Age and length data of 291 franciscana dolphins (Pontoporia blainvillei) incidentally captured on the coast of Rio Grande do Sul State (RS), southern Brazil, were used to fit growth curves using Gompertz and Von Bertalanffy growth models. A small sample of franciscanas (N = 35) from Buenos Aires Province (BA), Argentina, were used to see if there are apparent growth differences between the populations. Male and female franciscana samples from both areas were primarily (78–85%) <4 years of age. The Von Bertalanffy growth model with a data set that excluded animals <1 year of age provided the best fit to data. Based on this model, dolphins from the RS population reached asymptotic length at 136.0 cm and 158.4 cm, for males and females, respectively. No remarkable differences were observed in the growth trajectories of males and females between the RS and BA populations.

The biology of whiting in Manx waters has been investigated at different stages of the life-cycle, with special reference to their diet. Planktonic postlarvae occurred chiefly in May, these measured between 4.5 and 16.5 mm, and had fed chiefly on Pseudocalanus. Larger whiting (between 21 and 52 mm) were taken in association with Rhizostoma. They were approximately 2–4 months old, and had fed on copepods supplemented with Hyperia and euphausiid furcilia. Immature whiting 77 mm long appeared in July in a shallow sandy bay—a nursery area. The fish were about 4–5 months old, and fed on swarming amphipods, isopods and mysids after dark, when these organisms were free-swimming. This diet was supplemented to an appreciable extent during the following April-June quarter by the inclusion of juvenile Ammodytes. After staying for nearly 1 year in the nursery area, the bulk of the fish appear to migrate to the open sea.

In the open-sea habitat, the immature fish fed chiefly on euphausiids, decapods and sprats—nektonic forms particularly. These whiting are themselves eaten by larger whiting in the same habitat. Adult whiting (over 220 mm) were taken only offshore, and fed chiefly on euphausiids, Crangon, Pandalus, Pasiphaea, Clupea and gadoids. A few samples taken off the east coast of I.o.M. indicated that the whiting are capable of feeding on infauna and plankton in an environment deficient in active epifauna and nekton. The whiting is an active feeder throughout the year.

Two length-weight relationships have been calculated for Manx whiting: nursery-area, and open-sea fish—the latter gain weight more rapidly than the former would be expected to do.

The summer spatial distribution of the phytoplankton community in the Gulf of Gabès (Tunisia, eastern Mediterranean Sea), together with environmental factors, were studied during a preliminary study conducted in July 2005 aboard the RV ‘Hannibal’. The phytoplankton community, which showed a decrease in concentration along a coastal–open sea gradient, was dominated by Dictyochophyceae (41%) followed by Dinophyceae (25%), Bacillariophyceae (16%), Cyanobacteriae (17%) and Euglenophyceae (1%). The phytoplankton found along the coast was dominated by opportunistic species (e.g. Dictyocha fibula) associated with high nutrient availability. In the open sea, phytoplankton development seemed influenced by Atlantic hydrodynamics. In addition, the Gulf of Gabès is characterized by an oligotrophic status with a summer stratification that impacted on species composition especially in off-shore areas. The coupling of phytoplankton dynamics to nutrients, ciliates and copepods showed the potential role played by ciliates not only as predators of phytoplankton but also as prey for filter-feeding copepods accounting for the increased fisheries productivity of the Gulf of Gabès.

A new behavioural bioassay system has been used to examine chemical communication in the crab Carcinus maenas (Crustacea: Brachyura) and has demonstrated the sexually and temporally specific nature of a putative sex pheromone. Mature premoult and postmoult females evoked sexual behavioural responses from receptive male crabs. No response was obtained when intermoult female and premoult and postmoult male crabs were tested. Postmoult females continued to be chemically attractive to male crabs with a similar intensity to that of late premoult females for >8 d following moulting, and then with a reduced intensity for >14 d. Male C. maenas successfully entered copula with females >13 d after the female moult.

Several new symbiotic associations involving Syllidae (Annelida: Polychaeta) are reported. The number of known host sponge species infested by Haplosyllis spongicola is updated to 36, with seven hosts being reported for the first time (i.e. Aplysina corrugata, Aplysina sp., Cliona sp., Cliona viridis, Phorbas tenacior, one sponge from Iran, one sponge from Cambodia). Two infestation patterns (a few worms per host cm3 in temperate waters and 10s or 100s in tropical waters) are identified. The taxonomic and ecological characteristics of the species are discussed. Five associations occurring between four syllid worms and decapod crustaceans are fully reported for the first time. Syllis cf. armillaris, S.ferrani and S.pontxioi occurred inside gastropod shells occupied by hermit crabs as well as Pionosyllis magnifica, which was also found inside the branchial chambers of the giant crab Paralithodes camtschatica. The description of Pionosyllis magnifica is emended on the basis of the new specimens found, while some taxonomic remarks on Syllis cf. armillaris are given. In addition, further evidence of sexual (P.magnifica) and asexual (S. cf. armillaris) reproduction in symbiotic syllids is provided.

