Management strategies that exclude the harvest of mature female crawfish from culture ponds early during the harvest season (December to February) to maximize juvenile recruitment and subsequent yield is common in the procambarid aquaculture industry. However, the efficacy of these practices is not research based. Because procambarid crawfish commonly burrow prior to oviposition, this study observed month of spawning for crawfish that burrowed during the early months of the harvesting season (winter) in Louisiana. Natural burrows were excavated monthly over 2 consecutive crawfish production seasons, and crawfish were placed in a laboratory in artificial burrows to complete oviposition. Spawning generally occurred within 2 mo of crawfish relocation and averaged 35%. Mean number of young per weight (measured in grams) of females was 16.7 for season 1 and 10.6 for season 2, and although these were significantly different, no differences were noted for number of offspring among months of burrowing within seasons. Few differences were noted for tissue indices among crawfish burrowing at different months within a season, indicating similar body condition. On average, month of spawning occurred during mid February, late March, mid April, and mid May for the December, January, February, and March burrowers, respectively. Offspring from crawfish burrowing after January are unlikely to contribute to the annual harvest within the current production season.

Two crawfish baits and several bait quantities were evaluated in 2 trials conducted from January through May in four 2.0–2.5-ha experimental earthen crawfish (Procambarus clarkii and Procambarus zonangulus) ponds at the Aquaculture Research Station, Louisiana State University Agricultural Center, Baton Rouge, LA. In the bait-type trial, a freshwater cluepid, gizzard shad (Dorosoma cepedianum), a commercially formulated bait, and a shad formulated bait combination were evaluated. Highest daily crawfish catch per unit trap effort (CPUE) and bait margin (gross value of crawfish less bait cost) was with gizzard shad at water temperatures less than 20°C (January, February, March), and with formulated bait at 20°C and higher (April, May). The shad formulated bait combination was effective in attracting crawfish over a wide range of water temperatures from February through May. In the bait quantity trial, both gizzard shad and the formulated bait were evaluated singly at 113 g/trap, 150 g/trap, 227 g/trap, and 340 g/trap from February through May. As was observed in the bait-type trial, shad was more effective than formulated bait in cool water (≤20°C) and formulated bait was more effective in warm water (>20°C). With the exception of formulated bait in cool water, crawfish CPUE generally increased with an increase in bait quantity with both baits; however, bait margin did not differ among bait quantities, indicating that the additional revenue associated with increased catch did not compensate for the increased cost of bait. A wide range of bait quantities potentially can be used to maximize potential bait margin.

This article reports consumer perceptions of freshwater prawns sold in a Kentucky's farmers' market. Data were collected via a face-to-face survey of farmers' market patrons. A conjoint experiment was included in the survey that elicited respondent preferences for different characteristics of prawns. The results show that many consumers were equally accepting of both whole prawns and processed prawn tails. Other results show that having a certified “Kentucky-grown” product was as important as the product's price to consumers at the farmers' market.

Spider crab (Maja brachydactyla) juveniles inhabit shallow coastal areas until they reach maturity and start a mating migration toward deeper waters. Small-scale spatial distribution was analyzed for a shallow-water local population using data from a monthly trap sampling study conducted from December 1997 to November 1999. The trap arrangement formed a grid covering a total area of 3.2 km². Catch per unit of effort (CPUE) for each biological category (defined by sex and maturity status) was modeled using geostatistics to analyze the spatial structure and to map distribution. Juveniles showed persistent aggregations roughly 150–300 m in diameter and no large-scale movements. Juvenile patches were highly stable in time. During summer, some of the juveniles attained sexual maturity and the aggregation broke up. It was reestablished in September and October, when new juveniles recruited. Adults found in shallow waters did not show a clear spatial structure. The relation variance per mean CPUE was used as a dispersion index (DI). Juveniles were highly aggregated (DI » 1) throughout the whole year, except during the period when the terminal molt took place. Adults were almost randomly distributed (DI ≈ 0–1). In the case of juveniles, the DI was significantly and positively correlated with CPUE, and was negatively correlated with size, but did not show any significant correlation either with the percentage of individuals undergoing molt or with temperature.

