Using video and image analysis techniques we analysed the response of swarms of the mysid Paramesopodopsis rufa to food and predatory attack. After food was added to the tank, mysid aggregations initially (up to 45 s) increased in volume. Subsequently volume decreased significantly until it was smaller than the initial level. After a period of ~12 h during which no food was added, the swarm expanded to near its original volume. These changes are interpreted as resulting from a need by individuals to optimize food capture and protection. The pattern of volume changes in response to food was independent of aquarium size but the magnitude of the changes was reduced in a smaller tank.

Predatory attacks on mysid swarms were simulated using a model fish which ‘swam’ a single pass along the tank driven by an electric motor. Models (latex-covered real preserved fish), represented two different attack styles: ambush (seahorse Hippocampus abdominalis); and lunging (Australian salmon Arripis trutta). ‘Swimming’ speeds resembled those measured for real fish i.e. 0·5–2·0 cm s-1 for seahorse and 15 cm s-1 for salmon. Again changes in swarm volume were recorded. No obvious response by the swarm to the approaching seahorse was apparent; the aggregation simply parted to allow the fish through. No tailflips were seen among the mysids. The swarm resumed the original volume rapidly after the fish had passed. Approach of the salmon was evidently detected from further away, escape reactions were frequent and energetic, and tailflipping was common. After the fish had passed, it took longer for the original swarm volume to be restored. These results suggest that seahorse ambush techniques have evolved to minimize warning of the predator's approach. When the salmon ‘menaced’ the swarm at seahorse speeds, it appeared the mysids still reacted as though it was a ‘normal’ salmon attack so the fright response was not just a function of speed of attack.

Dynamic changes in swarm volume seem to be a useful simple index of motivational state of individuals.

1. The ions present in sea-water are normally adsorbed by sand.

2. Percolation of sea-water through sand causes a slight abnormality in the concentrations of calcium and magnesium ions, due to the fact that sand is not an inert adsorbing agent, but is capable of discharging calcium ions into the water in exchange for magnesium and sodium.

3. The extent of adsorption and exchange is insufficient to cause hydrolysis and alteration in pH if the bulk of the sea-water is large.

This paper is concerned with a re-examination of the pattern of nerve activity from receptors in ray fin muscles in response to stretch applied to the muscles. In earlier work receptors have been found in the fin muscles of elasmobranchs, those in rays being described in a recent paper by Bone & Chubb (1975 - which see for references to earlier anatomical work) and physiologically by Fessard & Sand (1937). The receptors are supplied by myelinated axons, and the endings take the form of beaded nerve strands associated with congregations of connective tissue lying between muscle fibres. In the pectoral fin muscles these structures lie between small-diameter muscle fibres, with multiple motor nerve endings, which occur superficially in the muscle. Most of these muscle fibres show a positive staining reaction for succinic dehydrogenase (SDH) and lipid, though some are negative for SDH. They contrast with the larger fibres, which show negative staining reactions for SDH and lipid, andhave focal motor innervation. The latter make up the bulk of the muscle (Bone & Chubb, 1975). It seems very likely that most of the small fibres are slow contracting (possibly with no propagated action potential in the muscle fibre), and the large fibres are of a twitch type. This would parallel the arrangement in dogfish myotomes (Bone, 1966). Bone & Chubb consider the coupling between the endings and the muscle fibres to be generally loose, although they also describe occasional sites of much tighter coupling. Such small muscle fibres are particularly concentrated in a superficial and rather discrete part of the muscle, here called the tonic bundle and used in the present experiments as an isolated preparation.

The aim of this study is to investigate the possibility of using the tensile strength and the elasticity as two, among others, objective criteria for the evaluation of the quality and commercial value of two ‘Elephant Ear’ commercial sponges (Mediterranean and Philippine). These criteria could also provide additional taxonomic characters for the distinction of ill-defined species. The average tensile strength of the Mediterranean Elephant Ear was found equal to 2.88 ±0.19 kg cm-2 and that of the Philippine Elephant Ear equal to 6.88 ±0.77 kg cm-2 while the corresponding values for elasticity were 26.1 ±0.79% and 7.8 ±0.6%. This difference is related to the structure and arrangement of the spongin fibres as seen under the scanning electron microscope. The arrangement of the secondary fibres (very compact and regular structure) as well as the abundance and the orientation of the primary fibres (arrangement in the form of bars perpendicular to the external surface) give to the Philippine Elephant Ear a higher tensile strength value, a roughness to the touch and consequently inelasticity and stiffness. In contrast, the large number of smooth secondary fibres in the Mediterranean Elephant Ear, their loose arrangement and the limited number of primary fibres give to this sponge a higher elasticity and a smaller tensile strength value.

