In 1993, sea scallop, Placopecten magellanicus, populations from the Jacques Cartier Bay on the North Shore of the Gulf of St-Lawrence of Canada, experienced masse mortality episodes with mortality rates reaching 80%. Both natural beds and aquaculture stocks were affected. Experiments were undertaken to determine if an unknown or unidentified pathogen could be responsible for the disease and if that disease was transmissible. Three experiments, in which scallops were inoculated with homogenate extracted from moribund and healthy scallop tissue, were carried followed by histopathological analysis. The results demonstrated that the scallops from the Lower North Shore were more vulnerable to external factors such as manipulations and injections than the scallops from other regions, like Magdalen Islands and Gaspésie. The histopathological analysis did not permit to identify the causal pathogenic agent but our results suggested transmission of infection. The exact cause of the mass mortality episodes remains unknown to date, but it could be caused by a combination of multiple factors including geographic distribution and inbreeding.

Competent larvae of the black scallop Chlamys varia (L.) were treated with the neurotransmitter gamma-amino-n-butyric acid (GABA), the catecholamine epinephrine, and 3-isobutyl-1-methylxanthine (IBMX), at different concentrations and times of exposure, to test the effects of exposure to the compounds on larval settlement. After 24 h, maximum percentage of settlement (>30%) was induced by 10⁻⁵ M epinephrine. After 48 h, maximum settlement rate was also achieved by 10⁻⁵ M epinephrine (>54%). Exposure to 10⁻⁶ M epinephrine and to 10⁻⁶ M GABA also induced significantly higher larval settlement than in control larvae. By contrast, IBMX failed to induce significantly higher settlement rates than in the control larvae. Epinephrine and GABA were identified as active inducers of settlement in C. varia, and were not toxic to black scallop larvae. This is the first report in which the involvement of epinephrine and GABA in the settlement of C. varia larvae is described.

A size-selectivity curve was constructed to characterize the performance of the New Bedford style Atlantic sea scallop (Placopecten magellanicus, Gmelin 1791) dredge when it is configured to meet the requirements of Amendment #10 to the Sea Scallop Fishery Management Plan. The curve was generated using the SELECT model on catch-at-length data, obtained by simultaneously towing a New Bedford style dredge and a nonselective National Marine Fisheries Service sea scallop survey dredge from commercial scallop vessels. Data were collected during three cruises in the Northwest Atlantic between 2005 and 2006. The resultant selectivity curve yielded a 50% retention length of 100.1 mm, a selection range of 23.6 mm, and a value of 0.77 for the efficiency of the commercial dredge relative to the survey dredge. A length of 100.1 mm corresponds to a meat weight of 17.2 g in Georges Bank and 16.8 g in the mid-Atlantic. These results can assist fisheries managers with stock assessments, fishing mortality estimates, and the interpretation of catch data from resource surveys. Additionally, the curve can be used as a baseline to evaluate the effect of future changes to sea scallop dredge configuration.

The Patagonian scallop (Zygochlamys patagonica) fishery started in the Argentine Sea after exploratory cruises developed during 1995. Knowledge concerning the habitat requirements involved in the settlement processes of the target species was lacking. The main objectives of this study are to find Z. patagonica spat and to assess the characteristics and distribution of its primary settlement substrate (PSS). We observed under binocular microscope different invertebrate species (potential PSS) collected during 2006 from 125 sampling sites between 37° to 44°S and 83–133 m depth. Spat were found on the hydroid Symplectoscyphus subdichotomus (n = 215) and on adult Patagonian scallops (n = 51, attached to the encrusting sponge Iophon proximum, amphipod, and polychaete tubes in nearly half of the cases). To analyze possible interactions between the benthic assemblage and scallop spat throughout the study area, we performed a faunal analysis including the species considered potential PSS (hydroids and scallops) and potential predators. The analysis showed a unique cluster of species closely associated, with variable abundance of hydroids (higher in samples with spat), scallops, and predators. A particular study in MDQ Area (38°S) shows that the sites where spat was collected presented lower density of potential predators and had been scarcely fished in comparison with the other sites within the area. The availability of PSS should be monitored and areas with dense patches of dichotomous hydroids should be protected from trawling.

