In recent years, the scientific publishing world has seen the creation and rapid growth of online journals, which do not respect the long-standing gentleman's agreement that has functioned as the primary quality-control mechanism for science: bona fide peer review and editorial oversight. Such predatory journals take advantage of the low cost and ease of online “publishing,” the open access movement, and use feigned associations with international standards and misleading claims of impact factors, aimed at deceiving researchers (especially inexperienced scientists) into believing they are legitimate. We present the history, evolution, and tactics of such journals, as well as recommendations for dealing with this threat to science itself.

One of the biggest problems faced by fisheries management is the issue of bycatch and discards. The target species of fisheries are often found in association with other organisms. Despite attempts to reduce bycatch through technical modifications, the indiscriminate nature of many fishing gears means that nontarget species become incidental catch or bycatch. This study assessed the spatial variation across four fishing grounds in the composition of bycatch of an otter trawl scallop (Aequipecten opercularis) fishery in the Irish Sea. The results showed that the percentage of bycatch in the fishery as a whole was relatively low at 7.42 ± 0.52 by weight of the total catch. In 2012, the total bycatch for the fishery was estimated to be 309 tonnes compared to landings of queen scallops of 2,410 tonnes, landed by Manx trawlers either to the Isle of Man or United Kingdom. Significant differences were found between the four fishing grounds in relation to mean catch by weight, mean bycatch by weight, and bycatch species composition; however, there was no significant difference found in diversity and species abundance among the four fishing grounds. The results demonstrated that fishing ground was the dominant factor controlling bycatch variation within this fishery, which was related to some extent to water depth. The findings of the study indicate that understanding variation in bycatch in relation to the characteristics of different fishing grounds would enable fishermen and managers to manage (minimize) bycatch through the use of temporary spatial management measures.

The senatorial scallop Chlamys senatoria (Gmelin, 1791) is a commercially important species but poorly understood in the Philippines. To provide biological information for future conservation and management, the ecology and reproductive biology of the senatorial scallop in Gigantes Islands, Carles, central Philippines were investigated from June 2013 to May 2014. Ecological parameters were monitored during the sampling period. Scallops were collected monthly from the catches of hired divers. The samples were measured, dissected, and processed for histological analysis and fecundity was also determined. Results demonstrated that C. senatoria occurs in rocky and sandy areas at 18–22 m. Physico-chemical parameters showed minimal variations over an annual cycle with sea bottom water temperature of 25–27°C, salinity of 33–35, pH of 8.0–8.4, and dissolved oxygen of 5.6–6.7 mg/l. Macroscopic and microscopic examination of gonads confirmed that this species is dioecious with no apparent external dimorphism. Five distinct gonad stages were observed: developing, ripe, spawning, redeveloping, and spent. This species spawns throughout the year (protracted or continuous) with a major peak from December to February and a minor peak in August. Size at maturity (50% of population is mature) was 57.1 and 59.5 mm shell height for males and females, respectively. Fecundity ranged from 5.8×10⁵ to 2.7×10⁶ oocytes/female with a mean of 1.3×10⁶ ± 5.4×10⁵ oocytes/female. Harvesting of scallops should be regulated during the months of peak spawning activities (August and December to February) and sizes should be limited to individuals >59.5 mm shell height.

This study describes the larval development of the Venerid bivalve mollusc Anomalocardia brasiliana “berbigão” under laboratory conditions. The clams were collected at Mangue Seco beach (Pernambuco, northeastern Brazil) and transferred to the laboratory where their gametes were released spontaneously. Trochophore and D larvae were identified in the hatchery from 18 to 24 h afterward. Dlarvae had an average length (L) of 71.9 µm, remaining at this stage until the 5^th day, when first umbo veligers appeared (L = 115.9 µm). Pediveliger larvae (L = 183.2 µm) were observed after the 9^th day. Within 15 days larvae reached juvenile stage (L = 282.0 µm) with growth lines in the shells. Survival was 58.8%, 20%, 60%, and 100% for D larvae, umbo veligers, pediveligers, and juveniles, respectively. To our knowledge, this is the first report of the hatchery rearing for A. brasiliana and serves as a basis for future research and culture of this species.

