During the past 40 y, commercial production of softshell clams,Mya arenaria, in the soft-bottom intertidal zone in Maine, United States, has decreased nearly 75%whereas dockside revenues have increased ca. 200%. The fishery is comanaged by coastal communities (some individually, some working together as a regional unit) and the state of Maine acting through its Department of Marine Resources. A number of shellfish management tools are available to clammers and stewardship committees to help increase or improve harvests. One of these, used by some communities, is the “conservation closure.” This is when large acres of mudflats (sometimes≥200) are closed to harvesting and fallowed for periods as long as a year because either the area is no longer productive, too few legal size clams (≥50.8-mm shell length) exist, or the community wishes to practice some direct measure to improve harvests such as transplanting clams from one area of the intertidal to another. A series of comparative, large-scale manipulative experiments were conducted at each of two intertidal mudflats in three geographically distinct coastal communities along the Maine coast during 2014–2015 to examine potential management tools for areas closed for conservation purposes. Specifically, tests were conducted to determine the efficacy of using plastic predator-deterrent netting (18.21 m²; 4.2- or 6.4-mm aperture) to enhance: (1) recruitment of 0-y class wild juveniles, (2) survival of greater than or equal to 1-y class wild juveniles, and (3) wild stocks using cultured juveniles. Findings demonstrated that indiscriminate placement of nets did not result in consistent enhancement of wild recruits (occurring once in 12 trials). Survival of greater than or equal to 1-y class individuals was not enhanced in netted versus control plots at any of the six sites in 2014, but occurred in four of six sites in 2015. Cultured clam survival (May to October 2015) at the four sites where nets functioned properly varied from 65% to 100% and was independent of aperture size; however, where siltation was heavy ormud snails [Tritia (=Ilyanassa) obsoleta] deposited massive numbers of egg capsules on the nets (both scenarios resulting in anoxic conditions in the protected plots), survival ranged from 0% to 48%. Average annual and wintertime seawater temperatures in the Gulf of Maine have risen gradually during the past two decades, and this has been accompanied by increases in clam predators such as the invasive European green crab, Carcinus maenas. In this climate, conservation closures or other large-scale, indirect shellfish management tools cannot be effective in creating new wealth or maintaining jobs associated with the clam fishery in most areas. Therefore, to adapt to changes and increase diversification in the clamming industry in Maine, clammers should be encouraged to farm small (ca. ≤ 10 acres) intertidal tracts where netting and other predator-deterrent measures can be maintained easily and routinely, and where exclusive rights to harvest the farmed shellfish are granted to the individual.

Age data play an important role in the Atlantic surfclam [Spisula solidissima (Dillwyn, 1817)] stock assessment and their accuracy depends on understanding the periodicity and timing of annulus formation. In the United States, the surfclam stock area spans approximately 5° latitude in the northwest Atlantic. In recent years, surfclams at the southern end of this area have undergone changes in abundance, distribution, and growth, all likely due to increasing ocean temperature. To determine whether the periodicity or timing of annulus formation has also changed, shells from live surfclams were collected during every month of the year from three regions spanning 4° latitude: southern New England (northernmost), New Jersey (middle), and the Delmarva Peninsula (southernmost). Edge analysis and marginal increment analysis indicated a single annulus was formed each year in each region and by all age groups, verifying surfclams can still be aged reliably throughout the managed area. Some regional or agespecific variations were also noted. The model-derived peak times of annulus formation were mid-December for southern New England, late November for New Jersey, and early December for Delmarva. The youngest clams in New Jersey and Delmarva formed annuli about a month earlier than the older age classes. Shell lengths at age, estimated from chondrophore heights and fit to a von Bertalanffy growth model, indicated a latitudinal gradient in growth and asymptotic size. Surfclams grew slowest and to the smallest size in Delmarva [k = 0.217 (0.002 SE), L_∞ = 153.0 (0.45 SE)] and fastest and to the largest size in southern New England [k = 0.298 (0.002 SE), L_∞ = 162.0 (0.35 SE)]. Historic von Bertalanffy growth parameters, some unpublished, are also reviewed. There is some evidence of a decrease in k and L_∞ since 1980, particularly in the New Jersey and Delmarva regions where fishing has been historically concentrated.

The yellow clam Amarilladesma mactroides (Deshayes, 1854) is considered a vulnerable species since the mid-1990s. Populations have experienced mass mortalities throughout their entire range of distribution (23–41°S) along exposed sandy beaches of Atlantic South America. Detrimental anthropogenic impacts have further contributed to failure of populations to make a recovery. To determine the factors involved in these events, density prior to a mortality event was calculated and live yellow clams encompassingmost of its geographic range distribution were analyzed histologically to describe parasites and pathologies. Moreover, moribund specimens were analyzed by molecular techniques to test for the presence of the virus OsHV-1. A mortality event was recorded after a maximum density of 127 clams/m² was attained. No clear pattern was found between the prevalence and intensity of infection and localities, mortality events, or sampling season. Although OsHV-1 was not observed in any of the yellow clams tested, the possibility that another viral agent was implicated cannot be ruled out. The presence of bacteria of the genus Vibrio in combination with stress caused by a relatively high population density is suggested as the likely cause of these episodic mass mortalities.

