Dolphinfish (Mahimahi) are a high-demand resource for sport and coastal fisheries, mainly in the Pacific Ocean. Due to their economic and ecological importance, studies of their biology are very important to understand their function in ecosystems. We used stable isotope and stomach content analyses to determine the most important prey of the common dolphinfish, as well as the trophic level of this species in two areas of the southern Gulf of California. Stomach contents of 445 specimens were analysed. Using both techniques, we found that the most important prey for dolphinfish in the southern Gulf of California were three invertebrate species followed by fish. This contrasts with results from other authors who found that this species was mainly piscivorous in other locations. Stomach content analysis indicated differences in prey biomass by area, season and size class. The isotopic analysis did not show significant differences between seasons or sexes. Both stomach contents and stable isotope analyses showed that although this predator consumed a wide prey spectrum, only a few prey items made up the bulk of the diet, which resulted in a low SD in δ15N values and low Levin's index values. We conclude that this fish is an opportunistic predator that may consume a wide prey spectrum, but that it mainly consumes prey that are abundant in the area, such as crustaceans and cephalopods in the Gulf of California.

The 230 km long coast of Alagoas State, in north-eastern Brazil, has diverse reef ecosystems, made from corals and of sandstone, that harbour a wide range of marine invertebrate fauna. Little is known about turbellarians of the order Polycladida in most parts of the Brazilian coast, with no record from Alagoas up to date. To fill this gap expeditions were conducted on the reefs from the central coast of Alagoas, where 11 Polycladida species were found: Pericelis cata, Enchiridium evelinae, Pseudoceros bicolor and a possible new colour variation of this species, Pseudoceros rawlinsonae, Pseudobiceros pardalis, Thysanozoon brocchii, Thysanozoon alagoensis sp. nov., Armatoplana leptalea, Adenoplana evelinae, Latocestus brasiliensis, Phaenocelis medvedica. The species are described in detail through photos of live specimens and histological sections. The present work adds six species to the north-eastern Brazilian coast, one of them a new species, and all 11 species are for the first time reported from Alagoas State. Also, it is the first time that Phaenocelis medvedica, Adenoplana evelinae, Latocestus brasiliensis and Armatoplana leptalea are illustrated by full colour photos of live specimens and histological sections.

Ceramaster grenadensis is one of the most abundant bathyal seastars in the north-western Mediterranean Sea and also presents a wide geographic distribution in the Atlantic Ocean. As with other species in this genus, little information is available on the biology and reproductive strategy of C. grenadensis. In this context, we describe for the first time the reproductive cycle of this species from bathyal depths in the north-western Mediterranean Sea. Specimens (N = 141) were collected seasonally from 194 benthic trawls (141 Otter Trawls and 53 Agassiz trawls) conducted during 10 cruises from October 2008 to April 2013. Open slope and canyon systems were sampled at depths between 900 and 2250 m. The population distribution of C. grenadensis showed a depth-related structure, with the smaller adult specimens and juveniles present at greater depths. Sex ratio was 2:1 females per male, constant among seasons and depths. Histological analyses of the gonads showed an asynchronous ovarian organization, with previtellogenic and vitellogenic oocytes throughout the year. These oogenesis patterns suggest a continuous reproduction. However, the Pyloric Caeca Index (PCI) decreased in summer while the Gonad Index (GI) increased in autumn in males, suggesting a higher spawning capacity in autumn. In both sexes, an increasing GI and PCI trend was observed with increasing depth.

The sea urchin Diadema africanum is considered a key herbivore in sublittoral ecosystems of the Canary Islands. Spatial and temporal variability in population structure was carried out at Gran Canaria. We performed a morphometric and population density analysis during 2005, 2006 and 2007 at four sites in zones of Gran Canaria. The study considered a vertical gradient (5, 10 and 20 m depth) during both seasons, the cold season (February and March) and the warm season (October and November). The sea urchin D. africanum in Gran Canaria exhibited an overall density of 7.59 ± 2.92 urchin m−2. A two-way ANOVA evidenced spatial differences in mean abundance of the species, while seasonality was not relevant. The vertical analysis of the abundance of D. africanum showed differences, the smaller sizes appeared at greater depths. The Aristotle's lantern width decreased in a vertical gradient, being remarkable between 10 and 20 m. Findings of uniformity in size over time, a stable range of high densities and the lack of a relationship between the size of the sea urchins and the season reveals that the density–size strategy displayed by D. africanum which explains in turns the high stability of the urchin barrens, which, once developed, remain as areas of permanent desertification in subtidal depths throughout the Canary Archipelago.