The alien bivalve Ruditapes philippinarum (Manila clam) was intentionally introduced along the Italian Coast of the northwestern Adriatic Sea for aquaculture purposes in 1983. In February 2013, R. philippinarum was recorded at a site of the northeastern Adriatic Sea (Zelena Laguna, vicinity of city Poreč, west Istrian Coast, Croatia). This finding represents the first record of R. philippinarum in Croatian waters. The colonized site is located at a distance of approximately 100 km by a straight line in the west east direction from the site where the mollusc was firstly introduced. At Zelena Laguna, R. philippinarum colonized the intertidal sandy substrate together with the native species Ruditapes decussatus. The two sympatric species were initially differentiated based on the morphology of the siphons. Molecular analysis of 16S rRNA gene confirmed the morphological distinction between the two species. Although the two species are very similar in shell morphology, the relationships width/length and width/height were negative allometric for R. decussatus and isometric for R. philippinarum. The relationship height/length was isometric for both species. Additionally, the length of the pallial sinus was significantly different between the two species (P < 0.001).

Capo Peloro Lagoon is a coastal brackish system in northeastern Sicily (Italy), consisting of Ganzirri Lake and Faro Lake. The biological effects related to physicochemical parameters were assessed in two autochthonous clam species, Tapes decussatus and Tapes laeta, chosen for their abundance and economic interest, collected from the two Ganzirri Lake subbasins. Higher temperature and salinity values along with lower dissolved oxygen levels were recorded at the southernmost (site B) relatively to northernmost (site A) subbasin. A battery of biomarkers was investigated in clam gills, including histomorphological endpoint, cholinergic neurotransmission, oxidative stress, and hypoxia biomarkers. Both clam species from site B showed altered gill histomorphology attributable to inflammatory processes. A compromised cholinergic neurotransmission, stimulation of the antioxidant defense system, and onset of hypoxic adaptive responseswere also observed. Overall, data suggest that the environmental variables, as those recorded in the southernmost subbasin ofGanzirri Lake, adversely interfere with the physiological function of the gills, triggering a number of adaptive responses in the clams.

Monitoring gonadmaturation for protandrous and functional hermaphrodite species such as the giant clamTridacna maxima is difficult due to the juxtaposition and relative proportion ofmale and female tissues in the gonad [gonadal sex ratio (GSR)]. Here, the relevance of the widely used gonadosomatic index (GSI) as proxy of giant clam gonad maturation is tested with a large dataset (n = 265). Gonadosomatic index is compared with other indices, namely the proportion of the male part harboring spermatozoids, the proportion of empty oocyte follicles, the mean oocyte diameter, and the oocyte elongation. At gonad scale, high index variability highlighted partial spawning. At individual scale, male and female maturation proxies were contrasted, showing either asynchronous emissions of male and female gametes or contrasted spermatogenesis and oogenesis duration. The GSI was mostly driven by the number and diameter of oocytes and therefore it is recommended here as primary proxy for female maturity. Except for the oocyte elongation, all indices were affected by the GSR, which ruled out drawing conclusions at population scale. These results highlight the need for maturation stage proxies that are optimized for functional hermaphrodite species.

Stable carbon and nitrogen isotope analyses were used to evaluate the influence of microalgal diet on growth and survival of hatchery-reared Pacific oysterCrassostrea gigas larvae.D-veliger larvae were fedmonospecific diets of Pavlova lutheri (P), Tahitian Isochrysis aff. galbana (T), and Chaetoceros calcitrans (C), and a standard hatchery trispecific diet of 25P:25T:50C (PTC). The dietary effects on nutrient assimilation, isotopic turnover rates, and discrimination factors were assessed using exponential models. Of the four dietary treatments evaluated over the 15-day feeding trial, larvae fed C. calcitrans and PTC had the best growth and high survival. Larvae in all dietary treatments had relatively high isotopic turnover rates (0.075–0.327/day), although some discrimination factors found in this study were out of the normal range for aquatic invertebrates (Δ¹³C: 0.4‰–4.1‰ and δ¹⁵N: 0.1‰–5.3‰). Overall, the turnover rates and discrimination factors for δ¹³C and δ¹⁵N indicated that C. gigas larvae assimilate C. calcitrans and PTC best under hatchery rearing conditions. The results demonstrated the application potential of stable isotope analysis to evaluate optimal diets and feeding regimes to enhance hatchery performance of bivalve larvae and postlarval stages.