In northwestern Mexico (Gulf of California and Pacific Coast), a fishery on the squalid callista Megapitaria squalida (Sowerby, 1835) was established four decades ago, but little is known about its growth. The objective of this study was to assess individual growth parameters by testing the best growth model fitted to M. squalida. Four growth models were tested, von Bertalanffy, Logistic, Gompertz, and Schnute. The best model was selected based on the Akaike information criterion (AIC) and Bayesian information criterion (BIC). The maximum log-likelihood algorithm was used to parametrize the models considering a multiplicative error structure. According to AIC and BIC, the Logistic model was hierarchically ordered in first place, but the Gompertz, von Bertalanffy, and Schnute models received strong support from the data with AIC and BIC. As no clear “best model” was found, the multimodel inference approach (MMI) was applied to estimate the asymptotic length (L_∞). The averaged L_∞ was 95.1 mm shell length (SL) with a 95% confidence interval (CI) of 86.2–104.1 mm SL using AIC and 95.7 mm (95% CI: 86.3–105.1 mm) using BIC. The conclusion was that MMI was the best technique for estimating L_∞ of M. squalida in the eastern Gulf of California, merely using a single model out of the four tested models.

Aquaculture of the northern quahog (=hard clam) Mercenaria mercenaria (Linnaeus, 1758) is widespread in shallow waters of the United States from Cape Cod to the eastern Gulf of Mexico. Grow-out practices generally involve bottom planting and the use of predator exclusion mesh. Both the extent and scale of clam farms have increased in recent decades resulting in concerns regarding the impacts of these practices on estuarine fauna. Seasonal distribution, abundance, biomass, species richness, and community composition of nektonic, demersal, epibenthic, and infaunal organisms were examined in cultivated and uncultivated shallow-water habitats in Virginia and New Jersey. The results reveal that clam aquaculture, as practiced in both Virginia and New Jersey, has remarkably few quantifiable impacts on estuarine fauna. Seasonal variations were observed in the biota, but of the 39 population and community metrics tested, mean values associated with 26 did not differ between cultivated and uncultivated areas, 5 had decreases and 8 had increases. For recently harvested areas, 32 of 39 variables were not different from uncultivated areas, 6 decreased in at least one season, and 1, blue crab biomass, had a marginal increase. Decreases were observed in the abundance and biomass of infauna (exclusive of the cultured clams) on clam farms, including in harvested areas, relative to natural uncultivated areas. This was accompanied, however, by substantial increases in epibenthic macroalgae, which in some cases supported increased epifaunal species richness and abundance relative to uncultivated areas. Habitat use by finfish, crustaceans, and terrapins was largely unaffected by the presence of clam farms.

This paper reports on embryonic and larval development of the giant clam Tridacna noae. Spawning was induced by serotonin injection into the gonad. Unfertilized eggs had a mean (±SE) diameter of 101.14 ± 0.47 µm and spermatozoa heads were 8.92 ± 0.09 µmlong. Embryonic development had progressed to the 8-cell and 16-cell stages by 3 h postfertilization and to the 32-cell stage by 4 h postfertilization. Rotating gastrulae accounted for 82% of developing embryos at 9 h postfertilization. Trochophore larvae accounted for 54% of embryos at 16 h postfertilization, and 98% of larvae at 20 h postfertilization. Straighthinged (D-stage) veligers comprised 74% of developing larvae at 22 h postfertilization with mean (±SE) anteroposterior measurement (APM) of 146.32 ± 0.58 µm, dorsoventral measurement (DVM) of 118.12 ± 0.74 µm, and hinge length of 77.46 ± 0.73 µmat 24 h postfertilization. At 96 h postfertilization, 74% of veligers had settled but had retained the velum without showing development of the foot and, by 120 h postfertilization, 78% of settled veligers had become pediveligers with a probing foot. The mean (±SE) APM of pediveligers at 144 h postfertilization was 176.50 ± 0.97 µm, DVM was 151.86 ± 1.01 µm, and hinge length was 63.50 ± 0.95 µm. Gills were first observed in settled individuals 11 days after fertilization, indicating completion of metamorphosis. The methods used in this study supported successful larval culture of T. noae and provide a basis for large-scale propagation of this species.

In Sasebo Bay, northwestern Kyushu, Japan, the population of the razor clam Solen gordonis inhabits a coarse sandy substratum at 5- to 20-m water depths. A bundle of long metal rods with cone-shaped tips is used to vertically pierce and harvest clams from fishing boats. Knowledge of the ecological traits of this species and the fishery impact on the population is crucial for sustainable management. In April 2014 to March 2015, quadrat sampling by divers, experimental fishing surveys, and retrieval of clams detached from the fishing gear were conducted monthly. The grand mean individual density at the fishing ground was 555.7 inds/m3. New recruitment occurred in mid-November 2014, and the population excluding the recruits was divided into four cohorts by age according to shell-length-frequency distribution. Individual growth was described based on von Bertalanffy growth function, with L_∞, K, and t0 being 95.7 mm, 0.548/y, and -0.109 y, respectively. The estimated mean shell lengths at the 1 , 2 , 3 , and 4 years of ages were 43.6, 65.5, 78.3, and 85.6 mm, respectively. The clams targeted for the fishery were mainly composed of the 2 and 3 years of age cohorts. Based on published information on the smallest mature sizes for other Solen species populations (46.1–58.2 mm in shell length), reproduction in the present population would begin at the 2 years of age cohort. The macroscopic observation for gonadal development in the population also indicated the occurrence of the spawning event only in October-November in the year. The population is harvested from January to May, and thus no reproductive clams just before spawning are removed. Fishing efficiency was about 50%, caused by a greater loss in the smaller clams that were detached and damaged from the fishing gear (noncatch mortality). Fishing size selectivity was determined from the relationship between the diameters of cross-sectional area of clams and of cone of the fishing gear tip (9.5 mm). Downsizing the cone diameter to 8.0 mm and lowering the fishing effort by 15% are recommended to attain the present yield level toward local population persistence.