Fatty acids (FA) are a non-protein energy source and can act as trophic biomarkers in benthic food webs. We analysed the FA profiles of sea cucumber Apostichopus japonicus, comparing tissues of body wall, gut sediment and ovaries in two habitats. Rongcheng Bay: kelp raft cultivation area with high organic matter in sediment; Laoshan Bay: strong current with low sediment organic matter. The results showed that body wall and ovary tissues were rich in long chain polyunsaturated FA (LC-PUFA), which contributed ~31% to the FA dissimilarity between the two tissues. SIMPER (similarity percentages routine) results showed that C20:5ω3 (EPA), C18:1ω7, C20:4ω6 (AA), C16:0, C14:1 and C20:1ω11 contributed to dissimilarity between the body wall and ovary tissues, while 16:1ω7, 20:5ω3, C16:0, C18:1ω7, C18:0 and C14:1 contributed more to the dissimilarity of body wall tissues between the two habitats. FA biomarkers showed that sea cucumbers from the two habitats had different food sources, with brown kelp and vascular plants being the main food for sea cucumbers in Rongcheng and diatoms for those in Laoshan. To better understand differences in FA composition in sea cucumbers, more research is needed examining a wider diversity of tissue types and habitats.

An in vitro bioassay has been developed which shows that oogenesis in Harmothoe imbricata is controlled by a gonadotrophic hormone which promotes egg protein synthesis in developing oocytes. A similar endocrine control mechanism is found in Eulalia viridis and analysis of in vivo assays indicate that the hormone acts as a transducer between the environment and the gamete. The timing of gametogenesis is controlled by environmental cues in both species and may be affected by predicted global climate change. With the development of these sensitive hormone assays it is possible to test the impact of climate change on both species, providing a possible early warning system for global warming and potential bio-indicators of climate change. Harmothoe imbricata is likely to be the more sensitive indicator species.

a total of 67 discopyge tschudii was captured. individuals were sexed, measured and their stomach content analysed. siphon tips of the bivalve amiantis purpurata from each stomach were individually counted, weighed and their length and width measured. the size–frequency distribution of the local population of a. purpurata was surveyed for two years. siphons of a. purpurata were the main food item in 90% of individuals having stomach contents. the clam population was markedly bimodal, with 24 mm and 46 mm mean shell length for the younger and older size-classes, respectively. grazing by d. tschudii on a. purpurata varied with size and sex of the fish. small rays mainly ingested small siphons and large rays large siphons. nipped siphon tips were longer in male than in female rays.

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.

The seasonality of sexual reproduction was studied in three photosymbiotic Trididemnum species, T. miniatum, T. clinides and T. nubilum, inhabiting the same site. In all species, the colonies lacked gonads and/or embryos during the cold season, while gonads were found in most colonies for several months in the warm season. There were some interspecific differences in the duration of the breeding season. Although water temperature is thought to be the principal factor confining sexual reproduction in these photosymbiotic ascidians, other factors, e.g. precipitation, potentially affect fecundity.

Geostatistical analysis was used to investigate the effect of drift kelp on the spatial distribution of the sea urchin Tetrapygus niger. The positions of all sea urchins were mapped in four experimental plots in the rocky intertidal zone of the central Chilean coast. When drift macroalgae were added, the sea urchins left the substratum irregularities, increased in number inside the experimental plots, and tended to form a dense aggregation around the kelp. After the drift macroalgae was removed, the aggregations disappeared and the sea urchins returned to the depressions and/or interstices of the substratum. The results suggest that the influx of drift kelp is the triggering factor in the formation of dense aggregations of this species.

