The role of habitat structure in controlling the composition of assemblages has often been studied, but is rarely manipulated so that it is distinguishable from other factors. Differences in habitat structure as determined by differences in mussel size structure may affect the diversity of assemblages associated with mussel beds. Previous studies examining the effect of the size of individual mussels in a patch on the diversity of associated macro-faunal assemblages confounded the age of the patch with the size of the mussels. We manipulated the age of mussel patches and the size of the mussels within them to test experimentally whether the size of mussels influenced the structure of associated assemblages. At one of the two locations considered, the structure of macro-faunal assemblages in patches of larger mussels differed significantly from those in patches of the same age composed of smaller mussels. At this location, the size of mussels did not affect species richness but the abundance and proportion of organisms present differed depending on the size of the mussels. Here patches of larger mussels contained greater numbers of Nematodes and Oligochaetes and a lower abundance of taxa such as Jaera forsmani and Lepidonotus clava. We also found that invertebrate assemblages in general differed between the two locations. The effect of the size structure of mussels, however, varied spatially demonstrating that the effect of habitat structure on the diversity of associated assemblages is context dependent.

The ribosome is the location of protein translation and therefore a pivotal macromolecular complex for all organisms. The RNA molecules involved in the formation and functioning of the ribosome (rRNA) are partially single-stranded (loops) and partially double-stranded (helices or stems) as a result of pairing of complementary regions in either their own or other rRNA subunits. This pattern provides the rRNA with a secondary structure crucial for its functionality. The stability of these secondary structures is mediated by their base compositions: a helix rich in G-C pairs possesses a higher thermodynamic stability than an A-T rich counterpart. However, the base composition of these structures is neither homogeneous throughout the molecule nor throughout the demosponge taxa. Here, we present patterns of biased nucleotide composition in demosponge 28S rDNA. We analyse their correlation in respect to environment and taxonomy. We find significantly higher G+C contents in haplosclerid demosponges compared to other orders and investigate evidence for an association between water temperature and rRNA base composition in demosponges.

The present study attempts to give timely information on the resource partitioning between the lessepsian migrant Siganus luridus and two ecological native analogues, Sarpa salpa and Sparisoma cretense. Sampling was carried out in concomitance with the first record of Siganus luridus in Linosa and fish were caught simultaneously, allowing direct comparison of diets. Gut-contents analyses provided a snapshot of the feeding habits of the three species: Siganus luridus fed on 34 taxa of benthic algae (mostly represented by Dictyota dichotoma) and a total of 27 taxa was identified in the stomach of Sarpa salpa, with the predominance of Sargassum vulgare. For the first time, a detailed picture of Sparisoma cretense diet was given (N=22 taxa of identified algae) albeit, due to the high percentage of digested food, this species was excluded from gut-content comparisons. A certain resource partitioning between Siganus luridus and Sarpa salpa was resolved on the basis of trophic indices and multivariate analyses, these latter also highlighting a more dispersed diet for Siganus luridus with respect to Sarpa salpa. Isotopic signatures were important towards defining the trophic level of the three species and particularly of Sparisoma cretense, whose gut-contents analysis was only partially informative. The values of δ15N confirmed a strictly vegetal diet for Siganus luridus and Sparisoma cretense while Sarpa salpa was significantly more enriched. According to δ13C, observed values matched the predicted ones for Siganus luridus and Sarpa salpa while both species presented less enriched δ15N values than expected.

Surface longline targeting mainly swordfish is considered a major threat for loggerhead turtle populations in the western Mediterranean Sea. For this reason, it is necessary to analyse the relationship between the characteristics of longline sets and loggerhead turtle by-catch. The objective of this study is to look for differential spatial distribution of loggerhead turtle and swordfish captures along the longline to gain insights that might be useful to diminish unintended, incidental catch of turtles without affecting the captures of the target species.

Longlines are divided into transects separated by two consecutives buoys. During the 1999 fishing period of the traditional (without roller) Spanish surface drifting longline fleet (August to November), 59 technically homogeneous fishing operations, composed of 23 sections each, were observed. Chi-square test was used to compare loggerhead turtle and swordfish distributions among transects with those expected at random. Significant differences were obtained only for loggerhead turtles, with 93% of the specimens caught in the second half of the longline transects, which were retrieved from the sea during daytime. Significant differences were not found for the swordfish along the whole longline or for loggerhead turtle captures retrieved during daytime. We conclude that swordfish captures are independent of retrieval time whereas the incidental catch of loggerhead turtles occurs mainly during daytime, probably because loggerhead turtles use vision to locate baits.

