This study monitored the abundance of the tropical/subtropical seaweed Caulerpa sertularioides (Chlorophyta: Bryopsidales) from a sandy beach from Balandra Cove, on the south-eastern coast of the Baja California Peninsula, Mexico, between April 1998 and April 2000, including consecutive El Niño and La Niña events. El Niño conditions, indicated by relatively high seawater temperatures, were associated with a high population abundance (April–June 1998), whereas La Niña conditions, indicated by relatively low temperatures, were associated with the absence of C. sertularioides (April–June 1999 and April 2000). Caulerpa sertularioides was present during other times of the year during the study period, but never with the high abundance reached during El Niño conditions. Seaweeds of temperate affinity occurring in Baja California, such as Gelidium robustum (Rhodophyta: Gelidiales) and Macrocystis pyrifera (Phaeophyceae: Laminariales), decreased sharply in abundance during El Niño conditions. Therefore, the biogeographic affinity of seaweeds from Baja California might be helpful in predicting the effects of El Niño and La Niña on their abundance, with implications for resource management and for the prediction of the effects of long-term oceanographic changes on seaweed distribution.

Fresh weight (FW), dry weight (DW), carbon and nitrogen content were measured for specimens of Laminaria saccharina (Heterokontophyta: Phaeophyceae) sampled in the eastern English Channel in order to conduct a biometrical study. The aim was to relate carbon and nitrogen masses of the algae to a simple and rapid morphological measurement of the total length of the sporophyte. These relationships were highly significant and appeared very useful to express the standing biomass of L. saccharina in terms of carbon or nitrogen and then to consider dynamic processes such as primary production. Variations in tissue carbon (C) and nitrogen (N) were examined over a complete seasonal cycle. Average carbon and nitrogen content ranged from 23·9 to 31·4% and 2·23 to 3·42% of the total dry weight, respectively. Variations in C/N ratio showed a clear seasonal pattern with an increase in the early spring corresponding to strong photosynthesis and growth.

The composition in terms of protozoan functional groups of three sublittoral areas (Castro Urdiales, Santoña and Isla) in the Cantabrian Sea was analysed. The different protozoan species were identified, and their density and biomass was measured. The pigmented protozoa were the most important group in the three areas throughout the year, followed by the bacterivores in Castro Urdiales and Santoña, and the non-selectives in Isla. Bacterivores constituted the most significant group in terms of biomass, after which came that of non-selectives. The parameters with the strongest influence on distribution in functional groups (respect to biomass) were pH, phosphate, organic matter and bacterial biomass, other significant factors being salinity, nitrate and mean grain size. Functional groups expressed as number of species were affected principally by phosphate, pH and, to a lesser extent, temperature and salinity. Statistical analysis using the present data, data regarding functional groups from previous studies in the same areas, and data from other areas, indicate that marine areas show similar characteristics. In the areas covered by the present study, there was a decrease in the number of algivore species and a rise in non-selective species, while bacterivores and pigmented protozoa maintained similar values. In comparison, freshwater areas showed noticeably lower percentages of algivore species and a significantly higher number of bacterivore species.

Developmental stages of a haemogregarine were found within polychromatocytes and erythrocytes in Giemsa-stained blood smears from six evileye pufferfish (Amblyrhynchotes honckenii) caught at Koppie Alleen in the De Hoop Nature Reserve, South Africa. This unusual haemogregarine, Haemogregarina (sensu lato) koppiensis sp. nov., was characterized by encapsulated gamonts with recurved tails, features more common in haemogregarines infecting amphibian and reptilian erythrocytes than in those from fish. Haemogregarina koppiensis is only the third species of fish haemogregarine to have been described from South Africa.

Freeliving marine nematodes were sampled on two occasions from an extensive grid of 20 stations in the Bohai Sea and its approaches. Differences within stations between sampling periods were small, resulting from small changes in abundance of dominant species. Differences between stations were significant, and were used to cluster stations into groups with similar species composition. These station groupings revealed a weak faunal gradient leading from the mouth of the Huanghe (Yellow River) to the Bohai Strait. Analyses relating faunal composition to environmental variables showed that there were significant differences in environmental variables between faunally-defined groups of stations. The variables most closely correlated with community structure were silt/clay and sand, depth, phaeopigment concentrations below the sediment surface, organic content and arsenic. These reflect natural processes within the Bohai Sea. A suite of univariate measures were related to distance from the river mouth, with a major discontinuity about 120 km into the Bohai Sea. Comparison of values of the biodiversity measures average taxonomic distinctness (Δ+) and variation in taxonomic distinctness (Λ+) suggest that the meiobenthos of the Bohai Sea as a whole is not under major pollution stress.