The present study reports polychaetes that bore into limestone rocks along the east coast of the Aegean Sea (eastern Mediterranean). Rock materials were collected at two depth intervals (0–5 and 5–10 m) at 15 stations in four localities of Ildırı Bay. A total of 276 specimens belonging to 12 species and four families (Eunicidae, Spionidae, Cirratulidae and Sabellidae) were recorded. Specimens belonging to Dodecaceria and Pseudopotamilla were identified at the genus level, because they differ from described species, were few in number or were in poor condition. Dipolydora giardia is a new species to the marine fauna of Turkey. The most dominant and frequent family in the area was Eunicidae, followed by Spionidae. Lysidice ninetta and L. margaritacea comprised 59% of the total number of individuals. The number of species and individuals, and the diversity index did not change with regard to depth or locality. Two species assemblages were found in the area, mainly formed by Dipolydora and Lysidice species. The Lessepsian species, Palola valida, which is a new record for the Aegean Sea, occurred abundantly at the study sites, posing a risk of damage to limestone rocks in the Mediterranean Sea. The morphological features of the species identified at the generic level and the burrow structure of these species are presented. The burrow shapes of Palola siciliensis and P. valida were described for the first time in the present study; they constructed complicated galleries, including more than four entrances.

In the frame of the COST ACTION ‘EMBOS’ (Development and implementation of a pan-European Marine Biodiversity Observatory System), coverage of intertidal macroalgae was estimated at a range of marine stations along the European coastline (Subarctic, Baltic, Atlantic, Mediterranean). Based on these data, we tested whether patterns in macroalgal diversity and distribution along European intertidal rocky shores could be explained by a set of meteo-oceanographic variables. The variables considered were salinity, sea surface temperature, photosynthetically active radiation, significant wave height and tidal range and were compiled from three different sources: remote sensing, reanalysis technique and in situ measurement. These variables were parameterized to represent average conditions (mean values), variability (standard deviation) and extreme events (minimum and maximum values). The results obtained in this study contribute to reinforce the EMBOS network approach and highlight the necessity of considering meteo-oceanographic variables in long-term assessments. The broad spatial distribution of pilot sites has allowed identification of latitudinal and longitudinal gradients manifested through species composition, diversity and dominance structure of intertidal macroalgae. These patterns follow a latitudinal gradient mainly explained by sea surface temperature, but also by photosynthetically active radiation, salinity and tidal range. Additionally, a longitudinal gradient was also detected and could be linked to wave height.

Recent events in world politics demonstrate that a part of society has lost faith in their institutions. The importance of facts and evidence in citizens’ decision making is weakened by opinions and belief systems. This post-fact or alternate facts era is a new challenge in the field of science communication as we urgently need to tackle global environmental challenges. Not only do scientists need to better communicate their work, they also need to explore alternative ways of transferring knowledge to help citizens reconnect with nature and actively take responsible decisions to protect it. The activity ‘I am the Ocean’ has been developed by an artist and a scientist with the goal to help students understand, connect and be equipped to take actions on marine global changes. The activity was a mix of field trips, open discussions and sensory immersion. It illustrates how art and metaphors can add an emotional and physical dimension to science communication, allowing a better understanding of otherwise invisible threats, and move from knowledge to passion.

The abundance and distribution of coastal cephalopods are strongly influenced by the environmental conditions. This study evaluates the seasonal distribution and density of Octopus tehuelchus in three intertidal environments of San Matías Gulf (Patagonia). To estimate and compare density and distribution, monthly transects were carried out, and analysed in relation to the coastlines obtained with satellite images. Densities of O. tehuelchus ranged between 0 and 34 individuals per transect (0–0.11 octopus m−2), and varied between sites. Islote Lobos (IL) had the highest densities (mean octopus per transect 7.32 ± 1.16) followed by El Fuerte (EF) (5.55 ± 0.94) and San Antonio Bay (SAB) (3.40 ± 0.85). Within each site, octopus densities varied between seasons. The highest densities were observed during warm months (SAB = 5.96, EF = 9.52, IL = 14.15) and the lowest during cold ones (SAB = 1.45, EF = 2.6, IL = 3.32). Octopus tehuelchus showed an aggregated spatial distribution, and the nearest neighbour value varied between 0.21 and 0.83 in SAB, 0.27 and 0.78 in EF and 0.23 and 0.53 in IL. Considering the coast lines, the distribution pattern along the intertidal varied seasonally. During warm months this species is widely distributed throughout the intertidal, from the low-tide line to 300 m (in SAB), 500 m (in EL) and 200 m (in IL). On the contrary, during cold months most individuals were found near the low-tide line. These results may be associated with the availability of shelter in the intertidal and the activity and physiology of this species.

