The third record of the sharpnose seven-gill shark Heptranchias perlo (Selachii: Hexanchidae) north of the Bay of Biscay is reported. The 101 cm total length specimen, which was taken incidentally on a commercial bottom-set longline at a depth of 166 m, was an immature female. Beaks belonging to the short-finned squid Illex coindetii (Cephalopoda: Ommastrephidae) were recovered from the stomach, and an unidentified species of nematode was found parasitizing the stomach mucosa.

Stable carbon isotope measurements (δ13C) were used to assess the sources of carbon assimilated by the fan mussel Pinna nobilis, in sea grass Posidonia oceanica meadows, and an associated shrimp Pontonia pinnophylax which occurs within this bivalve's mantle cavity. The primary carbon sources available to both animals displayed a wide range of δ13C values, from −12·3 to −22·3‰. The δ13C and δ15N of Pinna nobilis and Pontonia pinnophylax suggest that they assimilate carbon from similar sources, occupy comparable trophic levels and that their association is commensal.

In benthic intertidal studies it is common to standardize species density, and other variables, to a square metre, regardless of the surface area sampled. Using a fully-nested sampling design, with sampling unit surface areas ranging from 0·020 to 1 m2, the present study investigated the effect of this procedure on the accuracy of the results. It is demonstrated that this standardization has a profound influence on the resultant estimates, introducing a substantial error into inter-study comparisons.

Ecological aspects of the marine tucuxi dolphin, Sotalia fluviatilis (Cetacea: Delphinidae), remain poorly known. Important information can be gathered in long-term studies using photo-identification. Using this methodology, the authors present the first evidence of site fidelity for marine tucuxis in the Cananéia Estuary (25°03′S 48°01′ W), south-eastern Brazil. A total of 86 easily recognizable individuals was catalogued from June 1996 to August 2001, but most of them have been sighted from May 2000. From June 1997 to August 2001, three female tucuxis were sighted on nine (KN #19), 22 (KN #30) and 28 (KN #10) different days in a relatively small area (∼16 km2). Each of them was observed with a calf in 1997–1998 and again with a new offspring in 2000–2001. Thirteen other individuals were reported on eight to 19 different days in the same area between May 2000 and August 2001. Our observations lead to conclusions on the evidence of site fidelity and indicate that calving intervals may range between two and three years for this species in the surveyed area.

This study was conducted to research brachyuran crabs at the upper infralittoral zone of the Dardanelles from August 1997 to February 1998. The samples were collected by diving and dredge. The crabs were fixed and preserved in 5% formalin prepared in seawater. The brachyuran crabs were identified in systematic order according to literature records and data.

It was established that eight discernible species and eight genera belonging to five families on the shores of the Dardanelles existed, including: Eriphia verrucosa, Xantho poressa, Carcinus aestuarii, Liocarcinus depurator, Maja crispata, Pachygrapsus marmoratus, Ilia nucleus and Macropodia longirostris.

Ontogenic change patterns in otolith Sr:Ca ratios were examined in the Russian sturgeon, Acipenser guldenstadti in the Caspian Sea. Otolith Sr:Ca ratios fluctuated widely during the life history in accordance with the migration pattern from freshwater to brackish water habitats, i.e. all specimens exhibited a typical anadromous pattern in the ratio. Several specimens had two transition points in otolith Sr:Ca ratios from the low ratios to the high indicating that those specimens had a flexible migration strategy in the ambient water and had the possibility of migrating downstream to the Caspian Sea multiple times after spawning in a freshwater habitat.

The gastropod Littorina littorea shows increased mortality in the summer months when infected with digenean parasites. One possible cause of this mortality is impaired respiration in infected hosts. Respiration rates of L. littorea infected with three species of digenea of varying pathogenicity were measured: Cryptocotyle lingua, Himasthla elongata and Renicola roscovita. No evidence of altered respiration rates in infected snails was found.

Mysids have previously been shown to consume oxygen at much lower rates when in a swarm (cohesive group in which individuals are evenly spaced but not polarized) than when in uncohesive small groups. Thus the swarm represents a strategy for conserving energy. In this study different swarm sizes of mysids were forced to perform escape responses by exposing them to jets of ammonium hydroxide, while measuring their oxygen uptake. Swarms of 200 individuals showed no significant difference in oxygen consumption with or without the ammonium treatment. In contrast, swarms of 100 showed a significant increase of around 45% oxygen uptake when exposed to ammonium. In conjunction with earlier demonstrations of increased feeding success and lower oxygen uptake when aggregated, this work clearly confirms the energetic benefits of being in a larger social group rather than a smaller one or remaining solitary.

Geostatistical analysis was used to investigate the effect of drift kelp on the spatial distribution of the sea urchin Tetrapygus niger. The positions of all sea urchins were mapped in four experimental plots in the rocky intertidal zone of the central Chilean coast. When drift macroalgae were added, the sea urchins left the substratum irregularities, increased in number inside the experimental plots, and tended to form a dense aggregation around the kelp. After the drift macroalgae was removed, the aggregations disappeared and the sea urchins returned to the depressions and/or interstices of the substratum. The results suggest that the influx of drift kelp is the triggering factor in the formation of dense aggregations of this species.