Predation of newly settled juvenile Crassostrea virginica often dominates post-settlement mortality. Resident mesopredators such as the xanthid mud crabs are abundant (>200/m²) on constructed subtidal oyster reefs in the New York metropolitan region and may contribute to post-settlement oyster mortality. Two study sites with differing mesopredator species, Hastings and Soundview Park, were selected to examine the role of small crustacean predators in post-settlement mortality. The white-fingered mud crab (Rhithropanopeus harrisii) inhabits Hastings, whereas the flat mud crab (Eurypanopeus depressus) and Sayi mud crab (Dyspanopeus sayi) inhabit Soundview Park. Using size-selective mesh cages to exclude predators, the effects of predator size on oyster predation and recruitment at Hastings and Soundview Park were examined. Overall, Soundview Park had higher consumption rates than Hastings. The highest consumption at Soundview Park occurred when predators of all sizes had access to the oyster prey. Larger-sized predators were likely responsible for oyster mortality, as oyster mortality was not different between the mesopredator and no-predator treatment at Soundview Park. Few oysters recruited at Soundview Park; thus predator size effects on oyster recruitment could not be effectively evaluated between sites. Recruitment at Hastings was not affected by predator-exclusion treatments, in agreement with the oyster predation experiments. Though abundant, no mud crab mesopredator recovered at either site was greater than 22mmin carapace width. Mesopredators were likely not of sufficient size to be dominant predators of newly settled juvenile oysters at Hastings and Soundview Park. Instead, predation pressure at Soundview Park was likely due to larger mobile predators such as blue (Callinectes sapidus) and spider crabs (Libinia spp.). Mesopredator size is an important factor to consider when evaluating mesopredator roles on oyster reefs.

Freshwater input is thought to be a critical factor influencing estuaries through multiple direct and indirect pathways. In this study, findings of a key 1992 paper on Apalachicola Bay oyster fishery data and Apalachicola River discharge data from 1960 to 1984 were recreated, and the analysis extended to 1987 to 2013, to evaluate whether relationships previously reported between river discharge and oyster fishery catch per unit effort (CPUE) persist. The originally reported relationship between low river discharge and lower oyster landings 2 y later was confirmed, but when these same relationships for data from 1987 to 2013 were examined, correlation coefficients relating river discharge metrics to oyster fishery CPUE that were significant with 1960 to 1984 data did not persist with data from 1987 to 2013. Combining all available data (1960 to 2013, excluding 1985 to 1986), previously reported significant correlation coefficients were found to have generally persisted or strengthened and the total number of significant correlations increased. A surprising result is the general lack of association between river discharge and oyster fishery landings from 1987 to 2013, a period of frequent drought and generally lower annual river discharge compared with 1960 to 1984. There are multiple possible explanations for the observed relationships between river discharge and oyster fishery landings including (1) counterintuitive changes in oyster fishery landings due to a change in reporting requirements between the two epochs, (2) hyperstable relationship between oyster abundance and fishery CPUE, (3) failure of the Apalachicola Bay oyster population to recover after Hurricane Elena, and (4) ecosystem changes possibly related to nonstationary river discharge levels altering Apalachicola River or Bay ecosystem dynamics in unknown ways. The absence of simple relationships between freshwater input and oyster fishery responses complicates ongoing management and restoration decisions for Apalachicola Bay, and this work demonstrates that, even within the same system, the relationship between freshwater discharge and response by a key estuarine ecosystem constituent is uncertain.

In French Polynesia, the aquaculture of Pinctada margaritifera (Linnaeus, 1758) covers a large maritime exploitation area, spread over nearly 20 degrees latitude and longitude, with numerous pearl farms located in three archipelagos (Gambier, Society, and Tuamotu). As these archipelagos have specific seasonal temperature patterns each year, pearl oysters are subject to disparate and contrasting environmental regimes. This study aimed to examine the specificity of commercial pearl quality traits (n = 2,236 samples) at the archipelago scale, in such a way as to provide preliminary data to design the most appropriate strategy for the distribution of hatchery-produced phenotypes. A large and standardized grafting experiment using the same donor phenotype was designed and carried out over six grow-out locations, covering the three archipelagos. Results revealed significant differences in commercial pearl quality traits among archipelagos, giving these groups of growing sites distinctive “signatures”: (1) more color, less circles, and higher overall pearl grade in Gambier; (2) larger size with paler pearls in Tuamotu; and (3) darker pearls with intermediate size in Society. Characteristic differences in the environment and seasonal temperature ranges among the three archipelagos, corresponding to their distinct environmental conditions, can explain the specific variations between pearl quality traits among the sites. The strong disparities at archipelago scale should be taken into account in selective breeding programs for P. margaritifera so as to choose the most appropriate pearl oyster donor phenotype for use in each environment and thus enhance site-specific qualities for pearl production.

Tagging methods used in bivalve research can be broadly categorized into two groups: internal and external. External tagging methods are more commonly used; however, the legibility of external tags tends to decline over time, and tag recovery rates are often low due to the abrasion or biofouling of shells, particularly during long-term studies. The aim of the current study was to compare two external identification methods placed on or in the shells of adult Crassostrea gigas: (1) a plasticlaminated glue-on tag and (2) novel use of a t-bar anchor tag inserted into the upper shell, to determine the optimal methodology to use in longitudinal studies of greater than 1-y duration. Over a 15-mo period, 100% of glue-on numbered tags were lost or became overgrown and could not be read, whereas 91.5% of t-bar anchor tags were retained and remained legible. The results of this study suggest that t-bar anchor tags are a better choice for long-term longitudinal studies of adult C. gigas in temperate marine conditions than plastic-laminated labels glued to the exterior of the shell. These findings may be applicable to other bivalves.

