Two species of corophiid amphipods are described from the ‘Lucky Strike’ hydrothermal vent on the Mid-Atlantic Ridge near the Açores. One species, Bonnierella compar sp. nov. is new to science, the other, Autonoe longicornis has not been reported since the original description of a single female in 1909. Full descriptions are provided of the new species, and of the previously unknown male of A. longicornis.

The dietary compositions of Atherinomorus ogilbyi (Atherinidae), Sillago schomburgkii (Sillaginidae), Lesueurina platycephala (Leptoscopidae) and Ammotretis elongatus (Pleuronectidae) in three nearshore habitats on the lower west coast of Australia, which varied in their exposure to wave energy and the extent to which they contain sea grass, have been determined. The dietary compositions of these four abundant teleosts differed, reflecting marked differences between the location in the water column, head and mouth morphology and feeding behaviour of these species. Atherinomorus ogilbyi, which has a relatively high and large mouth, fed mainly on planktonic invertebrates in the water column, while S. schomburgkii ingested predominantly benthic prey, such as polychaetes and bivalves, which it extracted from the sediment using its downward-protruding mouth. Lesueurina platycephala employed its large mouth, cryptic coloration and ambush feeding to target relatively large teleosts and invertebrates, while the small mouth and flattened body of Ammotretis elongatus facilitated the ingestion of small crustacean prey, e.g. cumaceans and amphipods, which live on the substrate surface. Atherinomorus ogilbyi consumed predominantly calanoid copepods, cladocerans and insects during the day and mainly amphipods at night, when the latter taxon became abundant in the water column. The dietary composition of each species underwent a similar pattern of size-related change, being most pronounced in L. platycephala during the day. The diets of A. ogilbyi and S. schomburgkii, the two species for which the data were most comprehensive, differed among habitats and seasons, reflecting differences in the densities of their main prey. Comparisons between the day-time diets of the above four species with those recorded previously for a further four abundant species in the same habitats during the day, show that food resources are well distributed among the main fish species in nearshore waters along the lower west coast of Australia. This feature, together with the size-related changes in the diets of the different species, reduces the potential for inter- and intraspecific competition for food by fish species in this environment.

This study investigated the spatial distribution patterns of three shrimp species, Periclimenes holthuisi, P. brevicarpalis, and Thor amboinensis on the sea anemone Stichodactyla haddoni in the laboratory. Anemones were partitioned into five zones (mouth, inner tentacle, outer tentacle, upper column, and lower column), and shrimp distribution on these zones was determined. Regardless of species, significantly higher numbers of shrimps chose outer tentacles (>40%) over other zones during daytime. Such distribution might be attributed to their feeding practices as these crustaceans clipped and ate parts of the outer tentacles. Periclimenes holthuisi also showed varying temporal distribution patterns on their hosts. At night when anemones contracted their tentacles, shrimp moved in significant numbers from the outer tentacle region either to the column or off the anemones. Shrimps returned to the tentacles during daytime when anemones expanded their tentacles. Thus, spatial and temporal distribution of shrimps depend upon their feeding activities and degree of anemone expansion.

Fish assemblages associated with wave exposed and sheltered sides of breakwaters, and with adjacent sandy habitats were studied in western Calabria (Mediterranean Sea, south-western Italy). Overall, 26 fish taxa were recorded (21 associated with exposed breakwater sides, 21 with sheltered sides, and four with sand). Fish assemblages significantly differed between breakwaters (both sides) and sand, and, to a lesser extent, between exposed and sheltered sides of breakwaters in terms of whole assemblage structure, densities of species, and juvenile stages.

The Heteractis magnifica assemblage at the tip of the Sinai Peninsula was examined. The actinian size, location, and number of resident anemonefishes were recorded. The anemones were found at depths down to approximately 40 m and the sizes of clustering H. magnifica and clusters were positively correlated with depth. The shallow waters of the anemone assemblage contained few mainly small, solitary actinians. There seemed to be a tendency for solitary actinians to cluster once they reached a certain size-range. The resident anemonefishes Amphiprion bicinctus and Dascyllus trimaculatus were present in very large numbers (approximately 250 and 1800 respectively) and the A. bicinctus home range size was positively correlated with depth.

The lessepsian migrant Siganus luridus appeared along the shallower waters of the Pelagie Islands (central Mediterranean Sea). This is a new record of the species based on the capture of 40 specimens in Linosa Island during the summer of 2003. Some biological data are given and the relevance of this finding from the Sicily Strait is discussed.