The process by which molluscs form their shells is complex and not well understood. The bulk of the mineral component of the shell is calcium carbonate, appearing either in calcite form or as aragonite, and sometimes vaterite. Various models have been proposed to explain how the mineral crystal is produced, including direct secretion and also formation in hematocytes. When other metals are present in the environment around the oyster, they can be incorporated into the mineral crystal structure as much as their concentration and the steric constraints of the crystal will allow. The nature of how these metals get incorporated is also not well understood. The purpose of this study was to determine if the relationship between the concentrations of trace metals in the shells of the eastern oyster Crassostrea virginica reveals anything about the process of biomineralization in molluscs. Oysters were harvested from marked locations and selected to be of similar age and development. Their shells were cleaned and dried, and the mass and dimensions of each shell was measured. The shells were crushed to a fine powder, and 25 g of shell was dissolved in a 5:1 mix of metal-free concentrated nitric acid and 30% hydrogen peroxide, to liberate the metal constituents of the shell. The metal concentrations were measured by inductively coupled plasma optical emission spectroscopy. Metal concentrations were plotted against three separate health condition indices and against one another. Metal concentrations were also grouped by the oyster's geographic location and regression analyses were conducted to identify or eliminate site as a potential explanatory variable. There was no significant correlation between any metal concentration in the shell and the health of the oyster. Differences in metal concentration with geographic origin were very slight, with a single exception. Oysters taken from the Lynnhaven River had lower amounts of silicon and nickel than elsewhere, by a slight margin. Four groups of metals appear in proportional amounts. Silver and iron always appear in trace quantities but in a 1:6 ratio. Copper and boron also appear in trace quantities in a 1:4 proportion. A group including vanadium, thallium, manganese, strontium, magnesium, sodium, and potassium appear in proportion to one another, and together can account for as much as 3% of the metal mass of the oyster shell. A fourth group including antimony, nickel, and silicon also appears in constant proportions to one another, and also can account for 3% of the metal mass in the shell. The third and fourth groups of metals are totally exclusive of each other, such that if one group is present in the oyster, the other group is never detected. Proportional amounts of metals and exclusivity of groups of metals strongly suggests metabolic control of metal incorporation into oyster shells. It is also possible that more than one mechanism for shell formation exists.

A 717-bp 5′-flanking regulatory sequence of the metallothionein gene in Crassostrea hongkongensis (ChMT) was isolated using anchored polymerase chain reaction. Several regulatory elements embedded in the flanking sequence, including the central promoter region, five putative metal-responsive elements (MRE), and an octamer-binding site (OBS), were analyzed using online prediction software. Then, the effects of element-based promoter truncations in the upstream regulatory region of ChMT on the metal stress response were examined. The expression levels of the promoters of various lengths were determined individually using a luciferase reporter gene in HEK293T cells. Transfection assays revealed that MRE1- and MRE5-containing DNA fragments inhibited transcription, whereas MRE4-containing DNA sequences activated promoter expression under both metal-stressed and unstressed conditions. A 39-bp DNA fragment containing the OBS was shown to respond positively to metal stress induced by cadmium and copper, but not to mercury. MRE2- and MRE3-containing DNA fragments comprised a portion of the central promoter region, the loss of which resulted in a significant reduction in promoter activity. Interestingly, the loss of promoter activity due to MRE3 deletion could be rescued by copper-induced stress. This study demonstrates the importance of MRE and additional regulatory elements in the regulation of ChMT promoter expression in response to metal stress.

The Deepwater Horizon (DWH) oil spill in 2010 resulted in the release of millions of liters of oil into the Gulf of Mexico. Dispersants such as Corexit 9500A were used to disperse oil both at the well-head and at the surface. Polycyclic aromatic hydrocarbons and dispersants have been shown to deleteriously affect early life stages of organisms including oysters. This study examined the impacts of chemically enhanced water-accommodated fractions [CEWAF; 1.29–26.14 µg/l tPAH₅₀ (a sum of 50 different polycyclic aromatic hydrocarbons)], high-energy water-accommodated fractions (HEWAF; 16.53–248.89 µg/l tPAH₅₀), and dispersants (0.625–10 mg/l) on the cellular functions (viability, mitochondrial membrane potential (MMP), reactive oxygen species production (ROS), and acrosomal integrity) and resulting fertilization success of eastern oyster Crassostrea virginica spermatozoa. While viability of spermatozoa was not affected by CEWAF and HEWAF at concentrations tested, dispersant exposure caused significant decrease in viability at the highest concentration tested. Fertilization success as well as MMP and ROS production were significantly decreased upon exposure to CEWAF, HEWAF, and dispersants. Also, although not affected by HEWAF exposure, acrosomal integrity decreased upon exposure to CEWAF and dispersants at concentrations tested. The results of this study suggest that impaired fertilization and reduced viability observed after exposure to DWH oil spill contaminants may result, at least partially, from alterations of cellular functions of spermatozoa and contribute to negative effects on oyster populations, and thus the ecology and economy of the Gulf of Mexico.

