Bivalves have been grown and transported for culture for hundreds of years and the introduction of some species outside of their native range for aquaculture has been suggested to be one of the greatest modes of introduction of exotic marine species. However, there has yet to be a thorough assessment of the importance of aquaculture and bivalve culture in particular, to the introduction and spread of exotic species. This paper reviews some of the environmental and ecological implications of the relationship between bivalve aquaculture and the introduction and spread of exotic species, management implications and mitigation strategies. Two broad classes of introductions of exotic species may result from activities associated with bivalve aquaculture. First, the intentional introduction of exotic species into an area for aquaculture purposes, i.e. the “target” species. These are typically foundation or engineering species and may have a considerable influence on receiving ecosystems. Second, the introduction of species that are either associated with introduced bivalves or facilitated by aquaculture activities (i.e. structures or husbandry practices). These may include both “hitchhiking” species (organisms that grow in association with or may be transferred with cultured bivalves) and disease causing organisms. Management options should include the use of risk assessments prior to transfers and quarantines. Various types of mitigation for exotic species have been evaluated but are generally not very successful. Because the risk of exotic species to ecosystems and the bivalve farming industry itself may be great, effort should be directed to better predict and halt introductions of potentially harmful species.

Using stable isotope analysis, this study examined the potential food sources of the Japanese scallop, Patinopecten (Mizuhopecten) yessoensis (Jay) and determined whether the isotopic ratios inferred from tissues of cultured scallops varied according to culture systems (hanging and sowing). Different tissues (i.e., muscle, ctenidia, and digestive gland) of scallops nesting in Saloma Lake (18.3–113.0 mm shell height) and Tokoro (66.8–121.4 mm shell height) and their potential food sources were analyzed for stable carbon and nitrogen isotope ratios. Average isotope ratios obtained in scallop muscle and ctenidia (−20.6 and −21.0‰ for δ¹³C; 3.3 and 3.0‰ for δ¹⁵N) from Tokoro area (sowing culture; ∼65 m depth) had close affinities to suspended particulate organic matter (−21.6‰ and 2.7‰ for δ¹³C and δ¹⁵N, respectively) suggesting that the scallops from Tokoro area depends on detritus as an important food source. Saloma Lake (hanging culture; ∼20 m depth) scallop muscle and ctenidia tissues however had relatively enriched δ¹³C values (−17.7 and −18.1‰) and were relatively closer to either net plankton (−21.1‰) and particulate organic matter (−22.1‰). δ¹⁵N values were also higher in particulate organic matter taken in Saloma Lake (5.0‰) and showed a 5.1‰ difference when muscle tissues in two sites are compared. Digestive gland tissues however showed depleted δ¹³C and δ¹⁵N signatures relative to other tissues in both systems. The observed variations in isotopic ratios in scallops reared in two systems thus reflect differences in carbon and nitrogen sources related to culture habitats.

We have used molecular genetic methods to examine the question of the geographic origins of the newly returned Argopecten irradians populations in Barnegat Bay (BB), New Jersey. Using PCR to amplify specific polymorphic microsatellite regions for bay scallop, we have genetically compared the 2004 and 2005 BB populations to those from Long Island (LI), New York, and North Carolina (NC). Our studies indicate that the 2004 and 2005 BB populations are genetically similar with some allelic frequency differences. Five of the eight loci studied are identical for marker size among BB, LI, and NC populations. The S336 locus demonstrates polymorphic sequences of 138 and 158 basepairs in the NC population that are not observed in LI or BB. The C1832 locus appears identical (122 basepairs) between LI and BB, but demonstrates polymorphisms (132 or 142 basepairs) in the NC population. Additionally, the NC group manifests two further alleles in the M26 locus (135 and 149 basepairs) not seen in BB or LI. These results, along with genetic distance and mean estimated gene flow calculations, support a physical transfer of the Long Island bay scallop larvae down the Atlantic coast to the transition regions around Barnegat Bay.

