites presented significant differences on diversity, density and species dominance. CI presented the highest values, except for total density, which was higher at PV, probably due to its partial degree of protection. MI showed the lowest values, suggesting possible impacts from the proximity to the shore. The main trophic categories were omnivores followed by mobile invertebrate feeders, in similarity to what was previously observed for south-eastern Brazil. Inherent habitat features of each location regarding depth, declivity, visibility and rugosity resulted in different species distribution and dominance patterns.

The South American sea lion, Otaria flavescens, has been considered vulnerable and under the threat of extinction in Peru due to the drastic demographic changes as a result of the impact of low food availability and the unusual timing of the severe El Niño event of 1997–1998. We present the first estimate of effective population size (Ne) for the species that takes into account the effects of mating system and variation in population size in different generations caused by the severe El Niño event of 1997–1998. The resulting Ne was 7715 specimens. We believe that the estimated Ne for the Peruvian population is not a critical value, because it is higher than the mean minimum viable population generally accepted for vertebrates (ca. 5000 breeding adults). However, the viability of O. flavescens on the Peruvian coast may depend primarily on local availability of food resources. Climatic change models predict stronger and more frequent El Niño events. In this sense, the Ne of 7715 should be considered as a value to be maintained in order to keep the population large enough to avoid inbreeding or to retain adaptive genetic variation to survive to future El Niño events. Moreover, this Ne estimate is important data in discussions about resuming culling activities, based on the statement of an increasing competition between fishery activity and sea lions during El Niño events. Thus, this Ne should be taken into account in future management plans to ensure the conservation of the species on the Peruvian coast.

Partial fin-clipping is a non-lethal sampling technique commonly used to sample tissue for molecular genetic studies of fish. The effect of this technique was tested on seahorses (Hippocampus spp.) as they have several peculiar biological characteristics when compared with other fish and are on the IUCN Red List of Threatened Species. Partial fin-clipping of the seahorse dorsal fin was evaluated on Hippocampus kuda. The fish were assessed for short-term effects (fin re-growth time) as well as the longer term effects (growth and mortality) of partial fin clipping over a four month period. Total fin re-growth occurred between 2 and 4 weeks with no significant difference observed in the fin re-growth time between sexes. There was no significant difference between the mortality rate/growth rate of clipped versus unclipped seahorses. Results indicate partial fin-clipping has no significant effect on seahorses, and should be considered as a useful method for tissue sampling.

It has been suggested that the large grey seal colonies around the British Isles form local populations within a metapopulation, and that seal movements outside the breeding season lead to considerable overlap between individual home ranges. Individual behaviour and population dynamics of small peripheral colonies may also play a role in the metapopulation. We studied the French grey seal colony of the Molène archipelago, at the southern-most limit of the species' range. We analysed photo-identification data with capture–mark–recapture techniques in order to estimate the total seasonal abundance of grey seals in the archipelago and to quantify the seasonal rates of occurrence or movements of male and female seals. We found that between 58 (95% confidence interval: 48–71) and 98 (95% CI: 75–175) individuals hauled out in the archipelago during the summers of 1999 and 2000. The use of multistate models allowed the assessment of seasonal site fidelity and indicated that it varied between key periods of the annual cycle, particularly for females. Males showed a constant fidelity rate of 56% from one season to another. Hence, even though they showed high inter-annual site fidelity, they did not seem to have a preferred season for using the archipelago. On the contrary, female grey seals showed the highest site fidelity between moult and summer (around 80%), and the lowest fidelity between summer and the breeding period (34–43%). Thus, females seem to use the Molène archipelago preferentially in summer and leave the site before the breeding season, which explains the very low local pup production. Philopatry may explain this pre-breeding emigration, and we suggest that most grey seals observed in the Molène archipelago were born and breed in other local breeding populations, probably the south-western British Isles.

The gut contents of 99 ballan wrasse (Labrus bergylta: Teleostei; Labridae) sampled between April and July in Galway Bay, Ireland and 95 ballan wrasse sampled between April and June in Dinard, Brittany, France were examined. Decapods and bivalves were the major prey categories in both areas, algae and gastropods were also frequently eaten but in much smaller amounts. The volume of the major food categories did not vary significantly with fish length. However, fish longer than 20 cm did consume greater volumes of bivalves than smaller fish. An increase in dietary diversity during the breeding season was observed. Ballan and corkwing (Crenilabrus melops) exploited many of the same food categories but with different emphases. Bivalves, which were major prey of corkwing, were also very important to the ballan captured simultaneously at the same site.

