The Caribbean King crab Mithrax spinosissimus is the largest brachyuran found in the western Atlantic and it supports subsistence and small commercial fisheries throughout the Caribbean and Gulf of Mexico. Because of its short larval duration and rapid growth, M. spinosissimus is considered a good candidate for aquaculture. Our study documents for the first time the size at sexual maturity, sexual dimorphism, and allometric growth relative to carapace width for certain secondary sexual characters in male and female M. spinosissimus from the Florida Keys, Florida. Using principal component analysis, K-means cluster analysis, and discriminant analysis, we identified 2 major growth phases in the postlarval benthic life of this species (juvenile or prepubertal and adult or pubertal). The typical growth pattern for majoid crabs includes a third, intermediate growth phase that appears absent in M. spinosissimus. The major cheliped of males was larger than that of females and exhibited positive allometric growth to maturity, after which the level of allometry decreased. In females, both chelipeds exhibited positive allometry throughout ontogeny. Abdominal width was negatively allometric throughout ontogeny in males, whereas in females the abdomen exhibited positive allometric growth until reproductive maturity, at which point it became isometric. Logistic regression indicated that the carapace width at first maturity was 45.2 mm in males and 69.7 mm in females. This new information should be taken into account when assessing stocks and setting harvest regulations if this fishery is to be managed sustainably.

The Alaskan red king crab (Paralithodes camtschaticus) fishery was once one of the most economically important single-species fisheries in the world, but is currently depressed. This fishery would benefit from improved stock assessment capabilities. Larval crab distribution is patchy temporally and spatially, requiring extensive sampling efforts to locate and track larval dispersal. Large-scale plankton surveys are generally cost prohibitive because of the effort required for collection and the time and taxonomic expertise required to sort samples to identify plankton individually via light microscopy. Here, we report the development of primers and a dual-labeled probe for use in a DNA-based real-time polymerase chain reaction assay targeting the red king crab, mitochondrial gene cytochrome oxidase I for the detection of red king crab larvae DNA in plankton samples. The assay allows identification of plankton samples containing crab larvae DNA and provides an estimate of DNA copy number present in a sample without sorting the plankton sample visually. The assay was tested on DNA extracted from whole red king crab larvae and plankton samples seeded with whole larvae, and it detected DNA copies equivalent to 1/10,000th of a larva and 1 crab larva/5mL sieved plankton, respectively. The real-time polymerase chain reaction assay can be used to screen plankton samples for larvae in a fraction of the time required for traditional microscopial methods, which offers advantages for stock assessment methodologies for red king crab as well as a rapid and reliable method to assess abundance of red king crab larvae as needed to improve the understanding of life history and population processes, including larval population dynamics.

Stock assessment of Alaska red king crab, Paralithodes camtschaticus, can be improved by incorporating embryo production, which requires an understanding of the size-fecundity relationship and an understanding of interannual and seasonal variability in fecundity. We collected red king crab egg clutches from Bristol Bay, AK, during summer 2007 to 2010 and autumn 2007 to 2009 and estimated individual fecundity using dry weight methods. Fecundity increased with female size up to 138 mm carapace length (CL), at which point the slope decreased by 40%, suggesting senescence. Fecundity varied significantly but slightly (maximum, 5%) among years. Fecundity was consistently lower in autumn than spring, suggesting brood loss, with a 6% decrease between seasons in females smaller than 138 mm CL and a 10% decrease in larger females. When incorporating embryo production in stock assessments, differences in the size-fecundity relationship should be accounted for and rates of brood loss can be used to predict larval output more effectively if fecundity cannot be measured shortly before hatching. To include potential environmental effects on the relationship, time series of fecundity and female size should be extended over a wider range of future temperature conditions.

The seasonal brood size of the spiny lobster Panulirus gracilis in Mexican waters (southeastern Gulf of California) was estimated for 259 ovigerous females caught in commercial tangle nets at depths ranging from 8–25 m during spring, summer, fall, and winter between March 1993 and March 1994. The number of eggs per individual ranged from 76,727 eggs for a 60.0-mm carapace length (CL; 250 g total weight (TW)) female to 1,115,060 for a 80-mm CL (510 g TW) female. A brood size (BS) value was estimated from replicate counts and was found to vary with CL and TW according to the relationships BS = 0.6803CL^3.1007 (R²= 0.5203) and BS = 1236.7TW - 35548.9 (R² = 0.5781), respectively. The smallest egg-bearing female was 50.3 mm in CL. Significant differences were found in seasonal brood sizes, with lower values during the winter than during the remaining seasons. Egg loss during the incubation period was estimated at 7.9%.