Shrimp fisheries in the Mexican Gulf of Mexico arc limited to the 100-m-depth contour. We investigated potential penaeoidean shrimp resources on the continental slope of the Yucatan Peninsula (southern Gulf of Mexico) during 2 research cruises conducted during spring 1999 (cruise 1; number of hauls, 21; depth range, 300–599 m) and 2007 (cruise 2; number of hauls, 27; depth range, 300–999 m). During both cruises, the catch included 6 penaeoidean species: Aristaeomorpha foliacea, Aristaeopsis edwardsiana, Pleoticus robustus, Aristeus antillensis, Penaeopsis serrata, and Parapenaeus politus. The first 3 species constituted 85% and 91% of the total catch in weight obtained during cruise 1 and cruise 2, respectively. During cruise 1, the mean (± SE) biomass (1.05 ± 0.25 kg/ha) and catch per unit effort (CPUE: 3.21 ± 0.75 kg/h) of the combined species did not differ significantly between 100-m-depth strata. During cruise 2, by contrast, mean biomass and CPUE differed significantly between strata, with the highest mean values at the 600–699-m stratum (biomass, 1.37 ± 0.61 kg/ha; CPUE, 5.14 ± 2.30 kg/h) and the lowest at the 300–499-m stratum (biomass, 0.03 ± 0.01 kg/ha; CPUE, 0.10 ± 0.04 kg/h). High CPUE values (≥5.0 kg/h) were more prevalent at depths of 400–499 m during cruise 1 and 600–699 m during cruise 2. Mean size of shrimp differed significantly between and within species, except for A. foliacea. On average, our CPUE values compare with values obtained in fisheries for deep-water penacoideans around the world, and also with current CPUE values from the shallow-water shrimp fisheries in the southwestern Gulf of Mexico, suggesting that these deep-water shrimp represent a potential fishing resource.

Bivalve nurseries are important links between intensive hatchery productions of postlarvae and spat available for on-growing. Land-based raceway nurseries dependent on seawater natural production may be economically feasible for growing Pecten maximus spat during the summer season, but little is known regarding natural food conditions and scallop spat growth during autumn conditions. Scallop growth was monitored together with several water parameters from summer toward the end of the growth season in November. Three raceways were used for the experiment and were loaded with an increasing biomass of large scallops (26, 52, and 78 kg) to reveal the effect of different food concentrations being offered to the spat. Experimental scallop spat (12.94 ± 0.142 mm) were kept in stacked trays and placed after (downstream from) the biomass loads. Temperature, salinity, chlorophyll a, phaeopigments, particulate organic material, particulate inorganic material, algal species composition, and particle size distribution were monitored throughout the experimental period, but did not change systematically with the biomass loads. The temperature was 15°C at the start and 9°C by the end of the experimental period. Chlorophyll a values were low (<1.0 µg/L) except for the diatom bloom on September 13, when it reached 3.21 µg/L. Particulate organic material varied between 1.6–2.3 mg/ L. Shell height and live weight biomass differed significantly between the control group and the 3 experimental groups, whereas there was no significant difference among the experimental groups. Growth slowed after mid September and stopped in the experimental groups in October, whereas the control group continued growing until November. Growth was affected by increased biomass load in the raceways after the diatom bloom. We conclude that a raceway nursery could hold large biomass of scallop spat during early autumn conditions, but 4 wk after the autumn bloom the production was limited by the poorer quantity and quality of the particulate matter.

Genetic linkage maps were constructed for the noble scallop Chlamys nobilis Reeve on the basis of 373 amplified fragment length polymorphisms (AFLPs) and 9 microsatellite markers. The pseudo test-cross mapping strategy was used to construct the maps. The female linkage map contained 117 (115 AFLPs and 2 microsatellites) markers spanning 1,698.6 cM, with an average interval of 16.8 cM. The male linkage map had 108 markers (106 AFLPs and 2 microsatellites) covering 1,519.0 cM, at 16.5 cM per marker. Sixteen linkage groups were identified in both maps, which were consistent with the 16 chromosomes seen in chromosome spreads. The genetic length of the C. nobilis genome was estimated to be 2,235.1 cM for the female and 2,053.5 cM for the male. The observed coverage was 76.0% for the female map and 74.0% for the male map. When triplets and doublets were considered, the observed length of the map was calculated to be 2,002.1 cM with coverage of 89.6% for the female and 1,864.2 cM with coverage of 90.8% for the male. The genetic maps presented here will serve as a preliminary groundwork for the construction of a high-resolution genetic map of C. nobilis.

In the current study we provide information to aid in the identification of bivalve larvae in plankton samples based on the descriptions of recently settled spat of Zygochlamys palagonica and Hiatella meridionalis, 2 conspicuous bivalves commonly distributed in the shelf-break frontal system of the Argentine Sea. The first species is of particular interest given that it has been commercially exploited since 1996, and the phase between gamete release and larval settlement was unknown. We provide empirical evidence of a planktotrophic development for the larvae of both species.

The reproductive cycle of the eared ark Anadara notabilis and its relationship with environmental factors was evaluated every 15 days between March 2004 and February 2005 at the northern part of the Peninsula de Araya, Venezuela. Environmental factors measured included temperature, salinity, chlorophyll a, and total seston, including the particulate organic matter and particulate inorganic matter fractions. Adult specimens were collected using a net drag and then randomly selected to estimate wet live biomass and dry biomass of soft body tissues. Gonad samples were processed with histological analysis to determine sex ratio, developmental stages, and variations of follicle size. Reproduction in A. nolabilis was continuous throughout the year, with spawning peaks occurring in June and October, coinciding with the lowest water temperatures. In March, September, and November 2004, specimens attained the highest dry biomass values, whereas lowest dry biomass occurred in June and October 2004. Stepwise regression analyses demonstrated that temperature and particulate organic matter values are the main modulators of reproductive events. When temperature decreased, dribble spawning was detected in this species, possibly inducing a survival strategy whereby the spawning period is extended to increase reproductive success.