Terebellomorpha is a clade of predominantly tube-dwelling polychaetes, some of whose species are very abundant and whose habitats range from shallow to very deep waters. The group contains five families (Terebellidae, Ampharetidae, Pectinariidae, Trichobranchidae and Alvinellidae). This study of their inter-relationships uses DNA sequence data from five gene segments. Including outgroups, sequences were available for 15 species for 15 U2 snRNA, 14 for Histone H3, 23 for the D1 expansion region of 28S rDNA, 15 for the D9-10 region of 28S rDNA and 17 for subunit I of cytochrome oxidase. Outgroups included representatives of the polychaete families Cirratulidae, Sabellidae and Siboglinidae, and the clitellate Lumbricus. These sequences include eight GenBank entries for 28S D1 and one for CO1.

Generally, and in all analyses restricted to the data collected in this laboratory, but including all of these, Terebellomorpha is monophyletic. Within Terebellomorpha, the single maximum parsimony tree indicates that Alvinellidae (all data from GenBank) belongs to a clade with Terebellidae and some Trichobranchidae, contradicting morphological expectations. Terebellidae is paraphyletic with respect to Trichobranchus, this being associated with the subfamily Thelepodinae. The second trichobranchid genus Terebellides (for which only 28S D1 data is available from GenBank) is topologically very distinct to Trichobranchus. Additional data are needed to establish the family's monophyly. Also within Terebellidae, subfamily Terebellinae is paraphyletic with respect to Polycirrinae, supporting the suggestion that this subfamily's morphological simplicity is derived.

The naupliar development of the barnacle Balanus spongicola is described, from larvae reared in the laboratory. The planktotrophic nauplii of B. spongicola reached the cyprid stage 11 days after hatching, at 20°C, and only eight days after hatching, at 25°C. Larval development includes six naupliar and one cyprid stage, following the typical pattern of the thoracican Cirripedia. Naupliar stages have a broad pear-shaped cephalic shield with a straight anterior margin and a pair of fairly short posterior spines in stages IV–VI. Dorsal and marginal spines are absent. Frontolateral horns are of medium length, directed forward from stage III. Small teeth on the median labral lobe found in some warm-water species are only weakly pronounced. The arrangement of abdominal spines and larval setation are in the usual balanoid pattern. The larvae of B. spongicola share some features with earlier described nauplii of Solidobalanus fallax, a non-native UK species inhabiting British waters. Balanus spongicola, however, possess more typical balanoid larvae. Its nauplii are more elongated (the cephalic shield is longer than broad). Thoraco-abdominal processes and posterior shield spines in B. spongicola are shorter than those in S. fallax. The abdominal process remains shorter than the dorsal thoracic spine until stage VI in B. spongicola but becomes nearly equal in S. fallax.

The pedunculate barnacle Koleolepas avis is a symbiont of the sea anemone Calliactis japonica, which lives on gastropod shells carried by large hermit crabs, usually Dardanus arrosor. Relationships with the host sea anemone, distribution on the gastropod shell, left–right asymmetry and reproduction of the barnacle were investigated. A larger number of barnacles occurred on shells with greater ‘cylindroid dimensions’ of sea anemones. Distribution of barnacles on shells was not random: assuming the in situ position of the shell carried by the hermit crab (∼45° inclination), there were more barnacles along the lower part of the anemone disk than the upper part. Large barnacles lie on either the left or right sides of their capitula, and those lying on the left side (Type L individuals) tended to occur along the left side of the host, and those on the right side (Type R) along the right side. Barnacles [ges ]0·016 g in wet weight had egg masses, and there was a positive relationship between body weight and number of eggs. Koleolepas avis has both hermaphrodites and dwarf (complementary) males attached to them. Large hermaphrodites tended to have larger dwarf males than smaller hermaphrodites.

The population structure of the deep-sea sponge-associated shrimp Spongicola japonica was investigated, and the mechanism of pair formation analysed from field samples. The composition pattern of shrimp in host sponges was divided into three patterns by sex and number as follows: solitary, a solitary inhabitant; sexually paired, a pair with a male and a female; grouped, multiple individuals excluding those designated as sexually paired. Juveniles usually remained grouped or solitary in a host cavity until the size at which gonadal maturity starts. Before forming sexual pairs, shrimp appear to have a free-living period outside the host, when the ovarian stages of females correspond to early to late vitellogenesis. Re-invasion is just before the first spawning, when females are in the ovarian stage of late vitellogenesis.

