Successful management of fishery resources is dependent on understanding the exploited species' reproductive potential, which, in turn, requires spatially relevant estimates of the size at maturity and the size–fecundity relationship. This information is used by fisheries managers to implement regional maturity-based legal landings sizes and seasonal fishery closures aimed at protecting the spawning stock and maintaining the reproductive output of the fished population at a sustainable level, despite exploitation. Crab fisheries in particular depend on such information, which is often limited, even in long-established fisheries. To address this issue, size–fecundity relationships were obtained for two commercially exploited crabs in waters around the Shetland Islands (60°N 01°W). These species were Cancer pagurus and Necora puber. A statistically significant positive size–fecundity relationship was found for C. pagurus which describes a mean reproduction potential ranging from ~0.78 million eggs in females of 129 mm carapace width (CW) to ~2.4 million eggs in females of 212 mm CW. The positive size–fecundity relationship found for N. puber was not statistically significant, but describes a mean reproduction potential ranging from ~0.16 million eggs in females of 56 mm CW to ~0.19 million eggs in females of 96 mm CW. Morphometric assessments of reproductive capacity in C. pagurus support the notion that positive size–fecundity relationships are attributable to the combined capacities of specific morphological features, each of which contributes to a female's spawning output ability. Statistically significant positive linear relationships were found between the natural logarithms of crab size (CW) and pleopod capacity, sperm plug mass, spermathecae capacity and gonad capacity. Respectively, these structures are crucial for successful egg attachment and incubation, sperm retention and protection, sperm storage and oogenesis.

Two distinct species have been recently recognized for the genus Sotalia: S. fluviatilis, occurring in the Amazon River basin, and S. guianensis, from Honduras (15°58′N and 85°42′W) to Santa Catarina State (Florianópolis, southern Brazil—27°35′S and 48°34′W). For the first time the sternum and the appendicular skeleton of the two species of the genus Sotalia are compared. A comparative osteological work was performed with marine samples (from the States of Ceará, north-eastern and Santa Catarina, southern regions of Brazil) and riverine samples (Amazonas State) in relation to metric characters (scapula, flipper and sternum). There was a clear distinction of two species in relation to postcranial skeleton in the morphometric analysis (canonical variate analysis) presented. The flipper and the glenoid cavity of the scapula were proportionally wider in the fluvial species. The sternum, however, was smaller in this species in relation to the maximum width of the manubrium. Nevertheless, this structure still needs to be further studied.

Oil pollution in marine waters has been a subject of growing concern and has stimulated a variety of pollution studies. Past methods of dealing with the problem have been mechanical, which are effective on land, and chemical which, in the past, have used highly toxic detergents, usually in open waters (Spooner, 1969).

Structural adaptations of the mouthparts and digestive tract of four talitrid amphipods were examined in relation to diet, habitat and phylogeny. The species differed in their habitat relative to the shoreline and also in their diet: a 5-dentate ‘sandrunner’, Talorchestia species II (a mid to low shore intertidal diatom feeder), a 5-dentate sandhopper, Talorchestia marmorata (a strandline kelp feeder); a 4-dentate sandhopper, Talorchestia species I (extreme high shore, feeding on spinifex grasses), and a 4-dentate landhopper, Keratroides vulgaris (forest leaf litter, litter feeding). Gross structural characteristics of the mouthparts were similar among all three Talorchestia species reflecting their phylogenetic relatedness. Increased setation and minor structural differences among the Talorchestia species could be attributed to dietary differences, reflecting the zones across the shoreline that they inhabit. Mouthparts of K. vulgaris were elongate, with markedly different setation to the Talorchestia species, reflecting its more distant phylogenetic position and its diet of decaying leaf litter. Digestive tract structure was more conserved among all species due to their phylogenetic relatedness. The gross digestive structure conformed to the general plan exhibited by most gammaridean amphipods. However, an additional pair of lateral pyloric caeca was evident in all species, the function of which is uncertain.