Changes in biochemical composition during the transition from eggs to larvae in the blue crab Callinectes sapidus were documented. The amounts of proteins, lipids, and carbohydrates decreased from newly formed embryos (stage I) through prehatching embryos (stage II) to newly hatched larvae (stage III; P < 0.05), but the water content increased significantly from stage I to stage II (P < 0.05). Total saturated fatty acid increased significantly from stage I to stage II (P < 0.05), then the content of total saturated fatty acid in stage III decreased to a level similar to that in stage I. In contrast, total monounsaturated fatty acid, n3/n6, and docosahexaenoic acid-to-eicosapentaenoic acid ratios decreased significantly from stage I to stage II (P < 0.05), whereas these variables remained unchanged in stage III. The level of n6 polyunsaturated fatty acid increased significantly from stage I to stage II (P < 0.05) and then stabilized subsequently during stage III. Lipid class analysis revealed that the percentage of triglyceride decreased significantly from stage I to stage III, whereas the proportion of Cholesterin increased (P < 0.05). Phospholipids decreased significantly from stage I to stage II (P < 0.05), then returned to stage I levels during stage III. These data suggest that the embryos in stage II and stage III required more energy compared with those in stage I.

Growth and longevity of Glycymeris nummaria were determined from samples of shells, collected monthly by scuba divers between January 2010 and December 2010 from Mali Ston Bay, eastern Adriatic Sea. Acetate peel replicas of the shell margin (marginal increment analysis) and hinge region of the shell were used to validate an annual periodicity of growth lines and to determine shell age, respectively. Results indicate that G. nummaria forms a narrow growth line after February, when seawater temperatures are at a minimum. Growth lines, visible in the hinge region of all the shells, were used to estimate the age of 76 G. nummaria and provided an estimate of maximum longevity of the species at 20 y. Construction of a von Bertalanffy curve using shell length at age data produced a value of L∞ = 71 mm, a growth parameter (K) of 0.11/y, and time at length 0 was -3.74 y. The growth performance index was 2.74.

This study describes histologically the reproductive cycle of Barnea davidi inhabiting Hampyeong Bay on the western seashores of Korea. A total of 578 B. davidi, collected from February 2010 to January 2011 with a shell length of 89.5 ± 7.7 mm and a total weight of 47.5 ± 13.7 g, were used for analyses. The sex of B. davidi was distinguishable by both the ovary and testis, which were contained in multiple gametogenic follicles. The gonads displayed histologically definitive seasonal changes. Although the sex ratio (female to male) was 1:1.32 (n = 229:303), the proportion of males increased as the shell length increased. The gonad index (GI) of both males and females was the highest in May, and was the lowest in November for females and in December for males. The pattern of changes in the GI was similar to the pattern of seasonal changes in gonadal tissues and water temperature. The condition index was highest in April and lowest in October. The correlation between the pattern of monthly changes in condition index and the monthly changes in GI and development of gonads was low. The main spawning period of B. davidi was June to July, and the reproductive cycle was divided into the inactive stage (November to December), early active stage (January to March), late active stage (March to May), ripe stage (May to June), and the spent and degenerative stage (July to October).

Samples of live geoducks and intact dead geoduck shells were collected from sites near Tofino, on the west coast of Vancouver Island, British Columbia, in 2004, 2006, and 2008. Shells were aged by the Sclerochronology Laboratory at the Pacific Biological Station using the dendrochronological technique of cross-dating. The year of death of the dead shells was determined by using the novel technique of overlapping the synchronous growth patterns of the live and dead shells. Results indicate that most of the geoducks in the sample, regardless of age, died in 1991 and 1992. We investigated possible causes of their deaths. We conclude that the mass mortality of geoducks on the exposed west coast of Vancouver Island may be the result of wave-induced anastrophic (localized catastrophic) burial.

Exploitation rates for the Pacific geoduck commercial fishery in British Columbia are currently based on an age-structured model using geoduck age data derived from the ring-counting method. Since 2005, geoduck ages have been determined using the more accurate method of cross-dating. We assessed how the results of age-structured models are impacted by the aging method used by considering 2 data sets that were aged with both methods. Historical recruitment patterns were back-calculated and compared to examine the effect that the aging method had on trends in estimated recruitment over time. Through forward simulation, we examined the influence of alternative fishing intensities on geoduck stocks and evaluated the impact of increased accuracy in age determination on precautionary exploitation rates. Results indicate that the use of the cross-dating methodology has improved our understanding of geoduck recruitment patterns but does not suggest that a change in exploitation rates is warranted. The exploitation rates currently in use are still considered precautionary.

Giant clams need to establish a symbiotic relationship with the microalgae Symbiodinium in the environment to survive the juvenile stage. In seed production of giant clams, larvae are presented with Symbiodinium but the probability of symbiosis establishment (symbiosis rate) is low. To determine the characteristics of Symbiodinium that improve the symbiosis rate of giant clams (Tridacna crocea and Tridacna maxima), we conducted experiments simulating a typical Japanese seed production method that rears giant clams in unsterilized seawater with no food or antibiotics. After validating this experimental method, we obtained the following results. First, the symbiosis rate was greater than O for Symbiodinium isolated from giant clams, corals, anemones, and even coastal seawater. It was slightly higher, albeit not significantly, for the giant clam origin Symbiodinium. Second, the symbiosis rate was sometimes better for cultured Symbiodinium than fresh Symbiodinium. In conclusion, Symbiodinium cultured after being isolated from giant clams can promote a symbiotic establishment of giant clam juveniles that are reared in unsterilized seawater with no food or antibiotics.