Oysters provide a wide variety of ecosystem services including furnishing habitat, supporting an economic industry, and enhancing water quality. To identify suitable areas for oyster restoration and aquaculture, areas of oystersuitable habitat must first be identified. A habitat suitability model is an ideal tool for identifying sites for species restoration. Because it relies on presence-only data, MaxEnt is a particularly useful habitat-suitabilitymodel for identifying restoration and species introduction sites. Habitat suitability models rely on the selection of environmental factors, which are assumed to be important for the target species; however, this selection of environmental factors is often arbitrary and there are few existing guidelines. This work applies an oyster habitat suitability model to the St. Louis Bay in the northern Gulf of Mexico. Six environmental factors, namely average salinity, maximum temperature, minimum temperature, water depth, minimum dissolved oxygen, and average total suspended solids were chosen to simulate habitat suitability. The environmental factors were obtained from a calibrated hydrodynamic and water quality model of the estuary. The habitat suitability model was run with every possible combination of environmental factors, including one, two, three, four, five, and six inputs. Model results showed that at this location, salinity is the most important environmental input. Furthermore, model results showed that increasing the number of inputs optimizesmodel results. There is a diminishing return on the addition of environmental factors and there is a point at which the continued addition of environmental factors will not continue to notably improve model optimization. The ranges of simulated suitable values for the environmental factors were contextualized within measured values. This study shows how a statistical model can be used to identify restoration locations. It is a particularly compelling methodology because (1) it does not require prior information regarding suitable ranges of environmental factors; (2) it does not require information regarding the level of importance for those environmental factors; (3) it requires presence-only data; (4) results are based on spatiotemporal data at a finer scale than is generally measured in the field; and (5) model results can provide an additional line of evidence that complements knowledge by biologists and oystermen.

In the summer of 2010, the Damariscotta River Estuary, ME, experienced the first large multinucleate sphere X disease (Haplosporidium nelsoni) outbreak in commercial stocks of the eastern oyster (Crassostrea virginica). In 2012, biofouling organisms were sampled in and around the commercial oyster operations with the intent of looking for the presence of the parasite to see which, if any, biofouling species may be acting as a reservoir host and harboring the parasite. Organisms collected included tunicates, gastropods, polychaetes, and arthropods, as well as plankton samples from the surrounding water column. A quantitative polymerase chain reaction assay for H. nelsoni using a TaqMan minor groove binder probe, which was originally developed for detection of the parasiteDNAin oysters, was applied to biofouling species. The protozoan parasite H. nelsoniDNA was present in up to 70% of tunicate samples and about 30% of plankton samples. The highest parasite DNA copies (averaging 4 × 10⁴ copies) were detected in tunicates identified as Styela sp., which have been recognized as invasive species in many coastal areas. This study provides evidence for the presence of potential reservoir species that occur close to commercial oyster operations. Reduction or removal of these species may reduce the infectious pressure of this parasite on commercial operations.

Floodplains, considered hotspots of biodiversity, are used by a wide range of aquatic and terrestrial species. Over recent decades, floodplains have been modified for cultivation. This contributes to a loss of biodiversity, which has become a key issue in biological conservation in recent years. Paddy agriculture impacts substantially on the biodiversity of floodplains, including freshwater mussels and bitterlings. To model the habitat suitability for Unio douglasiae nipponensis, the itasenpara bitterling host mussel, we used geographical information system tools and field survey methods along with a generalized linear model to examine the environmental conditions of rivers surrounding paddy fields that were subject to water management practices. Water level fluctuations on the floodplains and artificial management of the water level in rivers around the paddy fields both influenced the spatial distribution of U. d. nipponensis, which suggests that traditional rice paddy management practices provide better support for floodplain species than artificially managed water levels.

Beginning in 2014, mussels have been found by shellfishers in parts of the Philippines that are morphologically distinct from native mytilids. These mussels, with a thick black periostracum, were first found in Manila Bay near an international shipping port, and later in 2014 appeared in western Tambac Bay (approximately 16.28° N, 119.9° E). The next year (July 2015), they were found near the village of Tucok (Dagupan City; 16.0272° N, 120.3147° E), and more recently (early 2016) they have been observed in Longos, San Fabian, Pangasinan (16.1887, 120.4043). About 50 mussels from Tucok were preserved in 95% ethanol and sent to the University of Maine for genetic evaluation. Sequencing of mitochondrial cytochrome oxidase I polymerase chain reaction products identified the nonnative mussels as Mytella charruana, the charru mussel, native to the tropical Caribbean and western Pacific coasts of South America. Further analysis indicates that populations on the Caribbean Coast of South America are the likely source of the Philippine charru mussels. Two salinity tolerance experiments were also conducted; in the first experiment, Philippine charru mussels were conditioned at salinity 5 (similar to the salinity of the collection site) for 7 days, then subjected to a salinity shock by directly transferring them to different salinity levels (10, 15, 20, 25, 30, and 35) for 12 days. In the second experiment, replicate groups of mussels were conditioned in 30 salinity, then for each replicate, salinity was gradually increased by five increments every 5 days until all mussels had died. In both the experiments, all mussels survived at salinities below 35. In the rapid salinity change trial, byssus formation was absent in mussels subjected to salinity 35 shock, and all mussels in this treatment died before the end of the experiment. In the acclimation trial, some mussels survived to salinity 60, but were inactive, and all died when salinity reached 65. These salinity shock and acclimation trials suggest that charru mussels may be best suited to Philippine waters during and after the monsoonal rainy seasons when salinities are routinely below 35, and may be spread among different estuaries via larval transport during the monsoonal rainy season. On the basis of these criteria, charru mussels may be a potential species for aquaculture complementing the culture of the native Perna viridis, a species with a higher preferred salinity that is traditionally cultured in the dry season.