Each spring, a localized stock of herring (Clupea harengus, Teleostei, Clupeidae) spawn in the Blackwater Estuary (Essex, UK). The eggs are laid on a gravel bank (Eagle Bank) at the mouth of the estuary. Incubation takes three to four weeks and, after hatching, the larvae can be caught in the area for several months. In this paper, results are presented from a finite-element circulation model used to simulate tidal and wind driven flow fields for the region. A particle tracking model was then used to simulate the dispersal of young herring larvae, up to first feeding, hatching from the Eagle Bank. The simulations predicted that, over a period of 12 d, around 63% of particles would be retained in the area of the Eagle Bank at high water whilst 22% of particles would be further south towards the Buxey Sands. Over the same time, ∼7% of the particles released would be found in the River Blackwater itself. Imposing a steady state wind of 10 m s−1 from the south-west (the dominant wind direction during spring in this area) or north-east had the effect of moving the majority of particles into the river or offshore to the south respectively.

A new species of leptostracan (Crustacea: Phyllocarida: Leptostraca) belonging to the genus Nebalia, N. troncosoi sp. nov., is described from specimens collected off the Galician coast (Iberian Peninsula, north-east Atlantic). The new species is relatively common in sandy bottoms. It is characterized by having a long rostrum, an eye with small distal lobes, an antennular flagellum with up to seven articles, the exopod of the second maxilla longer than the first article of the endopod, and acute denticles along the posterior dorsal border of pleonites 6–7.

Many preys retreat into a refuge as a response to the presence of a predator, a behavioural strategy which guarantees safety but is also costly due to a trade-off between hiding time and time spent in other essential activities. The balance between costs and benefits of hiding, which are influenced by different factors, determine the hiding duration. In a field experiment, the anti-predator behaviour of the mud crab Austrohelice crassa was studied to assess the effects of two factors, body size and neighbour density, on the time spent hiding in burrows following a predator threat. Hiding times, body size (estimated from burrow diameter) and neighbour density (number of other burrows within a 30 cm radius) were measured for 158 individual crabs during a snorkelling survey. Regression analyses showed that hiding time of individual crabs significantly increased with increasing body size, and decreased with increasing neighbour density. These trends are the result of three main selective pressures: size-biased predation risk, dilution of predation in dense clusters of burrows, and more intense competition in dense clusters. Variation among individual crabs probably reflects differences in the balance between costs and benefits for crabs differing in body size and neighbour density.

Thermal perception is crucial for the fitness of marine invertebrates in intertidal and shallow waters. TRPA1 is a non-selective cation channel that belongs to the TRP family with pivotal roles in initiating signal transduction of thermal perception. We investigated expression patterns of SiTRPA1 in different tissues (tube feet, coelomocytes, gonads and gut) of the sea urchin Strongylocentrotus intermedius. SiTRPA1 expression patterns under acute and long-term temperature stimuli were investigated in tube feet of sea urchins. In the present study, the highest expression of SiTRPA1 was detected in tube feet of S. intermedius. The SiTRPA1 expression level in tube feet were significantly 235.7-fold, 450.0-fold and 3299.7-fold higher than those in the coelomocytes, gonads and gut (df = 3, F = 47.382, P < 0.001). Expression levels of SiTRPA1 in the other tissues (coelomocytes, gonads and gut) were not significantly different (df = 3, F = 47.382, P = 0.972). There was no significant difference of SiTRPA1 expression among all groups in the acute temperature increase experiment (df = 4, F = 0.25, P = 0.902). In the acute temperature decrease experiment, the expression of SiTRPA1 showed no significant difference among all groups (df = 4, F = 1.802, P = 0.205). With long-term exposure (6 weeks) to different temperatures, SiTRPA1 expression in the low temperature group (10°C) was significantly higher than those in the high temperature (20°C) and the control groups (15°C) (df = 2, F = 9.57, P = 0.014). There was no significant difference of SiTRPA1 expression between the high temperature (20°C) and the control temperature (15°C) groups (df = 2, F = 9.57, P = 0.808). These results indicate that SiTRPA1 expression significantly responds to long-term low temperature but not to acute temperature decrease. The present study provides new insights on the distribution and temporal expression of TRPA1 in marine invertebrates after acute and long-term temperature stimuli.