The flag pen shell Atrina vexillum is probably one of the most economically important pinnid species in the Indo-West Pacific. Its populations have suffered a threatening decline during past decades. Despite the need for conservation, knowledge of the ecology of this pinnid is practically absent. The condition of the mollusc population is generally inferred from age- and growth-related data of the investigated mollusc. A combination of Mg:Ca ratios, growth increments on the external shell surface, and annual muscle scar rings on the inner shell surface were used to estimate the age and growth rates of 4. vexillum from 3 subareas in the Gulf of Thailand along the southwestern coast of Vietnam. This study showed that the molluscs were ≤10.5 y old and had a shell length of ≤438 mm. Shell growth rates had a seasonal pattern, with an extended period of very slow growth during the cold season and a short period of slow growth during late spring and summer. The growth rates of A. vexillum varied greatly with subareas. In moving inward in the Gulf (toward its top), the A. vexillum growth rates were slower and its life span was shorter. There were statistically significant differences between subareas in environmental parameters, such as water salinity, temperature, concentrations of suspended particulate matter and suspended organic carbon, chlorophyll a, and oxygen concentration. In the inner subareas, A. vexillum is subject to quite a set of unfavorable environmental factors, such as lower and more changeable water salinity, warmer water temperature, greater concentration of suspended particulate matter, and lower oxygen concentration in the water compared with the outer subarea of the Gulf. The obtained data are a first contribution to the knowledge of the ecology of this little-studied mollusc.

Atlantic salmon (Salmo salar) farms in the Southwest Bay of Fundy area of New Brunswick were investigated for possible advantages of nutritional enrichment for the blue mussel (Mytilus edulis) when grown in integrated multitrophic aquaculture (IMTA) systems. Mussels grown in IMTA systems may be exposed to higher concentrations of organic matter at the salmon farms that can enhance growth rates and decrease time to market for the grower. In this experiment, mussels were sock-cultured at 2 distances from 2 separate salmon farms (0 m and 200 m), with 3 growth parameters (shell length, wet meat weight, and condition index) measured monthly and compared with the same growth parameters in mussels grown at a reference site outside the aquaculture influence. After a12-mo period, mussels grown directly on the cages grew faster than mussels 200 m away on all parameters except shell length at 1 location. Mussels grown at 0 m and 200 m performed significantly better (P < 0.05) in all growth parameters compared with mussels grown at a reference site outside the aquaculture influence. Differences in growth and condition index were most pronounced in the fall and winter, when ambient seston concentrations were low. Results of a second study in which growth rates for individually tagged mussels was monitored for a 6-mo period confirmed that there is a significant growth benefit for mussels in integrated aquaculture with salmon compared with mussels grown 500 m away at a reference site.

The majority of recent studies investigating the habitat value of intertidal oyster reefs have compared the nektonic assemblages on natural oyster reefs, salt marshes, mud bottom, and subtidal oyster shell habitats using methods that involve some degree of habitat disturbance. The current study used a novel, non-destructive sampling approach involving the deployment of a drop net around study plots to compare the nektonic assemblages associated with intertidal oyster reefs (natural and enhanced) with those of neighboring soft sediment habitats at 3 sites in South Carolina. At each site, the nektonic organisms collected on a reef plot were compared with those collected on an adjacent control plot lacking a structurally complex habitat. Nekton abundance was significantly higher on the reef plot compared with the control plot at all 3 sites. Nekton abundance also varied among seasons, with the greatest numbers occurring during summer compared with spring and fall. Notably, grass shrimp (Palaemonetes spp.) were especially dominant on reef plots. A total of 60 taxa were identified, 57 of which were identified to species level. Reef plots exhibited significantly greater taxon richness than control plots. The number of taxa present also accumulated over time at a higher rate on the reef plots than on the control plots at 2 of the 3 sites. Among the 60 taxa collected, 36 were found on both the reef and control plots, whereas 14 taxa were unique to the reef plots. For data pooled across all sites and seasons, 33 taxa were more numerous on reef plots than control plots, 3 taxa occurred in equal numbers, and 24 taxa were more numerous on control plots. For taxa collected on more than 1 occasion, paired t-tests performed with Bonferroni-adjusted significance thresholds revealed that Alpheus heterochaelis and Palaemonetes spp. were significantly more abundant on the reef plots than on the control plots, whereas unadjusted analyses revealed the same pattern for Gobiosoma bosc, Menidia menidia, and Fundulus heteroclitus. In contrast, no taxa were significantly more abundant on the control plots at either significance threshold. Although nekton abundance was generally higher on the reef plots, measures of diversity were significantly higher on the control plots, regardless of season, site, or date. Greater abundance of a limited number of species on the reef plots accounted for lower evenness and therefore lower diversity measures for this treatment. Overall, community structure was driven more by site than by treatment, whereas the seasonal occurrences of certain species on the reef plots highlighted the importance of oyster reefs as essential fish habitat for the critical life stages of finfish species with complex life histories.