The North Fork Holston River (NFHR) historically supported 33 unionid mussel species downstream of Saltville, VA. Because of industrial contamination over decades from a chlor-alkali plant, a U.S. Environmental Protection Agency Superfund Site (SITE) was created with Hg and MeHg designated as contaminants of concern. Mussel surveys were conducted at 18 NFHR locations to determine abundance, species richness, and recruitment upstream and downstream of the SITE. Seventeen unionid species were collected, and mean species richness of upstream sites (8.8 species, n = 6 sites) was greater than the mean of downstream locations (3.8 species, n = 12). The catch-per-unit-effort mean from upstream sites (10.4 mussels/h, n = 3 sites) was greater than the mean of downstream sites (3.5 mussels/h, n = 12). Mean density of upstream (1.8 mussels/m², n = 6 sites) sites was higher than observed at downstream (1.0 mussels/m², n = 8) locations. Results show that species richness in the entire lower NFHR is less than observed upstream, and measures of mussel abundance and recruitment also are severely depressed in the ∼35 km reach downstream of the SITE, where no juvenile and very few adult mussels were collected. The influences of a wide array of contaminants, including Hg, MeHg, Cl^-, major ions, and trace elements, from the SITE on downstream recovery of unionid mussels are discussed.

The veined rapa whelk (Rapana venosa) invasion of the Chesapeake Bay in the United States was first observed in 1998. Chesapeake Bay rapa whelk population demographics, age-at-length relationships, and invasion progression (temporal, spatial) from 1998 to 2009 are described. Between June 1998 and November 2009, 27,624 rapa whelks, ranging from 11- to 195-mm shell length (SL), were collected fromthe lower Bay.Using a Von Bertalanffy age-at-length model (R² = 0.99), the 195-mm-SL whelk collected in 2007 was 26 y old, making 1981 the estimated year of first introduction. Age-frequency distributions for Ocean View, Hampton Bar, and the lower James River showed increased whelk numbers per age class and consistent representation of Age 2–3 through Age 7–8 whelks throughout the time series indicating recruitment and establishment. Whelk range expansion into James River oyster habitats began in 2004 and continued through 2009. Whelks occupy shallow areas during warmer months, move into deeper habitats during cooler months, and annually reinvade shallow areas as temperatures warm seasonally. Channels act as salinity refugia and conduits between foraging habitats. Salinity tolerances allow rapa whelk use of epifaunal habitats bounded by the 10–12 isohalines formerly used by native oyster drills [Urosalpinx cinerea (Say, 1822); Eupleura caudata (Say, 1822)] as juveniles and infaunal habitats with salinities of 15–25 that do not overlap with native whelks (Busycotypus canaliculatus, Busycon carica) as adults. Establishment was facilitated by local disturbance of native species distributions by Tropical Storm Agnes (1972).

Foraging behaviors of juvenile Hexaplex trunculus (Linnaeus, 1758), a predatory snail, preying on the Mediterranean mussel Mytilus galloprovincialis were investigated. To understand the mechanisms of the prey-predator relationship between young forms of these species and assess the foraging capabilities of the snails, size selection and attacktype experiments were set up. Furthermore, the predation signatures, which are used as a valuable tool for ecology and paleoecology studies, were measured with an alternative method; their locations were classified and related with the predator-prey sizes to make some descriptions. Snails (as two size categories, about 2–6 and 6–11 mm shell length (SL) during the experimental period) typically accessed the mussel (as four size categories up to 20 mm SL) flesh by drilling and/or marginal chipping. About 90% of the shell samples had at least one attack signature from each attack type. By the end of the experimental period, 74% of all of the attacks with the visible predation signature were made by drilling and 26% by chipping; attack type did not differ according to predator or prey size. Group-attacking events were observed frequently during the experiments as well as solitary attacks; 48% of the mussel shells that had at least one attack signature had multiple attack signatures. Positions of the drill holes were dense over anterior-dorsal areas and their distributions did not differ according to snail size. Drill hole diameters were found to be related with snail and also mussel sizes by linear regression. Even though both small and large juvenile snails were capable of foraging on mussels that were three or four times larger than themselves, they showed size preference for particular mussel size classes. The ratio of the prey size/predator size did not have any effect on the attack type of the snails. After reaching 9 mm (auxiliary experiments), snails started to consume larger mussels (more than 40 mm) as well as the individuals from smaller groups.

For marine benthos with planktonic larval stages, demographic metapopulation and empirical metacommunity studies are scarce. Asink nature was shown for a local intertidal sandflat population of the gastropod Umbonium moniliferumin an estuarine to coastal oceanic region in Amakusa, Kyushu, Japan. The gastropod has a 3-day planktonic larval duration (PLD). It inhabited 11 sandflats, which were shared by the ghost shrimp Nihonotrypaea harmandi. The shrimp is a burrow-dwelling bioturbator with a 30-day PLD. On one sandflat (hereafter U0) in Amakusa, the density and distribution of the two species was monitored from 1979 to 2014. All their main local populations were surveyed in 1998. In July 1979, the gastropod and shrimp were distributed on the lower and upper zones of U0 separately, with mean densities of 1,740 and 170 ind/m². The gastropod population declined to extinction in 1986, associated with the increase in shrimp density to 440 ind/m² and distribution to the lowest shore. Shrimp sediment destabilization was most likely to inhibit gastropod recruitment. The gastropod population began to recover in 1997 owing to shrimp population shrink. The regional survey results showed that (1) eight local populations (U0–U7 sandflats) of the two species along a 25-km shoreline of Amakusa, presumably, constitute each substantial metapopulation, and (2) their largest populations were at the shoreline opposite ends. These features would be generated by the interaction of speciesspecific larval dispersal traits and shoreline physiography. The threshold shrimp density of 160 ind/m² precluding gastropod recruitment was detected from U1–U7. In 2001 and 2009, gastropod population density on U0 reached respective peaks comparable to that in 1979. This population fluctuation was due to varying recruit abundance, which corresponded well with the year-to-year change in shrimp population density across that threshold. The recolonization of the U0 gastropod population ought to be made by allochthonous larvae from the U1–U7 populations, especially U6–U7, suggesting a rescue effect in the source—sink relationship. The degree of self-persistency of the U0 gastropod population was estimated by calculating net reproductive rate (R₀) based on the parameters about pre-settlement larval return-home and survival rates and post-settlement juvenile and adult survival rates. The availability of data set restricted the estimation to potential R₀ for four year-segments, with each 1-y parameter set extrapolated to the gastropod 4-y life span. On U0 in 1979 to 1981, despite with minimum shrimp influences, the gastropod population could still be a demographic sink probably due to a limited larval return-home rate and due to a low post-settlement survival rate of juveniles caused by epibenthic predation or storm for their first 1 y to reach sexual maturity.