The life spans of eukaryotes can be determinate or indeterminate. Examples of the latter are found from sponges to lobsters to rainbow trout that reproduce and grow until disease, predation, or environmental circumstances end their lives. Their tissues continually express the enzyme telomerase, keeping sufficient telomeres on the end of their chromosomes to avoid individual cell senescence and subsequent death. Bay scallops, on the other hand, have a well-defined life span, generally between 18–22 mo in the northeastern USA, and reproduce usually once. Argopecten irradians irradians (L.) has been found to possess fewer telomeres than a close relative, Argopecten purpuratus (L.), a cold water species found along the coasts of Peru and Chile that can live to 7 y or more. A. purpuratus contains significantly more telomeres than A. irradians in their respective tissues. It is proposed that the short lifespan of A. irradians may not be a selective advantage, but rather because of an evolutionary loss of telomeres through Robertsonian fusion and extensive chromosome arm loss. Evidence for this is seen by the bay scallop doubling its weight postspawning and storing nutrients in the form of carbohydrates, lipids, and protein for the upcoming winter and the subsequent initiation of gametogenesis in the spring. However, they rarely survive to complete a second reproductive event. This life history suggests that A. irradians is not a semelparous species (one-time reproduction) but rather an example of interrupted iteroparity (repeated reproduction) caused by losses in its genome. Adding telomeres to the ends of chromosomes of A. irradians may extend the life span of this species, possibly permitting several reproductive seasons ahead. In years when larval recruitment failure occurs without concomitant loss of adult spawners, local populations could recover in as little as a single season.

In Chile, various species of keyhole limpet of the Fissurella genus constitute a multispecific fisheries activity. Nevertheless, management of these species is limited because of insufficient understanding of their reproductive biology. Fissurella nigra Lesson, 1831, is one of the species currently extracted by local fishermen in southern Chile. The breeding cycle of F. nigra was studied through changes in the stages of gonad maturity using histological techniques, as well as monitoring the temporal variations in the gonadosomatic index (G.S.I.). Minimum maturity size, spawning induction, artificial fertilization and early larval development were also studied to obtain data on the biological background of this species that will facilitate management and enhance culture feasibility. Fissurella nigra is characterized by a unimodal reproductive cycle with one breeding season between October and December, coinciding with the period when gametes are spawned. Fertilization is external and mainly nocturnal spontaneous spawning occurred between August and November (most abundant in October and November) in adult organisms kept under laboratory conditions. Spawning was induced in October by combining thermal shock with desiccation. This method proved successful, provoking massive spawning. The gonad became visible in 50% of organisms within a size range of 26.0–35.9 mm. Early development occurs within the egg membrane and the veliger larval stage is reached approximately three days after fertilization.

This study reports on a new parasite of the digestive gland of the queen conch, Strombus gigas. An intense and generalized sporozoan infection was detected during a reproductive study of S. gigas in San Andres island (Colombia). The parasite was found in the digestive gland of every sampled S. gigas, with a heavy intensity of infection (invasion of every cell) in many animals. The infection of the digestive gland began in the cryptic cells and later secretory cells were also infected, giving way to discharge of sporocysts to the stomach through the digestive gland ducts. Apicomplexa-like trophozoites were embedded in the digestive gland epithelial cells and attached to host cell wall by their conoid end. Several stages were detected: trophozoites, sporocysts, and gamonts containing macrogametes or microgametes. Given the presence of multiple stages at the same time, the entire life cycle of the parasite is assumed to occur within the same host and tissue. The taxonomic position of the parasite should be ascertained by DNA analysis.

