The seasonal variation of the inshore fish assemblage of Anegada Bay, North Patagonia, Argentina is described here. Three areas were seasonally sampled from 2007 to 2009 by means of a gang of bottom gill-nets. We found 21 coastal fish species, but species richness and fish number and weight changed throughout the year. The six species classified as dominant have national and regional value for artisanal and recreational fishing and were responsible for the seasonal variation in the fish assemblage. Both cluster and non-metric multidimensional scaling analyses based on fish number and fish weight indicated two major sample groups encompassing spring and summer (the warmer seasons) and autumn and winter (the colder seasons). The fish assemblage had higher species richness, dominance and abundance during the warmer seasons than during the colder seasons in the same years and at the same sites. Water temperature was the main environmental factor structuring the fish assemblage in Anegada Bay. We suggest that partial breeding migration toward the bay during warmer months could explain the seasonal pattern observed. Nevertheless, variation in temperature conditions agreed well with the pattern of seasonal changes, leading to an interaction between abiotic and biotic influences in determining the variability in this seasonal fish assemblage. We conclude that an understanding of species temporal and spatial patterns in areas of high ecological and economic value, as exemplified by Anegada Bay, are essential for the implementation of a management approach oriented toward ecosystem sustainability.

Fisheries by-catch is considered to be a major threat to loggerhead turtles in the Mediterranean Sea. Technical differences in both gear configurations (e.g. hook and bait type) and fisheries operations carried out by the Spanish Mediterranean surface longline fleet could have an effect on by-catch rates and size selectivity. The aim of the present study was to test the differences in by-catch per unit effort and body size of loggerhead sea turtles caught using different gear types in the Mediterranean surface longline fishery. Our results suggest that differences in the gear type used have an effect on catch rates and size selectivity. Thus, surface longliners targeting albacore (LLALB) using smaller hooks tend to capture smaller loggerheads but have the highest by-catch per unit of effort (BPUE), whereas other longlines, such as surface longliners targeting bluefin tuna (LLJAP) and traditional surface longliners targeting swordfish (LLHB), using larger hooks tend to select the larger animals; moreover, LLHB had the lowest BPUE. Disproportionate rates of fisheries-induced mortality on certain size/age-classes can differentially affect sea turtle populations, as each sea turtle age-class contributes differently to current and future reproduction. Thus, fisheries management should not only be focusing on preserving the large juvenile and mature turtles, but also on reducing the total by-catch. Thus, we recommend encouraging the use of LLHB versus other surface gears. We suggest that it is very important to take into account the gear type (and its particular catch rates) when making inferences about the impact of longline fisheries on sea turtle populations.

Information on the ontogeny of complement system might help us better understand the anti-infection mechanism in the early fish life. The ontogenic expression of the representative complement genes and their response to lipopolysaccharides (LPS) challenge in zebrafish larvae are reported here. The expression of C1r/s, C3, C4, C6 and MBL steadily increased before 21 days post-fertilization (dpf) and a decrease was detected thereafter. MASP expression elevated and peaked on 14 dpf and a decline followed. Bf expression fluctuated during the experimental period. Moreover, Bf (involved in alternative pathway, AP) expressed at higher levels than C1r/s (involved in classical pathway, CP), MASP (involved in lectin pathway, LP) and C4 (involved in both CP and LP) in the normal adult fish and larvae, suggesting the more significance of AP than CP and LP during the development of zebrafish. LPS challenge induced up-regulation of all the genes at 12 h in the adult fish. For the larvae, Bf, C3 (key complement component) and C6 (involved in lytic pathway) responded to LPS challenge at earlier stages than the other complement genes, with the up-regulation detected since 14, 14 and 7 dpf, respectively. In the larvae at 28 dpf, all the above three genes responded to LPS challenge by up-regulating their expression in a fashion similar to that of the adult fish, hinting that complement operating via AP develops earlier and plays a key role in protecting the larvae; it showed effective responses to LPS challenge from 14 dpf and might mature before 28 dpf.

The phenotypic shell shape variation of Mactra isabelleana was tested using the geometric morphometric method. Four localities were sampled along the Río de la Plata estuary and the coast of Buenos Aires province. Principal component analysis and canonical variates analysis of the first principal components were performed to reveal the shell variation and differences among localities, respectively. The specimens from different microhabitats mostly overlapped, although differences in shape were observed in the development of the umbo, the enlargement of the dorsoventral axes and the elongation of the posterior end. The ecological and physical parameters that could influence shell shape variation are discussed.