The early life history traits of the labrisomid blenny Auchenionchus crinitus (Jenyns, 1842) from subtidal rocky reefs were studied, based on microstructure analysis of sagittae of their pelagic larvae (4.01 mm NL −12.50 mm SL). Ichthyoplankton was collected in shallow (<20 m) nearshore waters off Isla Santa María, Antofagasta, northern Chile every 15 days during austral autumn–winter 2014 (five sampling days). During late May and early June, larval abundance was low (median ± MAD, 39.06 ± 5.08 ind. 100 m−3), increasing significantly during mid-June to early August (110.98 ± 47.66 ind. 100 m−3). Using 354 sagittae, the back-calculated hatch dates indicated the occurrence of three hatching events, two in autumn and one in winter. Hatching occurred mainly during the illuminated phases of the lunar cycle. All three batches had similar estimated larval sizes at hatch (3.2–3.7 mm SL), as well as similar growth rates (0.19–0.22 mm day−1) during the first 30 days of life. During the study period, shallow waters were well mixed, with seawater temperature of 14.73 ± 0.58°C and salinity of 34.84 ± 0.04. This is the first estimation of early life history traits of this cryptobenthic species from rocky reefs of Chile.

This paper describes the responses of a squid (Alloteuthis subulata) and a fish (Trachurus trachurus) to changes in the angular distribution of light.  An apparatus was made that simulated the angular distribution of daylight in the sea. The apparatus enabled the direction of the brightest light to be changed and the positions of the animals in response to these changes were observed. Squid viewed head-on were observed to roll by a maximum of 20° when the incident light source was at angles between 20° and 90° (where 0° is vertically downwards). When viewed laterally, i.e. in the pitch plane, the squid were observed to position themselves more closely with respect to the angle of the light source, they swam in a near vertical plane when the incident light source was at an angle of 90°. Swimming movements in the roll and pitch plane became more horizontal with positions of the light source between 90 and 180°. Horse mackerel, in contrast, inclined their dorsal surfaces to almost perfectly match the angle of the incident light source, even swimming upside-down when light came from below. These experiments also revealed that squid display a counter-shading chromatophore pattern (‘Flexible Countershading’) in response to light coming from the sides, which involves darkening the side of the body facing the brightest light. The use of chromatophores in this way may explain why the dorsal light reflex in squid is so weak compared to that of fish.

Endocrine disruption has rarely been reported in field populations of the edible cockle and the context with the general health of the shellfish is unclear. This study examined the reproductive state of two Cerastoderma edule populations over a 6-month period to assess their reproductive condition, the incidence of intersex and presence of parasitic infection. A further seven native sites from south-west England were examined during the peak reproductive season to identify the presence of intersex within the region. Laboratory exposures of organisms collected from field populations showed a significantly female-biased sex ratio compared with controls when exposed to the endocrine disrupting chemicals, bisphenol-A (nominal concentration: 0.1 µg L−1) and 17β-oestradiol (nominal concentration: 0.1 µg L−1), but none of the chemical exposures induced intersex. Intersex was revealed in seven out of the nine native populations of C. edule sampled at peak reproductive season. The highest incidence and most severe case of intersex were reported at Lower Anderton on the River Tamer which also had a significantly female-biased sex ratio. Additionally, the dominant trematode family was the Bucephalaidae. Parasitic infection influences the maturity of C. edule by lowering both mean gonad index and condition index. These results suggest that endocrine disrupting chemicals could be contributing factors towards the development of intersex in C. edule.