Sampling of the demersal ichthyofauna of Guanabara Bay was conducted bimonthly for 2 years at 10 stations distributed along a hydrobiological gradient. A total of 16,081 Tetraodontiformes specimens were collected, representing 10 species distributed among Ostraciidae, Monacanthidae, Tetraodontidae and Diodontidae. Tetraodontiformes appear to be well adapted to hydrological variations and inhospitable conditions prompted by intense eutrophication. However, abiotic factors traditionally considered important in estuarine community structure play a secondary role in the distribution of Tetraodontiformes. The type of sediment appears to be the most important physical factor but acts only as an indicator of ecological domain. The low explanatory power of physicochemical variables, in addition to the relative stability of the bay's ichthyofauna, suggests an influence of biological parameters. The species exhibited wide variation in their use of Guanabara Bay and utilized it as a resting, feeding and growing area. Among the species captured, Stephanolepis hispidus, Lagocephalus laevigatus, Sphoeroides greeleyi, Sphoeroides testudineus, Sphoeroides tyleri, Chilomycterus reticulatus and Chilomycterus spinosus were categorized as marine estuarine opportunists, and Aluterus heudelotii and Aluterus schoepfii were classified as marine stragglers. Acanthostracion sp. could not be categorized. The boom of C. spinosus indicates an ecological misbalance and must be carefully investigated.

In the English Channel and Celtic Sea mackerel spend the winter months on the sea floor densely packed in places where its level is interrupted by banks and gulleys.

In the early spring the fish rise to the surface and migrate to a common spawning ground that lies far out to the westward of the Scilly Islands in the vicinity of the 100-fathom contour.

The very localized positions in which mackerel spend the winter are widely distributed throughout the area in both deep and shallow water. Large schools of migrating fish converge upon the spawning ground from many directions, therefore, in the spring for spawning.

Fish that have wintered near the land must migrate offshore to reach the spawning ground; those that spend the winter on the bottom to seaward of the spawning ground must migrate shorewards to reach it. Off the south-west of England there is no single shoreward migration to spawn in shallow water as has previously been thought.

In the North Sea the chief spawning grounds of the mackerel are also near the 100-fathom contour which, in that region, happens to lie very close to the land in the Skagerrak and along the Norwegian coast. The chief spawning migration of the North Sea mackerel is therefore towards the coast from offshore localities.

This migration is, at the same time, chiefly from shallow to deeper water.

Existing information concerning the mackerel populations on the westernside of the North Atlantic points to the probability that their spawning habits and migratory movements do not differ greatly from those of the mackerel in North European waters.

The muscle lipid, fatty acids and total cholesterol profiles of the spiny cheek grouper, Epinephelus diacanthus, collected from south-west (Arabian Sea) and south-east coasts (Bay of Bengal) of India were evaluated over four years (2008–2011) with regard to three seasons (pre-monsoon, monsoon and post-monsoon). Fatty acids were correlated with chlorophyll-a concentration and sea surface temperature. Lipid content, total polyunsaturated, eicosapentaenoic and docosahexaenoic fatty acids of the samples from the south-west coast showed positive correlation with chlorophyll-a concentration during the monsoon (r2 = 0.93, 0.97, 0.97 and 0.99, respectively). Higher hypocholesterolaemic/hypercholesterolaemic ratio (>1.0) and low atherogenic (<1.2), thrombogenicity (≤0.6) indices make the groupers collected from the coast of the Arabian Sea a valued candidate species for human nutrition. High levels of n-3 fatty acids (>19% during post-monsoon), important in the human diet for their platelet anti-aggregating and blood pressure-reducing properties, for groupers collected from the south-west coast, with higher n-3/n-6 fatty acid ratio (>5.1) proved this species from the coast of the Arabian Sea to be a desirable item in the human diet.