Stocks of eastern oysters (Crassostrea virginica, Gmelin 1791) have undergone dramatic declines in the Chesapeake Bay since the mid 1800s. As a result, substantial efforts have been made to try and reverse this decline to provide support for a commercially and socially important fishery and, more recently, to restore the oyster's important ecological role. Since 1939, juvenile oyster abundance has been measured at sentinel oyster bars in the northern portion of Chesapeake Bay, Maryland. We conducted a cluster analysis on these data and detected 4 distinct spatial patterns. These patterns were related to juvenile oyster abundance (i.e., bars that experienced high overall juvenile abundance grouped together) and salinity. Of the sentinel bars sampled since the mid 1980s, our analysis identified 13 bars that were characterized by high juvenile oyster abundance and low variation among years, which makes them prime candidate bars for protection to aid in restoration. A comparison with bars already protected within oyster sanctuaries revealed some overlap (4 total bars in common); however, the 13 bars we identified were found over broader geographical and salinity ranges. Juvenile oyster abundance on this group of 13 prime bars was intercorrelated significantly, suggesting that interannual variability in juvenile oyster abundance affects each region similarly. Significant correlations between the juvenile oyster abundance time series and the Palmer hydrological drought index suggest that variations in wet/dry cycles are the cause of this interannual variability. Our analysis also indicates that the entire oyster population of the northern Chesapeake Bay may respond in similar manner to climate change effects.

A polyclonal antibody specific to an egg protein of the Suminoe oyster, Crassostrea ariakensis, was developed to assess reproductive effort. After 2 mo of immunization, rabbit antiserum showed strong specificity to the egg protein in an enzyme-linked immunosorbent assay (ELISA). The rabbit antioyster egg immunoglobulin G detected as little as 0.2 µg/mL of Suminoe oyster egg protein by ELISA. The quantity of eggs present in an oyster was estimated using ELISA and was expressed as a gonadosomatic index (GSI). Gonadosomatic index values of Suminoe oysters were assessed monthly from January to July 2007 at the Seomjin River estuary off the south coast of Korea. Histology indicated that most oysters were mature and ready to spawn by the middle of July. Mean GSI values for oysters collected in April, when most female oysters are in early developmental stages, varied between 0.6% and 14.0%. In July, most oysters were ready to spawn and GSI values ranged from 17.5–67.0%, with a mean of 47.7%. The potential fecundity of ripe oysters was determined by dividing the number of eggs, which was estimated by ELISA, by the mean dry weight of a single egg (14 ng); fecundity ranged from 162–910 million eggs. The immunological technique used in this study was affordable and sensitive enough to measure variation in the number of eggs present among gametogenic stages.

Patterns of settlement and postsettlement mortality determine the distribution and abundance of sessile marine organisms. In mangrove forests and on rocky shores of eastern Australia, the Sydney rock oyster, Saccostrea glomerata, displays a pattern of declining abundance with increasing tidal elevation that might be related to or independent of the tidal elevation gradient in the substrate (bare, dead conspecifics, live conspecifics) available for attachment. We conducted parallel manipulative experiments on a rocky shore and in a mangrove forest to assess (1) the relative importance of tidal elevation and substrate type (bare, live oysters, or dead oysters) in determining the spatial distribution of new (<1 mm) S. glomerata recruits and (2) the contribution of settlement and postsettlement processes in setting patterns of spatial variation in established oyster populations. Patches of habitat with either live oysters, dead oysters, or no conspecifics were established at 3 tidal elevations at each site, and natural settlement and postsettlement mortality were monitored through time. At each site, and regardless of the substrate provided, we detected a similar pattern of fewer new S. glomerata recruits and greater postsettlement mortality on the high intertidal shore rather than the mid or low intertidal shore. Substrate type, by contrast, influenced the abundance of new recruits, but not subsequent postsettlement mortality. Consequently, over a period of months, direct effects of tidal elevation rather than effects of substrate type determined spatial patterns of oyster recruitment on the rocky shore and in the mangrove. Consequently, we documented that on a rocky shore and in a mangrove forest, settlement and early postsettlement mortality vary similarly across tidal elevation gradients and substrate types to determine the distribution of S. glomerata.