The acorn barnacle Balanus glandula (Darwin 1854) is native to the Pacific coast of North America and was accidentally introduced in Argentina in the early 1970s. Here the invasion status of this species is reviewed in the south-western Atlantic focusing on geographical patterns of density, cover, biomass, size and recruitment, and also estimating its rate of spread. Field surveys along rocky shores and a literature review show that B. glandula invaded most of the rocky shores of Argentina at a high rate of spread. Density and cover of barnacles do not follow a latitudinal trend; instead both variables show a bimodal pattern with the highest values in two distant locations (Puerto Lobos and Bahía Bustamante). However, the size of the barnacles increases with latitude, and is positively related to biomass. Recruitment of this species varies between wave exposed and protected areas, and over time. At lower latitudes barnacles recruit in winter, while at higher latitudes they recruit in spring and summer. The differences observed in density and recruitment suggest that along the Argentinean coast, oceanographic processes have a stronger influence in the distribution and success of the barnacles than the gradient in wave exposure. Balanus glandula is a successful invader which has completely re-shaped the native intertidal landscape. Moreover, considering the wide temperature range that this barnacle tolerates in native and invaded regions, the entire coastline of South America could be colonized by this species in the future.

The genus Tethya represents a large cosmopolitan group of 81 recognized and a significant number of additional, still undescribed sponge species. The phylogenetic relationships within this old taxon are almost unknown. This is represented by the fact that several species are regarded as cosmopolitan. However, some of them might represent groups of closely related but distinct species. Using molecular and morphological characters, we aimed at a fundamental phylogenetic study for the genus Tethya, evaluating an existing morphological matrix and the cytochrome oxidase subunit I (COI) as a molecular marker. Intending to create a basic phylogenetic framework for the genus we selected a number of species from main biogeographic regions covered by Tethya species: from the Mediterranean Sea (T. citrina and T. aurantium), the northern European seas (T. citrina, T. norvegica and T. hibernica), the western Atlantic (T. actinia), the eastern Pacific (T. californiana), the Indo-Pacific (T. seychellensis) as well as three species of unknown biogeographical origin, originally described from aquarium habitats (T. wilhelma, T. gracilis and T. minuta). Both the morphological matrix, consisting of 29 characters and 131 character states, as well as the molecular matrices (COI nucleotide sequences of 658 bp as well as deduced amino acid sequence of 219 aa), resolved major biogeographical subgroups within the genus. However, the nucleotide based matrices revealed a higher resolution. Two major branches seem to have diverged early: an Indo-Pacific (T. seychellensis, T. wilhelma, T. minuta) and a Pan-European clade (T. citrina, T. norvegica, T. hibernica). For T. aurantium as well as a North-American group (T. californiana, T. actinia and T. minuta) our results are not conclusive. The morphological character set will have to be re-evaluated to gain a higher phylogenetic resolution. The addition of more species to our basal phylogenetic framework will allow analysing the evolution of the various biogeographical subgroups in the genus Tethya.

The harbour porpoise is the only resident cetacean species in the German Baltic Sea. Within the last several decades this harbour porpoise stock declined drastically, causing deep concern about its status. Plans of the German government for proposing Marine Protected Areas (MPAs) to implement Natura 2000 and for assessing the impact of offshore windmill constructions on the marine environment led to an increased research effort on the harbour porpoise in German waters. For the first time, long-term passive acoustic monitoring has been conducted in the German Baltic Sea from the Kiel Bight to the Pomeranian Bay from August 2002 to December 2005. Porpoise detectors (T-PODs) have been installed five to seven metres below the water surface at up to 42 measuring positions throughout the investigated area, registering the exact times of echolocation signals of passing harbour porpoises. The proportion of monitored days with porpoise detection in each quarter of the years has been analysed. A correlation of the results with the longitude of the measuring position revealed a significant decrease from west to east in the percentage of days with porpoise detections. Comparison of data gathered in the first quarters with the third quarters of the monitoring years displayed a seasonal variation with fewer days of porpoise detections in winter time than in summer time. Nevertheless, harbour porpoises have been detected year-round at most of the measuring positions in the German Baltic Sea. The present study clearly indicates a regular use of the German Baltic Sea by harbour porpoises with a geographical and seasonal variation in the usage of the German Baltic Sea. The larger numbers of harbour porpoise detections in spring to autumn compared with winter suggests that the German Baltic Sea is an important breeding and mating area for these animals.