Diatoms are widely used in abalone hatcheries to induce larval settlement (=attachment and metamorphosis) but there are few data on the factors that influence their effectiveness as settlement cues. Of 16 diatom strains tested in Experiment 1, half induced ≥80% attachment and >50% metamorphosis within 4 days. Settlement success did not correlate significantly with diatom abundance or adhesive strength (P > 0.05). Several diatom strains interfered with settlement. Examples included (1) smothering by highly mobile diatoms (Nitzschia longissima); (2) shells becoming stuck to sticky secretions (Navicula britannica, Achnanthes longipes); and (3) unstable diatom cells preventing pedal attachment (Licmophora sp.). In Experiment 2, only 1 of 15 diatom strains induced over 70% metamorphosis, and three others induced 22–36% metamorphosis, within 4 days. Older cultures of a strain induced higher attachment and metamorphosis than younger cultures of the same strain (P < 0.001), but some old cultures still gave poor settlement. For the young diatom cultures, larval attachment correlated positively with diatom percent cover (r = 0.89, P < 0.05), and metamorphosis with the growth phase of the diatom film (r = 0.91, P < 0.05). Experiments 3–5 examined the role of bacteria in settlement induction by diatom films. In Experiment 3, films of 8 diatom species from Experiment 1 were regrown from ∼6 individually isolated and rinsed cells, likely altering the associated bacterial flora. Metamorphosis was 179 fold lower on average than in Experiment 1 (P < 0.0001), but attachment and diatom density were not significantly different (P = 0.87 and P = 0.75 respectively). In Experiment 4, Nitzschia ovalis grown and assayed with antibiotics had lower metamorphosis after 2 days than the same strain grown and assayed without antibiotics (6 vs 64%, P = 0.004), whereas attachment after 2 days did not differ (94 versus 92%, P = 0.49). In Experiment 5 bacteria from a Nitzschia ovalis culture induced as much attachment and metamorphosis as the intact diatom film, whereas cell-free supernatant was much less effective. The presence of antibiotics in settlement assays reduced attachment and metamorphosis by biofilms, but not by coralline algae (Phymatolithon repandum) or GABA. In Experiment 5 metamorphosis on diatoms and bacteria occurred gradually over 2 wk, whereas on coralline algae and GABA it occurred within a few days. This study suggests that many diatoms cue rapid larval attachment, but few induce consistently strong metamorphosis within 4 days in laboratory conditions. The bacteria present in diatom films affect the settlement-inducing activity of the film in at least some cases. The effectiveness of diatom films was generally higher for more mature films but overall, physical factors explained little of the variation in the activity of diatoms.

We evaluated the capacity of metallothioneins (MT) in maintaining anaerobic metabolism in the green lipped mussel Perna viridis during experimentally induced oxidative stress. Mussels were exposed to 50 μg/L of cadmium during seven days, followed by recuperation in the sea during 35 days. Other groups of cadmium pre-exposed organisms and their respective controls were exposed to 200 and 500 mM of ferric iron/100 mM ascorbate to promote the formation of reactive oxygen species (ROS) by the Fenton reaction. Oxidative damage was evidenced by the malondialdehyde (MDA) production through thiobarbituric acid reactive substances (TBARS). The activities of the enzymes, hexokinase (HK), piruvate kinase (PK), and glucose-6-P dehydrogenase (G6PDH) in the digestive gland and the survival during anoxia were evaluated. Exposure of organisms to cadmium led to a significant bioaccumulation of this metal with concomitant high MT levels. Survival during prolonged periods of anoxia was reduced only in the iron/ascorbate exposed organisms, which exhibited an increase in MDA concentration; however, the cadmium-preexposed and control organisms showed similar resistance to anoxia. The iron/ascorbate-exposed organisms showed a decrease in the activities of HK in the cytosol and HK, PK, and G6PDH of the particulate fraction. In comparison with the control group, the cadmium pre-exposed/iron-exposed organisms did not show significant differences in lipid peroxidation, associated with elevated MT levels. In conclusion, the data obtained suggest that of the glycolytic enzymes, HK and PK and G6PDH are targets to the attack by ROS and that the MT can protect molecules against these effects. MT appears to protect against ROS induced injury, allowing maintenance of metabolic control by glycolytic enzymes that are important during anaerobic metabolism.