During the course of a survey into the distribution and growth of the fan mussels Pinna nobilis and Pinna rudis from the coastal waters of the Spanish Mediterranean the presence within the mussels of Pontonia pinnophylax has been recorded. Pontonia pinnophylax typically occurred in adult pairs, but occasionally solitary male individuals were found. The width of the cephalothorax is greater in females than males, whereas the chelae of the second periopods, which are unequal, are larger in males. There is a general relationship between the size of P. pinnophylax and its pinnid host; the largest individuals were found in the largest Pinna and vice versa.

The study describes the seasonal density and age structure for splashpool metapopulations of Tigriopus californicus (Copepoda: Harpacticoida). Natural populations were highly variable, ranging from 217 ± 401·7 ind 1−1 in winter (mean ± SE) to 835 ± 1750·6 ind 1−1 in summer, with some populations approaching 20,000 ind 1−1 in all seasons except winter. Male-to-female ratio ranged from 1·36 in spring and summer to 1·84 in autumn, and reproduction was observed throughout the year. Nauplii abundance averaged 28 + 7·4 ind 11, a value much lower than expected for in situ copepod populations and possibly due to behavioural processes such as cannibalism and inhibition of egg deposition. The densest assemblages of splashpool microcrustacea were almost entirely T. californicus, principally mature adults and including clasped male-female pairs and ovigerous females. A simple population growth model is presented, along with parameters for calculating the instantaneous rate of increase, birth, and death in the absence of disturbance.

Several studies have been conducted to explain patterns of the abundance, richness and diversity of sandy-beach macrofauna; however, such analyses have ignored the overall functional structure of macrofauna communities. Few studies have examined polychaete feeding guilds on sandy beach environments. To examine the effects of environmental factors on polychaete feeding guilds on sandy beaches, 12 sandy beaches from five islands in Sepetiba Bay were sampled. A total of 24 polychaete morphospecies, grouped among 21 families, were identified in these sandy beaches. The polychaete species were classified into 10 feeding guilds, and the SDT guild (suspended-deposit feeders, discretely motile, with tentacles) was the most abundant feeding guild, with 34.2% of total number of organisms. The highest trophic importance index and index of trophic diversity values were recorded on the sheltered beaches. A canonical correspondence analysis showed that the exposure rate, beach length, and grain size of the beach sediment significantly affected the polychaete feeding guild distribution and abundance. We can conclude that sheltered beaches have a higher diversity of feeding guilds than exposed beaches and that the biological descriptors of the feeding guilds are directly associated with the grain size of the sediment.

Observations on breeding (1, 1914; 2, 3, 1920) and experiments on the rate of growth of marine invertebrates (4, 1914; 5 to 9) have been carried out since 1911 (excepting the war period).

Establishing baseline data on the abundance of threatened shark species is critical for monitoring site- and region-specific population tends over time. This is of particular importance for monitoring sharks at remote locations or in regions where there are no reliable data on shark numbers, fishing effort and current population status. Through establishing a standardized recreational SCUBA diver observation programme, this study examined the number, size and sex-composition of grey reef sharks, Carcharhinus amblyrhynchos, on a remote coral reef system off the Red Sea coast of Sudan. In addition, placard tags were attached to individual sharks to examine coarse scale residency and movement patterns and to determine the effectiveness of this technique. Over a 4.5 month period (December 2007–April 2008), a mean (±SE) of 5.9 ± 0.3 grey reef sharks were observed per diving day with peak numbers of sharks associated with temperatures of 26–26.9°C and strong currents. Estimated mean (±SE) total length of observed sharks was 1.9 ± 0.03 m identifying that most animals were mature. Female sharks were dominant on the site and pregnant females were recorded. Placard tagged sharks (N = 4) were observed by recreational SCUBA divers throughout the study period (23.1%, 20.0%, 16.9% and 3.1% of total observation diving days) indicating sporadic site attachment. The placard tags remained intact and were free of fouling for a total of 175 days. The numbers of grey reef sharks seen on this Red Sea coral complex suggest a healthy, relatively unexploited population. This study demonstrates that the recreational diver community, which forms a large pool of skilled volunteers, can generate baseline data on shark numbers at regularly dived sites and provide insights into the ecology of the observed species. Modification of placard tags, including attachment to the dorsal fin and time corrodible release systems may provide an inexpensive and accepted tool for monitoring individual shark residency and movement patterns. Engaging the recreational SCUBA diver community in a standardized scientific monitoring programme has the potential to monitor trends in shark populations over large spatial and temporal scales.