The feeding habits of Euthynnus alletteratus and its variations compared to predator size in the central Mediterranean Sea were investigated. The stomach contents of 187 specimens were analysed, ranging from 26.8 to 50.3 cm total length, caught by authorized experimental drift-nets. The difference in food items found in the stomachs was evaluated by occurrence of prey frequency, prey weight, and prey abundance; these criteria were used to calculate an index of relative importance. Fish were the dominant food detected according to all numerical indicators examined and were mainly represented by Maurolicus muelleri and larval stages of teleosts. Hyperiid amphipods, dominated by Anchylomera blossevillei and Phrosina semilunata, were well represented in terms of frequency of occurrence. Variations in the diet composition compared to fish size were observed. Comparative analysis performed on prey abundance highlighted a trend of increasing predator size-classes among prey items. The specimens of the smallest sizes ate mainly adult clupeiforms and larvae or other juvenile teleosts. As fish grew, there were increased amounts of adult teleosts, crustaceans (hyperiids and isopods) and cephalopods. Maurolicus muelleri was the most important prey for the largest specimens analysed. Significant differences among size-classes, both in prey abundance and in prey weight, were confirmed by non-parametric multivariate analysis of variance (NP-MANOVA).

To assess whether Mytilus edulis is selective in its secretion of byssus threads and entrapment of gastropods, experiments were conducted in laboratory aquaria and in the field. Exposure to dogwhelks (Nucella lapillus) or their effluent induced mussels to produce twice as many byssus threads as mussels exposed only to winkles (Littorina littorea) or those exposed only to seawater. There were no significant differences among treatments in the area over which byssus threads were secreted. Significantly more byssus threads were attached to the shells of dogwhelks than to winkles. Laboratory experiments produced broadly similar results to those in the field, but the level of response in the laboratory was greater. It is concluded that byssus threads were attached selectively to dogwhelks and that they may serve as a defence against predation.

Gut content and stable isotope analyses were used to investigate the feeding habits of loggerhead sea turtles (Caretta caretta) inhabiting the Balearic archipelago. Turtles caught in the pelagic realm (δ13C: -16.0±0.6‰ and δ15N: 8.5±0.9‰) and turtles caught on the continental shelf (δ13C: -16.7±0.6‰ and δ15N: 8.4±1.3‰) did not differ in their isotopic signatures, suggesting that their diets include the same prey types. A mixing model revealed that for the turtles here analysed, squid and the jellyfish Cotylorhiza tuberculata were the most relevant prey, although stomach contents analysis revealed that carnivorous jellyplankton, neuston, fish and other cephalopods were also consumed. Gut content analysis also indicated that most of the prey identified, including all fish and most cephalopods, were of pelagic origin. Thus, loggerhead sea turtles inhabiting central regions of the western Mediterranean appear to seldom exploit benthic prey, even while on the continental shelf.

The effects of algal diet on larval survival and growth of the barnacle Amphibalanus improvisus was for the first time examined under controlled laboratory conditions. Larvae were obtained by dissecting egg lamellae at later developmental stage out of the adults. Hatched nauplii were reared in 0.6-l glass beakers (200 larvae l-1) on a monoalgal diet of Chaetoceros calcitrans, Chlorella vulgaris and Scenedesmus quadricauda at 1x105 and 2x105 cells ml-1, under continuous light at 25 ±1°C. The rate of development, survival and size (at Stage V) of the larvae were measured for each diet. The majority of nauplius II larvae (~70%) fed with Cha. calcitrans and Chl. vulgaris developed into cyprids within seven days while those fed with S. quadricauda remained at Stage II. A shorter time interval for Stage II to III was observed in larvae fed with a Chl. vulgaris monoalgal diet than Cha. calcitrans. Larvae fed with Cha. calcitrans had shorter developmental intervals for later larval stages (Stages IV–VI). The highest mortality was observed in the treatment with a monoalgal diet of S. quadricauda, while the highest survival was achieved with a diet of Cha. calcitrans. The mixed diet of Cha. calcitrans, Chl. vulgaris and S. quadricauda resulted in a shorter developmental duration of larval cycle (six days). Both food type and food concentration significantly affected the length and width of the nauplius larvae.

A total of 235 bullet tunas (Auxis rochei) was caught off the north-eastern coast of Sicily between March 2003 and March 2004 for the purpose of studying their feeding habits. The fish were caught by means of an experimental surface gill-net during fishing surveys carried out on a monthly basis. The stomach contents were analysed and the prey identified, counted and weighed. The importance of the different prey types was assessed utilizing several feeding indices while possible size-related changes of the diet composition were highlighted by means of hierarchical cluster analysis, nMDS and SIMPER analysis. The results of this study showed that the bullet tuna is an epipelagic off-shore predator feeding on whatever abundant resource is available in the environment with a preference for planktonic crustaceans, small cephalopods and fish larvae. Among crustaceans, hyperiidean amphipods were the most important prey, with Anchylomera blossevillei as the dominant species, followed by the euphausiacean Stylocheiron maximum. Among cephalopods, Heteroteuthis dispar was recorded frequently while fish larvae showed high values of all indices. All prey were pelagic organisms. A size-related change in the diet composition was observed, even if it seemed related to the temporal fluctuations of the zooplanktonic assemblage in the environment. The average prey weight per stomach increased significantly in the larger predators which mostly fed on fish larvae belonging to several commercially important demersal and pelagic species.