The effects of different diets on the survival, growth, food consumption, and conversion factor of juvenile red abalone (Haliotis rufescens) under tank culture conditions were investigated. The algae Macrocystis pyrifera, Gracilaria chilensis, and Sarcothalia crispata were administered as mixed diets, mono diets, or in rotation changing weekly. Additionally, an artificial pellet feed (ABfeed) was administered alone using a feeder or as part of a mixed diet. The experiment lasted 10 mo. The 100% S. crispata diet was suspended after 4mo due to low survival rates (92.1% ± 3.4%). Treatments had significant effects (P < 0.05) on survival, growth, food consumption, and conversion factor. The lowest survival rate was obtained using the artificial feed with a feeder (94.2% ± 4.3%) and the highest with a mix of M. pyrifera and artificial feed (99.0% ± 0.8%). The highest growth rates were obtained with the mix of M. pyrifera, G. chilensis, and artificial feed (0.044 ± 0.007 mm/day per 0.054 ± 0.005 g/day) and with 100% M. pyrifera (0.043 ± 0.002 mm/day per 0.054 ± 0.01 g/day). The lowest growth rates were obtained with 100% G. chilensis (0.026 ± 0.01 mm/day per 0.021 ± 0.01 g/day). Food conversion factor was highest with the mixed M. pyrifera (16.0) and G. chilensis (12.7) diet, whereas the lowest food conversions rates were obtained using artificial feed with a feeder (1.4) and artificial feed without a feeder (1.6). In this study, the M. pyrifera mono diet produced the highest growth rates in H. rufescens juveniles. Given that it is also the most abundant alga in terms of biomass and is easily managed during the feeding process, this would appear to be the best option for the culturing red abalone in southern Chile.

White abalone Haliotis sorenseni was studied in the mariculture laboratory of the Channel Islands Marine Resource Institute in southern California to determine the effect of environmental factors such as temperature, diet, light, and cultivation density on growth and survival. Fertilized eggs and larvae were raised at water temperatures of 9°C, 12°C, 15°C, 18°C, and 21°C in two separate trials. The rate of larvae development increased significantly with each 3°C change in temperature. Survival from fertilization to settlement stage was greatest (56%) at 12°C, followed by survival of 23% at 15°C, and 2% at 18°C. Larvae raised at the extremes of 21°C and 9°C had 100% mortality by 90 and 100 h posthatch. The biological zero temperature, the point at which growth stops, is projected to be 3.04°C for white abalone, significantly lower than that of sympatric species. Fecundity was determined as 7,271 eggs/g for wild-caught abalone and 6,128 eggs/g for hatchery-reared abalone and was not significantly different from previous estimates based on gonad bulk index. The effect of feed and temperature on the growth of juvenile abalone was studied. Juvenile abalone 28 mm in length were held for 147 days at 12°C, 15°C, and 18°C and fed diets of kelps Macrocystis pyriferia (L.) C. Agardh, 1820; Laminaria farlowii (Setchell, 1893); Chondracanthus exasperatus (Harvey & Bailey, 1996); Palmaria mollis (Setchell & N. L. Gardner, 1903), or combinations of these algae. Juveniles displayed fastest growth at 15°C when fed M. pyriferia. Juvenile survival was highest at 12°C and lowest at 18°C, at which temperature animals succumbed to withering syndrome. Optimal seawater temperatures for both larval and juvenile white abalone were determined to be significantly lower than previously reported. In other experiments, animals 20mmin length stocked at 25 gm/L grew at 41 µm/day versus 32 µm/day for those at 50 gm/L. No significant difference in growth was observed for abalone grown under low lighting conditions (3%–5% ambient) and almost complete darkness (1% ambient light).

The purple dye snail Plicopurpura pansa is recognized as the most important species within the Huatulco National Park (HNP) because its dye is used by Mexican ethnic groups from Oaxaca to dye cotton yarn used to produce ceremonial clothing with cultural value. In the HNP, reproductive and recruitment seasons of this species are scarcely documented, and this information is essential to understand its complete life cycle. The aim of this study was thus to establish when reproductive and recruitment seasons began, reached their maximum, and ended in the HNP. Snail length records were obtained for both sexes, and the mean value of age was estimated using length parameters reported in the literature. For each of the estimated age classes, ranging from 0.5- to 4-y-olds, snail abundance was calculated on a monthly basis. Based on a monthly natural mortality rate estimate of 0.53, virtual population analysis was performed to obtain two population indices: (1) snail spawner virtual abundance (or SS index), and (2) snail recruit virtual abundance (or SR index). The SS and SR indices were subjected to time series analysis. With the SS index, a complete reproductive season spanned from March to October/November, with maximum abundance of spawners during June/July; reproductive recovery was observed from October/November to March, between reproductive seasons. With the SR index, a complete recruitment season spanned from August to January/February with a maximum abundance of recruits during November/December. Monthly sea surface temperature changes showed a significant positive correlation with the SS index, and a significant negative correlation with the SR index. Results provide evidence that cultural exploitation is negatively affecting these snails, and support the view that this population is being overexploited within the HNP. Recommendations for improved management of this resource that will prevent its overexploitation are proposed.