Near-infrared IR reflectance spectroscopy (NIRS) was applied to the compositional analysis of oysters (Crassostrea gigas and Saccostrea glomerata). Homogenized meat samples of 332 oysters were scanned by NIRS, subsamples were analyzed chemically, and, by combining the sets of information, calibration models were developed to allow prediction of proximate composition (moisture, protein, glycogen, and fat). Predicted and actual (chemically measured) data in independent validation sample sets were compared using R² and the ratio of the SE of chemical data to the SE of NIRS prediction (RPD). For S. glomerata, models gave excellent prediction for all components (R² = 0.95–0.97, RPD = 2.7–5.5). Prediction within the C. gigas validation set was generally less precise, but still very good for all components (R² = 0.92–0.96, RPD = 2.7–4.8). With a smaller subset of samples (n = 48), prediction models were also developed for estimating concentration of polyunsaturated fatty acid and long-chain polyunsaturated fatty acid (R² = 0.94 and 0.93, respectively). The major advantages of the methodology are its speed—250—300 samples can be analyzed simultaneously for all components each day—and cost-effectiveness when a large number of samples (e.g., several hundred or more per year) are analyzed. Therefore, the method is ideally suited to applications requiring the rapid analysis of many individuals, such as selective breeding programs for which chemical compositional data can provide information on traits associated with oyster condition or quality.

The Pacific oyster Crassostrea gigas is cultured at 8 commercial farms in South Africa. Worldwide, environmental-specific intensive selection on the species optimizes commercially beneficial traits, but its performance has not been studied in South Africa. From May 2010 to March 2011, we compared 2-mo measurements of growth rate, condition, and survival of 3 cohorts of different origin in longline culture at 3 different South African environments: 2 sea-based farms located in Saldanha Bay (Western Cape) and Algoa Bay (Eastern Cape) and a land-based farm at Kleinzee (Northern Cape). Overall, Saldanha Bay was cooler (mean sea surface temperature of 16.0°C; CV, 16.2%) than the other 2 localities, which did not differ significantly from one another (Kleinzee: 18.6°C; CV, 20.4%; Algoa Bay: 17.8°C; CV, 8.9%). The high variability at Kleinzee reflected stronger summer warming than at the other 2 farms. Saldanha Bay had higher phytoplankton biomass (mean, 14.3 mg chlorophyll a/m³; CV, 54.2%; May 2010 to March 2011) than did Algoa Bay (mean, 5.3 mg chlorophyll a/m³; CV, 81.0%; September 2010 to March 2011). The 3 cohorts showed similar trends in growth and condition. Growth rates, expressed as live or dry mass gains, were 2–10 times those reported elsewhere in the world, and dry weight condition indices were also high. High live mass growth rates in Algoa Bay, despite its relatively low phytoplankton biomass, seem to reflect a similar phenomenon to that reported in other relatively phytoplankton-poor grow-out environments, such as the Mediterranean Thau Lagoon in France. Dry meat mass gain and condition were highest for oysters in Saldanha Bay, with high food availability offsetting the thermal advantages of the warmer Algoa Bay site. Oysters in the bottom layers of the cages grew significantly faster than those in the top layers, particularly in Saldanha Bay, possibly reflecting fine-scale vertical differences in phytoplankton biomass. Saldanha Bay is the best of the 3 locations to produce market-ready oysters. Algoa Bay yields faster growth but leaner oysters and is a good nursery location, as is Kleinzee, which yields overall slow growth but good shell quality in winter and early spring.

Quantitative measurements of phytoplankton removal in a natural setting are needed to evaluate interactions between aquacultured bivalve populations and the surrounding environment. We report high-frequency (15-min) measurements of environmental variables relevant to oyster feeding and excretion at the inflow and outflow of an oyster nursery—floating upweller system (FLUPSY)—from June through September 2010 in the East Creek embayment, Peconic Estuary, NY. We demonstrated large variability in oyster particle clearance rate on short- (minutes to hours) to long-term (seasonal) timescales, including oyster responses to environmental variation, such as diurnal temperature and dissolved oxygen cycles, wind-driven turbulence, and the presence of harmful algae. A diel cycle in clearance rates calculated from whole FLUPSY measurements was apparent, with a maximum weight-specific clearance rate (CR_W) of 2.21 L/h/g occurring around midnight, and a minimum CR_W of 0.32 L/h/g at 0740 HR, coincident with the lowest concentration of dissolved oxygen in the water. Throughout the season, oyster growth and feeding showed constant, high values from June 12 to July 21, with a median CR_W of 0.95 L/h/g. From late July to September, a toxic dinoflagellate, Cochlodinium polykrikoides, was present frequently in the water, and was coincident with depressed oyster feeding, slow/no growth, and increased mortality. Overall, the FLUPSY in East Creek did not have a large impact on the abundance of phytoplankton in the water. Future modeling efforts projecting carrying capacity and ecosystem services of shellfish aquaculture and restoration need to take into account the potential for temporal variability in feeding resulting from environmental variation, as observed in this study.