The northern quahog Mercenaria mercenaria, also known as the hard clam, is an important aquaculture species in the United States. Genetic and genomic studies in this species require a large set of genetic markers. In this study, microsatellite markers were developed from an enriched DNA library. Five hundred sixty-seven clones were sequenced, producing 337 microsatellite-containing sequences with di- (82.0%), tri- (7.8%), tetra- (7.8%), hexa- (1.1 %), hepata- (1.1%), and octanucleotide (0.2%) repeats. Sixty primer pairs were designed and screened in 24 clams from a wild population, of which 30 primer pairs showed good amplification and produced no more than 2 alleles per individual. The other 30 primer pairs either failed to amplify consistently or amplified multiple fragments. Of the 30 primer pairs with good amplification, 29 were polymorphic with allele numbers ranging from 3-21 per locus. The expected and observed heterozygosity ranged from 0.5381–0.9628 and from 0.0417– 0.9167, respectively. Fourteen of the 29 loci showed significant (P < 0.05 after Bonferroni correction) deviation from Hardy— Weinberg equilibrium, probably because of the presence of null alleles. Most of the microsatellite markers developed here should be useful for genome mapping and some for population genetics studies in this species.

A field experiment was conducted to compare the performance of different hard clam (Mercenaria mercenaria) strains in local clamming waters of New York state. Experimental clams included a Mercenaria mercenaria notata seed obtained from a Florida broodstock, and 2 New York seed strains obtained from local hatcheries, including a cultured M. mercenaria notata strain and a first-generation “wild-type” strain. Quahog parasite unknown (QPX) was acquired by the Florida clams in less than 2 mo of a July deployment of grow-out cages. Prior field studies comparing susceptibility of northern and southern hard clam strains observed QPX acquisition after clams had overwintered in the field, raising the question that higher susceptibility observed in southern seed clams could be a result of poor adaptation to winter water temperatures. Our results show that the southern strain acquired QPX after the clams had only been exposed to the warmest period of water temperatures for this field site (22.3°C on average), thus excluding poor acclimation to winter temperatures as the main aggravating factor. In contrast, QPX was not observed until the second summer in the cultured New York (M. mercenaria notata) strain in which clam survival was high and infection prevalence remained minimal. The New York “wild-type” clams displayed good growth and did not acquire QPX at all, providing evidence for the potential utilization of local wild broodstocks to enhance the resistance of cultured strains. Histopathology observations offered further insights to infection dynamics, with early, light infections almost exclusively localized in mantle and gill tissues, clearly supporting the theory that these organs (predominately the mantle) are sites of acquisition for QPX infections.

The seasonal variations in biochemical composition and reproductive activity of the venus clam Cyclina sinensis (Gmelin) from the Yellow River delta in China were investigated from April 2007 to March 2008 in relation to environmental factors. According to histological observations, gametogenesis began in January when the water temperature was low. Gametes matured mainly in June and July when the condition index (CI) and mean oocyte diameter peaked. Spawning occurred primarily in August when the temperature was highest, and coincided with phytoplankton bloom. The CI and oocyte diameter decreased sharply after spawning occurred, as mostly larger, mature gametes have been released. In autumn, the plentiful phytoplankton and higher water temperature were fit for the larvae to grow. Biochemical analysis indicated that gametogenesis took place at the expense of reserves accumulated in the various tissues previously during winter. A slight increase in lipid and protein content in female gonad—visceral mass during sexual maturation was observed, demonstrating that lipid and protein would be accumulated as vitellin in oocytes. Conversely, the lipid and protein content in the male gonad—visceral mass decreased during sexual maturation. The biochemical compositions in the adductor muscle and mantle varied during the study period, suggesting that they could support reproduction and growth. Seasonal variation in the RNA-to-DNA ratio suggests that it cannot reflect the situation of gonad development in this species.

The pill clams Pisidium chilense (d'Orbigny, 1846) and Pisidium huillichum (Ituarte, 1999) showed a 2C DNA content of 4.04 ± 0.4 pg and 2.35 ± 0.24 pg, respectively. The somatic DNA content of these 2 Chilean Pisidium Pfeiffer 1821 species is within the range described previously for diploid Heterodonta, despite the fact that both showed a high chromosome number (> 100–120 chromosomes) equivalent to the polyploid level described for other species of the genus. The nuclear DNA content is shown here for the first time for species of the family Sphaeriidae. The Pisidium, like other species, are not economically important as edible species, but they play a significant role in the dynamics of nutrient and energy cycles in freshwater bodies similar to that described for other Sphaeriidae species.