Ommastrephid squids have a pelagic lifestyle, with reproductive behavior that is characterized by the extrusion of fragile, neutrally buoyant egg masses, the release of paralarvae into the surface plankton, and the use of large-scale current patterns for larval transport, leading to the assisted migration of populations. Although the exact process of egg mass formation is unknown, the most accepted hypothesis suggests that, at spawning, eggs are first coated with oviducal gland secretion and released with nidamental gland secretions. Subsequently, the eggs mix with broken spermatophores or spermatangia for fertilization. The fertilized eggs are then extruded into the seawater to form a globular mass. These neutrally buoyant gelatinous egg masses are thought to maintain their location in the water column by floating at the interface between water layers of slightly different densities (above the pycnocline). The embryos develop within a favorable temperature range. Once hatched, the paralarvae leave the egg mass and swim to the surface. This review assimilates and assesses all available literature on the egg masses of ommastrephid squids. The data presented here clearly show how fragmentary our knowledge is about this important reproductive stage. Thus, increased efforts are required to develop observation and sampling techniques in the wild to obtain more direct evidence about reproduction in squids.

In the United States, populations of nonindigenous Pomacea spp. have been reported in at least 10 states, and the rate of spread has been greatest in the southeastern United States, particularly in Florida. Factors impacting successful establishment of molluscs include salinity, pH, and desiccation tolerance. This article reports on median survival and growth of Pomacea canaliculata and Pomacea maculata (hatchlings through adults) in 28-day trials focused on these factors with an ambient condition serving as a control (e.g., 0 = salinity control). Overall hatchlings had the lowest survival, followed by juveniles then adults. Median survival was less than 28 days for all salinity treatments greater than 16. Median survival was 28 days for all pH levels (5.5–9.5) for juveniles and adults of both species. Median survival in desiccation treatments (>80% relative humidity and wet sand or <60% relative humidity and dry sand) was 28 days for adults of both species and for juvenile P. canaliculata. The closer a treatment was to the control level, the greater the increases in shell length and width. In all treatments, snails experienced a loss in mass; the closer a parameter to the control typically resulted in the greatest loss in mass. The ability of these species to tolerate such diverse conditions will leave many systems vulnerable to invasion.

Stock assessment in wild populations and research involving reproductive biology of crabs rely greatly on the ability to accurately determine sexual maturity status. Although determination of sexual maturity in male mud crabs was commonly based on the presence of spermatophores in the vas deferens, preliminary studies on the mud crab Scylla spp. showed that this method is inconclusive and was reevaluated in this study. In addition, the feasibility of using male abdomen looseness as maturity indicator was explored. Spermatophores were present in the vas deferens of all Scylla spp. regardless of maturity status and body size. Spermatophores also significantly increased in size as the crabs reached sexual maturity. Examination of the vas deferens external morphology (e.g., color and size) consistently differentiated immature from mature males. The size at maturity (CW₅₀) was successfully estimated using three maturity indicators, that is, the looseness of the abdomen, the observation of mating scars, and the vas deferens development. The estimated sizes obtained using all three indicators showed no significant differences, but varied significantly among species. A positive relationship was observed between body size and sexual maturity in all three Scylla species. Determination of sexual maturity using the presence of mating scars as indicator was inconsistent as some crabs that were mature in terms of looseness of abdomen and vas deferens development showed no presence of mating scars. On the other hand, male crabs with loose abdomens were found to be sexually matured with enlarged, milky white vas deferens. This finding suggests that abdomen looseness is an accurate sexual maturity indicator in males. Using looseness of abdomen as sexual maturity indicator in the male Scylla spp., therefore, is feasible and superior to conventional methods, with the advantages of being practical, easy to carry out, and does not require sacrificing of the crabs.

In many decapod fisheries, claws are removed and the animal is returned to the sea with the assumption that there is little impact on the fitness and welfare of the animal, or on the productivity of the population. Here, the impact of claw loss, by two methods of claw removal, is examined during competition between males for access to females in the crab Cancer pagurus. Males induced to autotomize a claw showed little reduction in their competitive ability; however, those subject to the fishery practice of manual declawing showed a marked decrease in their competitive ability. Compared with autotomized males, these declawed crabs displayed activities that suggest an awareness of the wound caused by the appendage being twisted off and the data are consistent with an impaired welfare for these animals. They were also less likely to display to their opponent compared with autotomized crabs. Intact males showed high aggression toward declawed males, which showed low aggression in return. Further, declawed crabs showed particularly high levels of submissive acts. The declawed crabs thus rarely gained the female compared with autotomized crabs. The present study demonstrates that manual declawing has a major detrimental impact on fitness and welfare of edible crabs and we suggest that this method of harvesting should be replaced with induced autotomy of a single claw.

Although the native red rock crab Cancer productus is an important component of Pacific northwest nearshore communities and recreational crab fisheries, little is known about its life history. Growth in crustaceans is incremental and age classes overlap, making these investigations difficult. An array of techniques was used to estimate growth and longevity of C. productus in a marine preserve at the University of Washington Friday Harbor Laboratories. These included size-frequency distribution analysis of young crabs in their nursery habitat, growth inside cages, and mark-recapture studies. The growth rate in C. productus varies greatly, with adult males exhibiting greater molt increments and molt frequencies than females. For crabs less than 80 mm in carapace width, males and females grow at the same rate: attaining 30–65 mm carapace width at age 1, and 60–95 mm at age 2. Maximum carapace widths of males and females were 171 and 150 mm, respectively, and maximum longevity is estimated to be at least 5 and probably more, much longer than previously estimated.