Changes in the timing and interaction of seasonal high temperatures and low salinities as predicted by climate change models could dramatically alter oyster population dynamics. Little is known explicitly about how low salinity and high temperature combinations affect spat (<25mm), seed (25–75mm), andmarket (>75mm) oyster growth and mortality. Using field and laboratory studies, this project quantified the combined effects of extremely low salinities (<5) and high temperatures (>30°C) on growth and survival of spat, seed, andmarket-sized oysters. In 2012 and 2013, hatchery-produced oysters were placed in open and closed cages at three sites in Breton Sound, LA, along a salinity gradient that typically ranged from 5 to 20. Growth and mortality were recorded monthly. Regardless of size class, oysters at the lowest salinity site (annualmean = 4.8) experienced significantly highermortality and lower growth than oysters located in higher salinity sites (annual means = 11.1 and 13.0, respectively); furthermore, all oysters in open cages at the two higher salinity sites experienced higher mortality than in closed cages, likely due to predation. To explicitly examine oyster responses to extreme low salinity and high temperature combinations, a series of laboratory studies were conducted. Oysters were placed in 18 tanks in a fully crossed temperature (25°C, 32°C) by salinity (1, 5, and 15) study with three replicates, and repeated at least twice for each oyster size class. Regardless of temperature, seed and market oysters held in low salinity tanks (salinity 1) experienced 100% mortality within 7 days. In contrast, at salinity 5, temperature significantly affected mortality; oysters in all size classes experienced greater than 50%mortality at 32°C and less than 40%mortality at 25°C. At the highest salinity tested (15), only market-sized oysters held at 32°C experienced significant mortality (>60%). These studies demonstrate that high water temperatures (>30°C) and low salinities (<5) negatively impact oyster growth and survival differentially and that high temperatures alone may negatively impact market-sized oysters. It is critical to understand the potential impacts of climate and anthropogenic changes on oyster resources to better adapt and manage for long-term sustainability.

Oyster production in Connecticut historically has had large fluctuations due to two major factors: disease epizootics caused by a protozoan parasite multinucleate sphere X (Haplosporidium nelsoni), and long periods without successful natural sets. A field trial was performed to investigate whether the remote set of oysters can be used to restock natural beds during mortalities caused by disease epizootics and lack of recruitment due to periods without sets. Disease-resistant oysters were remote set in a hatchery and placed either in or without biodegradable nets on a natural bed. Aged, clean cultch was used as the control, and the growth, mortality, predation, fouling, and prevalence of disease were monitored for two growing seasons. The oysters grew to market size (3 inches, 76.2 mm) in 15 mo. Predation, due mainly to Atlantic oyster drills Urosalpinx cinerea, and overgrowth of oysters caused a mortality of 72% in the oyster seed during the first growing season. More abundant wild oysters set but fewer fouling organisms landed on the remote-set shells than on the clean cultch. To evaluate the effect of siltation on mortality, the oysters were left on the natural bed instead of being transplanted to growing areas, as is standardly done in commercial shellfishing operations. During the second growing period, siltation caused additional mortality until only 1.5% of the oysters deployed were alive. The method of restocking natural beds in Connecticut with remote-set oyster seed for use by the oyster industry looks promising due to the fast growth of the oyster seed. This experiment also demonstrates the challenges presented by nonharvest oyster restoration activities due to significant siltation-associated mortality.

The utility of shell overlays to oyster (Crassostrea virginica) plantings as a cownose ray (Rhinoptera bonasus) predator deterrence mechanism was examined. Typical industry practice of oyster seed planting was followed in an experimental design employing treatment areas of 0.5–1.0 acre (0.2–0.4 hectare). Areas were prepared in the Lower Machodoc Creek, Virginia, by the initial application of shell to insure a stable substrate under planted seed oysters. Seed oysters were planted using standard industry methods. Experimental areas were located, two upstream and two downstream, of a constriction in the Lower Machodoc that dictated differing physical environments in the respective locations with downstream locations being more exposed to northeast wind-driven stresses and, historically, a greater incidence of ray predation. Once oysters were planted, two of the areas, one upstream and one downstream of the aforementioned constriction, were additionally treated with a shell overlay as a predation deterrent. Oyster seed were planted in the experimental plots in February 2012. Market oysters were harvested from the experimental plots in December 2013 and January 2014. Final harvest data demonstrated that shell overlays do not offer additional protection to planted oyster seed with respect to possible cownose ray predation. Evidence of predation in the form of characteristically broken oyster valves were recorded in all treatment areas. Concurrent stomach content analysis of rays captured at the study location and observations of fouling community associated with the cultured oysters taken during the harvest operation indicate broad dietary preferences for rays when such a variety exists in the foraging region. For rays, oysters are not the singular preferred diet item, although localized and intensive feeding on oysters remains an option with a wide foraging range. Areas without overlay demonstrated higher production than those with shell overlay. Shell overlays are not recommended as predator deterrents for cownose rays in large deployments of unprotected oyster seed.