The reproductive cycle of Pecten sulcicostatus is described as part of an investigation into the potential commercial culture of this species in South Africa. Scallops were collected monthly from False Bay, from August 2004 to October 2005, to determine seasonal variation in the gonadosomatic index (GSI) and to assess associated histological changes within the gonads. The reproductive cycle of P. sulcicostatus demonstrated clear seasonality. The mean GSI was highest from June to September (winter to early spring), and lowest from November to January (late spring to summer). The GSI findings were corroborated by histological analysis of the gonads with the mean oocyte diameter reaching a maximum in August and a minimum in November. Seasonal stratification and corresponding changes in phytoplankton biomass are considered to control the reproductive cycle of P. sulcicostatus in False Bay as winter spawning and the subsequent decline in the GSI coincide with the transition to spring upwelling conditions and a decline in bottom water temperature and food availability.

The accuracy and reliability of abundance estimates of the infaunal propellerclam, Cyrtodaria siliqua, derived from their burrow openings was tested over a three-year period after experimental hydraulic clam dredging. Abundances of C. siliqua were obtained from hydraulic grab samples at the same locations as photographs taken to count their burrows. Correlations between abundances of clams and burrows in dredged and nondredged areas were monitored over a three-year period. All correlations between burrows and clams were positive in nondredged areas and three of six correlations were significant. There was a natural trend over time of decreasing numbers of visible burrow openings, whereas abundances of the architect of these burrows, C. siliqua, remained relatively constant. Possible explanations for this phenomenon are discussed. All postdredging correlations in the two dredging boxes were negative and nonsignificant. It is concluded that, in this habitat, counts of burrow openings in photographs are not reliable surrogates of abundances of C. siliqua in grab samples. Monitoring recovery in these populations will require traditional grab sampling.

Northern quahogs (=hard clam; Mercenaria mercenaria) is a commercially important bivalve naturally distributed along the American Atlantic coast. Because the hard clam was first introduced into China as a candidate for aquaculture in 1997, research has been conducted on its ecologic habits, ecological physiology, metabolism, growth, reproduction, artificial propagation, and seed culture. Little information about their chromosomes and karyotype is available. The present study is designed to study the karyotype of the diploids and triploids to provide a reference to genetic research on introduced M. mercenaria. Triploids were produced by inhibiting the release of second polar body (PBII) with a treatment of 450 μmol/mL 6-deimethylaminopurine (6-DMAP), with untreated fertilized eggs developing as normal diploid controls. Chromosome preparations were made from trochophore larvae with drop-splash method. Chromosomes were measured and classified according to Leven criteria. Statistical analysis of relative length and arm ratio revealed that, this species had a normal diploid chromosome number of 2n = 38, and the karyotype consists of 15 pairs of metacentric (M) and 4 pairs of submetacentric (SM) chromosomes, NF = 76. The triploid karyotype formula was 45 M 12 SM, NF = 114. The heterochromosomes and satellite chromosomes were not observed in all chromosomes in the complement.

We have designed a set of exon-primed intron-crossing (EPIC) PCR primers to amplify introns at the genes TBP and SRP54 in the Manila clam (Ruditapes philippinarum) and the grooved carpet-shell clam (R. decussatus), and also one intron at a histone 3 homologous gene in the Manila clam. The primers were developed by using “universal” EPIC primers available in the literature and by searching for intron locations in cDNA sequences taken from public databases. The identity of the amplified products was checked by sequencing. The three introns of the Manila clam, and one in the carpet shell clam (TBP), exhibited length polymorphisms. The number of alleles was two at the TBP locus of the grooved carpet-shell clam, and ranged from three to five in the three loci of the Manila clam. The locus without length polymorphism in the carpet-shell clam exhibited polymorphism when digested with the restriction enzyme EcoR I (4 haplotypes). The variability of the markers was examined in two population samples in each species.

Chromosomal location of the major ribosomal RNA genes (rRNA) were studied in the dwarf surfclam (Mulinia lateralis, Say) using fluorescence in situ hybridization (FISH). FISH probes for the rRNA genes were made by polymerase chain reaction (PCR), labeled with digoxigenin-11-dUTP and detected with fluorescein-labeled antidigoxigenin antibodies. Mulinia lateralis had a diploid number of 38 chromosomes and all chromosomes were telocentric. FISH with the rRNA probe produced positive and consistent signals on two pairs of chromosomes: Chromosome 15 with a relative length of 4.6% and Chromosome 19, the shortest chromosome. Both loci were telomeric. The rRNA location provides the first physical landmark of the M. lateralis genome.