Cuvier's beaked whale is a poorly-known species. It has been considered common since 1980 in the Pelagos Sanctuary (north-western Mediterranean Sea), but it has hardly been studied, chiefly due to difficulties in sighting. Stranding data indicates that the beaked whale is present all along the Ligurian coast. As with any deep-diving odontocete, Cuvier's beaked whale feeds mostly on deep-sea squid, but also on some fish and a small number of crustaceans. As a consequence, it is thought to be found mainly in waters deeper than 1000 m, where the sea bed has a particular slope. The aim of this work is to analyse a large quantity of sightings in order to define the favoured habitat of the beaked whale. Topographic features such as depth, depth gradient and bathymetric anomaly were analysed due to their direct influence on the prey of Cuvier's beaked whales. Data were registered between Genova and Imperia, from 2000 to 2006. Two hundred and forty-seven sightings were recorded, a total of 532 whales. The mean herd size observed was 2.3±1.5 (range=1–11). For 40 sightings, the group composition was divided into maturity categories, using results obtained by photo-identification. Seventeen groups consisted of purely immature animals, and 4 groups consisted of only mature animals. The 19 mixed herds were composed mainly of 4.0±2.2 individuals (range=2–8) and consisted of 58% mature individuals. The 17 immature groups consisted of 2.1±0.9 individuals. Mature animals were usually found alone. Forty-eight per cent of beaked whales were seen where the depth was between 756 and 1389 m but the encounter rate was higher between depths of 1389 and 2021 m. The sightings were more frequent (34%) where the sea floor slope was between 31 and 51 m/km but the encounter rate was higher where the sea floor slope was between 11 and 31 m/km. The encounter rate for Cuvier's beaked whales was higher where the depth anomaly was positive with values between 342 and 586 m.

Sponges (Phylum Porifera) are among the most ancestral metazoans and are frequently difficult to identify, even by taxonomic experts, due to their lack of complex morphological characters. However, poriferans are highly diverse, ecologically important and of significant importance to pharmaceutical and biomaterials industries. Therefore, means of unambiguous identification are urgently needed. A DNA taxonomic system, and in particular sponge DNA barcodes, will provide a set of indispensable tools to aid taxonomists and ecologists in the rapid identification of sponge species, which will enhance the discovery of drug-producing species. Here, we will argue for the implementation of a DNA supported taxonomic system and introduce the Sponge Barcoding Project.

Molecular analyses of 13 species of the marine bivalve family Thyasiridae, using sequences from 18S rRNA and 28S rRNA genes, showed that the family is monophyletic despite the anatomical disparity and inclusion of both chemosymbiotic and asymbiotic species. This new analysis also confirmed that the three families (Thyasiridae, Lucinidae and Ungulinidae), previously included in the Lucinoidea, were not closely related. Four species of Ungulinidae grouped within a clade containing Veneridae, Arcticidae and Mactridae. In relation to a range of other heterodont bivalves, Thyasiridae occupied a near basal position, apart from a clade comprising Carditidae/Astartidae/Crassatellidae. The earliest thyasirid recognized in the fossil record is a species from the Lower Cretaceous of England. Within the Thyasiridae, some groups can be identified but relations between these are weakly supported. Amongst the taxa analysed, those with symbiotic bacteria and two ctenidial demibranchs belong to at least three groups, while there is some support for a clade of asymbiotic taxa with single demibranchs. In recognition of the monophyletic status of the Thyasiridae, distinct from all other heterodont bivalves, we elevate the rank to superfamily Thyasiroidea.