The flat oyster Ostrea edulis (Linnaeus, 1758) is a commercially valuable species in Europe. The production of O. edulis natural spat has decreased in the past, and it is insufficient to meet demand. Thus, the importance of hatcheries in the production of oyster spat is increasing. The conditioning of O. edulis broodstock may be improved by manipulating several external factors such as temperature, food supply, and photoperiod; however, few studies have reported the effect of these parameters on O. edulis gametogenesis and conditioning. In this report, the combined effects of temperature and photoperiod on broodstock conditioning of O. edulis in winter were studied to provide a protocol that improves flat oyster conditioning. After a resting period in autumn, in winter, oysters' gonads are restructured, and the natural process of gonadal maturation is initiated. Oyster gonads showed follicles in intermediate maturation stages, with the presence of both male and female germinal cells in the same follicles but at different stages of maturation. The combined effect of temperature (TG14-18) and photoperiod on oyster conditioning in winter was evaluated by using direct indexes. Oysters conditioned with a gradient of temperature and a gradient of daylight (PG8-16), a P16 regime or under natural environmental conditions began to spawn 4 wk after the beginning of conditioning. Oysters treated with a P8 regime needed a week more to start spawning. Spawning was a continuous process that lasted for 7 wk. When the total amount of released viable larva was compared, the positive influence of photoperiod was much more evident. Total larval production was two or three times higher in the oysters treated with a gradient of daylight (PG8-16). In summary, using the conditions of temperature and photoperiod described in this study (TG14-18 and PG8-16), it was possible to improve flat oyster conditioning in winter, producing an important amount of viable larvae over a period of 2 mo.

The protozoans Perkinsus marinus, Perkinsus olseni, Bonamia ostreae, Bonamia exitiosa, and Marteilia refringens are responsible for some of the most detrimental diseases in the production of cultivated shellfish worldwide and are classified as notifiable diseases by the World Organization for Animal Health (OIE). This study examined the general health status of wild and cultured bivalves from southern Brazil and included diagnostic tests for the presence of Perkinsus sp., Bonamia sp., andMarteilia sp. Cultured bivalves included the mangrove oyster Crassostrea gasar (syn. Crassostrea brasiliana), the brown mussel Perna perna, the lion's paw scallop Nodipecten nodosus, andwing pearl oyster Pteria hirundo. Themangrove oyster Crassostrea rhizophorae and the carib pointed venus clam Anomalocardia brasiliana (syn. Anomalocardia flexuosa) were collected from wild populations. A variety of parasitic or commensal organisms were detected by histology including Ancistrocoma-like and Spenophrya-like organisms; Bucephalus genus, Nematopsis sp., Steinhausia sp., and Tylocephalum sp.; unidentified trematode; unknown protozoan and metazoans; and an amoeba parasite. Hemocytic infiltration was most commonly associated with parasitized animals. Histological, culture and molecular diagnostic tests did not find any evidence of the presence of OIE-listed pathogens or related species in this study. Although the current survey did not identify any pathogens or diseases of concern, it provides baseline health assessment data for these species against which any future disease developments or significant changes in population health can be compared. These data are also valuable with respect to the development and implementation of public policies related to aquatic animal health.

Understanding the population dynamics and complete life cycle of bivalves is important for effective management of these commercially and ecologically important organisms. Most of the literature and research on bivalves to date has focused on juvenile and adult bivalves, but much less is known about larvae. The larval stage has been difficult to study due to the lack of a rapid automated approach for identifying the species. A new technique, called ShellBi, utilizes color patterns on the larval shell under polarized light to identify bivalve larvae. The objective of our research was to review the scientific basis for ShellBi and to apply it to bivalve larvae from the Choptank River in mesohaline Chesapeake Bay, with the goal of distinguishing larvae of the eastern oyster (Crassostrea virginica) from seven other species that spawn at the same time. A digital camera and polarized light microscope was used to capture images of the larval shells of the eight species under standard and cross-polarized light. Images of C. virginica were distinguishable from those of other species based on color patterns, especially at later stages of development. These images could serve as a visual guide to distinguish larvae of C. virginica from other bivalves inhabiting mesohaline tributaries of Chesapeake Bay.