The status of the Kumamoto oyster Crassostrea sikamea in its native Japan is uncertain because of a lack of information about its abundance and distribution and a suggestion that C. sikamea and the Pacific oyster C. gigas hybridize in the northern Ariake Sea. Furthermore, broodstock populations on the United States Pacific coast have been hybridized with C. gigas in the past and may suffer inbreeding depression from multiple generations of hatchery-propagation. As a result, Japanese conservationists and United States oyster growers share an interest in the status of this species in the wild. We collected wild oysters from three sites in Saga Prefecture located in the northern portion of the Ariake Sea, Kyushu, Japan, in September 2006 and used molecular methods (species-specific PCR of the mitochondrial COI gene and PCR-RFLP of the nuclear ribosomal ITS1 gene) to assign 628 sampled oysters to one of three species found in this region. C. sikamea proved to be the dominant organism on artificial hard substrates, comprising 91% of the oysters sampled and typed. Many individuals confirmed as C. sikamea by diagnostic DNA markers had C. gigas-like phenotypes, such as striped shells. Crassostrea ariakensis was present (8% of typed oysters) but only at the lowest intertidal levels, and C. gigas was rare (1%) at these sites. We found no evidence of hybridization between any of the species and were unable to repeat a previous study, which suggested hybridization between C. sikamea and C. gigas based on sharing of a calmodulin allele. We conducted gamete compatibility tests among all combinations of Japanese (Ariake Sea) and United States C. sikamea and C. gigas broodstocks and found strong one-way gamete incompatibility (male C. sikamea × female C. gigas) between species of Japanese stocks, supporting the molecular diagnosis of C. sikamea. However, this one-way incompatibility was less evident in United States stocks, indicating lower barriers to potential hybridization in commercially cultured stocks.

Inbreeding has profound implications in fields ranging from evolutionary biology to medicine. Most cultured aquatic species are only partially domesticated and highly fecund and are, therefore, expected to have higher genetic load and more severe inbreeding depression than species with lower fecundity and/or longer histories of domestication. Marine bivalves such as oysters are extreme in this regard, and previous studies have demonstrated that self-fertilization, brother/sister matings, and cousin/cousin matings in Pacific oysters (Crassostrea gigas) reduce growth and survival. It is unclear, however, whether these effects can be extrapolated to lower levels of consanguinity such as those expected in natural populations or the founders used to initiate cultured strains or selective breeding efforts. To address this without the need for extensive pedigree information, we studied inbreeding in a naturalized population of Pacific oysters using molecular marker-based estimates of parental relatedness calculated from multilocus microsatellite genotypes. We produced 34 full-sib families using randomly mated parents collected from a naturalized population in Dabob Bay (Washington, USA) and planted them in intertidal and subtidal conditions in Dabob Bay and Yaquina Bay (Oregon, USA). Using 16 microsatellite loci, we estimated the degree of inbreeding of each pair's progeny in three ways: (1) identity ( I ) or the expected homozygosity of the progeny based on their parents' genotypes estimated using the IDENTIX program, (2) a moment-based estimator of the pair-wise coefficient of relatedness ( W ) of each parental pair estimated using the MER program of Wang, and (3) a modified estimator of the pair-wise coefficient of relatedness ( K ) designed specifically to accommodate null alleles, which were common in the Dabob Bay population and estimated using the ML-RELATE by Kalinowski. Using a composite analysis of variance approach to partition the total among-family variation into components attributable to inbreeding and all other family-level effects, we found statistically significant negative relationships between all three estimators of inbreeding and the survival of their progeny when we analyzed all location/exposure combinations simultaneously and in 7 of the 12 separate tests examining each location/exposure combination separately. However, for 4 of the 5 nonsignificant tests, P < 0.07 using K estimator of relatedness, which makes the potentially unreasonable assumption that all parents have inbreeding coefficients (F) of zero. Further, these relationships were strongest at the site with the highest mortality, indicating that inbreeding depression may be more severe in a more stressful environment. Finally, we briefly outline potential strategies for using molecular marker-based estimates of relatedness to improve the genetic composition of new founder populations, incorporation of relatedness information in selective breeding efforts, and minimizing inbreeding effects in established cultured oyster populations.