We studied the communities of the invasive Balanus improvisus and native Cerastoderma glaucum populations in the south-western Caspian Sea. The massive movement of live Bivalvia attached to Cirripedia colonies along the studied coastline strengthens the hypotheses asserting the possible negative effects of exotic species on endemic species. Different live stages of both animals including meroplankton and macro-invertebrates were considered in the analysis. Bivalvia larvae showed a downward trend in population, in contrast with an upward trend of Cirripedia larvae from 1996 to 2013. The abundance of C. glaucum decreased west to east along the sea shore in contrast with increasing biomass of B. improvisus. Both Bivalvia and Cirripedia larvae did not show any overlapping temporal abundance. The Cirripedia larvae showed its highest abundance in winter while the bloom of Bivalvia larvae occurred in April and May during 2004–2013. The biomass of B. improvisus reported in this study was higher than those reported for the northern parts and for the middle parts. Distribution patterns of both species were described based on temperature, salinity gradient and local nutrient content. A non-linear growth model of Bivalvia showed the short-term effects of Cirripedia on Bivalvia growth. The controversy between the effects of Cirripedia on the movement of two different Cardiidae (C. glaucum, which is affected by the presence of B. improvisus, and Adacna vitrea with no attached Cirripedia) highlights the contributing role of several other factors including ecosystem degradation.

The spatial settlement of marine invertebrate larvae is not a random process. The distribution of the adults of a particular species is influenced by the behavioural responses of the animal to a range of environmental stimuli which, in the case of many sessile invertebrates, result in the display of clear substrate selection. The role of habitat selection in determining the distribution of aquatic invertebrates has been the subject of a review by Meadows & Campbell (1972). The selection of algal substrata by the larvae of various intertidal species of Bryozoa has been demonstrated by Ryland (1959); among these, the ctenostomatous bryozoans Alcyonidium hirsutum and A. polyoum were shown to exhibit a strong preference for fronds of the alga Fucus serratus, an experi-mental result which accorded well with the distribution of the two species on the shore (Ryland, 1962).

The genetic diversity of the soft-shell clam Mya arenaria from seven locations in Europe (two stations in the southern Baltic Sea (the Gulf of Gdansk) and two in the North Sea (Veerse Meer and Oosterschelde), and three additional stations in the Denmark Straits and Bay of Biscay) was determined using starch gel electrophoresis of allozymes. The results showed a low level of genetic variability and a lack of genetic differentation among the populations studied. Basic polymorphism characteristics calculated for populations from the North Sea estuaries and the Gulf of Gdansk were: He 0·094–0·145, Ho 0·092–0·130, percentage of polymorphic loci 33 (0·95 criterion), mean number of alleles per locus 2·0–2·7. The mean value of FST was 0·0133 and not significant. It is concluded that in spite of a low level of genetic polymorphism the soft-shell clam is a successful colonizer. The genetic homogeneity among the populations reflects rapid population extension, alleles neutrality and a high gene flow.

A new pedunculate barnacle, Ashinkailepas seepiophila gen. and sp. nov. has been recovered from a hydrothermal cold seep at 1175 metres of depth off Hatsushima Island, Sagami Bay, central Japan. It is the second record of a Neolepadinae, otherwise known from vents, from a seep, but the two are not closely related. Its coarsely ornamented capitular plates, and primary peduncular armament being in whorls of six plates, distinguish it from all previously known neolepadines, not only as a new genus and species, but also as a distinct clade, and therefore a new tribe is proposed to accommodate it. There is a slight bilateral asymmetry in the proportions of the capitular plates as well as a marked bilateral asymmetry in the arrangement of the peduncular scales related to bending over to one side. This apomorphic characteristic distinguishes the new species from all other Scalpellomorpha. While leaning over to one side is suggestive of verrucomorphs, it is not judged a sign of affinity. Ashinkailepas is apparently the most primitive of the vent/seep barnacles, which are considered relics largely of the Mesozoic age.