This study concerns the cephalopod species that are part of the diet of the small-spotted catshark Scyliorhinus canicula and the longnose spurdog Squalus blainville sampled by commercial trawlers in the Aegean Sea from 2005 to 2012. Based on the examined cephalopod beaks, 15 species were identified belonging in six families of Teuthida, one of Sepiida and two of Octopoda. The diversity of cephalopod prey species was higher for S. canicula (N = 15) than for S. blainville (N = 10). Nektonic cephalopods comprised the majority (>72%) of the preyed species by both sharks, among which about 55% inhabit the demersal zone and 45% the mesopelagic. In the diet of S. canicula, the demersal squid Illex coindetii and the pelagic sepiolid Heteroteuthis dispar were equally represented composing 20% of prey specimens, followed by the small-sized squid Abralia veranyi and the demersal sepiolid Rossia macrosoma. The latter species was substituted in the diet of S. blainville by the demersal medium-sized octopod Scaeurgus unicirrhus, which with the equally represented three other species, composed 50% of the cephalopod prey. Differences observed between S. canicula and S. blainville in the condition of beaks retained in their stomach contents and in the variation of prey species diversity by predator specimen size, may imply differences in their foraging tactics (hunting for prey vs scavenging on the bottom), habitats and stomach evacuation frequency.

The chub mackerel (Scomber japonicus) has been one of the important commercial pelagic species in the East China Sea since the decline of traditional demersal economic species. Although chub mackerel resources are suffering over-exploitation with the increase of fishing effort, their response to fishing and changing trends have not been analysed because of a shortage of data. In this paper we separated sample catches of chub mackerel from the central East China Sea during 2009 and 2010 into three age groups based on the age–fork length key. We then estimated the maximum sustainable yield (MSY) and built a spawner–recruitment relationship based on the fishery statistics of purse seine vessels, lighting purse seine vessels and deep-water purse seine vessels from 2006 to 2012. We predicted the biomass, spawning biomass, catches and the length compositions of catches when fishing at the current intensity (fishing mortality (F) = 0.7). The results showed that the MSY of chub mackerel is about 18.8 × 104t, and the fishing effort at MSY (EMSY) is about 72 standard purse seine vessels (both the lighting purse seine vessels and deep-water purse seine vessels were standardized to purse seine vessels), which is equivalent to F = 0.4. If F remains at the current level, the biomass of chub mackerel will remain at 45.3 × 104t. At the same time, more than 40% in the catch will be the individuals smaller than 200 mm, and only about 8% will be larger than 300 mm. Therefore, there is little potential for further exploitation of the chub mackerel resources in the central East China Sea, and it is better to reduce F to less than 0.4 for sustainable utilization.

An intensive study of the benthos at six deep-water stations in the Gulf of Gascogne was undertaken by the Centre Océanologique de Bretagne, Brest (during 1972–4) (Laubier & Sibuet, 1977, fig. 1). These stations were repeatedly sampled with a variety of gear during seven different ‘Biogas’ cruises, and over 1900 sipunculans belonging to 16 species including one new to science were collected. Table 1 lists these species and their abundance at the six stations. Specific station data on the samples can be obtained from the authors.

The ubiquitous nature of sipunculans is well documented by this work. Of the 72 dredge hawls made, 86% contained sipunculans, while 80% of the 54 trawl collections yielded sipunculans. Sample CP 01 with 165 sipunculans belonging to five species was the richest collection. The efficiency of the collecting gear and richness of the fauna is indicated by the fact that 24% of the individual collections yielded four or five species while 12% yielded 6–9 species, compared with the usual 1–3 species often collected. At Sample DS 62 a single haul yielded nine out of the 12 species at Station 1.

The following section contains brief comments on the species and their distribution. Full descriptions of these species and additional references can be found in Stephen & Edmonds (1972) and Cutler (1973). The subgenera of Golfingta follow Cutler & Murina (1977) and Cutler (1979).