Daily censuses of the hawksbill turtle Eretmochelys imbricata were taken during the nesting seasons 1995–2001 in three sandy beaches of the Yucatan Peninsula, Mexico (Celestun, El Cuyo and Isla Holbox), to evaluate aspects of its reproductive biology. A total of 9059 hawksbill turtle clutches was estimated for the study period. Nesting seasons began in mid-April and ended in early September, peaking in May–June. No significant differences were detected in the mean number of clutches per km among beaches. The largest number of clutches was observed in the supralittoral zone (6341: 70%), followed by the dune (2491: 27.5%) and the intertidal (227: 2.5%) zones. Variation in number of clutches showed a main peak in 1999, decreasing in 2000 and 2001. A significant decrease (3 cm) in body size of nesting females was detected between 1995 and 2001. Mean clutch size was 140 eggs/clutch, and a significant positive relationship between curved carapace length and mean clutch size was found at the three beaches. Incubation period, hatching success and emergence success varied between years (lowest values in 1998) and beaches (highest values at Isla Holbox), with no significant differences between the supralittoral and dune zones. Even though there was no evidence of a decreasing trend in nesting activity for the study period, the decrease in 2000–2001 suggests that additional beach monitoring is necessary to identify long-term trends, and to reduce potential losses of nests by human and natural causes in this globally important region for the hawksbill turtle.

Weights of kidneys, heart, lungs, liver, adrenals, eyes and tongue of the northern form of franciscana (Pontoporia blainvillei) and the estuarine dolphin (Sotalia guianensis) incidentally caught in fishing nets are presented and related to total body weight. Because of the smaller body size of the northern form of P. blainvillei, its actual organ weights were all smaller than those of the southern form reported in the literature. However, the lungs and adrenals of the northern form were proportionally greater than those of the southern form. The relative weight of the males' left kidney (N=18) and females' liver (N=17) were significantly heavier in this study than the proportions presented elsewhere in the literature for the southern form of the species. However, the females' kidneys, males' right kidney and males' liver did not differ between the northern and southern forms, and a larger number of individuals of both geographical forms should be analysed. The actual weights of the S. guianensis internal organs were all greater than those reported in the literature for S. fluviatilis. Additionally, the body-to-organ mass proportions of kidneys, heart and lungs of S. guianensis were also greater than those of S. fluviatilis. This study provides comparative data that can be used when examining the systematics of both species and provides a baseline for future examinations of the post-mortem conditions of these cetacean species.

The Marine Protected Area in Gilbert Bay, Labrador is the first established in the subarctic coastal zone of eastern Canada. A standardized survey of the fish fauna of Gilbert Bay was initiated during the ice-free season of 2004 to provide baseline information on the fish present in water less than 15 m deep. Beach seines and gill-nets sampled three management zones within the bay which are afforded different levels of protection from human activity. The 25 species in 15 families recorded belong to five ecological guilds: (1) estuarine and marine fish resident in the bay; (2) anadromous species transiting the bay; (3) marine species which migrate into the bay to spawn; (4) offshore-spawning marine fish for which the bay is a nursery area; and (5) marine species which occasionally migrate into the bay to feed. Gilbert Bay lies in a transition zone between Arctic and cold-temperate biogeographical provinces, and its fish fauna is dissimilar from a cold-temperate fish assemblage described for Trinity Bay in eastern Newfoundland.

Here I record the cleaning activity of the occasional cleaner Diplodus argenteus at rocky reefs off southern Brazil. Diplodus argenteus juveniles are referred to as occasional cleaners, but there is no further description of their cleaning activity in the literature. Only two fish species were here recorded as clients, which I hypothesize to be related to a lack of visual attractiveness of D. argenteus cleaning services.

Crab species had not been exploited until recently in the San Matías Gulf. An experimental trap fishery plan was developed to provide information on the feasibility of their potential extraction. Sampling was carried out using an artisanal shellfish boat in the San Matías Gulf. Nine baited traps, three of each type (cubical, tubular-conical and tubular-pyramidal) were intercalated along a master line. The total number of crabs of each species caught was compared among lines (N=27), types of trap and soaking times (6, 24 and 48 h). A total of 137 traps of 243 traps employed caught crabs. More crabs were caught in the cubical traps than in the other types. Comparisons of numbers of crabs among lines allowed identification of areas having different relative abundances, with an average of 3.56 crabs per trap. The catch of Ovalipes trimaculatus was significantly greater in lines on the 10-m isobath. Two lines, on the 50-m isobath, showed the best results for Platyxanthus patagonicus. The total number of crabs per trap obtained during a soaking time of 6 h was significantly less than the number caught with longer soaking times. Only individuals exceeding 50 mm in carapace width were caught. The size-frequency distributions differed significantly between sexes for the two species, with males larger than females. In O. trimaculatus, males made up 29% of the catch and the remainder was constituted of non-ovigerous females; mean carapace width was 92.93 mm for females and 105.93 mm for males. Forty per cent of P. patagonicus were males (mean carapace width: 99.33 mm). Females bearing eggs amounted to 45% of the total females. Females' mean carapace width was 90.58 mm. Based on the results obtained, preliminary suggestions for management of a potential fishery for these species are made within a precautionary approach.