We compared lifetime and population energy budgets of the extraordinary long-lived ocean quahog Arctica islandica from 6 different sites—the Norwegian coast, Kattegat, Kiel Bay, White Sea, German Bight, and off northeast Iceland—covering a temperature and salinity gradient of 4-10°C (annual mean) and 25–34, respectively. Based on von Bertalanffy growth models and size—mass relationships, we computed organic matter production of body (P_SB) and of shell (P_ss), whereas gonad production (P_G) was estimated from the seasonal cycle in mass. Respiration (R) was computed by a model driven by body mass, temperature, and site. A. islandica populations differed distinctly in maximum life span (40 y in Kiel Bay to 197 y in Iceland), but less in growth performance (φ;′ ranged from 2.41 in the White Sea to 2.65 in Kattegat). Individual lifetime energy throughput, as approximated by assimilation, was highest in Iceland (43,730 kJ) and lowest in the White Sea (313 kJ). Net growth efficiency ranged between 0.251 and 0.348, whereas lifetime energy investment distinctly shifted from somatic to gonad production with increasing life span; P_s/P_G decreased from 0.362 (Kiel Bay, 40 y) to 0.031 (Iceland, 197 y). Population annual energy budgets were derived from individual budgets and estimates of population mortality rate (0.035/y in Iceland to 0.173/y in Kiel Bay). Relationships between budget ratios were similar on the population level, albeit with more emphasis on somatic production; P_S/ P_a ranged from 0.196 (Iceland) to 2.728 (White Sea), and P/B ranged from 0.203–0.285/y. Life span is the principal determinant of the relationship between budget parameters, whereas temperature affects net growth efficiency only. In the White Sea population, both growth performance and net growth efficiency of A. islandica were lowest. We presume that low temperature combined with low salinity represent a particularly stressful environment for this species.

A survey of surfclam (Spisula solidissima) stocks was conducted in an area from northern New Jersey to southern Virginia during June and July 2004 to evaluate the progress of mortality, apparently related to warming of the Mid-Atlantic Bight. One component of the survey was the measurement of condition index at 146 locations from the Delmarva Peninsula to northern New Jersey. The program followed a pilot study in 2002 that suggested that surfclam mortality off Delmarva was likely caused by warmer temperatures that decreased feeding and subsequently led to starvation. Condition index was highest inshore, with the exception of a few of the most inshore stations, and lowest at the offshore edge of the clam's range. An estimate of meat weight for a standard 120-mm clam, from site-specific length—weight regressions, revealed that the animals near the center of the inshore— offshore distribution had a greater weight per length than those living at the edges of the clam's range, probably a result of the influence of temperature on feeding and growth. Low condition in the extreme inshore locations suggests that warmer temperatures continue to affect surfclam nutrition negatively and indicates the continued susceptibility of clams along the southern and inshore range boundary to warming in the Mid-Atlantic Bight. Low condition offshore may be the result of a delay in gametogenesis or inadequate nutrition resulting from low temperatures reducing feeding rate and food supply.

The purpose of this study was to develop an oocyte maturation scale and to retrace the development of the oocyte cohorts in razor clam populations of Solen marginatus (Bivalvia: Solenacca Mollusca) sampled in the tidal area of Maltine Wadi (El Mares, Gulf of Gabes, Southern Tunisia). The development of an oocyte maturation scale could help reproductive cycle monitoring and the assessment plan in the search for populations. The results included 7,535 oocyte measurements during a 1-y sampling period from May 2007 to May 2008. Based on the qualitative and quantitative analyses of the oocyte measuring activities, we assume a 4-stage maturation process: I, gametogenesis commencement from November through to March, the oocyte diameters are smaller than 15 µm; II, oocyte growth from April through to May, the oocyte diameters range between 15 µm; and 25 µm; III, oocyte maturation from May through to October, oocyte diameters range between 25 µm and 40 µm; and IV, resorption of the gonads from May through to October, the oocyte aspects are irregular, disrupted, or burst. The development of the indices of the dry condition and the oocyte cohorts shows major reproductive activity of the species from April through to October. Initial maturation commences in May followed by a major gamete emission in June. Maturation recovery occurs in July followed by oocyte growth, which continues, and appears to be more rapid during summer and early autumn. The first gamete emission occurs in May during the first oocyte cohort maturity accession and continues until late October, with an irregular time interval between the emissions.

This article describes the timing of gametogenic development and spawning in a population of geoduck clams, Panopea globosa (Dall 1898), from the Upper Gulf of California and its relationship to temperature changes and primary productivity. Clams were collected monthly over 1 year (March 2008 to March 2009), and salinity, dissolved oxygen, and substrate type were recorded during each survey. Standard histological analyses and measurements of oocyte diameters were used to describe the timing of gametogenic development and spawning. Satellite data for temperature and chlorophyll were gathered to test a general conceptual planktonic larval development model. The results demonstrated that reproductive activity was triggered by a steep decrease in temperature 4 months prior to the peak of productivity. Thus, larval development matches favorable conditions, as predicted by Cushing's Match—Mismatch Hypothesis.