Cadmium, chromium, copper, nickel, lead and zinc concentrations in the bivalve mollusc Macoma balthica and the polychaete annelids Hediste diversicolor and Arenicola marina were measured, during winter and summer, at sites throughout the Severn Estuary and Bristol Channel. The mean concentration of each metal in A. marina was greater in the lower Severn Estuary than in the far less contaminated outer Bristol Channel and the concentration of a given metal, e.g. Cr, in a species occasionally peaked at a site, reflecting local metal contamination. The concentrations of each metal in each of these biomonitor species almost invariably differed significantly among sites and often seasons and there were sometimes interactions between site and season. This indicates that the various factors that determine the concentration of a metal in a species operate in a complex manner and that their individual effects can vary among sites and/or seasons. The rank order of each metal concentration in each species at a site within the estuary frequently did not match the sequence for the concentration of that metal measured in the sediment at that site at the same time. This lack of correspondence is likely to be due, at least in part, to one or both of the following: (1) variations in the bioavailability of certain metals among sites due to differences in such features as the metal-binding properties of the sediments; (2) the effects of the constant transport and redistribution of the sediments and thus also of their associated trace metals by the very strong tidal action that characterizes the Severn Estuary. This would mean that single time measurements do not accurately reflect the overall trace metal environment to which the biomonitor organism had been exposed in the weeks/months prior to sampling. Marked differences in the concentrations of certain metals, e.g. Cu and Zn, in co-occurring biomarker species could frequently be related to differences between the ability of these species to regulate certain metals. Non-metric multi-dimensional scaling ordination and associated tests emphasize that the relationships between the concentrations of the various metals differed markedly among species and between sites and seasons in individual species and elucidated which metals contributed most to those differences. If the proposed scheme for harnessing tidal power in the Severn Estuary proceeds, the data in this paper provide a baseline for assessing the impact of such major changes on the bioavailability of trace metals in this estuary. This information will also be invaluable for predicting the changes likely to occur in other estuaries that become subjected to major structural changes.

Analyses of the natural abundance of carbon and nitrogen stable isotopes were performed to investigate the feeding habits of two ophiuroids, Ophiomastix venosa and Ophiocoma scolopendrina, and to assess the potential benefit obtained by the symbiotic Ophiomastix venosa juveniles. A tracer experiment was also carried out to clarify the contribution of algae to the nitrogen uptake amongst the tested ophiuroids. Our results suggest that Ophiocoma scolopendrina adults occupy a higher position in the food web than Ophiomastix venosa and mainly feed on neuston. In contrast, O. venosa adults feed on the alga Sargassum densifolium and on organic matter associated with sediment. Free juveniles and symbiotic juveniles of O. venosa have intermediate δ13C values between both adult species. The high proportion of 13C in the symbiotic juveniles compared to the one in their conspecific adults indicates that their diet slightly differs from the latter and is closer to that of Ophiocoma scolopendrina. This raises the hypothesis that symbiotic juveniles steal neuston from their associated host, O. scolopendrina.

Iranian coastal fishers targeting narrow-barred Spanish mackerel (Scomberomorus commerson) recently replaced their historical multifilament gillnets with those made from monofilament, evoking management concerns over potential increases in catch-per-unit-of-effort. During 20 fishing days, we compared catches from replicate surface-set gillnets that were identical in terms of mesh size (140 mm stretched opening), length (180 m), depth (30 m), hanging ratio (0.56) and spatio-temporal deployment, but had different materials: multifilament (1.8-mm diameter twisted twine) vs monofilament (0.8-mm diameter twine). Compared with the multifilament gillnet, there was a trend of greater catches (up to 1.3×) of S. commerson and another retained species, mackerel tuna (Euthnus affinis), along with one discarded species, giant catfish (Netuma thalassina) by the monofilament gillnet. However, statistical significance was restricted to E. affinis catches and a bias towards smaller S. commerson. These differences were attributed to species-specific catching mechanisms within gillnet material, with larger S. commerson retained by their teeth in the multifilament and all E. affinis more securely retained by their deeper bodies in the monofilament. Gillnet materials require regulation to preclude excessive effort on fully exploited stocks of species such as S. commerson.

A species of the genus Amorphinopsis is described for the first time for the Atlantic Ocean. The new species was described based on the study of 25 specimens, collected in the area of the São Sebastião Channel and its environs (northern sector of São Paulo State coastline) and in the Cabo Frio region (Rio de Janeiro State). The form is massive cushion-shaped, lobate, occasionally encrusting. The megascleres are styles [160–260 (N=20)/5–10 (N=10) μm; length/thickness] and oxeas [150–900 (N=100)/5–18 (N=20) μm]. Amorphinopsis atlantica sp. nov. differs from the other species of Amorphinopsis by its colour, dark-greyish-green with or without yellow tinges on the exposed surface, and the smaller size of its oxeas. Amorphinopsis excavans is the closest species to the Brazilian material, but can still be set apart by a series of smaller traits, such as oxeas and styles never overlapping (the smaller oxea is always larger than the larger style).