Burrow morphology and mating behaviour of Upogebia noronhensis was studied using resin casting of burrows in the field and observation of laboratory maintained animals. Burrows of U. noronhensis showed a typical Y-shaped pattern in over 70% of the cases analysed. The remaining 30% comprised U-shaped burrows lacking the lower tunnel (shaft) and burrows with long additional branches projecting from the U portion. Results from animals left to construct burrows in the aquarium closely matched those found in nature. Field and laboratory burrows showed that different shapes are related to the collapse of the burrow walls, the burrowing activities of other individuals and species, and to the behaviour of the species itself. U-shaped burrows form as a result of the partial construction of the burrow (the U part is always built first) or owing to the collapse of the shaft. Burrows with additional branches always belonged to males and result from their search for a female with which to reproduce. This process also produced connected burrows. Mating occurs within the female burrow and this is the only time when two animals occupy the same burrow. After mating, the male returns to its burrow and immediately closes the connection. Larvae are planktonic and probably settle in adult areas, since the smallest juvenile burrows were always associated with adult burrows. This may contribute to the high population densities found in the field (∼200 ind m−2), which in consequence facilitates fossorial encounters for reproduction. This is the first time fossorial encounters for reproduction are reported for an Upogebia species and probably for all Thalassinidea.

Weight–length relationships of some of the most abundant bivalve species from the Algarve coast (southern Portugal) captured during several exploratory fishing surveys carried out during 2000 on a soft bottom in the subtidal zone down to 25 m depth are reported. For this study a total of 7429 individuals were sampled, belonging to 25 bivalve species in nine families. The most represented families were Mactridae and Veneridae with six species, immediately followed by the families Cardiidae (five species) and Donacidae (three species). The results revealed that most species presented isometric (11 species) or positive allometric relationships (11 species), while only a small minority of species displayed negative growth (three species).

The annual pattern of burial depth in natural populations of the infaunal bivalves Tagelus dombeii (Tellinacea) and Venus antiqua (Veneracea) is described in relation to annual food availability in both the water column and the sediment and abiotic factors (temperature and salinity) at Coihuín tidal flat, in southern Chile. A field experiment in which burial depth was measured in situ each month (over 14 months), with the aid of a fixed-length nylon thread attached to the shell. For T. dombeii the results showed a significant increase in burial depth with increasing bivalve size and syphon weight. Tagelus dombeii had a mean burial depth of 17·5 cm, which was three times more than in V. antiqua (5·30 cm). The burial depth dynamics for both species displayed a strong correlation with food availability in the water column. Approximately 60% of the variability in burial depth in T. dombeii and V. antiqua was explained by concentration of chlorophyll-a in the water column. Food concentration on the sediment surface did not effect burial depth, i.e. deposit feeding seems to be of minor significance in either species.

Specimens of the chemoautotrophic symbiont-bearing hydrothermal vent clam Calyptogena pacifica were collected from hydrothermal vents at the Endeavour segment of the Juan de Fuca Ridge. Total lipid was extracted from gill, foot and mantle tissues, and lipid class and fatty acid composition determined by thin layer chromatography with flame ionization detection (TLC–FID), gas chromatography (GC) and gas chromatography with mass spectrometry (GC–MS). An abundance of n–7 monounsaturated fatty acids (MUFA), especially in the gill, reflected the large contribution of chemoautotrophic symbiotic bacteria to the nutrition of this clam. The absence of n–8 MUFA suggests that C. pacifica does not contain methanotrophic symbiotic bacteria. Low levels of highly unsaturated fatty acids (HUFA) such as 20:5 n–3 and 22:6 n–3 were detected in C. pacifica and their presence is attributed to a source other than chemoautotrophic symbiotic bacteria. Significant levels of non-methylene interrupted dienoic fatty acids and eicosatrienoic acid (20:3) were also detected in C. pacifica and it is suggested that these fatty acids are synthesized from n–7 MUFA as alternatives to HUFA. In contrast to shallow water bivalves, elevated levels of triglyceride were detected in the gills compared to the mantle.

Large numbers of small individuals (pediveligers and juveniles <5 mm) are routinely recorded in size–frequency distributions of mussel samples collected from deep-sea chemosynthetic environments. If recruitment of invertebrates to deep-sea hydrothermal vent sites were via long-distance dispersal, as is typically assumed, one would expect recruitment ‘events’ recorded in size–frequency distributions to be difficult to detect, due to loss of larvae in an open system over large distances. If one imposes mesoscale oceanographic phenomena that minimize dilution of larvae (such as eddies shed from hydrothermal vent plumes) and episodic spawning, expression of this mesoscale corralling at the level of population structure would likely be limited to discrete records of recruitment events encountered serendipitously during haphazard sampling in space and time. The ubiquity of large numbers of post-larvae in mussel samples from a number of disparate sites is likely not serendipitous, but instead may reflect the importance of local sources and sinks of propagules in maintenance of mussel populations.