In this study we describe spawning induction, fecundity estimation, and the early life history of the rock scallop Spondylus calcifer under laboratory conditions. We collected adults of S. calcifer from a natural stock in the Gulf of California, Mexico (28°37′N, 112°15′W). We induced spawning by means of thermal shocks (10°C magnitude) and estimated species fecundity as a function of size. We evaluated the effects on growth rate and final survival of larvae reared with 3 dietary treatments: (1) 30 cells/µL, (2) 50 cells/µL, and (3) 75 cells/µL. We reared larvae in 15-L containers at a density of 3 larvae/mL at 30°C, and renewed 100% of the water culture every 48 h. The diet comprised a combination (1:1) of Isochrysis galbana (clone T-ISO) and Chaetoceros calcitrans (clone C-CAL). Both females and males responded positively to thermal shock induction. Mean size of oocytes was 56.0 ± 4.2 µm (standard deviation; n = 30). Mean number of oocytes spawned was 48.9 × 10⁶ ± 13.2 × 10⁶ with the smallest female (shell height, 110.5 mm) spawning 28.95 × 10⁶ oocytes and the largest (shell height, 180 mm), 71.76 × 10⁶ oocytes. We observed the first group of throchophore and D-larvae at 7 h and 17 h after fertilization, respectively. At the beginning of the experiment, the mean shell height of D-larvae was 79.8 ± 8.54 µm (n = 35). Two weeks after fertilization, larvae reached the pediveliger stage and we ended the experiment. We found that S. calcifer larval growth rates were significantly different between diet treatments (F_2.2.703 = 24.65; P < 0.001), with larvae reared at 50 cells/µL exhibiting the highest growth rate (12.42 µm/day) of all treatments. At the end of the experiment, larvae fed at 50 cells/µL attained a larger size (mean height, 234.01 ± 28.03 µm; n =115) than larvae from the other 2 treatments (30 cells/µL: mean height, 210.48 ± 30.81 µm; n = 107; 70 cells/µL: mean height, 221.81 ± 29.81 µm; n = 104). We did not find significant differences in larval survival between diet treatments at the end of the experiment (F_2.6 = 0.63; P = 0.56). Our findings suggest that the minimum period for larvae of S. calcifer to begin settlement is approximately 15 days after fertilization under the experimental conditions assessed. The first appearance and the extension of the planktonic stage represent the minimum extension that the larvae can be subject to dispersion by oceanographic currents. Whether S. calcifer can delay settlement if no suitable substrate is found was not addressed in this study. These results will be used as an input for the development of a coupled biological—oceanographic model that can assist in management of the rock scallop fishery in the Gulf of California by predicting species larval dispersion patterns from known reproductive sources.

Both wild and cultivated oysters are consumed in South Africa. Edible wild oysters include Striostrea margaritacea, Saccostrea cucullata, Ostrea atherstonei, and O. algoensis, all of which occur along the south and east coasts, but not on the west coast. Wild oysters are exploited commercially, recrcationally, and by subsistence fishers, with S. margaritacea being by far the most intensively targeted species. Commercial harvesting of S. margaritacea takes place along the southern Cape coast and in KwaZulu-Natal (KZN), with the southern Cape hosting 102 of the 145 commercial pickers. Data on total annual commercial catch of oysters in the various harvesting areas are presented, but these are minimum estimates, because collectors do not always comply with harvesting regulations or fully report catches. Subsistence harvesting remains largely unmanagcd, except in KZN, and is particularly prevalent in the eastern Cape Province. The culture of oysters is dependent on imported Crassostrea gigas spat, mostly from Chile. Accurate annual oyster production statistics arc only available since 1985, although approximately 2 million C. gigas oysters are known to have been cultured annually throughout the 1970s and early '80s. Since then, production increased steadily from 1985 to 1991, peaking at some 8 million individuals, then declined to 2–4 million individuals from the mid 1990s onward. Although the market for oysters has grown, production has not kept up with demand, largely because of a lack of suitable locations for oyster culture. Finding suitable sites for cultivation along the northern Cape Province coast and establishing local oyster hatcheries for C. gigas are suggested as future priorities for the industry.

Three strains of specific pathogen-free (SPF) oysters (Crassostrea virginica) were set on shell and deployed on 3 oyster bars along a salinity gradient in the Patuxent River, MD, to determine whether oyster strains selected or bred for enhanced disease tolerance would outperform a generic control strain in survival and/or growth while under pressure from Perkinsus marinus (the agent of dermo disease). A local Standard oyster strain was used as a reference control, and selected oysters belonged to disease-tolerant DEBY and CROSBreed strains. Initial deployment was in September 2003, during a period of unusually low salinity. Mean river salinities during the first 2 y were 8.5‰ and 9.0‰, respectively, but these rose to historically typical levels of 11.5‰ and 11.3‰ during the third and fourth years. Although measuring possible differential effects of dermo disease pressure on the 3 strains was our primary goal, disease pressures were only slight or moderate during all but the final year of the study. Oysters grew well during most of the study, except at the upriver station, where salinities were less than 5‰ during much of the first year. The DEBY strain showed the best overall growth and survival. Standard and CROSBreed strains were similar in both growth and survival, and did not perform as well as DEBYs. Although P. marinus infection prevalences approached 90–100% among oysters at the 2 downriver sites, even during the first year, and were generally high in late summer each year, oyster body burdens of pathogen cells increased slowly throughout the study, with means reaching lethal levels of 10⁶ parasite cells/g tissue only among Standards and DEBYs, and only during the fourth year. P. marinus infections among sympatric feral oysters (the probable source of disseminated cells infecting SPF oysters), were low during all years at the upriver site, but increased each year with increasing salinities at the downriver sites. As measured by better growth and survival, DEBYs performed best among the 3 strains tested. Whether DEBYs have a use in oyster restoration efforts is controversial, but their value in aquaculture applications appears evident.