Adult fecundity and reproductive potential can be critical determinants of subsequent larval supply and juvenile recruitment, and important determinants of placed-based management, especially when selecting sites for marine reserves where larval export is an expected outcome. We quantified spatiotemporal variation in fecundity and reproductive potential of female oysters (Crassostrea virginica) within a network of no-take oyster broodstock reserves by sampling over 3 y at 3 spatial scales: (1) per capita, (2) per square meter, and (3) per reserve. A total of 2,596 oysters were collected using scuba from six reserves in Pamlico Sound, NC, during 2006 to 2008 and processed in the laboratory for fecundity. Per-capita fecundity ranged from 0–340,500 eggs, and increased exponentially with oyster size, peaking in May of all years. In general, per-capita fecundity was highest at more inland mesohaline reserves, whereas reproductive potential per square meter and reserve reproductive potential were highest at more seaward polyhaline reserves as a result of a combination of relatively high density, and large oyster size and reserve areas. All 3 reproductive metrics increased in general over time. These results suggest that inland broodstock reserves should be prioritized for stock enhancement/seeding—and more seaward reserves for reserve expansion—and highlight the need to consider spatiotemporal variation and the scale at which a key demographic rate (fecundity and reproductive potential) is expressed when assessing the efficacy and conservation/restoration targets of marine reserves.

A numerical model is presented that defines a sustainability criterion as no net loss of shell, and calculates a sustainable harvest of seed (<75 mm) and sack or market oysters (≥75 mm). Stock assessments of the Primary State Seed Grounds conducted east of the Mississippi from 2009 to 2011 show a general trend toward decreasing abundance of sack and seed oysters. Retrospective simulations provide estimates of annual sustainable harvests. Comparisons of simulated sustainable harvests with actual harvests show a trend toward unsustainable harvests toward the end of the time series. Stock assessments combined with shell-neutral models can be used to estimate sustainable harvest and manage cultch through shell planting when actual harvest exceeds sustainable harvest. For exclusive restoration efforts (no fishing allowed), the model provides a metric for restoration success—namely, shell accretion. Oyster fisheries that remove shell versus reef restorations that promote shell accretion, although divergent in their goals, are convergent in their management; both require vigilant attention to shell budgets.

The successful induction of triploid embryos or larvae has been performed in Patinopecten yessoensis during the past 2 decades. However, no research has been reported about the performance of triploid P. yessoensis cultured in the field. This study induced triploidy in P. yessoensis by hypotonic shock and compared the growth and reproductive performance of triploids and diploids reared under commercial conditions for up to 24 mo. The main results of this study are as follows: Triploid scallops were smaller in size and weight compared with diploids and had a retarded absolute growth rate (AGR). After 24 mo of cultivation, the mean shell height, shell length, shell width, and body weight of triploids were 9%, 10%, 9%, and 25% less than diploids, respectively (P < 0.01). Although normal in sex ratio, the reproductive potential of triploids was significantly reduced. Only 87% of the triploids exhibited sex-discernible gonads during the breeding season. None of the male triploids spawned, and the percentage of female spawners among the triploid population was only 27% of that for the diploid population. The relative fecundity of triploid females was only 4% of diploid females. Triploid eggs produced mostly aneuploid larvae and had an extremely small chance of generating viable offspring when fertilized by sperm from diploid males. Most aneuploid larvae died before the D-shaped stage, and no survival exceeded 7 days. The potential to yield viable offspring from the triploid population was estimated to be only 4% × 10^-6 of that of the diploid population. Despite the growth disadvantage of triploids, this study may support, in part, the energy reallocation hypothesis, because triploid AGR was similar to diploid AGR (2% variance) during the sexual maturation season. Our results also indicate that there would be no growth advantage, but instead a disadvantage, for triploid P. yessoensis growing at the experiment site. In addition, this research provides the first evidence that viable triploid molluscs can be induced by hypotonic shock, of which the practical and evolutionary implications are also discussed.

Weathervane scallops (Patinopecten caurinus) have been harvested commercially in Alaska since 1967. From the beginning, vessel operators in the eastern Gulf of Alaska have reported poor scallop adductor muscle quality characterized by tissue of stringy texture that tears easily during shucking. The Alaska scallop industry designates these scallops as “weak meats” and has difficulty marketing the product. Our research objective was to quantify variability in the quality of adductor muscle of Alaskan weathervane scallops. Physical measurements and chemical composition analyses were conducted for 2 groups of whole scallops from Yakutat (weak and standard) and 2 groups of scallop adductor muscles from Kodiak (Kodiak 1 and Kodiak 2). Moisture content was significantly higher (P < 0.05) in weak than in standard adductor muscles. Glycogen content was similar (P > 0.05) for standard, Kodiak 1, and Kodiak 2 adductor muscles, but was significantly lower (P < 0.05) in weak adductor muscles. Muscle condition indices were significantly lower (P < 0.05) in weak than in standard adductor muscles. Results indicate that weak adductor muscle samples were lower in overall quality than the other 3 groups. Further investigation into the biological causes of weak adductor muscle in the eastern Gulf of Alaska scallops is warranted.

Generalized linear mixed models were developed for allometric relationships in Atlantic sea scallops (Placopecten magellanicus). These models used environmental covariates such as depth, latitude, geographic area, fishing pressure, population density, and season. This study makes several technical improvements to existing allometric models. We found depth, latitude, and geographic area to be important covariates in models for scallops on Georges Bank, whereas depth and fishing pressure were important for mid-Atlantic scallops. Our allometric relationships have important implications for stock assessment and fisheries management.