The distribution, abundance and seasonal occurrence of larvae of mackerel (Scomber scombrus L.) are described from routine Continuous Plankton Recorder (CPR) sampling around the British Isles over the period 1948–78, and from more intensive CPR sampling in the Celtic Sea in 1977. There were two main areas of larval concentration: in the North Sea and over and adjacent to the Celtic Plateau; subsidiary aggregations were observed to the northwest of Ireland and to the west of Norway. There were some similarities between the distribution of larvae around the British Isles and that of adult Calanus spp. In the North Sea there was a southerly shift of larval distribution over the period 1948–77; over a similar period the abundance of larvae increased to reach high numbers by the late 1950s and subsequently declined after the mid-6os. To the south-west of the British Isles numbers of larvae showed a long-term decline. The long-term trends of distribution and abundance are discussed in relation to concurrent biological and environmental change. The clearest relationship was found between the numbers of mackerel larvae in the North Sea and sea-surface temperature in the North Atlantic, which suggests a common causative agent for both sets of observations; also, there was a weak relationship with both spawning stock biomass and sea-surface temperature at the spawning areas. In the North Sea the seasonal occurrence of larvae was from May to August, the majority being taken in June and July; over the period 1948–77 the seasonal time of occurrence of highest numbers of larvae has remained relatively constant. In the Celtic Sea the seasonal occurrence of larvae was spread over a longer period, from March to August, with relatively high numbers from March to June; over the period 1950–78 the time of occurrence has been variable, possibly with a tendency towards later timing in more recent years.

Introduction

During the last fortnight in September of 1965, 1966 and 1967 littoral species of Spirorbis were collected by the author and, during the early part of April 1966, sublittoral species were collected by the British Museum (Natural History) and University of London Sub-Aqua Expedition. Ten species, including one new to the British Isles and two new to science, were found to be present. Details of their occurrence, together with the descriptions of the new species, are contained in this report. Representative series of the material collected are deposited in the British Museum (Natural History). In this account, specimens collected by the author are indicated by (T.H.) and those collected by the Sub-Aqua Expedition by (S-Aq. Ex.).

Information regarding spawning grounds of the Atlantic herring Clupea harengus Linnaeus has been based mainly on the collection of spawning fish, newly hatched larvae, or the presence of eggs within the stomachs of predators (Postuma, Saville & Wood, 1977). This type of evidence indicates general areas of spawning, rather than accurately delineating the spawning grounds. Though samples of spawn have been obtained from several localities in the North-East Atlantic (Ewart, 1884; Runnström, 1941; Fridriksson & Timmerman, 1951; Bolster & Bridger, 1957; Parrish et al. 1959; Hemmings, 1965; Bowers, 1969; Anthony, Sauskan & Sigaer, 1970), few quantitative studies of individual grounds have been made. In consequence, little is known of the factors influencing the selection of grounds by Atlantic herring, the shape of these grounds and egg distribution within spawning areas.

In India 14 seagrass species can be found with monospecific genera (Enhalus, Thalassia and Syringodium), Cymodocea with two species and Halophila and Halodule represented by more than two taxonomically complex species. Considering this, the present study was made to understand the level and pattern of genetic variability among these species collected from Tamilnadu coast, India. Random amplified polymorphic DNA (RAPD) analysis was used to evaluate the level of polymorphism existing between the species. Out of the 12 primers tested, 10 primers amplified 415 DNA fragments with an average of 41.5 fragments per primer. Of the total 415 amplified fragments only 123 (29.7%) were monomorphic and the remaining 292 (70.3%) were polymorphic for Indian seagrass species. Among the 10 primers used four are identified as the key primers capable of distinguishing all the Indian seagrasses with a high degree of polymorphism and bringing representative polymorphic alleles in all the tested seagrasses. From the present investigation, this study shows that the RAPD marker technique can be used not only as a tool to analyse genetic diversity but also to resolve the taxonomic uncertainties existing in the Indian seagrasses. The efficiency of these primers in bringing out the genetic polymorphism or homogeneity among different populations of the Halophila and Halodule complex still has to be tested before recommending these primers as an identification tool for Indian seagrasses.