This paper describes the first screening in the Philippines of slipper-cupped oysters (Crassostrea iredalei) for the presence of parasites. Slipper-cupped oysters were sampled at 2 sites in Ivisan, Capiz, from September to December 2007. Macroscopical and histological analyses were carried out in oyster tissues. Histological examination showed gregarine protozoan Nematopsis sp. as the most prevalent parasite (71.33% and 65.0%) at 2 sites with a moderate intensity of infection. Tylocephalum sp. cestode was found in the connective tissue around the digestive gland, with a prevalence of 60% and 52.3% in 2 sites, with a moderate intensity of infection. Digenean trematodes had a 37.80% prevalence at site 1 and a 22.45% prevalence at site 2. Ciliates were also observed with a prevalence of 18.75% (site 1) and 13% (site 2). The observed infection of oysters had no apparent effect on oyster production at these sites maybe due to low infestation levels or to the fact that the parasites have no pathological effect.

The Olympia oyster (Ostrea lurida) is the only oyster species native to British Columbia, Canada. Despite management regulations designed to protect this species, populations continue to decline in many locations. In an effort to determine whether parasites or disease are contributing to the population decline, oysters were collected from 5 locations and examined for the presence of pathogens and disease using histology and polymerase chain reaction (PCR) assays. Five parasite/symbiotic organisms were detected by histology, including Rickettsia-like prokaryotes, Mytilicola sp., Rhynchodida-like ciliates, encapsulated copepods, and an unknown protist. Six pathologies of unknown etiology were also detected, including hemocytic neoplasia, basophilic inclusions in the digestive gland epithelium, metaplasia of digestive gland tubules, diapedesis, and diffuse and focal hemocyte infiltration. Despite the variety of histological findings, most were detected at low prevalence and intensity, and are not believed to have a significant impact on the health of oysters at the individual or population levels. In addition, 7 different PCR assays were conducted for known bivalve pathogens, including Mikrocytos mackini, Haplosporidium spp., and Bonamia spp. Although all PCR test results proved to be negative, some assays did produce nonspecific amplification products, emphasizing the need for caution and validation when applying PCR assays to new hosts and new geographical regions. Although the current study did not identify any pathogens or diseases of concern, it provides important baseline data for future health assessments.

Urastoma cyprinae is a turbellarian that infects the gills of numerous species of bivalves. In the current study we investigated the seasonal behavior and microhabitat preferences of this parasite in wild mussels (Mytilus galloprovincialis) from the Vigo estuary (northwest Spain). U. cyprinae exhibited a marked seasonal pattern, with the highest levels of infection occurring during summer and autumn, coinciding with the highest abundance of juvenile worms in the gills, and the lowest in winter. We observed a positive correlation between host size and parasite intensity, with the highest values of prevalence and intensity being detected in the largest mussels (>60 mm). The number of worms observed in the posterior region of the gills was significantly higher than that observed in the middle and anterior regions. Along the dorsoventral axis, worms were especially abundant in the ventral and middle regions. Implications of these findings for clarifying the life cycle of U. cyprinae in the Vigo estuary arc discussed.

The distribution of carbohydrates on the surface of freshwater and marine bivalve gametes was examined based on labeling by 5 lectins. The 3 species of interest were Dreissena bugensis, Mytilus galloprovincialis, and Crassostrea virginica. The lectins used to identify the surface carbohydrates are Arachis hypogaea (PNA), concanavalin A, Griffonia simplicifolia, Lens culinaris (LcH), and wheat germ agglutinin. Live eggs and sperm from each species were examined for lectin affinity. Lectin labeling differed greatly between the 3 species, with very few, if any, conserved trends. Furthermore, there was no obvious difference in labeling between marine and dreissenid species. Of particular interest were LcH labeling of M. galloprovincialis sperm that labeled the tip of the outer sperm acrosome and PNA labeling of C. virginica gametes that was specific only to the sperm inner acrosomal membrane. Fertilization series looking at the distribution of PNA labeling of the sperm acrosome showed localization to the basal ring associated with sperm-egg binding.