The production of toxic secondary metabolites by marine phytoplankton and their accumulation in molluscs and fish has ecosystem-wide and human health impacts. The potent neurotoxin saxitoxin and its analogs, which can cause paralytic shellfish poisoning, are produced by species of the dinoflagellate genus Alexandrium. These toxins can accumulate in filter-feeding molluscs, including commercially grown species of shellfish. A feeding experiment was designed to assess the use of quantitative polymerase chain reaction to detect a gene involved in saxitoxin biosynthesis (sxtA) in two commercial oyster stocks. Both diploid and triploid Crassostrea gigas were fed with toxic cultures of Alexandrium minutum over a period of 12 days to allow toxin accumulation. A barcoding gene specific to Alexandrium (ITS 5.8s rRNA) and the sxtA gene, domain 4, which is specific to the saxitoxin synthesis pathway, were assayed. Both targets were detected in oysters collected after 6 and 12 days feeding with A. minutum, and after 24 h of depuration during which the oysters were fed nontoxic microalgae only. The target genes were not detected in control oysters. These methods can be used as a relatively rapid and inexpensive screen that is indicative of the presence of saxitoxin-producing microalgae in shellfish.

Molluscs belong to one of the two protostome superphyla, the Lophotrochozoa. Among molluscs, bivalves show a characteristic shell morphology separated bilaterally into two plates. The connection between the modification of the development and evolution of the molluscan body plan can be study identifying and obtaining information on the genes that regulate the development of bivalves. Homeobox genes are involved in body plan formation and in the regulation of many developmental processes in bilateria. For this reason, the evolutionary history of Hox, ParaHox, EHGbox, and NK homeobox gene families could be crucial to understand the evolution of molluscan body plans and phylogeny. The aim of this work was to compare these genes from different Bivalvia families. In this study, 22 homeobox gene fragments from five bivalve species were identified, and then these homeodomain sequences were compared with those available from other bivalves. The Hox cluster in bivalve molluscs has 11 genes. Regarding the ParaHox cluster, current data suggest that the ParaHox genes are also conserved in bivalves. Two EHGbox genes are well conserved in bivalves (en and Gbx); however, there are no data about the presence of the third one (Mnx). The NK cluster has not been examined in depth in Bivalvia; however, the conservation of Tlx and NK2 genes in different species can be confirmed. The study of the genes reported here might contribute to the understanding of their evolutionary history within the phylum and the involvement of these genes in the body plan of bivalves.

The wavy turban snail Megastraea undosa and keyhole limpet Megathura crenulata, two gastropods with commercial importance, five macroalgae, and one seagrass were collected at Bahía Tortugas, Baja California Sur, Mexico, for analysis of stable isotope ratios. The δ¹³C and δ¹⁵N isotope signatures obtained from gastropod muscle tissue were different between the two gastropods. Isotope signatures of M. crenulata had more enriched δ¹³C (-14.35‰ ± 1.66‰) and δ¹⁵N (15.48‰ ± 0.67‰) than M. undosa isotope signatures for δ¹³C (-17.59‰ ± 2.43‰) and δ¹⁵N (12.42‰ ± 0.61‰). Seaweed isotope signals varied from -21.8‰ to -11.4‰ for δ¹³C and 9.3‰ to 10.9‰ for δ¹⁵N. The δ¹³C of detritus was -7.93 and of tunicates was -9.3‰ and the δ¹⁵N of detritus was 12.4 and of tunicates was 8.1‰. Mixing models showed that the greatest contribution to the diet of M. undosa was from Prionitis cornea and Gelidium robustum. For M. crenulata, it was from detritus and Macrocystis pyrifera. A higher trophic position (3.1) was observed for M. crenulata than M. undosa (2.3), which clearly reflected the differences in their feeding habits: M. undosa is a herbivore and M. crenulata is an omnivore.

This article describes the changes in the concentration of lipids, proteins, and carbohydrates in the gonad, digestive gland, foot and mantle of Haliotis fulgens over a reproductive cycle. An average of 30 specimens was collected each month between September 2011 and August 2013 from La Bocana, Baja California Sur, Mexico. The biometrics of each specimen were recorded, and gonads were processed using a standard histological method. Additionally, from February 2012 to February 2013, portions of nonfixed organs were frozen at -54°C for use in proximal analyses. This species showed gonadal development and spawning throughout the study period, with a peak in spawning from September through February, coinciding with sea surface temperatures near 20°C and the beginning of the decline in daylight. This study demonstrates that this species utilizes proteins, lipids, and carbohydrates stored in the foot during gonadal development and that lipid levels decrease in both the digestive gland and the gonad during spawning.