A large caprellid amphipod recently discovered at a salmon farm in the Lynne of Lorne near Oban, Scotland, has been identified as Caprella mutica, a species indigenous to north-east Asia. The caprellid population appears to have become established in the last four years at the site with a high abundance of animals occurring year round on the farm nets, mooring ropes and on artificial experimental structures located <10 m from the fish farm. This paper briefly describes C. mutica found in Scotland. Application of Chapman & Carlton's criteria for determining introduced species suggests that C. mutica is non-indigenous to the area.

The identification keys of the zoeal stages of Pleocyemata decapod larvae from the coastal region of south-western Europe, based on both new and previously published descriptions and illustrations, are provided. The keys cover 127 taxa, most of them identified to genus and species level. These keys were mainly constructed upon external morphological characters, which are easy to observe under a stereomicroscope. Moreover, the presentation of detailed figures allows a non-specialist to make identifications more easily.

The reproductive biology of the king weakfish, Macrodon ancylodon, inhabiting the estuarine waters of the Río de la Plata (Argentina–Uruguay), was studied using macroscopic and histological analysis of the gonads. The samples were collected from commercial landings and from three research cruises carried out between 1999 and 2001. King weakfish is a multiple spawner with indeterminate annual fecundity. Spawning of this species extends from October to March with two main peaks of gonadal index in November and March. Based on the incidence of females with new postovulatory follicles, the evening near sunset was the estimated time of spawning for M. ancylodon. Spawning frequency, determined using the percentages of females with postovulatory follicles, was about 17% during March 2001, indicating that females spawn once every six days at the second peak of the reproductive season. Batch fecundity ranges from 12,400 to 225,700 hydrated oocytes and was fitted to a linear function of total length and ovary-free female weight. The number of hydrated oocytes decreased at the end of the spawning season. In addition, a decline in hydrated oocyte size and weight was also observed during this period.

Sperm whale social distribution was investigated in the Mediterranean Sea, using data collected during summer surveys from 1997 to 2002. Variations in the size of sperm whale schools/underwater aggregations were assessed using both visual and acoustic data. Individual body lengths were estimated acoustically, using the click inter-pulse intervals. Regional comparisons were undertaken, taking the 41° parallel as a north/south boundary. In the southern region, schools of up to seven sperm whales were sighted and calves were relatively frequent. The animals ranged between 8·6 m and 13·1 m long. In the northern region, school sizes were significantly smaller, with a maximum of three whales sighted at the surface. However, the acoustic survey showed that sperm whales form loose aggregations of up to five animals in certain areas. Whales detected in the north were 12·6 m long on average, and the body size range was relatively small. This summer survey demonstrated a segregation of males, in the north, from larger schools including calves, which seemed to be confined to the southern region.

Bathymodiolus thermophilus is a mixotrophic mussel capable of deriving nourishment from sulphur-oxidizing, bacterial endosymbionts in its gills and from suspended particulates through mucociliary feeding. These mussels become nutritionally stressed when removed from sulphide-rich fluid, but the dynamics of the host/symbiont relationship during this process are still not fully understood. Bathymodiolus thermophilus mussels were collected from an active and a waning hydrothermal site on the southern East Pacific Rise (EPR) and were removed from active venting for 12 d at a site on the northern EPR. Light and transmission electron microscopy showed that gill symbionts were lost from gill bacteriocytes in transplant mussels and that mussels exposed to longer periods of sulphide deprivation suffered deterioration of gill structure and body condition. There was no evidence to support the hypothesis of a shift toward reliance on photosynthetically derived organic material in mussels at the waning vent site.

A new species of pleustid amphipod of the genus Pleusymtes is described from the west coast of Ireland. It was found to be common in association with an Acanthogorgia sp. gorgonian at 725 and 900 m depth on coral habitats in the continental shelf-break areas of the Porcupine Seabight and Porcupine Bank. It is assumed to be a commensal due to its modified pereopod dactyls.

A study of Conger conger diet was carried out with 213 specimens from Irish inshore waters (0–200 m) collected from winter 1998 to spring 1999 and 96 from offshore waters (200–600 m) from spring to summer 2000. The primary diet in both areas was fish, with a complete species shift in diet between areas. The dominant species inshore were Merlangius merlangus and offshore Micromesistius poutassou. Decapod crustaceans and cephalopods were observed in stomachs, but contributed little to the overall diet.

Morphometric measurements were collected on red porgy, Pagrus pagrus, red seabream, Pagellus bogaraveo, and common dentex, Dentex dentex samples, from four countries along the south European Atlantic coast and the Mediterranean Sea (Portugal, Spain, Italy and Greece). Multivariate statistical analysis was used to discriminate populations. Stepwise discriminant analysis yielded a reduced variable set that identified significant differences among all four countries. The overall per cent-correct classification rate for the four samples from the stepwise discriminant analysis, based on 18 adjusted morphometric characters for Pagrus pagrus samples, and 14 (for both Pagellus bogaraveo and D. dentex) samples were 99·6%, 100% and 97·9%. There was a significant degree of morphological dissimilarity between countries (samples), for each species. A clear difference was displayed between the Atlantic and the Mediterranean samples, and a geographical gradient was found for the common dentex.