Red vent syndrome (RVS) has previously been reported in returning wild Atlantic salmon, Salmo salar from Canada, Iceland, Ireland, Norway and the UK. Affected fish show reddening and swelling in the perianal/vent area, with scale loss, ulceration and bleeding in severe cases. Studies in the UK and elsewhere report the condition to be induced by Anisakis simplex sensu stricto (s.s.) larvae. This parasite, commonly reported in several marine fish species, is typically found in the body cavity and the skeletal muscle, but has recently been reported within the vent tissues of salmon. This latter finding may reflect greater efforts in examining this body portion due to current awareness of the parasite presence in this atypical location. Based on clinical observations, affected fish are classified into three categories according to the severity of the external lesions, but quantification of the vent parasite numbers in relation to the categories, and assessment of the relative importance of this area as a site of infestation, are missing to date. This investigation aimed to provide data on parasite number and distribution in the viscera, skeletal muscle, peduncle and vent area and to confirm the identity of the larvae found in the vent and the viscera. The study showed the perianal/vent region harbours the highest total number of A. simplex larvae per fish and, proportionally to fish biomass, is the most heavily infested body location irrespective of external severity levels of RVS.

Cephalopods are common inhabitants of the deep ocean's mesopelagic zones worldwide, yet very little is known about their behaviour due to the inaccessibility of this environment. Recent studies suggest that, contrary to historical predictions, deep-sea cephalopods exhibit a wide array of visual behaviours. We used in situ footage from remotely operated vehicles, coupled with laboratory observations to assemble the first behavioural ethogram for the juvenile and subadult life stages of the mesopelagic squid, Chiroteuthis calyx. The number of behavioural components we described is comparable to or exceeds those recognized in ethograms of shallow-water teuthids. We used the ethogram to make a detailed behavioural comparison between the juvenile and subadult life stages, and found distinctly different patterns. Behavioural and morphological differences between the two life stages support the hypothesis that juvenile C. calyx mimic the abundant siphonophore Nanomia bijuga, in order to deter predation.

Brachidontes rodriguezii and Brachidontes purpuratus have a wide geographic distribution along the Argentinean coast. Both species are abundant in the intertidal area of rocky shores. We used transmission electron microscopy to study the spermatogenesis of B. rodriguezii and the structure of mature spermatozoa from B. rodriguezii and B. purpuratus. Our results show that spermatogenesis in B. rodriguezii is very similar to that reported in other mytilids. The spermatozoa of both Brachidontes are of the primitive or ect-aquasperm type showing a spherical nucleus capped by a conical acrosome with an anterior extension. The chromatin was electron-dense, homogeneous and compact. The mid-piece region consisted of 5 spherical mitochondria grouped in a ring around a pair of short cylindrical centrioles. The flagellum exhibit the typical 9 + 2 microtubule structure. Studies of spermatozoa ultrastructure are considered a useful tool in bivalve phylogeny. Characters in the spermatozoa morphology of these two species were observed and a brief discussion about the sperm morphology along the distribution of both species is presented. We suggest that the acrosome complex presents the most significant differences between both species.