Apple snails of the genus Pomacea native to South America have invaded and become established in Europe, Asia, and the United States. Both the channeled apple snail Pomacea canaliculata and the island apple snail Pomacea maculata have been reported in theUnited States. The two species are difficult to distinguish usingmorphological characters, leading to uncertainty about the identity of the animals from populations in the United States. Because the snails are subtropical, their tolerance of low temperatures is a critical factor in limiting the spread of the animals from present localities along the coast of the Gulf ofMexico to more northern areas. The tolerance of P. maculata collected in Louisiana to temperatures as low as 0°C was examined. There was no mortality among animals maintained in water at temperatures of 20°C or 15°C for 10 days. Survival of animals during a 10-day exposure towater at temperatures 10°C and 5°C was 50%. The LD₅₀ for a 10-day exposure was 7°C. Snails did not survivemore than 5 days in liquid water at 0°C. Ammonia excretion by animals in temperatures of 20°C and 15°C was comparable to values reported for freshwater gastropods; at very lowtemperatures, excretion of ammoniawas decreased.Therewas no difference in themean values of the osmolality of the hemolymph of animals exposed to 20°C, 15°C and 10°C for 10 days. Sequencing of mitochondrial cytochrome oxidase 1 identified the animals in the Louisiana population used in this study as P. maculata.

Population dynamic studies of Dosidicus gigas have not been reported in Ecuadorian waters. The number of cohorts in the population and reproductive features such as sex ratio, seasonal changes in maturity stages, and size at first maturity are unknown. This knowledge is crucial in the study area, because it can provide fishery management support to Ecuadorian stakeholders. Biological data from 2013 (March–December) and 2014 (January–December) in Ecuadorian waters were analyzed. Biological sampling per month was carried out during every year in different coastal waters off of Ecuador. The biological findings indicated the presence of three size groups in the Ecuadorian squid stock, which estimated to be individuals less than 50 cm mantle length (ML). The monthly size groups changed between one and three size groups in 2013 and 2014. The ML at first maturity for females of jumbo squid estimated in 2013 was L_50% = 32.4 cm ML, and L_50% = 35.5 cm ML in 2014. For both fishing seasons, the ML-mantle weight relationship estimated for jumbo squid presented isometric growth, and the sex ratio for D. gigas showed that females were more abundant than males. This study found that the ML structure of jumbo squid, the number of size groups, and ML at first maturity are different from that previously estimated in traditional fishing areas of D. gigas in the eastern Pacific Ocean.

The nacre color of the pearl mussels is one of the most important traits for the pearl industry. In this study, to evaluate the effectiveness of the nacre color selection of the freshwater pearl mussel Hyriopsis cumingii, the characteristics of nacre color from a purple, white, and a commercial farmed strain were detected, respectively, by measuring the color parameters of CIEL*a*b* (CIELAB) system. The analysis of the variation among the color parameters showed that the uniformity of the nacre color in purple or white strain had been significantly improved over that of the farmed strain. The principal component analysis indicated that the first principal component (PC1) was most affected by color parameter a* where a positive value indicates a hue of red and a negative value indicates a green in the CIELAB color space. The second principal component (PC2) was most affected by color parameter b* where a positive value indicates a hue of yellow and a negative value indicates blue. The contribution rates of these PCs were 63.64% and 23.81%, respectively. The results also showed that the nacre color was obviously different among purple, white, and farmed strain, and the difference of nacre color between purple and white strain was primarily caused by color parameter a*. The discriminant functions for nacre colors were established and the rate of discriminant accuracy (P₁ and P₂) was 100% for all three strains. The results indicated that purple, white, and farmed strains could be clearly identified and differentiated on the basis of their nacre color, and the traits of nacre color could be purified through selective breeding.

Freshwater unionid bivalves play an important role in nutrient cycling and organic matter transportation and provide hard substrates for other benthic animals in freshwater ecosystems. Therefore, the conservation of unionid bivalves is considered essential for maintaining aquatic biodiversity. In this study, the assimilated food sources of six species of freshwater bivalves, Unio douglasiae, Unio douglasiae nipponensis, Unio biwae, Anodonta japonica, Pronodularia japonensis, and Lanceolaria grayana, were investigated using fatty acid trophic markers. The contribution (percentage of total identified fatty acids) of the trophic markers showed a similar tendency in all the bivalve species, even though they were sampled from various habitats. Fatty acid trophic markers of diatoms (20:5n3) and green algae and/or cyanobacteria (18:2n6 18:3n3) were dominant in all bivalve samples, ranging from 4.8% to 10.2% and 7.3% to 10.6%, respectively. Bacterial fatty acids were also detected in large amounts, ranging from 1.7% to 5.4%. In this study, all unionid bivalves contained diatom, green algal/cyanobacterial, and bacterial markers in substantial proportions, and no individual depended on a single food source, stressing the importance of ingesting and assimilating various food types.