Over a period of five years (1997–2002) the euphausiid Thysanoessa inspinata has been recorded in plankton samples from the eastern Gulf of Alaska, as far north as 59°N. Until recently the northern limit of distribution of the species was assumed to be little further north than 50°N but the species is present in oceanic samples off the Alaskan continental shelf throughout the year and occurs regularly in the waters of the eastern Gulf.

Genetic variation was investigated in five subtidal locations from the north of San Matías Gulf (42°23′S) to the north of San Jorge Gulf (45°02′S). Fifteen loci were studied by means of vertical starch gel electrophoresis; ten loci were polymorphic. The percentages of polymorphic loci (P0·99 and P0·95 criteria) varied between 40% and 53·33% and between 33·33% and 46·67%, respectively. Expected mean heterozygosity per locus (He) ranged from 0·128 (Bajo Oliveira-El Sótano) to 0·160 (Puerto Madryn); this range is similar to those observed for other scallop species. All the loci were in Hardy–Weinberg equilibrium. The estimated genetic distances among populations were significantly lower than those reported for comparisons between populations of different pectinid species, suggesting that the five populations studied belong to the same species (Aequipecten tehuelchus). The absence of exclusive fixed alleles also supported that assumption. The results obtained suggest: (i) assignment of species or subspecies status to some morphological variants of the shells, like the ‘madrynensis’ form is not supported; (ii) the commercially exploited Tehuelche scallop from San Matías and San José Gulfs should be managed as distinct stocks.

Concentrations of elements in the sagittal otoliths of juvenile white anglerfish (Lophius piscatorius) from five locations in the north-east Atlantic were measured to test for evidence of segregation in the early life stages. The concentrations of some elements, notably copper, were different between locations. As such, the results suggest limited exchange between locations during some period of the early life history. The relevance of these results to our understanding of population structuring is discussed in relation to recent information on anglerfish movements and genetic structuring.

The pattern of somatic energy storage, measured as body lipid proportion, was investigated in the grass goby Zosterisessor ophiocephalus, by comparing the per cent lipids across three reproductive groups—large males (territory holding, caring for eggs, males), small males (sneaker males) and females—and across a seasonal phase including the entire breeding season and a post-reproductive period. Furthermore, the pattern of some indicators of somatic and reproductive investment, such as gonadosomatic index (GSI) and liversomatic index (LSI), was investigated, as well as the relationship between lipid content and fish body size was studied over time in both sexes. Results showed that the amount of somatic lipids depends largely on the different levels of reproductive investment shown by the breeding individuals. Females had the lowest levels of somatic lipids at the beginning of the breeding season when large males reached, by contrast, the highest levels. Large males showed a strong decrease in their reserves as the breeding season proceeded, and their replenishment was significantly slower than that of smaller males, which had relatively high levels already in September. Analysis of the trends of GSI and LSI revealed that the difference between females and males in the primary reproductive investment (gonadic mass) can explain most of the differences in the levels of somatic energy storage. The relationship between body size and lipid content changed over time, being positive and statistically significant at the beginning of the breeding season for each reproductive group, indicating that during these phases all the breeding individuals had accumulated energy in their tissues and that the breeding season reduced their somatic energy storage although with different intensity.

A single ovigerous female of Bythocaris cosmetops is recorded from the Bay of Biscay. This specimen is described and illustrated. This rare shrimp was previously known by a single specimen collected off tropical West Africa.

In July 2002 the southern hemisphere ascidian Corella eumyota was detected in the northern hemisphere for the first time, attached to floating docks in two harbours in north-western France: Perros-Guirec and Camaret-sur-Mer. Most individuals in the large clumps of tightly packed aggregations contained a clutch of brooded embryos in the atrial cavity, resting on the posterolateral epithelium overlying the ovotestis very close to the openings of the sperm duct and oviduct which are immediately adjacent to each other on the surface of the ovotestis, a morphological peculiarity not previously reported. These openings are far from the atrial siphon; it is possible that the species routinely self-fertilizes. The larvae are retained after hatching until they are competent to settle, resulting in a very short free-swimming larval period, limited dispersal, and a tendency for the larvae immediately after release to settle on the parent tunic or adjacent adults. It is hypothesized that individuals attached to some type of hard substrate were transported anthropogenically to France. Because the two harbours in which these nonindigenous ascidians were living are small, they probably represent secondary sites of invasion into France; the primary sites have not yet been identified.