Silver bellies, Leiognathus splendens were studied for their spatial (south-west and south-east coasts of India), annual (2008–2011) and seasonal (pre-monsoon, monsoon and post-monsoon) variations of protein, amino acids, vitamins and minerals. The monthly mean Sea Viewing Wide Field-of-view Sensor data for the period from January 2008 to December 2011 were taken into account to indicate the distribution of the photosynthetic pigment chlorophyll-a to test the hypothesis that surface productivity might be related to nutritional biochemistry of this species. The four year average total protein content and chlorophyll-a showed good correlation during monsoon on the south-west coast and monsoon/post-monsoon on the south-east coast, suggesting that the protein content is prejudiced by the chlorophyll-a concentration. Amino acid scores observed monsoon maxima along the south-west and south-east coasts. Significant seasonal variations in vitamin content were observed at the study locations with high content of vitamins D3, E, K1 and C on the south-west coast. Na content was maximal during pre-monsoon on the south-west coast, while post-monsoon maxima of Ca and K content were observed. The Fe, Mn and Zn were abundant in the samples collected from the south-west coast. The concentration of Se exhibited maximum values post-monsoon along the south-west and south-east coasts. The present study demonstrated L. splendens as a valuable source of the protein, amino acids, minerals and vitamins, showing that this low-value species is a good source of well balanced proteins with high biological value to be qualified as a preferred healthy food for human consumption.

Blue jack mackerel Trachurus picturatus monthly samples were collected between 1998 and 2011 to determine morphometric relationships, maturity, growth rates, reproduction and spawning seasonality in north-east Atlantic waters (ICES area Xa2). A total of 2895 specimens were sampled, ranging from 98 to 542 mm in fork-length (LF). The morphometric relationships (length-length and length-weight) showed statistically significant differences between sexes. Ages were estimated by counting growth bands on otoliths and verified by marginal increment analysis, with specimens ranging from 0 to 18 years. The von Bertalanffy models used to estimate growth parameters for both observed and back-calculated length-at-age data gave good fits. The gonads were analysed macroscopically and the spawning season found to occur from December to May. The length at 50% maturity for females and males occurred at 277 mm LF (4.3 years) and 288 mm LF (5.1 years), respectively. The results provide important biological information for fisheries assessment of a species that plays an important key role in the surrounding ecosystem.

Cephalopods (Mollusca: Cephalopoda) play an important role as keystone invertebrates in various marine ecosystems, as well as being a valuable fisheries resource. At the World Malacological Congress, held 21–28 July 2013 in Ponta Delgada, Azores, Portugal, a number of cephalopod experts convened to honour the contribution of the late Malcolm R. Clarke, FRS (1930–2013) to cephalopod research. Endorsed by the Cephalopod International Advisory Council (CIAC), the meeting discussed some of the major challenges that cephalopod research will face in the future. These challenges were identified as follows: (1) to find new ways to ascertain the trophic role and food web links of cephalopods using hard tissues, stable isotopes and novel concepts in theoretical ecology; (2) to explore new approaches to the study of cephalopod morphology; (3) to further develop cephalopod aquaculture research; (4) to find new ways to ascertain cephalopod adaptation and response to environmental change; (5) to strengthen cephalopod genetics research; and (6) to develop new approaches for cephalopod fisheries and conservation. The present paper presents brief reviews on these topics, followed by a discussion of the general challenges that cephalopod research is bound to face in the near future. By contributing to initiatives both within CIAC and independent of CIAC, the principle aim of the paper is to stimulate future cephalopod research.

The estimation of age and growth of cephalopod stocks is a key issue for their sustainable management. Recently, several studies have successfully validated the daily deposition of growth rings in the vestigial shell or stylets of several octopus species. Octopus vulgaris eggs were incubated at two different temperatures, 18 and 22°C, until hatching to determine stylet size at hatching and assess the effect of temperature in the stylet dimensions. The 3-day-old hatchlings were sectioned transversally and 6 μm sections were stained to enhance the stylet position and visibility. The sections were observed under transmitted light microscopy at a magnification of 1000×, and the stylets identified as blue/green structures inside the mantle–funnel retractor muscle. The transversal sections of the whole paralarvae allowed the diameter of the embryonic stylet of an octopus species to be measured for the first time. The mean stylet diameter in 3-day-old paralarvae is 3.99 μm independently of the thermal conditions. Moreover, significant differences in stylet size between captive and wild paralarvae were observed; the latter showed significantly larger stylets, an indication that they are over 3 days old. Our results also indicate that the stylet nucleus is much smaller than previously thought based on measurements in stylets of juveniles and adults.