This work concerns the effects of cadmium exposure on the anaerobic and oxidative metabolism in tissues of the hypoxia-tolerant green mussel Perna viridis from Venezuelan coastal waters. The mussels were exposed to different Cd concentrations (0, 20, 40 and 60 µg/L Cd) for 7 days, and were subsequently exposed to anoxia. Prior to anoxia exposure, Cd concentration was determined in the digestive gland and adductor muscle. After 24 h of anoxia, the activities of pyruvate kinase (PK), phosphoenolpyruvate carboxykinase (PEPCK), and cytochrome c oxidase (CCO), and catalase (CAT) were measured in the digestive gland and adductor muscle from Cd-treated mussels. Also, effects of the Cd treatments on the median survival time (LT₅₀) during anoxia were determined. The short-term Cd-exposed mussels augmented the metal uptake in the tested tissues in a dose-dependent manner, associated with a concomitant reduction in the ability to withstand anoxia. During normoxic and anoxic conditions, the Cd-cxposed individuals displayed decreased levels of PK, PEPCK, and CCO in comparison with controls, with the change being most evident during anoxia. Conversely, an increase in CAT was observed in Cd-treated organisms. This effect was further potentiated during anoxia. The toxic action of Cd uptake on PK and PEPCK could reduce the tolerance of anoxia, because these are regulatory glycolytic enzymes in mussels. Moreover, the decreased CCO activity could limit the capacity to recuperate from anoxia. The enhanced CAT activity in Cd-exposed organisms may have been in response to H₂O₂ produced during oxidative stress, and was likely accentuated during anoxia.

The identification of hatchery-reared larvae and juveniles is fundamental to assessing the success of their release when restocking. Hatchery-reared Haliotis rubra larvae and juveniles were successfully batch-tagged with distinct and persistent marks, enabling unambiguous differentiation from wild conspecifics when recaptured. Larvae were batch-tagged with the epifluorescent dye calcein. Experiments demonstrated that the batch-tagged larval shell was clearly visible in the spire of juvenile shells after 260 days. The recapture of batch-tagged and released larvae from natural reefs after 533 days at liberty also confirmed the persistence of this tag. A reliable and cost-effective method for batch-tagging juveniles was achieved with the use of an artificial diet that resulted in a distinctive blue-green coloration of the shell. This coloration differentiated released juveniles from wild conspecifics, was easily observed with the naked eye, and persisted on the spire of individuals for 777 days at liberty. These batch-tagging protocols allow large numbers of H. rubra larvae and juveniles to be distinctly tagged for long periods of time, enabling reliable estimation of survival after release and individual growth. It is likely that these techniques could also be applied to other abalone species.

We examined field distributions of the scavenging snail Amphissa columbiana and looked for evidence of fish predation. In the laboratory, we tested for predation by 6 crab and 10 sea star species and measured the ability of A. columbiana to chemically detect and respond to the sea star Leptasterias hexaclis. A. columbiana occurred from the low intertidal zone to depths of at least 92 m. We found no evidence of fish predation, but 4 crab species readily fed on A. columbiana. Only 3 of 10 sea star species fed on A. columbiana and predation rates were low. The inability of many sea stars to prey on A. columbiana was related to an unusual defense in which the snail inserted its proboscis deep into one of the sea star's ambulacral grooves and bit the radial nerve. The injury, which generally repelled the attacking sea star, immobilized the affected arm, rendering it useless for several days. The biting defense appears to be effective against several sea star species and may reduce predation on A. columbiana.

The predatory naticid snail Euspira lewisii, Lewis' moon snail, native to the west coast of North America, is stated to be an economic threat to the shellfish aquaculture industry in British Columbia (BC). This species is being manually removed from the intertidal ecosystem, yet little is known about the ecology of this species. Enclosures and beach shell assemblages were used to determine the prey preference, feeding rates, and community impacts of E. lewisii. In the enclosures, Protothaca staminea, the native little neck clam, was found to be the preferred prey, whereas the commercially valuable Manila clam, Venerupis philippinarum, was avoided when E. lewisii was offered other clam prey choices. Drilled shells collected from the intertidal revealed similar feeding preferences. The feeding rate averaged for a variety of clam species was found to be 0.09 clams/day or 1 clam every 14 days. The feeding rate was dependent on prey species, and was highest for the preferred species and significantly lower on avoided species. The overall impact of E. lewisii to the bivalve community was found to be low. Based on these results, E. lewisii consumed only approximately 3% of the clam population over 1 y, assuming maximal feeding rates and typical population densities found on the west coast of BC. E. lewisiih has minimal impacts to the Manila clam industry in BC and control measures are not necessary for this species. Baseline ecological field studies arc important for gaining an understanding of poorly understood species, especially those considered threats to industry.