Fouling communities of commercial oyster crops in San Quintin Bay (Baja California, Mexico) were investigated to understand patterns of shell cover, species composition, and colonization. Historically dominated by soft sediment systems, San Quintin Bay currently supports a large oyster (Crassostrea gigas) aquaculture industry. Oyster shells are the main source of hard substratum in the bay, without which fouling communities would be mostly absent. Fouling communities are a nuisance to oyster farming because they result in increased handling time in cleaning and packaging oysters. To investigate the previously undocumented fouling communities of San Quintin, 3 sites within the bay were surveyed for 18 mo (2004 to 2005). Every month between July 2004 and December 2005 samples were deployed and collected so as to obtain shells that had been submerged for either 1, 2, 3, 6, or 12 mo. The majority of the fouling organisms were ascidians, with bryozoans, sponges, hydrozoans, and algae also present. Results show that fouling cover increases with length of time shells were submerged, with an average of ∼75% of shell surfaces covered by fouling organisms after 12 mo, the maximum time oysters are grown before harvest. Colonization in the system is variable throughout the year, with ascidian colonization being positively correlated with warmer water temperatures. Several of the species, mostly ascidians, of the fouling community are nonindigenous to the Pacific coast of North America and account for up to 40% of the total fouling cover. Fouling community cover and colonization is similar to what has been documented in other bivalve aquaculture systems. But, because most aquaculture ventures in San Quintin are small, family-based artisanal enterprises, the socio-economic impact of fouling is larger and more difficult to manage. Understanding patterns of fouling cover, colonization, and species outbreaks is necessary to develop feasible rearing solutions that can reduce the impact of fouling.

A European oyster population (Ostrea edulis) was recently discovered off the Eastern coast of Canada. The occurrence of this population led various aquaculture stakeholders to consider this species commercially. The aim of this study is to determine the best time to collect the European oyster larvae to maximize their collection. Gonad observations and plankton tows were carried out in 2005 and 2006 to estimate the time of settlement. Nine days after the first free-swimming larvae were observed, Chinese hat collectors were suspended in the water column every three days at two sites. The collectors were removed from the water after a mean streaming duration of 35 days. Spat were thereafter numbered on each collector. The spawning period lasted from mid-July to the end of August in 2005 and from mid-July to the beginning of August in 2006. Temperature was approximately 18°C during that time. The major peaks of free-swimming larvae were observed at the beginning of August (43,276 larvae m⁻³) in 2005 and at the end of July (224,322 larvae m⁻³) in 2006. Spat numbers were higher in 2005 (22,791 spat collector⁻¹) than in 2006 (124 spat collector⁻¹). The lower spat collection in 2006 might be related to nonfavorable environmental conditions observed during that summer. Salinity, in 2006, varied from 18‰ to 30‰ compared with 25‰ to 30‰ in 2005. Spawning in Eastern Canada is apparently occurring at a higher temperature (18°C) compare with other populations around the world (13°C to 16°C). This difference may be related to several factors such as the geographical location and food availability.

The purpose of this study is to examine the response of the oyster Crassostrea gigas to sulphide at different biological scales. A first experiment was designed to measure for 20 h the clearance (CR) and oxygen consumption (OC) rates of oysters exposed at different concentrations of sulphide (0, 3, 6, 12, 20, and 40 μM). The second experiment was carried out to evaluate the metabolic adaptations to chronic sulphide exposure for 10 days by measuring PK and PEPCK enzyme activities, succinate and alanine content, the adenylate energy charge (AEC), and the activity of the electron transport system (ETS) in whole oysters at above 20 μM. PK and PEPCK mRNAs and enzyme activities have been measured in adductor muscle. When exposed to sulphide above 20 μM, CR stopped, whereas oyster maintained their average OC rate between 1 and 2 mg O₂ h⁻¹ g⁻¹ dw. In the second experiment, sulphide exposure of oysters resulted in higher mortality, reduced the glycolytic flux by inhibiting the PK activity and decreased the ETS activity leading to a lower AEC. At day 10, a kind of recovery took place: the ETS activity and AEC of oysters exposed to sulphide increased to the level of the control oysters. In the adductor muscle, sulphide did not affect the transcriptional level of PK; PK was only regulated at enzyme level. Conversely, PEPCK was regulated only at transcriptional level. Nevertheless, muscle exhibited a wholly anaerobic metabolism by the significant increase of alanine and succinate contents followed by the significantly decrease of the ATP content during the 10 days of the experiment. This experiment showed that sulphide involved partially the whole oyster and wholly the adductor muscle in an anaerobic pathway of energy production; but oxygen was needed for the detoxification of the organism.