The tropical Asian green mussel, Perna viridis (Bivalvia: Mytilidae) is a recent invader in the Caribbean Basin, including the subtropical southeastern United States. In this study we examined the (1) range of P. viridis in the southeastern United States, (2) relative abundance of P. viridis across habitats and (3) density of P. viridis in Tampa Bay, FL. The invasion and spread of P. viridis in the southeastern United States was estimated by a combination of first-hand qualitative sampling and second-hand observations. There were apparently at least two discrete introductions, each followed by natural dispersal. The initial invasion was discovered in Tampa Bay in 1999, and was followed by rapid spread of P. viridis south as far as Marco Island, FL, but limited spread northward. In 2002, a second invasion occurred in northeast Florida, separated from the west Florida population by 650 km of coastline. On the east coast, P. viridis appeared to be distributed discontinuously between South Carolina and the Indian River Lagoon, FL by 2007. The literature concerning native distribution, habitat use and invasion history, and vectors of P. viridis is also reviewed.

In the present study we evaluated the musselspat feed MySpat formulated by INVE Technologies (Dendermonde, Belgium) in combination with small quantities of microalgae as a complete diet for young mussel seed Mytilus galloprovincialis (Lamarck 1819). Three different food levels were tested: a continuous algae supply over a period of 24 h of 150 cells μl⁻¹(Control diet 1, C 1), 75 μl⁻¹ (C 2) and 24 cells μl⁻¹ (C 3). In three additional treatments C 2 was supplemented with 2.8% and C 3 with 2.8% and 4.3% MySpat respectively. Percentage was calculated on life weight (LW). Mussel spat belonging to treatments C 3 2.8%MySpat and C 3 4.3%MySpat gained almost twice as much weight as the mussels fed the nonsupplemented algae diet C 3. There was no significant difference between the two supplementation levels, indicating that a level of 2.8% was sufficient. The mussel spat that received the supplement MySpat grew as fast as the animals that received 75 cells μl⁻¹ being 702% increase in wet weight (WW) in 3 wk, so the same result was obtained with only 1/3 of the algae. This is interesting when one considers that the mussel spat in the last week of the experiment received 95% dry weight (DW) formulated feed and only 5% DW algae. The growth was well balanced between shell growth and increase of tissue weight, because the organic matter content of the animals was equal to or even higher than the positive control animals. Mussel seed on the C 3 diet had a fatty acid methyl ester (FAME) content of 6.6 mg gDW⁻¹, whereas this content quadrupled to 28.1 mg gDW⁻¹ when 2.8% MySpat was given in addition to the algae diet, reaching levels even higher than for the positive control treatment. The fatty acid composition reflected the diet-composition, hereby proving the ingestion and assimilation of the diet. It is suggested that mussel seed regulate arachidonic acid (ARA) levels and keep the absolute amount in their tissues at 0.4 mg gDW⁻¹.

The contamination with norovirus (NV), a causative agent of gastroenteritis, in wild Pacific oysters Crassostrea gigas and Mediterranean blue mussels Mytilus galloprovincialis was surveyed from 2005 to 2006 by RT-PCR, collecting monthly 10 ∼ 20 samples for each species in Shiogama Bay (Shiogama Port), northeastern Japan. The bivalves examined were highly contaminated with NVs, especially with Genogroup 2 (G2), in winter and early spring, with the peak of 91% (G2) for oysters in April and 74% (G2) for mussels in March. The contamination rates in cultured Pacific oysters, concomitantly collected in a different bay (Onagawa Bay) in the same period of time, were much lower than those in wild oysters. When the contamination rates were compared among wild oysters collected at three sites with different distances from a sewage treatment plant, the incidence of G1 genogroup of NVs was higher in the oysters collected at sites nearer to the treatment plant, indicating that the drainage from the plant is the major virus source in this area. An improvement of virus inactivation in the treatment process is believed to be necessary to prevent viral contamination in coastal populations of bivalves.