The effects of clove oil, xylazine, cooling, carbon dioxide (CO₂), and magnesium sulfate (MgSO₄) were evaluated separately, in normal, mature crabs (n = 55) of Portunus sanguinolentus having an average weight of 69.98 ± 3.56 g (mean ± SE). In general, crabs may be anesthetized by exposure to the gaseous anesthetic agent, by immersion in a solution or by injection. Induction was stress free with clove oil and anesthesia was maintained for 100.6 ± 8.1 (mean ± SE)minutes at a ratio of 0.25 ml/lof seawater. The shortest induction time was obtained by cooling at crash ice. Thus, induction time 223.3 ± 24.77 sec and rapid recovery 100.67 ± 21.4 sec was obtained by 165 mg/l CO₂ with sea water bath immersed at 15 min. The duration of anesthesia was also longer with clove oil compared with other anesthetic agents. The objective of this study was to evaluate the effects of some selected anesthetic agents on P. sanguinolentus.

Understanding aspects of reproduction is important for studies of life history strategy and for resource management. The influences of nine factors (five intrinsic, four extrinsic) on the reproductive attributes egg diameter, egg dry weight, and clutch size (i.e., number of eggs in egg mass) of female stone crabs (genus Menippe (Say)) from Tampa Bay, FL, waters were investigated. Two intrinsic factors influenced reproductive attributes: carapace width was positively correlated with clutch size, and egg stage was positively related to egg size. Three intrinsic factors—genotype class, damaged or missing pleopods, and missing claws or legs—had no influence on any reproductive attribute. The four extrinsic factors each influenced at least two reproductive attributes. Egg diameter and weight were significantly larger and clutch size was significantly smaller (1) in females uninfested by Octolasmis mülleri; (2) during the early part of the spawning season, when water temperature was 27°C or less; and (3) during the first year of the 3-y study. In addition, egg diameter varied significantly among season/year combinations. In all cases, when egg diameter and weight decreased, clutch size increased; suggesting that, in female stone crabs, selection for filling the available abdominal space with eggs is strong. Large eggs are known to produce larvae of high fitness in crabs. Because the largest eggs are produced during the early part of the spawning season, females should be protected from harvest during that time. Shortening the harvest season in spring would eliminate those females from vulnerability to the fishery.

Temperature strongly influences the growth of crustaceans and directly controls distribution. Despite being commercially important, there are no data on temperature effects upon growth in newly settled southern Tanner crab Chionoecetes bairdi. Recently settled crabs were reared through three consecutive molts, both individually and in groups, at four different temperatures; 2°C, 6°C, 9°C, and 12°C. Survival was higher for crabs grown individually (92%) than those in groups (66%) owing to cannibalism, particularly during molting. There were no temperature effects on survival. Growth rate (mm/day) increased linearly with temperature, a product of exponential decline in intermolt period with increasing temperature and amolt increment that was relatively constant across temperatures. Growth rate, intermolt period, and growth increment did not differ between crabs grown singly or in groups. These data suggest that growth in 0 y aged southern Tanner crabs is strongly inhibited at temperatures less than 2°C. A small mesh beam trawl survey was conducted in the southeast Bering Sea during September 2012, a year when a cold pool (<2°C bottom water) dominated the middle shelf. Southern Tanner crab less than 12 mm (carapace width) were concentrated just north of the Alaska Peninsula and along the outer shelf where bottom water was more than 2°C, but largely absent from the middle shelf. In contrast, adult southern Tanner crabs were widely distributed across the middle and outer shelves. It was hypothesized that early juvenile southern Tanner growth is inhibited by cold pool conditions, prolonging vulnerability to predation, and reducing survival. In the future, if sea temperature rises and sea ice is diminished, less frequent and less intense cold pool events may lead to increased persistence of thermally suitable juvenile southern Tanner crab habitat across the southeastern Bering Sea middle shelf region.

The effects of seawater acidity induced by intraspecific competitor on food ingestion behavior of the white Pacific shrimp Litopenaeus vannamei were investigated. By using shrimp biomass as a proxy of their body odor concentration, food ingestion responses of the shrimp, as influenced by conspecific excreta-borne chemical cues, were monitored. The treatments produced pH variations, which in turn, affected ingestion responses. The effect of conspecific chemical cues on foraging behavior was monitored while presenting pelleted food amounting to 5% of the shrimp biomass. In aged seawater (ASW) containing chemical cues from conspecifics, L. vannamei food ingestion rose with increasing body odor concentration. The hypothesis that food ingestion is mediated by chemical cues excreted or secreted by shrimps was supported. Water acidification, however, as a result of shrimp soluble excreta, seemed to counteract the effect of those chemical cues. During the 24 h of shrimp fasting, acidification of odorless ASW increased with increasing shrimp biomass, from pH 8.08 to 7.90. After 2-h feeding, the same experimental set gained body odors generated during the feeding period and pH decreased to 7.2. Results show that, to an increase in ASW acidity corresponds an increase in food ingestion rate to those values observed for odorless ASW.