Extensive field observations were made in the Mingan Islands, northern Gulf of St Lawrence, to evaluate spatial and temporal variations in the use of habitat and prey resources by two major subtidal predators, the seastars Leptasterias polaris and Asterias vulgaris. Although both seastars have similar size structures and generally overlapped in their spatial and temporal distribution, the degree of overlap varied in different sites and appeared to be related to prey abundance, substratum type and slope. Three general patterns were observed: (1) both species aggregating in shallow water and decreasing in numbers with depth; (2) the two species showing inverse depth distributions; and (3) both seastars occurring in low numbers across the subtidal zone. Temporal changes in availability of the preferred prey of the two seastars, the mussel Mytilus edulis, appeared to be a major factor affecting their abundance and distribution. The two seastars occurred together in dense aggregations on mussel beds in shallow water. They consume similar-sized mussels until the number of mussels becomes reduced when A. vulgaris, but not L. polaris, begins to select larger mussels. Once a mussel bed is decimated, the seastars appear to move away, possibly in search of other beds. Intensive seastar foraging limits the distribution of mussels to a few metres in depth. Below the mussel zone, the two seastars are spatially segregated at a small spatial scale (1 m2 quadrat) and select different alternative prey, L. polaris feeding mainly on the crevice-dwelling clam Hiatella arctica and A. vulgaris on the ophiuroid Ophiopholis aculeata. The size partitioning of the preferred prey in shallow water, and spatial segregation and selection of different alternative prey at greater depths may reflect mechanisms permitting the two seastars to coexist.

Preferences of the sea urchin Diadema antillarum (Echinodermata: Echinoidea) feeding on five species of brown macroalgae (Padina pavonica, Dyctiota dychotoma, Cystoseira abies-marina, Lobophora variegata and Halopteris filicina) have been studied using caging field experiments on Gran Canaria Island during August to October 2000. Results of three assays of both single and multiple diet experiments rejected the null hypothesis that Diadema does not feed selectively on the five selected algal species. In the multiple diet assays, Diadema consumed an average of 68–98 mg algae urchin−1 h−1 and 4–120 mg algae urchin−1 h−1 in the single diet experiments. On the basis of consumption, the five species of algae eaten can be divided into three groups. Thus Halopteris, Lobophora and Dyctiota were considered preferred algae, while Padina was considered an intermediate alga. Finally Cystoseira was significantly the less preferred and consumed seaweed in all sets of assays.

Mustelus schmitti (Carcharhiniformes: Triakidae) studied in the present work were caught incidentally in the shrimp fishery of the south of Bahía Engaño (Patagonia, Argentina). This bay is a shallow water, high productivity coastal area where shrimps and small fish are abundant throughout the warmer months. Young of M. schmitti are found in the bay from late spring to mid autumn. The analysis of stomach contents showed that the young feed mainly on crustaceans; the shrimp Artemesia longinaris being the main prey item. The bay serves as a nursery area for M. schmitti, and the length range and umbilical scars present in all the specimens studied revealed that the individuals were newborns.At Bahía Engaño, fishing trawls in the intertidal and surf zone are common, and ∼80% of the total number of species caught is considered as by-catch. The newborns and juvenile M. schmitti are an important element of this by-catch. Since the reproductive potential of the smoothhound shark is low, the protection of these newborns and juveniles from fishing pressure is of great importance.

Sixty-eight tides were sampled consecutively to study the retention of fish larvae transported into estuaries. The experiment was conducted at Beaufort Inlet, North Carolina, USA, in March 1996. The inlet is primarily tide-driven and meteorological forcing has a minor influence. Four species of winter-spawning fish were abundant in the samples: Atlantic menhaden, Brevoortia tyrannus; Atlantic croaker, Micropogonias undulatus; spot, Leiostomus xanthurus; and pinfish, Lagodon rhomboides. Across-shore winds significantly affected flow and physico-chemical characteristics of the water. Across-shore winds also positively influenced the larval retention provided larvae did not present a clear tidal rhythm of vertical migration within the water column and that winds pushed in the water during flood tides. The retention of larvae migrating vertically in respect to the direction of the flow was independent of meteorological forcing of the water.

Depth patterns of size and abundance in a pelagic bristlemouth fish Cyclothone pallida (Stomiformes: Gonostomatidae) are reported. Sampling was conducted during the day and night at two sites in the Bahamas using a Multiple Opening and Closing Net and Electronic Sensing System (MOCNESS). All samples show peak abundance in the 500–700 m depth range irrespective of time or sampling location. The mean and variance of body length increased with depth, and size–depth patterns do not significantly differ among samples. Results suggest that these populations of C. pallida do not exhibit diel vertical migration.

Data on stomach contents of ten bottlenose dolphins (Tursiops truncatus) stranded and by-caught around Scotland (UK) between 1990 and 1999 are presented. Although the species is resident in the Moray Firth (north-east Scotland), little previous information exists on the feeding habits of the species in Scottish waters. Cod (Gadus morhua), saithe (Pollachius virens) and whiting (Merlangius merlangus) were found to be the main prey eaten although several other fish species were also found, including salmon (Salmo salar) and haddock (Melanogrammus aeglefinus), and also cephalopods.