The branching structure of the coral colonies from the genus Millepora provides substrate, shelter, and food resources for several reef organisms, such as fish and invertebrates. The present work analysed the association and behaviour of reef fish on the fire coral Millepora alcicornis and M. brasiliensis from September 2010 to February 2011, on the coastal reefs of Tamandaré, north-east Brazil. A total of 473 reef fish individuals of 27 species were sighted associated with the coral colonies, mainly composed of juveniles (65%). The most frequently observed behaviours were sheltered/stationary and swimming close to the coral; however, individuals were also observed foraging and breeding among Millepora spp. branching colonies. The agonistic behaviour performed by Stegastes fuscus individuals was highlighted in the present study, especially against Chaetodon striatus, Diodon holacanthus and Ophioblennius trinitatis individuals. Millepora spp. hydrocorals are ecologically important for juvenile and adult reef fish belonging to several trophic guilds. The complex structure of the coral colonies provides a wide variety of ecological functions on coral reefs (e.g. shelter, reproduction area, food and even territory). Nevertheless, the abundance of branching fire coral in Brazilian reefs have been declining over the past years; therefore, efforts must be made to protect this key habitat.

The common starfish, Asterias rubens, occurs in fluctuating environments in the North Atlantic. To better understand energy allocation dynamics, we recorded gonad, body wall, and pyloric caeca (storage organ) indices between 2000 and 2004 from three different habitats. We applied a Fourier transform to the data to evaluate and compare the seasonal variation in these indices. Specific effects of emersion and salinity variation were examined in two laboratory studies. Differences in energy allocation were found between sites and temporally within sites. Food availability appeared to be the most important factor controlling allocation dynamics while fluctuating salinity and/or emersion had a significant but smaller impact. Only severe food shortage reduced reproductive investment indicating a preferential energy allocation to gonads. This study is the first to encompass a broad range of populations over several reproduction cycles and emphasizes the ability of A. rubens to adapt to a fluctuating environment.

Mussels are important components of rocky shore assemblages throughout the world. Several mytilid species are found as multilayered beds in the intertidal along the coasts of the south-western Atlantic. However, in contrast to the north communities in the Pacific and Atlantic, those of the south-western Atlantic are dominated by species of small size, locally named mejillines. These mid-intertidal beds attached to consolidated substrates are dominated by virtual monocultures of two small-sized species of Brachidontes: B. rodriguezii (d'Orbigny, 1842) and B. (Perumytilus) purpuratus Lamarck, 1819, respectively distributed in the warm and cold temperate sectors of the south-western Atlantic; both coexisting in the transition zone between 40° and 44°S latitude. Nevertheless, there has been some confusion about the separation of B. rodriguezii and B. purpuratus, as well as about the boundaries of their distribution ranges in the south-western Atlantic. Here, on the basis of a morphogeometric analysis of shell morphology, we describe a feasible way for the identification of both species.

The Cortes geoduck (Panopea globosa) has been considered a Gulf of California (GC) endemic but anecdotal and unpublished evidence has suggested its presence in Bahía Magdalena (BM), on the Pacific coast of southern Baja California. Establishing the identity of geoduck clams and their distribution limits is not only of clear biological significance to understand their structural and functional variation, but is also of consequence for their conservation and management, given the multi-million dollar fishery they support in north-west Mexico. We analysed Panopea clams from Mexican populations, including BM, using an integrative approach including genetics, morphometrics, and an ecological niche model. Our genetic results (restriction fragment length polymorphisms of nuclear ribosomal DNA and mtDNA cytochrome c oxidase subunit I sequences) clearly identify BM geoducks as P. globosa, implying a significant geographical range expansion outside of the GC and refuting its status as endemic to the Gulf. On the other hand, clams from BM were phenotypically different (shell significantly higher) from other Mexican P. globosa and Panopea generosa specimens, which may account for the confusion in their morphological identification. The ecological niche model for P. globosa, integrating ecological and distributional data from the GC, revealed a very low probability (<10%) that this species could successfully occupy BM. Our results and those of others suggest that the Cortes geoduck population in BM may be adapted to specific environmental conditions differing from those experienced by conspecifics inside the Gulf and is likely isolated. This is highly relevant for the management plans of Mexican geoducks.

The warm water Ophidiaster ophidianus has a protected status in the Mediterranean Sea and also occurs in the shallow subtidal of the Azorean Archipelago. From April 2007 to August 2009, the population structure and seasonal abundance of O. ophidianus was studied at different depths within a marine conservation area offshore from São Miguel (SAC: PTMIG0020, Natura 2000). Ophidiaster ophidianus showed a marked seasonal trend in abundance, with higher numbers being recorded from 5 m depth during spring and autumn, and higher numbers at 10 m depth in summer and winter. Densities ranged from 9 to 16 individuals per 100 m2 over the sampling period. The size–frequency distribution of O. ophidianus was uni-modal for each sampling month. Small individuals dominated at 5 m depth, intermediate-sized individuals at 10 m and larger individuals were more frequent at 15 m. The present study establishes population parameters for O. ophidianus and provides the necessary information for management purposes at the north-western periphery of its range in the Azores.