Two antimicrobial peptides (AMPs) of marine origin, tachyplesin from the Japanese horseshoe crab, Tachypleus tridentatus, and pleurocidin-amide from the winter flounder, Pseudopleuronectes americanus, were tested for their potential effectiveness in disease treatment in oyster aquaculture. Tachyplesin had a greater antimicrobial effect than pleurocidin-amide against a range of gram-positive and gram-negative bacteria, with minimum inhibitor concentrations in the range of 0.625 to 5 μg mL⁻¹. Tachyplesin (50 μg mL⁻¹) was also more effective than pleurocidin-amide (250 μg mL⁻¹) against the oyster protozoan parasite Perkinsus marinus, reducing its viability to 9% versus 22% in vitro. Both peptides were unaffected by variations in pH and salinity that would be encountered in marine culture conditions. Candidate algal and yeast for expression and feed-based delivery of recombinant AMPs were largely unaffected by tachyplesin and pleurocidin at concentrations that inhibited bacterial growth but were sensitive to concentrations that reduced the viability of P. marinus. Several proteases, including those of oyster and parasitic origin, decreased AMP activity, but tachyplesin was affected to a much lesser degree than pleurocidin-amide. Coincubation of homogenates from oyster digestive tissues with tachyplesin and pleurocidin-amide was found to reduce the abundance of colony forming units in the tissue. Tachyplesin was more effective against gram-negative bacteria present in oyster tissues, whereas pleurocidin-amide was more effective against gram-positive bacteria. Tachyplesin was considered a better candidate than pleurocidin-amide for feed-based delivery applications in oyster aquaculture.

Seasonal variations in storage, partitioning, and allocation of energy reserves (proteins, carbohydrates, lipids, and triglycerides) between germinal and somatic tissues (gonad, digestive gland, mantle tissue, and adductor muscle), were investigated related to reproduction of Pacific winged pearl oyster Pteria sterna. Tissue samples were collected every three months and analyzed with histological and biochemical techniques. Energy coefficients were also calculated with data from chemical composition of tissues. Gonad samples in almost all developmental stages occurred throughout the year, suggesting that P. sterna is a multispawning species. The evidence indicates that the main reproductive season runs from January through April (21°C to 22°C) and was identified by higher frequency of ripe gonads, more and larger postvitellogenic oocytes and higher protein, lipid, and triglyceride levels in gonad tissue. Within this study period, there were two spawning peaks, July 2003 and January 2004. Gametogenesis was sustained from energy mainly obtained from the digestive gland and secondly from the adductor muscle. Only proteins from these two tissues were mobilized to the gonad for maturation of sex organs, because carbohydrates were stored despite the progress of gametogenesis. The role of mantle tissue was negligible. P. sterna appears to use a combination of stored reserves (conservative strategy) and food supply (opportunistic strategy) as an overall strategy to regulate reproduction.

A mussel's shell records its history of growth. We investigated variability in the size and shape of mussel shells of Mytilus californianus Conrad (1837) to test the hypothesis that the mussel shell provides information on the contemporary condition of the mussel. Two factors were associated with shape: an epithelial discoloration and the Sr/Ca in the shell nacre. Sr/Ca data distinguished the mussel populations as did a discriminate analysis that included the trace metal ratios; Sr/Ca, Mg/Ca, Mn/Ca, Ag/Ca, Cd/Ca, Ba/Ca, and Pb/Ca. Size varied independently of shape and was not associated with the two factors. However, a null model that describes the morphological variability in height and width suggests that mussel size also plays a central role in partitioning phenotypic variability. These analyses of contemporary factors coupled with analyses of morphological variability holds promise for addressing the functional roles of mussel height and width and what proportion of phenotypic variability can be attributed to environmental factors.