The landing obligation of the reformed European Union Common Fisheries Policy is designed to encourage more selective fishing strategies and improve recording of catches. There are allowable exemptions to this landing obligation including for species with high post-release survivability. Discarding patterns of prawns (Nephrops norvegicus) were evaluated in a trawl fishery in the Firth of Clyde, West Scotland, which supplies the live-catch market. Around 30% of the Nephrops caught were discarded, but the reasons for discarding changed seasonally. Using visual indices, physiological biomarkers, and video recordings, this study evaluated the physiological condition linked to short-term survival and predator avoidance behavior of the discarded animals. Although short-term survival after 48-h recovery was high (around 90%) and physiological measures indicated that discarded Nephrops can recover from trawling, survival was negatively affected by levels of physical damage and Hematodinium infection. Taking into consideration these factors, a conservative estimate for discard survival was 63%-88%. Underwater video showed that Nephrops discarded in good condition rapidly recovered normal behavior when placed on the seabed. Moribund animals, however, took up to 10 min to return to an upright posture and this time was sufficient for predators to be attracted. Since around 20% of Nephrops were in a moribund condition immediately after trawling, the survival estimates based on enclosed recovery experiments may need correcting by up to this amount to account for potential interactions with predators on the seabed. The post-release survival rates in discarded Nephrops suggested for this fishery are relatively high compared with other Nephrops trawl-fisheries which have been studied. This could be explained because this fishery targets the live market, prioritizes product quality over volume, and uses short-duration tows leading to relatively low levels of physical damage to the Nephrops.

The American lobster [Homarus americanus (Edwards, 1837)] is an omnivore decapod with generalist and opportunistic feeding habits, in which gastric fluid cysteine and aspartic peptidases are the main proteolytic enzymes. Using in vitro assays, the network of concerted acting peptidases belonging to aspartic and cysteine catalytic mechanisms that hydrolyze bovine serum albumin (BSA), hemoglobin, and actin was elucidated. The role of each class of peptidases in protein digestion was evaluated by monitoring the hydrolysis of each substrate in the presence of single or mixed specific peptidase inhibitors. Peptidases of the gastric fluid can hydrolyze BSA, actin, and hemoglobin. Hemoglobin was hydrolyzed by cysteine and aspartic peptidases but not by serine ones. Results suggest that hydrolases act synergistically. Hydrolysis of BSA and actin is carried out by a multienzyme network mechanism. Although cysteine peptidases hydrolyze about 50% of BSA and actin, aspartic peptidases are required to fulfill the task; when aspartic and cysteine peptidase activity is absent, no hydrolysis of the substrates happens at all. Serine peptidases seem not to contribute to the analyzed substrates hydrolysis at the conditions of the assay.

The aim of this study was to determine if the Amazon river prawn [Macrobrachium amazonicum (Heller, 1862)] population structure is affected by habitat heterogeneity. An experiment was conducted in mesocosms to emulate conditions from a natural aquatic environment. Twelve rectangular earthen ponds of ∼100 m² each were used as mesocosms. Each mesocosm was stocked with 22 juveniles/m² of Amazon river prawn in three different treatments: GB: mesocosm with substrate made of geotextile blanket, BB: mesocosm with substrate made from bamboo, and WS: mesocosm without substrate. The prawns were sampled monthly for 5 mo to analyze the male morphotypes, incidence of eggs in female pleopods, ovarian stage, body mass, and sex ratio. Both geotextile blanket (GB) and bamboo (BB) substrates increased frequency of the Cinnamon Claw morphotype, accelerated the appearance of Green Claw 1 and 2 morphotypes, and decreased the frequency of the Translucent Claw morphotype at the 5^th mo. The substrates also increased the size of both sexes of prawn and increased the frequency of ovigerous females and females with ovarian stages IV and V. The effect was more pronounced with the presence of the GB, which imitates natural substrates with large and flat surfaces such as leaves and stones. Sex ratio did not differ significantly between treatments. Data showed that the presence and the type of substrate in the environment can play an important role in M. amazonicum population development, supporting the hypothesis that the population structure of M. amazonicum depends on the habitat characteristics.

Sea urchins have been used as a source of food from prehistoric times and as a research animal model since the 19^th century. They presently are harvested in many parts of the world. In Argentina, sea urchins have been studied only from biological perspectives. Of the 14 species of sea urchins found off the coast of Argentina, Arbacia dufresnii is the most abundant. It is an omnivorous species that exists in dense populations in Nuevo Gulf. Biomass production in sea urchins, especially gonad yield, is related to food quantity and quality. In the field, A. dufresnii has a small size and low gonad biomass and gamete production. Therefore to test the hypothesis that a high-quality formulated food would produce more biomass and gonad yield than that found in the sea urchins from a natural population, sea urchins were reared in a laboratory aquaculture system for 8 wk in autumn when gametogenesis occurs. In April, 30 sea urchins were collected and dissected to establish the initial condition (Baseline). Another 32 sea urchins were collected in April and maintained until June in aquaria at constant temperature and salinity and fed a formulated feed (Fed). At the conclusion of the experiment, 30 sea urchins were collected from the field population in June (Field) to establish the population condition in the Field and for comparison with the Fed sea urchins. Fed sea urchins had a 20% greater gain in weight resulting from an increase in both somatic and gonadal tissue beyond that of the field population. All organs increased in weight in females and all organs except the lantern in males. The absorption efficiency in Fed sea urchins was over 80%. Fed sea urchin had organic biomass production higher than Field sea urchins. Differences were found in the gonad cellular composition: Fed females had a unimodal oocyte size-frequency distribution, in contrast to a multimodal distribution in Field females. Fed males had fewer mature gametes than Field males. Both testes and ovaries had more nutritive phagocytes in Fed sea urchins than in Field sea urchins. Proximate composition of gonads, however, was similar in Fed and Field sea urchins. Fed individuals showed a remarkable increase in biomass production. The biochemical and cellular composition of the gonads reflected this. This indicates that A. dufresnii fed a highly nutritional food is able to assimilate nutrients with high efficiency and produce an increased gonad yield.