Oyster population reproductive capacity and dynamics are controlled at the most basic level by the observed sex-ratios. Since oysters are sequential, protandric hermaphrodites the population sex-ratio is related to the demographics (shell length, age, and biomass). Oysters were collected from June through to August 2008 at twelve bars in the James, Rappahannock and Great Wicomico Rivers, Virginia, USA. Bars were aggregated into five groups on the basis of similar age–length relationships. Sex-ratios (fraction female), age–length, and biomass–length relationships were determined for each group. The fraction female increased within increasing shell length, age, and biomass at all sites. Simultaneous hermaphrodites were rarely observed. Group specific differences in shell length (SL, mm) and age (yr) for the timing of the protandric shift were observed with the earliest shift from male to female occurring at ~60 mm SL and ~1.6 yr. The proportion of females observed in the larger or older individuals was at least 70–80%. Sex-ratios from summer 2008 were used to develop sex–length, sex–age, and sex–biomass keys that were applied to autumn-survey data from 2006, 2007, 2008 and 2009. In these years, sex-ratios by shell length and age were strongly biased towards males while the sex-ratio by biomass was strongly biased towards females. Disease mortality compounds natural and fishing mortality resulting in age/size specific cropping yielding truncated population demographics and an earlier protandric shift in populations on the extremes of the range examined. Regardless of location, market (>76 mm SL) oysters are predominantly female.

The biocrystallization process and the prescence of manganese in sagitta otoliths is described for the first time via electron paramagnetic spectroscopy. Spectra of Mn2+ are applied to verify inter-species differences in 12 Sciaenidae species and geographic variations among three stocks of banded croaker Paralonchurus brasiliensis and rake stardrum Stellifer rastrifer. Similar spectra shape and zero-field splitting D (22.4 mT) indicated that the biocrystallization process is the same for all fish species, at any stage of development and under different environmental conditions, corresponding to Mn2+ in the aragonite (CaCO3). Inter-species differences in Mn2+ concentration were detected regarding the otolith shape. Elongated otoliths have higher manganese concentrations compared to rounded otoliths. Geographic variations among stocks of P. brasiliensis and S. rastrifer could be detected. Fish stocks under riverine influence have less Mn2+ concentration than ones under marine influence. Manganese detection via electron paramagnetic spectroscopy is a non-destructive approach that can be useful in fish stocks studies.

The sailfish Istiophorus platypterus is one of the most common billfish species in the Mexican Pacific. Information about its feeding habits in the coastal region of Acapulco, Guerrero is extremely limited. In the present study we quantified the diet of sailfish, based on captures made from March 2008 to December 2009 by the sport fishing fleet of Acapulco. We analysed a total of 561 stomachs, of which 254 contained food (45%). The size interval of examined specimens was between 101 and 212 cm postorbital length and between 15 and 47 kg total weight. In general, teleosts were the most important prey, followed by cephalopods. According to index of relative importance, the most important species in the diet were the fish Auxis thazard (63.04%) and Fistularia commersonii (6.62%), followed by the cephalopod Octopus spp. (4.58%). There were no significant differences in the diet by sex (males and females), sexual maturity (immature and mature), or by season (warm and cold seasons). In all cases the most important prey species was A. thazard. We conclude that the sailfish I. platypterus off Acapulco behaves as a specialist predator because, despite the consumption of a high number of prey items, it feeds preferentially on a reduced number of prey species that form schools, and are available and abundant in the ocean.

This study was conceived to evaluate seasonal changes in the lipid reserves of the digestive gland of the carnivorous intertidal caenogastropod Nucella lapillus, using a stereological approach. Volume density of lipid droplets in the digestive gland, digestive gland weight and volume were assessed in animals collected in March, June, September and December on the Portuguese coast. Gonad development was evaluated to detect any relationship between lipid content in the digestive gland and the reproductive cycle. The quantitative light microscopic analysis demonstrates that lipid droplets are a major component of the digestive gland. In males, the digestive gland and its lipid reserves were quite stable without significant variations throughout the year. In females, the percentage of digestive gland volume occupied by lipid droplets was higher in June and December, coinciding with the highest values of digestive gland volume. Due to the conjugation of these two factors, in June and December the total amount of lipids in the digestive gland was substantially increased in females. In both males and females a relationship between the development status of the gonad and the lipid reserves of the digestive gland was not evident. However, significant differences in the digestive gland lipid reserves were detected between males and females in June and December, pointing to a sex related effect on lipid reserves. To evaluate the use of lipid reserves as energy source in N. lapillus, the consumption of digestive gland lipids was followed during a starvation experiment.

The snailfish Liparis tanakae is an annual fish, growing up to >300 mm in total length. This species is known as a predator of 0-year-old Japanese flounder Paralichthys olivaceus. To reveal when and where the predation occurs, monthly collections of both species at various depths were conducted off Fukushima, Japan. The snailfish inhabited shallow areas ≤50 m deep until June. Thereafter, they shifted their main habitat to offshore areas ≥100 m deep from July to September. The snailfish migrated to inshore areas with depths of ≤50 m again around October–December, during which time the habitat overlap between snailfish and 0-year-old Japanese flounder was observed. In that period, >40% of 0-year-old Japanese flounder were vulnerable to the snailfish. Larger snailfish showed stronger piscivory, and some flatfish were found in their stomachs. These results suggest that by not releasing hatchery-reared Japanese flounder until September can forestall predation by the snailfish.