Selective breeding and crossbreeding are seen widely in genetic improvement of crops as well as molluscs. In this study, we constructed complete 4×4 diallel crosses using broodstock from 4 geographical subpopulations of sea scallops along the Atlantic coast of Canada, and heterosis and combining abilities in growth and survival rates at larval and adult grow-out stages were analyzed. The results indicated that variable heterosis in growth and survival exist in larval and adult stages. In many cases, the fitness traits increased with general combining abilities, especially at the larval stage, but in some cases, groups with high growth or survival rate but low general combining abilities were also observed. Reciprocal effects and maternal reciprocal effects were observed in growth and survival at the larval stage and also in adult growth. Two hybrid strains with superior growth and survival traits over purebred and other hybrid groups were selected that can be used in future culture practice.

Algal blooms produced by toxic dinoflagellates have increased worldwide, resulting in economic losses to aquaculture and fisheries. In New Zealand, the effects of paralytic shellfish poisoning (PSP) toxins on the physiology of the native scallop, Pecten novaezelandiae, are relatively unknown. Adult scallops (shell length, 94 mm) were exposed to low concentrations of the toxic PSP-producing dinoflagellate Alexandrium tamarense for 10 days followed by 8 days of depuration during which clearance rate, excretion rate, and the level of PSP toxins accumulated in the tissues were measured. For the first 6 days, scallops that had been exposed to toxic dinoflagellates had significantly lower clearance rates than the control group that was exposed to nontoxic dinoflagellates. By day 10, scallops had recovered their original clearance rate, and this rate continued throughout the depuration period. Excretion and oxygen uptake were unaffected by the PSP toxins. Differences in the toxin profile of the toxic dinoflagellates and the tissues of the scallops confirmed biotransformation of PSP algal toxins in the scallop digestive gland, where the majority of the PSP toxins were located. After 10 days of feeding on the toxic dinoflagellate, the PSP toxin level of the tissues reached 297 µg STX di-HCl equivalents/100 g. A depuration period of 8 days was insufficient to reduce the PSP toxin to safe levels (80 µg STX di-HCl equivalents/100 g) for consumption of the whole scallop.

Saucer scallops, Amusium balloti, are targeted by Shark Bay prawn and scallop trawl fisheries where regulatory discarding can occur during summer and winter months that may adversely impact the recruitment of this resource. Survival of repeatedly discarded saucer scallops was thus estimated for the Shark Bay trawl fisheries using short-term tag—recapture experiments under various fishing and environmental conditions. Estimates of apparent survival of discarded scallops was significantly higher during the postspawning winter period (>90%) than during the prespawning summer period (20–90%), but no differences in survival between fishing grounds or between postcapture treatment groups (air exposed vs. those kept in a holding tank) were observed. This suggests that thermal stress from large differences in seasonal temperatures was more critical to scallop survival than differences in scallop reproductive condition. Thus past (pre-2004) management regulations that imposed regulatory discarding during the warmer summer months would have incurred high discard mortalities. Under current management measures, however, regulatory discarding is predominantly during winter months, when scallops exhibit higher resilience to trawlinduced stress. The results support the current management strategy of fishing during the warmer prespawning summer months when the amount of discards is less. Regulatory discarding during the winter spawning period may generate a higher discard rate but the associated discard mortality is at its minimum.

Indirect methods such as length—frequency analysis have not been recommended for growth estimation in octopus (length is not a good measure of size for soft-bodied organisms; size is not a good indicator of age because of the high interindividual variability in growth rates and an asymptotic growth is often assumed). However, these methods are still applied in various places where octopus fisheries exist because they are low cost and easy to apply in most fisheries where there are no financial resources or scientific capacity to use direct methods. The purpose of this study was to investigate whether length—frequency analysis is an appropriate method for determining the growth pattern of Octopus bimaculatus from the Gulf of California. We tested the widely used methods ELEFAN I and NSLCA, and a modal progression analysis with a multimodel approach. The results showed that the growth pattern of O. bimaculatus was reasonably described using these analyses. First, the suitability of using mantle length as a measure of size was confirmed through a significant length—weight relationship. A length—age key was also generated in terms of probability to take into account the variability in growth rates, and with the multimodel approach it was not necessary to assume asymptotic growth. Population size structure is the most readily obtained and probably the most commonly used or only available information in a large number of fisheries. Therefore, the usefulness of length—frequency analyses should not be underestimated when direct methods are available.