Manta ray (Manta birostris) is the largest ray species, but little information is available regarding its biology, distribution and migratory pattern. During an aerial survey conducted in French Guiana waters (South America) in 2006, the observation of several dozen individuals all swimming in the same direction prompted us to develop a research programme on this species as part of an environmental impact assessment for oil drilling. Overall, 117 aerial surveys were performed over 3 years in order to complete a database for this species. In 54 of these flights, a total of 138 individuals were observed. A phenological analysis of this species in French Guiana waters shows a peak presence between July and December, which correlates with sea surface temperature and net primary production in the ocean. The primary production in French Guiana waters is particularly active during this period and could explain the annual pattern for this filter-feeding animal.

Nebalia mediterranea sp. nov. (Crustacea, Leptostraca) is described from the Aegean coast of Turkey and Northern Cyprus. The new species is closely related to other sympatric species in the eastern Mediterranean, N. strausi and N. kocatasi, according to general body appearance. The new species differs, however, from other Nebalia species in having a rostrum about 2.5 times as long as wide, the antennular scale is clearly more than twice as long as wide, the fourth article of the antennule has only one short thick distal spine, the third article of the antenna has three similar spine-like setae on external lateral face, the first article of the second maxilla endopod is 1.2 times as long as the second article, the exopod of the second maxilla is longer than the first article of the endopod, pleonites 5–7 have distally rounded to slightly truncated denticles along posterior dorsal borders, the protopod of pleopod 4 has 4 serrations along posterior border, and the terminal seta of the uropods is about 1.8 the length of rami.

The present work aimed to investigate possible spatial and seasonal patterns in the distribution of two sympatric serranids, the painted comber, Serranus scriba and the comber, Serranus cabrilla. The research took place at a NATURA 2000 site located at Sithonia peninsula, N. Greece. Underwater visual census was used for data collection; specifically, individuals from each species were recorded along four isobathic transects of 200 m2 each, placed every 5 m and ranging from 5 to 20 m depth. A total of 27 samplings were conducted between September 2010 and August 2011. The results clearly demonstrated complementary bathymetric distributions for S. scriba and S. cabrilla, the former mostly occurring until 10 m depth, and the latter in deeper layers. This pattern was maintained during the whole season. In addition the two species exhibited differences in their preferred substrate type and their pattern of association to the sea bottom. Our results were viewed under the light of resource portioning between the two sympatric species.

The mass mortality suffered by the sea urchin Diadema antillarum between 1983–1984 is considered one of the major causes of coral reef degradation in the Caribbean. Its near disappearance resulted in a disproportionate growth of macroalgae that has led to a ‘phase shift’ from coral-to-algal dominated reefs. The close relationship between this echinoid and the functioning of coral reef ecosystems makes it imperative to better understand the potential for recovery of its populations. From 2009 to 2011, we assessed the density and size structure of D. antillarum in various reefs where previous population data were available. Results indicate a modest increase in density in all localities with respect to the last time they were surveyed in 2003/2004. Nevertheless, density values are still lower than values reported for the island prior to the die-off. Overall density did not surpass 1.49 ind. per m−2, and did not change considerably during the studied period. Lack of population growth coincided with a lack of juveniles; suggesting that population growth at the studied sites may be limited by the number of individuals recruiting into the juvenile stage.

We examined the distribution, hatch-date, growth, and mortality of larval Benthosema pterotum, a dominant pseudoceanic myctophid in the shelf region of the East China Sea, during early autumn when the main spawning has been predicted. This species is a key species in the food web of this area. Larvae were abundant in the area south of Cheju Island (60–80 m depth), corresponding with the adult habitat. Occurrence of the larvae was restricted to the onshore side of the shelf-break salinity front, indicating that this front acted as a barrier restricting the offshore dispersion of the larvae. In the area where the larvae occurred, a cyclonic eddy is formed, which is considered to limit the dispersal of the larvae, enabling them to recruit into the area of adult habitat. Modes of hatch-date appeared from late August to early September and from mid to late September, suggesting that large-scale spawning events occurred at least twice during the spawning season. Since the modes coincided with the new moon period, B. pterotum is suggested to spawn periodically once a month around the new moon, resulting in efficient mating and fertilization. Mean absolute growth rate (0.26 mm d−1) and weight-specific growth rate (18.8% of dry body weight d−1) were higher than previously reported values of other subtropical–tropical myctophids, which would be related to the high food availability in the study area. Daily instantaneous mortality coefficient during the first two weeks after hatching was estimated to be 0.28 d−1 (equivalent to 24.7% mortality d−1).