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.

Published information on the diet of bass in U.K. waters is limited. The very young fish, mainly 0- and 1-groups, have been investigated in the Fleet (Dorset) by Bass et al. (1983), in the Severn Estuary by Aprahamian & Barr (1985), and at the Kingsnorth power-station outfall in Kent by Langford (in preparation). Limited data for older fish have been given by Sant (1978) for the central Welsh coast and by Hester (1980) for the Cornish coast. An early report by the present author reviewed the feeding habits of 250 bass aged 3–16 years caught in 1946–52 in Devon and Cornwall (Kelley, 1953). Data for southern Irish waters have been given by Kennedy & Fitzmaurice (1972), and for west Brittany waters by Boulineau-Coatanea (1969). Other reports from mainland Europe are concerned chiefly with young bass reared in the etangs of the south and west coasts of France and in similar habitats on the coasts of Spain and Italy. There are similar reports from Tunis and Israel. These more specialised studies are listed by Barnabe (1980).

This is preliminary to a series of papers resulting from SOND 1965 Cruise aboard R.R.S. ‘Discovery’. The cruise was designed as an ecological study of sonic scattering layers at a certain season in a restricted volume of ocean in the region of the Canary Islands. These papers will appear periodically in this journal.

Growth of seed mussel Mytilus galloprovincialis (Bivalvia: Mytilidae) from two origins (rocky shore and collector ropes) placed on raft culture was compared. Mussel seed were cultivated following the commercial culture phases commonly used in Galician Rías: (a) from seeding to thinning-out and (b) from thinning-out to harvest. Differences in growth rate were clearly related to the phase of the culture, being significant during the first phase from seeding to thinning out (January–November 1998). In the latter phase, weight values observed for collector rope mussels were significantly higher than those for rocky shore individuals (0·65 vs 0·45 g total dry weight, 0·11 vs 0·08 g tissue dry weight, 0·53 vs 0·37 g shell dry weight and 0·09 vs 0·07 g tissue organic weight per month, respectively; P<0·001). Neither shell length nor weight (soft tissue or shell) growth rate showed differences during the second phase of the culture from thinning out to harvest (November 1998–July 1999; P>0·05). Nevertheless, in terms of output, the higher number of individuals above 70 mm (77% vs 61%) and the heavier soft tissue (and total) weight (23–30%) for collector ropes mussels when compared to rocky shore ones at harvest, highlighted the importance of choosing the former stock. Condition index (CI) did not differ at the onset of the culture between both origins (P>0·05), but mussels from collector ropes showed significantly higher values than those from the rocky shore from May to November 1998 (P<0·001) before thinning-out was undertaken. No differences in CI were observed from thinning out to harvest between both types of mussels (P>0·05). Although both populations showed normal (unimodal) size distributions at the onset of the culture, mussels from rocky shore origin fitted better to bimodal profiles throughout the first phase of the culture. These bimodal distributions of rocky shore population did disappear during the second phase suggesting a more uniform size spectrum as a consequence of the thinning out process, which involves a selection of size.

Morphology of larval, postlarval, and early juvenile stages of the red king crab is described and illustrated from laboratory reared material; attention is directed to certain aspects of morphology not previously considered. Some behavioural patterns are clarified, with special emphasis on locomotion and feeding. Morphological criteria for distinguishing the first two juvenile stages are proposed; additional morphological criteria for distinguishing zoeal stages are reported. Data on development and growth rates under laboratory conditions at 7–8°C are given for early life history stages. No major morphological differences were observed between early life stages of the red king crab from the native area in the Pacific Ocean and from the Barents Sea.