Sperm motility, fertilization, and embryonic development were investigated in the hermaphroditic basket cockle, Clinocardium nuttallii. Motility of the sperm was more prolonged over a 2-h storage period at 4°C than at 19°C. The sperm-to-egg ratio resulting in the highest fertilization rate was 10,000:1, or an equivalent final sperm concentration of 6 × 10⁵ cells mL⁻¹, using a density of 60 eggs mL⁻¹. However, at least some degree of self-fertilization appeared to be unavoidable during the release of the eggs from the broodstock. The biological zero point, below which embryonic development ceased, was estimated to be 2.8°C to 2.9°C for C. nuttallii.

Factors affecting broodstock conditioning in the hermaphroditic basket cockle, Clinocardium nuttallii, were examined in laboratory experiments. Although a 13-wk experiment conducted at 16°C failed to bring C. nuttallii broodstock into spawning condition under different dietary treatments, initiation of gametogenesis was apparent for those broodstock maintained at 2.5°C. Condition indices were significantly greater when broodstock were fed a combination of Isochrysis galbana (Tahitian strain, T-iso) and Chaetoceros gracilis (CG) or T-iso and Thallasiosira pseudonana (3H) than when fed a combination of Tetraselmis suecica (TS) and 3H or TS and CG, indicating that T-iso may be a better food source than TS for cockle broodstock conditioning.

Seasonal variations in condition index and biochemical composition of the cockle Fulvia mutica (Reeve) were studied from March 2004 to February 2005 in eastern coast of China in relation to reproductive cycle. The condition index declined during gametogenesis and spawning, recovered when the gonad was in resting phase. Histological analysis and measurements of protein, glycogen and lipid levels and RNA:DNA ratio from gonad-visceral mass, mantle, adductor muscle, and foot of F. mutica were performed. Gametogenesis took place during winter and spring at the expense of reserves (glycogen in various organs, protein in the foot, lipid in the adductor muscle), which were accumulated previously during summer and autumn. Spawning occurred in May to June when water temperature was higher and food availability was abundant. The RNA:DNA ratio is a good indicator of sexual maturity in the gonad-visceral mass; the increasing RNA:DNA ratio in the gonad-visceral mass appears to show the rising synthetic activity of vitellin within the gonad. The results demonstrated that F. mutica may be considered a conservative species in gametogenic pattern. The useful information obtained in this study can be applied for management of populations and to initiate aquaculture activities in this species.

Interleukin-4 (IL-4) plays an important role in several areas of T-cell biology, including the development of Th2 responses and blocking Th1 effector mechanisms mediated by gamma interferon (IFN-γ), such as inducible nitric oxide synthase (iNOS) induction. In this study we investigated the effects of alcohol fractions of the blood shell (blood ark shell), Scapharca broughtonii, on the production of IL-4 from mouse EL4 T cells. Two alcohol fractions (SIII and AII) of the blood shell had stimulatory effect on IL-4 production. The SIII fraction itself significantly induced IL-4 production and IL-4 mRNA expression in a dose dependent manner by EL4 T cells. In contrast, the AII fraction enhanced IL-4 expression in PMA-activated EL4 T cells, whereas the AII fraction itself did not. Furthermore, the stimulatory effect of the alcohol fractions on IL-4 production was closely associated with the increase of NF-AT binding activity, indicating that the alcohol fractions of Scapharca broughtonii stimulated IL-4 production in EL4 T thymoma cells via increased NF-AT DNA binding activity.

Volutid snails have been identified as a potential resource for artisanal fisheries in northern patagonic gulfs. We explored their availability in two gulfs of Chubut Province (Patagonia, Argentina) by means of SCUBA diving and baited traps. CPUE and biomass were estimated from visual counting densities. CPUE of all the volutes was 65.85 kg·diver⁻¹·h⁻¹ and 59.5 kg·diver⁻¹·h⁻¹ in San Matías (SMG) and San Jorge (SJG) Gulfs, respectively. Estimated biomass was 89.7 (±28.9) and 44.4 (±19.2) tons in SMG and SJG. The species Adelomelon ancilla and Odontocymbiola magellanica could supplement the potential clam fishery existent at SJG. In SMG Zidona followed by O. magellanica could be the main commercial target. We suggest minimum catch sizes of 16 cm for Z. dufresnei, 9 cm for O. magellanica, and 12 cm for A. ancilla. Protection of the egg capsules and females would help the protection of the resource. These measures could ensure the sustainability of a small-scale multispecific fishery.