Water samples, taken from station El in the English Channel, were incubated in 12–1 bottles and monitored for nine days. The distribution pattern of photosynthetically incorporated 14C was followed in three different size-fractions (0·2–2 μm, 2–10 μm and >10 μm) during the development of a bloom.

A rapid increase in chlorophyll was observed just after enclosure, the highest values being reached by day 5, when a mixed community of diatoms and small flagellates formed the bulk of phytoplankton biomass. As the bloom developed, nutrients were depleted and, consequently, a decay of the phytoplankton populations occurred. Growth rates, estimated as chlorophyll-specific production rate, were higher for the largest size-fraction (0·53 d−1) than for the intermediate and smallest ones (0·32 d−1 for both).

Throughout the bloom, the proportions of 14C incorporated into protein and low molecular weight metabolites (LMWM) were small, whereas the synthesis of storage products appeared to be enhanced. Carbon fixed into protein was higher during the exponential growth phase in all size-fractions, and incorporation into LMWM increased sharply when the bloom declined. Storage product synthesis varied between size-fractions.

A close relationship was observed between growth rates, estimated as chlorophyll-specific production rate, and the protein/metabolite synthesis ratio (r2=0·90; n=24). These results suggest that, within the range of environmental variation we studied, this ratio would be a good estimator of growth rate for field studies.

The importance of feeding pattern is well documented in fish (Jenkins & Green, 1977; Simenstad & Cailliet, 1986) but there are not many reported studies in cephalopods. Feeding patterns, as defined by Jenkins & Green (1977) have been studied, to our knowledge, only in Todarodes pacificus (Okiyama, 1965), Loligo pealei (Vovk, 1972), Loligo opalescens (Karpov & Cailliet, 1978), Illex illecebrosus (Amaratunga et ah, 1979; Amaratunga, 1980) and Nototodarus gouldi (O'Sullivan & Cullen, 1983). Boyle (1983) dealt with aspects of feeding in several cephalopod species but not specifically with feeding pattern. Aspects of feeding in Sepia officinalis have been reviewed by Nixon (1987). The present work describes the daily feeding pattern in Sepia officinalis from data collected in the field.

The Marine Biological Association (1957) lists the poor cod Trisopterus minutus minutus (L.) (=Gadus minutus) as being parasitized by two monogenean gill parasites Diclidophora luscae and D. denticulata but at various times over the past 25 years we have, between us, examined the gills of upwards of 1000 specimens of T. m. minutus without ever having found a monogenean parasite. We concluded that the 1957 records were probably due to a misidentification of the hosts. However, in January 1979 one of us (J. E. G.) found several specimens of a monogenean very closely resembling D. luscae (Beneden & Hesse) on the gills of poor cod. D. luscae is normally found at Plymouth (Llewellyn, 1956) on only the pouting Trisopterus luscus (L.), a fish which from time to time is caught in the same trawl as T. m. minutus, e.g. in a total of 46 standard hauls between July 1976 and June 1978 (information supplied by Mr A. D. Mattacola), on 11 occasions (23%)T. luscus and T. m. minutus were caught together. On eight of these 11 occasions the lesser abundant of the two fish species constituted 10% or more of the combined total, and on three occasions the lesser abundant fish made up at least 40% of the combined total. Thus there is evidence that T. m. minutus and T. luscus from time to time occupy the same or neighbouring habitats (a standard haul may be over a distance of up to 8 km) and so presumably there has been opportunity for parasitic invasion from one species to the other to take place. That this has not in fact happened we have regarded as an example of the very strict species-specificity to their hosts manifested by most monogeneans and especially by diclidophorans on gadoids (Llewellyn & Tully, 1969). It was decided therefore to investigate how the sudden appearance in 1979 of a monogenean parasite on a previously uninfected population of poor cod may have come about.