Greater understanding of patterns of distributions of organisms and their causal mechanisms are required if the consequences of climatic change are to be fully realized. Associations between topographic features of the environment and distributions of organisms are frequently assumed to be a consequence of provision or modification of local conditions by those features. Such assumptions are rarely supported empirically and there is increasing evidence that topographic features do not always influence variables in the way we might anticipate. Thus, data about how features of habitat influence environmental conditions, including availability of food, are likely to be useful for understanding how and why organisms are found where they are. Such data are few and rigorous descriptions about what defines particular features of habitat are seldom provided or are simplistic. For hard substrata in aquatic environments, crevices are often prominent features with which many species associate. Crevices have frequently been assumed, but not demonstrated, to ameliorate conditions by increasing humidity, moderating (usually reducing) temperatures and by decreasing forces from wave-impacts and water-flow. This study provided clear definitions and tests of various hypotheses about how crevices altered the local environment. The main predictions were that crevices would be cooler, more humid, more sheltered from water-movement and support more micro-algae than areas away from crevices. Manipulative experiments using artificial habitats and measurements on natural rocky shores were carried out on multiple shores over two years to understand how crevices affected local conditions. Crevices were indeed cooler, more humid, supported more micro-algae and more sheltered from water-flow than open areas nearby, but conditions did not always vary in ways that were expected. Effects were often complex, with factors such as season, height on the shore and tidal conditions interacting to influence how crevices affect environmental conditions. Without this detailed information, assumptions about the reasons animals associate with features of habitat cannot be tested.

The present study aimed to describe the reproductive cycle and estimate the size at sexual maturity of the Manila clam (Ruditapes philippinarum) in the Tagus Estuary (Portugal). Specimens were collected monthly from September 2013 to December 2015 during fishing surveys using bivalve dredges. The gametogenic cycle was described in detail using gonad histology and monitored throughout the study period by the monthly variation in the frequency of gonad maturation stages, mean gonadal index and mean oocyte diameter. This invasive population of R. philippinarum displayed synchronous gonadal development between sexes, with ripening occurring mainly in April and May followed by an extensive spawning period until November–December. Individuals reached the size at first sexual maturity at 29.4 mm in shell length (i.e. before 1 year old). Furthermore, the reproductive strategy, dynamics and potential were compared between the invasive R. philippinarum and the native congeneric carpet shell clam (Ruditapes decussatus). Overall, the data gathered in this study constitutes valuable baseline information to propose conservation strategies and implement management measures to minimize the harmful impacts caused by this invasive species on local ecosystems and native biodiversity, particularly over populations of autochthonous bivalves.

The swimbladder of teleost fishes is a gas-filled sac which serves primarily to make the fish neutrally buoyant in sea water, but occasionally assumes other functions. The gas contained in the swimbladder is largely oxygen, at a pressure very close to the external hydrostatic pressure. The difference in gas partial pressure between the gaseous contents of the swimbladder and the blood and tissue fluids is large in fishes living at any considerable depth, for the hydrostatic pressure increases about 1 atm with each 10 m depth, while the partial pressures of gases in sea water and body fluids are relatively independent of depth and together give a pressure of only about 1 atm. The difference in partial pressure of oxygen alone across the wall of the swimbladder of a fish living at 3000 m depth is close to 300 atm.

The connective tissue layer of the large intestines of Brissopsis and Echinocardium spp. is shown to contain a massive quantity of ferric iron in the form of ferric phosphate. The ferric phosphate is present as a granular extracellular deposit. In large mature specimens of Brissopsis, the weight of iron present may account for almost 30% of the dry weight of large intestinal tissue. The iron deposit appears to be cumulative with age. It is speculated that the deposit is derived from oxidative deposition of a soluble ferrous salt ingested in reducing conditions.

The growth patterns of juveniles of Solea solea and Solea senegalensis were compared, within the nursery areas of the Tagus estuary. Growth was estimated by modal progression analysis of length–frequency data, using the Bhattacharya method based on 1327 and 3255 individuals of S. solea and S. senegalensis, respectively. For the two species several cohorts of the same age-group were identified, being the number relative to S. senegalensis higher compared to S. solea. 0-group individuals of S. solea begin to occur within the nursery in May, while for S. senegalensis the recruitment is longer (from June to October). The number of individuals of the first cohort was higher relative to those belonging to the subsequent cohorts. The growth rate of S. solea juveniles varied from 0·01 mm d−1 to 1·51 mm d−1 and that of S. senegalensis was between 0·22 mm d−1 and 0·89 mm d−1. Although no significant differences were found when comparing growth rate values determined for the different cohorts, age-groups and species, it was noticed that the estimates determined for cohort I were generally higher at the beginning of the nursery colonization period. The differences in the seasonal variation of growth rate of S. solea and S. senegalensis reflected their spawning behaviour and time spent in the plankton and also their differential habitat use pattern.