Knobbed whelk, Busycon carica (Gmelin, 1791), age and growth were estimated using tagged and recaptured individuals (n = 396) from areas off South Carolina coastal islands. Recaptured whelks were at large an average of 298 d (4–2,640 d). Growth, an increase in shell length (SL), was evident in 24% of the recaptured whelks, whereas 29% of recaptured individuals were the same size as when released and 47% were smaller than the released size. Mean growth rate was <0.001 mm SL/d and 0.022 mm SL/d if decreases in SL were assumed to be zero. Smaller whelks (≤90 mm SL) at large for over one year grew seven times faster than larger whelks. The von Bertalanffy growth model: SL_t = 159.5(1 − e^{−0.0765(t 0.4162)}), was developed from the mark—recapture whelks exhibiting growth. Based on a South Carolina minimum legal size of 102 mm SL, whelks recruit into the fishery at 13 y of age. The longevity, large size at maturity and slow growth suggest the potential for over harvest of knobbed whelk. Future whelk management plans may wish to consider whether economically viable commercial harvest can be sustainable.

Various biological characteristics of the exotic green crab (Carcinus maenas) were studied in 2000 and 2001 to describe its population structure and reproductive strategy off the coast of Prince Edward Island (PEI), Canada. This particular population is found at the northern limit of the green crab distribution off the east American coast. Results showed that the number of female crabs was higher during springtime compared with the rest of the year. Male crabs were found in higher numbers from August to December. Ovigerous females were observed from early July to mid-September, their numbers peaking in early July. This was confirmed by a gonadosomatic analysis, which showed that the relative gonadal wet weight dropped from late July to mid-September 2001. Fecundity was estimated at 140,000–200,000 embryos per mass. Mating occurred after larval release, which occurred from late August to December with a peak in September. Mature males were molting from June to December, but mainly in July. This was observed a few weeks before mating. Size at maturity was estimated at a carapace width of 21.30–34.49 mm for males. Size at maturity for females was estimated at 28.66–41.43 mm. Overall, our results showed that most reproductive characteristics of the green crab's life cycle tend to occur about a month later in PEI in contrast to what is usually observed in Maine (USA).

As ocean temperatures increase, crustaceans become subjected to more immediate, microecological impacts because of their exothermically-driven growth and development. In this laboratory-based study, ovigerous American lobster (Homarus americanus) were allowed to incubate their eggs for either a normal period of time (7–9 months including time at temperatures <10°C), or were held in water >10°C to speed up the rate of egg development (4–6 months). Females that had shorter incubation times had longer periods of larval release compared with females that incubated eggs for a normal period of time. Females incubating eggs for a shorter period of time also produced more larvae, and this was explained by the daily loss of a small number of eggs. Subsequent modeling of the relationship between dates of egg extrusion and hatching using data compiled from Massachusetts Bay demonstrated that there was a critical period in the fall at which larval development would switch from a resultant hatch in the spring to a hatch in the late fall or winter. The short-term implications of global warming on egg development and hatching in lobsters is discussed, including the production of larvae at suboptimal times of the year, as well as a temporal change in the abundance of larvae during the hatching season. Either of these events can lead to an increase in larval mortality and hence a decrease in population productivity.

Quantifying growth rate in microcrustacea is important to plankton biologists when determining primary productivity. RNA:DNA ratios have been widely used as an indicator of instantaneous growth rate in microcrustaceans in nutritional and environmental studies. It is important when measuring nucleic acids in these small organisms that it is done efficiently and with high sensitivity, so that small differences in nucleic acid content can be accurately detected. A technique is presented for the accurate, high-throughput determination of RNA and DNA content in individual microcrustacea, based on two new generation fluorescent dyes that bind preferentially to either RNA (Quant-iT™ RNA) or DNA (Quant-iT™ DNA). Contaminant interference (either from detergents or enzymes used in the chemical cell lysis process, or cell based contaminants such as proteins) can significantly affect fluorescence readings of these dyes. Through the development of our protocol, we show that proteinase K was an ineffective cell lysis method, whereas sarcosyl efficiently lysed cells and could be used when its final assay concentration was diluted to avoid interference with dye fluorescence. Organic solvents were also utilized to remove cell based contaminants that caused an interference with the Quant-iT™ DNA dye fluorescence. Through the use of specific RNA and DNA dyes and by achieving low levels of technical variation, this study developed a rapid and reliable method for nucleic acid extraction and quantification in Artemia.