Survival and growth rates of juvenile turban snail (Turbo cornutus) reared on 2 red algae, an articulated coralline alga (ACA) Marginisporum crassissima and a gelidiccan alga (Agar) Gelidium elegans, with natural and reduced diatom densities were compared to examine the relative importance of algal fronds and epiphytic diatoms as diets for the juvenile turban snail. Laboratory experiments were conducted for 8 or 9 wk with turban snail of 3 size groups, early juveniles with 1.26-mm and 2.89mm shell diameters and juveniles with an 8.1-mm shell height. The 2 diameter size groups of early juveniles grew well (22.3 ± 5.5 µm/day and 16.4 ± 4.2 µm/day, respectively; mean ± SD) on ACA with natural diatom densities, whereas the growth rates were significantly lower on ACA with reduced diatom densities in both size groups (6.7 ± 0.8 µm/day and 4.0 ± 2.2 µm/day, respectively). A significant difference in growth rate was also found between early juveniles of 1.26 mm on Agar with natural and reduced diatom densities. In contrast, no significant difference was detected in juveniles of 2.89 mm on Agar with natural and reduced diatom densities. Although turban snail juveniles of 8.1 mm reared on Agar with natural diatom densities had very high growth rates (106.1 ± 18.3 µm/day), the mean growth rate of juveniles on ACA with natural diatom densities was relatively low (10.9 ± 5.8 µm/day). The results of the 3 feeding experiments indicate that diatoms are an important food source for juvenile T. cornutus from 1.25 mm to approximately 4.0 mm, and that the importance of fronds of G. elegans as a food source increases as juveniles increase in size. In addition, the species composition and density of diatoms on ACA fronds collected from a nursery habitat of the turban snail were observed continuously for approximately 2 y. From the information gained on seasonal changes of diatom communities and experimental results, the importance of ACA turf in providing suitable diets for turban snail juveniles is discussed.

Pairs of Sepiola atlantica maintained in aquaria at ∼17°C successfully mated in the “male parallel position” for between 21 min and 77 min. Over a period of several weeks after mating, female S. atlantica laid egg masses containing 8–161 eggs. At 14.4°C, embryonic development took 33 days and the hatching phase lasted for 23 days (mean hatching success, 32%). Hatchlings emerged from the eggs at a mean dorsal mantle length (DML) of 1.91 mm and entered a pelagic paralarval phase lasting 6 days. Ten to 20 days after hatching, the internal yolk sac became exhausted, whereupon hatchlings were fed ad libitum on wild-caught Zooplankton at a density of ∼90 organisms/L or with enriched adult Anemia (density, 50 organisms/L). Hatchlings maintained on the Artemia diet all died within 38 days, whereas ∼38% of those fed on Zooplankton survived to this point, and the remaining juveniles subsequently attained adulthood when reared on a diet of Crangon crangon. These laboratory-reared juveniles matured and successfully mated, but the females did not lay any eggs. Females subsequently died 230–250 days after hatching and 10–19 days after mating, at a DML of between 21.7 mm and 23.2 mm, whereas the smaller males died 265–293 days after hatching (DML, 17.4–21.4 mm). Growth (increase in DML) of S. atlantica had 2 phases. Growth during the first 120 days was relatively slow at 0.05 mm/day (0.043 mm/day in males and 0.055 mm/day in females), increasing slightly thereafter to day 210, after which growth leveled off. These data indicate that S. atlantica has a similar life cycle to other scpioids.

Harvested for their gonads, sea urchin populations are declining worldwide primarily as a result of overfishing. Consequently, research is now focusing on full life cycle aquaculture of these organisms. If juvenile or adult sea urchins are to be fed macroalgae (a preferred food of echinoids) in commercial-scale operations, suitable methods for storing large amounts of algae will be required. In this study, the effect of various storage methods for the kelp Saccharina latissima on somatic growth of juvenile green sea urchins, Strongylocentrotus droebachiensis, was evaluated. Juvenile S. droebachiensis (initial test diameter, 4.5–10.7 mm) were held in laboratory tanks, supplied with flow-through seawater, and fed ad libitum one of the following S. latissima treatments: (1) frozen long term (>2 mo), (2) frozen short term (1 wk), (3) air-dried, or (4) fresh. Measurements of test diameter and whole wet weight of the sea urchins were taken monthly for 16 mo. Mean (±SE) final sizes in the treatments ranged between 17.7 ± 0.4 mm and 21.7 ± 0.4 mm for test diameter and between 2.9 ± 0.2 g and 4.9 ± 0.2 g for wet weight (sea urchins fed long-term frozen kelp and air-dried kelp, respectively). There were no significant differences in growth rate—for either test diameter or wet weight—among sea urchins fed short-term frozen, air-dried, or fresh kelp, but those individuals fed long-term frozen kelp grew significantly slower than those on any of the other 3 diets. It is unclear, however, whether this difference is the result of the long-term freezing process per se or the result of differences in the biochemical nature of the kelp plants when they were collected for freezing. Because air drying should be relatively cheaper than freezing (in terms of energy cost), and air-dried kelp may be more easily stored and transported than frozen or fresh kelp, air drying is an obvious choice for long-term storage of kelp if it is to be used as a food for juvenile green sea urchins.