Settling cues in the form of coralline algae were presented to groups of hatchery-reared red abalone (Haliotis rufescens, Swainson 1822) larvae daily from day 4 to day 32 posthatch (temperature, 14°C). Survival of postlarval abalone after settlement was monitored for 30 days to quantify the effect of delayed metamorphosis on the subsequent survival of benthic juvenile abalone. After exposure to live coralline algae, an average of 85% of the larvae metamorphosed and settled the following day. The number of settled postlarvae increased gradually the longer the settling cue was withheld. Postsettlement juveniles were raised in individual containers on mixed diatoms for up to 34 days. Red abalone larvae remained competent to settle 32 days after fertilization. Larvae that metamorphosed from day 4 through day 19 had longer survival during the next 30 days (average, 19%) than those presented with a settling cue from day 20 to day 32 (average, 8%). Statistical analysis using a threshold cut point indicated that the 20-day threshold marked a significant change in subsequent postlarval survival. A receiver—operating characteristic curve analysis indicated that the 20-day cut point predicted high or low future survival of postmetamorphic abalone 73.4% of the time. Larvae that swam for less than 20 days had postmetamorphic survival of 8 days or more, whereas survival was 7 days or less for postmetamorphic abalone that had swam previously for 20–32 days. A larval competency period of 20 days is significantly longer than the 5–7-day larval stage often used to estimate transport times for this species.

Settlement of Haliotis tuberculata coccinea larvae was examined in the presence of crustose coralline algae (CCA), Ulvella lens, and Ulva rigida. Germlings of the 2 green macroalgae of different age, enrichment level, and in combination were tested as settlement cues, and CCA was tested as a positive control. Larval settlement was the highest on CCA (61 %) tailed by a 45-day-old mix of U. lens and U. rigida (52%) and 45-day-old U. rigida (46%). Settlement was the lowest (about 3%) on a mix of 4-day-old U. lens and U. rigida and 45-day-old enriched or unenriched U. lens. In all treatments, postlarvae were fed for 4 wk with a mix of diatoms (Amphora sp., Proschkinia sp., Nitzschia sp., and Navicula incerta); postlarval growth was the best on the 45-day-old mix of U. lens and U. rigida. This substrate was also the best of the green macroalgae germlings substrates tested for settlement induction and provided good survival rates. The substrate protein content correlated negatively with larval settlement and survival. The algal cues were differentiated by their fatty acid composition. Fatty acids such as 18:ln-7, 18:2n-6, 16:4n-3, arachidonic acid, and eicosapentaenoic acid were suggested to affect settlement and survival. The fatty acids correlated with settlement were different from the ones associated with survival rates, except eicosapentaenoic acid, which correlated with both. The results of this study show the high value of U. rigida for H. tuberculata postlarvae, and the influence of substrate age on the settlement success.

The presence of the lipophilic toxins okadaic acid (OA), dinophysistoxin-1, pectenotoxin-2, and yesso toxin (YTX) in the abalone Haliotis discus hannai collected between March 2009 and May 2010 was analyzed via liquid chromatographytandem mass spectrometry (LC-MS/MS) and the mouse bioassay. Thirty abalone samples collected from 2 sites, Geumdang and Chungdo on the southwest coast of Korea, were submitted for toxin analysis. Lipophilic toxins OA and YTX were detected in the digestive gland of the abalone by LC-MS/MS, but no toxins were detected in the foot muscle. The highest toxin concentrations in the digestive glands of the abalone were 4.7 ng/g OA and 1.3 ng/g YTX. Okadaic acid and YTX were detected mainly during winter and spring. However, dinophysistoxin-1 and pectenotoxin-2 were not detected in any of the samples by LC-MS/MS. Diarrhetic shellfish poisoning toxins were not detected in the digestive gland or the foot muscle by mouse bioassay. Although low levels of toxins were detected, this is the first report identifying lipophilic toxins in abalone.

Dreissenid mussels invaded and colonized waters of the Laurentian Great Lakes during the late 1980s. Their colonization and resulting impact have been characterized as one of the most important ecological changes in freshwater systems in North America. The need for information on dreissenid mussels has grown during the past 2 decades, which has prompted the compilation of this bibliography. Two previous bibliographies of dreissenid mussels indicate average publication rates were 6 publications/year between 1771 and 1964 (1,180 in 194 y) and 30 publications/year between 1964 and 1993 (885 in 30 y). In the current bibliography, the average rate of publication doubled during the past 23 y (1989 to 2011) to 66 publications/year based on a total of 1,502 publications. These rates may be biased by increased numbers of researchers and journals over time but, at a minimum, these rates indicate continued interest and concern by humans about the impact of dreissenid mussels on water availability and the expanding range of dreissenids throughout the world. The current bibliography has a 94% efficiency rate for subject and 100% efficiency for title search criteria when compared with references in published studies of dreissenid mussels in 2011. In addition to publications, we included 206 student theses and 225 chapters in 26 books including 6 books devoted solely to dreissenid mussels. A vast majority of student theses were about dreissenid mussels in North America, especially in the Laurentian Great Lakes. The 6 books devoted to dreissenid mussels contained a variety of chapters that described biology, impact, control, and ecology of dreissenid mussels in both Europe (published in 1992 and 2010) and North America (1993, 1994, 1997, and 2000). In addition, there is a 7th book devoted solely to dreissenid mussels that is near completion.