The grouper Cephalopholis taeniops is a carnivorous fish of the Cape Verde coastal marine ecosystem. Nothing is known regarding the age and growth of this epinephelid. In this study, the age and growth of C. taeniops was investigated by annual growth increment counts from 2804 specimens (7–51 cm total length) collected between January 2005 and December 2011. Whole otoliths underestimated the age indicated in sections by approximately 70%; therefore, sectioned otoliths were used in this study. A year's growth was represented by one opaque and one translucent ring. There was no apparent time lag from the start of the increase in the seawater temperature and the beginning of the formation of the opaque ring. The formation of the translucent rings coincided with a decrease in surface seawater temperature. Cephalopholis taeniops is a slow-growing and long-lived species, with ages of up to 20 years recorded. The seasonalized von Bertalanffy growth function was the best fitted among the four models tested, with an Akaike weight higher than 0.99. Growth was described by the seasonalized von Bertalanffy growth function as follows: L∞ = 54.26 cm, k = 0.135 year−1, t0 = −0.853 year, C = 0.439 and ts = 0.667.

Specimens of European hake were collected by a traditional demersal trawl between July 2004 and June 2007 from İzmir Bay, Central Aegean Sea. A total of 2108 individuals were sampled during the study and the female: male sex ratio of the stock was 1:0.89. The length–weight relationship was W = 0.00341L3.24 (R2 = 0.994) for all individuals. A high gonadosomatic index was evident over most of the year but it was minimal from August to October. The estimated age composition was 1–5 years; the length and weight at infinity were calculated as L∞ = 54.53 cm and W∞ = 1455.77 g respectively. In addition, growth coefficient was found to be k = 0.315 y−1 and to = −0.223 y (R2 = 0.99). Total mortality ratio of the stock was calculated as Z = 1.539 y−1, while natural and fishing based mortality ratio were estimated as M = 0.579 y−1 and F = 0.959 y−1 respectively, with the exploitation ratio (E) of the stock estimated to be 0.624.

Latitudinal patterns of composition, biogeographic affinity and indicators of taxonomic diversity are described for the by-catch fish community in five typical shrimping areas in the Mexican Pacific (Upper Gulf of California, Sinaloa-Nayarit, Jalisco-Colima, Michoacán-Guerrero and Gulf of Tehuantepec). The taxonomic composition included two classes, 20 orders, 65 families, 147 genera and 292 species. The family Sciaenidae was the best represented with 33 species, whereas at the genus level, Anchoa was represented with eight species. A high percentage of the species showed wide distribution ranges (30.2% for Cortez Province ~ Panamic Province; 21.3% for San Diego Province ~ Panamic Province); nevertheless, each ecosystem included a characteristic combination of species, apparently related to the physiographic conditions of the ecosystems. Species richness showed a pronounced decrease from the Upper Gulf of California, which has warm-temperate features, to the Gulf of Tehuantepec, which has tropical conditions; this is an opposite trend to that observed in the taxonomic diversity indicators, suggesting that a taxonomic redundancy was present in tropical areas and higher taxonomic diversity was present in the Upper Gulf of California, despite the lower species richness. This is explained by the prevailing environmental conditions and isolation processes generated during the formation of the Gulf of California.

Recent observations of unusual mass stranding and mortality of two Indian Ocean crustacean species, the swimming crab Charybdis smithii and the mantis shrimp Natosquilla investigatoris, are documented and analysed. Strandings of C. smithii were observed for the first time in the equatorial Indian Ocean, the main area of its pelagic distribution. Strandings of mantis shrimps are reported from throughout the western Indian Ocean; occurrences of mass stranding in the Maldives Archipelago mark an extension of the known range of N. investigatoris into the central Indian Ocean. Mortality of crabs probably represents a ‘catastrophic event’. In contrast, mantis shrimp strandings, which were always associated with a sudden increase of its biomass (‘blooms’), are apparently post-reproduction mortalities indicating potential semelparity for this species.