The reproductive cycle of the pedunculate barnacle Pollicipes pollicipes from two intertidal levels (mid and low) at Cabo de Sines, south-west coast of Portugal has been described. Pollicipes pollicipes larger than 12.5 mm (rostrocarinal distance, RC) are simultaneous hermaphrodites. Minimum size for maturity of the female gonad was 12.5 mm (RC) whilst sperm production is achieved at a smaller size (10 mm). The breeding season was from April to September. Reproductive activity was similar at both tidal levels and was significantly correlated with seawater temperature. Brooding activity was most pronounced in late spring and summer when seawater temperature ranged from 18 to 21°C. Throughout the year, sperm was stored in the seminal vesicles, although the testes regressed from October–December. The female gonad was resting in October–January and active during March–September. During resting, only a few empty ovarioles were observed. At the beginning and in the middle of the reproductive season (March to August), the ovary was completely disrupted after fertilization and ovary recovery occurred simultaneously with egg development. During the end of the reproductive season (September–October), synchrony was retarded as recovery of the ovary was slower than egg development. The pattern of functioning of the female gonad should allow production of several broods during the season.

Protandric oysters generate a relatively uniform reproductive potential over a wide range of environmental conditions that impose variations in growth rate and life span. Sex-at-length keys applied to survey data show that the female fraction routinely fell between 0.4 and 0.5, regardless of location in the salinity gradient. About 70% of population biomass is female over the same salinity range. Due to the necessary local modulation of the rate of male-to-female conversion to limit the influence of varying growth and life span over the salinity gradient, the number of males always exceeds by a small amount the number of females; thus improving the likelihood of a female having neighbouring males, a necessity for an immobile broadcast spawner. However, oysters at the extremes of the estuarine gradient all yielded populations with divergent sex-ratios. One consequence of reduced generation time brought about by increased mortality from disease should be selection favouring the switch from male to female at smaller size, if disease mortality is strongly female-biased. The site with the longest record of high mortality manifests such an increase. Sites up coastal rivers, putative refuges from disease, harbour animals with the slowest male-to-female conversion rates. Arguably these animals are most similar to the ancestral oyster pre-disease. Marketed animals range from 62% to 69% female. The principal influence of the fishery, and of oyster disease, would seem to be a reduction in lifetime egg production. Dermo disease may have reduced lifetime fecundity of females by nearly a factor of four.

Observations were made on the reproduction and life history of five species of polychaetes collected from the continental slope off North Carolina, USA. Three species were studied at a 2000-m lower slope station off Cape Lookout (Aurospio dibranchiata, Microrbinia linea, and Pholoe anoculata) and the other two at a 600-m upper slope station off Cape Hatteras (Cossura longocirrata and Scalibregma inflatum). Aurospio dibranchiata, a surface feeding spionid, exhibited seasonally in egg diameter and size-frequency data, with the larger sizes occurring in late summer months. Pholoe anoculata, a small carnivorous scale worm, did not exhibit any evidence of seasonality in size-frequency data at the 2000-m station. Sexually mature specimens were absent from this population, but were present at shallower slope depths, indicating year-round recruitment into the lower slope from middle and upper slope populations.

Ilyanassa obsoleta is mainly an eastern North American estuarine gastropod. Previous work on growth rate revealed a longevity of 30–40 y for this snail. Trematode infections retard growth, appear to be long-lived ([ges ]10 y) and can be frequent in this host. In 1995 a population made up of unusually large, trematode-parasitized individuals was located in Rehoboth Bay, Delaware. It was interesting to discover whether the oversized snails were the result of locally faster growth or greater age. Therefore in 1996 individually marked snails, uninfected and infected, were deployed to assess growth rates. Uninfected snails were tracked mostly in summer and autumn 1996; infected snails could be tracked longer, some through autumn 1999. Estimated growth rates of uninfected (1.5 mm y−1) and infected (0.2 mm y−1) snails in this habitat were similar to previous results and the large size of individuals in this population must be explained by greater age. Habitat history and growth rate evidence indicate the population includes snails as old as about 70 y. If correct, this becomes the greatest documented snail longevity. Trematodes gain long-term reproduction by their association with this host. By virtue of the enduring effects of long-lived individuals, and the wider potential effects of their long-lived infections (on the snails themselves and on other hosts in their life cycles), I. obsoleta stands to contribute more to the stability of coastal ecosystems than heretofore recognized.

Pandalus borealis Krøyer is a protandric hermaphrodite. In some populations, e.g. that found off the Northumberland coast, the hermaphroditism is partial (Allen, 1959). That is to say only certain individuals undergo sex reversal, while others are primary females, never going through a male phase; all the males undergo sex reversal. In the terminology proposed by Carlisle (1959 a) such populations exhibit partial obligatory protandric hermaphroditism. By contrast, the population of the Gullmarf jord, Sweden, which I have been investigating, appears to exhibit full obligatory protandric hermaphroditism: the population contains no primary females; all the females have passed through a male phase. The data presented in this paper have no bearing, therefore, on the factors regulating the production of primary females, since I have never encountered one.