The stomach contents of 16 bottlenose dolphins Tursiops truncatus (Cetacea: Odontoceti) stranded in the Spanish Mediterranean coast were examined. Remains and size of prey were analysed and correlated with the ecological characteristics and behavioural patterns of this dolphin. Fish and cephalopods represented the main diet components, and hake Merluccius merluccius was the most important prey. The food habits were considered as mainly demersal according to the characteristics of the prey. The study suggested ontogenic and sexual differences in feeding behaviour based on diet composition and hake size. The potential causative factors, particularly as they relate to dolphin social structure, are discussed.

The astigmatid mite species, Tyrophagus putrescentiae, was found to occur in meiobenthic collections from the Mdloti Estuary on the eastern seaboard of southern Africa. To examine whether these mites are actually components of estuarine systems or the result of contamination of collecting and laboratory materials, special sterilization procedures were incorporated into the collection protocol. Samples employing sterilization procedures still yielded Tyrophagus mites, providing evidence for their existence in the estuarine sediments. The origination of these mites in estuarine and fringe marine systems, in general, is discussed. These findings are significant in terms of the potential trophic importance of Tyrophagus mites.

Sex reversal is common in the animal kingdom, yet nothing has thus far been known about it in amphioxus. The present study showed that female amphioxus reared in the laboratory was sexually reversed into the male, but not vice versa. This is the first report on the existence of sex change in the cephalochordate.

The beryciform fish Hoplostethus mediterraneus (Beryciformes: Trachichthyidae) is a species discarded from the southern Portuguese coastal fisheries. It is taken as by-catch by deep water trawls, at depths of between 234 and 618 m, more than 80% being taken at depths of between 234 and 422 m. Immature fish ranged from 4 to 13 cm in length and were present at all seasons. Of the mature individuals, males ranged from 7 to 17 cm and females from 7 to 21 cm. From autumn until spring, fish with gonads at various stages of maturation were present, although there were no specimens with mature gonads.

This study investigated the features of mudballs produced by male and female Uca annulipes. Both sexes formed mudballs from mud excavated from within the burrow during the final hour of the low tide period. Males placed the centre of the mudball aggregation and the furthest mudball significantly further from the burrow than females. These observations suggest that the placement of male mudballs was not simply a by-product of burrow excavation.

Amphipod traps baited with crab carrion caught significantly greater numbers of the specialist crab necrophage, Orchomene nanus in the South Basin of Lough Hyne than in the North Basin. The results can be explained with reference to the known distribution of crab species in the lough and also the hydrographical characteristics of the two basins.

Biological data are presented on two specimens of Taningia danae, an adult female caught by a trawler in Galician waters (north-west Spain) and a juvenile caught in a deep-water research trawl in Scottish waters (UK). The species has not previously been recorded in either area, although its presence has been inferred from beaks found in sperm whale stomach contents.

Time series of ichthyoplankton surveys targeted at herring larvae describe the distribution of spawning in the north Irish Sea by mapping the occurrence of very young larvae. The surveys suggest, that like other herring stocks, the spawning grounds of Irish Sea herring vary over the years. Currently, spawning at the Mourne location is greatly reduced whereas spawning has occurred at a newly described site to the north of the Isle of Man (off the Point of Ayre). Whilst spawning is dominated by autumn spawners in late September, some spawning occurs through to January.

At the period of sexual reproduction of the rhizocephalan parasite, Sacculina polygenea, the sacculinized crab, Hemigrapsus sanguineus, can serve as a temporary carrier for juvenile bivalve molluscs, Mytilus trossulus and Hiatella arctica as facultative epibionts. Such epizoans are never found on the crabs without the rhizocephalan externae or scars produced by the externae. The correlation between sacculinization and the bivalve epibionts is presumably due to maternal ‘brooding care’ with altering grooming behaviour of the crabs infested by S. polygenea.

This is the first report on the presence of basking sharks Cetorhinus maximus in Galician waters (north-west Iberian Peninsula) from sightings, strandings and incidental catches by fishing gear. Morphometric, biological, geographic and temporal data on 19 basking sharks recorded from 1988 to 1998 are presented. Average total length is 401·4 cm. Male:female ratio is 0·6. Seventy per cent of records are from incidental fishing catches in bottom gill nets. Approximately 74% of sharks were recorded during February, March and April, which may suggest that the species occurs seasonally in this area.

Evidence of sexual dimorphism in the mud-shrimp Upogebia stellata was observed in the abdomen length, total length, and also in the chelae. For the same carapace length, males had a shorter abdomen and, therefore, total length, whilst their chelae were larger and more robust than the females. Of the 91 U. stellata individuals examined, a single specimen was found to be of an intersex type, i.e. it exhibited both male and female external characteristics. Sexual dimorphism and intersexuality are discussed.