The economically important marine bivalve mollusc, Mercenaria mercenaria, (commonly called a northern quahog or hard clam), has endured considerable mortalities caused by a thraustochytrid pathogen called Quahog Parasite X (QPX). Data on the percent prevalence of QPX infections were compiled from published reports along with our data to describe the epizootiology of QPX disease. QPX infections occurred in clams collected from both cultured beds and wild populations, but a higher percentage of QPX cases (76.5%) were from cultured clam beds. In addition, samples from cultured beds had a significantly higher prevalence (29.2 ± 27.2%) of QPX infections compared with samples from wild populations (9.6 ± 9.6%). The highest prevalence of QPX infections occurred in clams from samples with an intermediate size range (shell lengths 20–55 mm). QPX infections occurred in both male and female clams, but infection prevalence does not appear to be correlated with sex or sex ratios. The geographical range of QPX-related clam mortalities was Atlantic Canada to the Eastern Shore of Virginia, USA. Only marginally significant differences were detected between the prevalence of QPX at different locations. There were no latitudinal gradients in QPX prevalence or frequencies, suggesting local factors were important in determining its distribution. Although QPX infections occurred throughout the year, no seasonal trends in the prevalence or frequencies of QPX were discernable. This summary of information available on QPX disease highlights the need for more thorough data collection regarding factors believed to be associated with its presence and severity in hard clams.

Quahog Parasite Unknown (QPX) disease has significantly impacted cultured and wild hard clam, Mercenaria mercenaria, populations in the Northeastern United States and is the first formidable disease issue concerning near market sized clams for the industry. Most of what is known about this protistan infection comes from diagnostic reports of mortality events and some preliminary field investigations. Disease dynamics and details of parasite pathobiology are somewhat of an obscurity. This study fostered a laboratory approach towards the experimental induction of infection to confirm direct transmissibility of the disease and to verify trends, observed in the field, of varied host susceptibility based on hard clam stock origin. Evidence of QPX as a directly infective pathogen was achieved, through the utilization of laboratory maintained QPX isolate cultures, as injection of QPX cells into hard clam tissue resulted in infection and subsequent mortalities in matter of a few months. Laboratory conditions did not promote transmission in a trial that aimed to mimic ‘natural’ methods of infection by the cohabitation of infected adult hard clams, obtained from the field, with naïve seed clams. Histopathology of the adult hard clams, at the end of the cohabitation trial, displayed a significant amount of dead and degrading QPX cells, which suggests that laboratory conditions may have promoted healing and resistance of the host. This study has established an experimental infection method that can be used for future investigations concerning crucial aspects of the QPX/hard clam disease system. Laboratory conditions that led to the healing of field infected animals require more investigations and may promote a better understanding of factors affecting disease development.

Stock enhancement of the infaunal bivalve, Mya arenaria, is becoming an increasingly important strategy for fisheries managers and the clamming industry in eastern Canada and the New England states. There is also a growing interest towards softshell clam culture. A fast burial after the seeding should decrease (1) passive dispersion by currents and waves; (2) exposure to extreme changes in temperature; and (3) predation by crabs, flatfishes, birds, and similar. Thus, a fast burial could reduce losses shortly after seeding and possibly benefit later harvests. However, little is known about factors acting on burial. This study provides clam growers in our area with general guidelines to better manage their seeding operations. Five factors possibly influencing the burial rate were examined in the present study: clam size, seeding density, emersion period prior to seeding, substratum softening prior to seeding, and seasonal period. Most experiments were performed in field conditions on sandy beaches in Iles-de-la-Madeleine, (southern Gulf of St. Lawrence). Only clam size and seasonal period showed significant effects. Clam size (15–40 mm SL) was inversely related to burial rate. Clams buried faster in late August when water temperature reached 23°C and then slowed down steadily as temperature dropped to 7°C in early October. An increase in clam density from 100–350 clams (25–30 mm SL) · m⁻² had no negative effects on burial rate as well as emersion periods up to 4 h prior to seeding. Softening of the sandy substratum had no positive effects on burial rate.

Sand was added to the mudflat in a small bay on the southern coast of Korea in an attempt to create a new habitat for the Manila clam (Tapes philippinarum) in the muddy intertidal zone. To evaluate whether the newly created sandy habitat was functionally similar to natural ones, seasonal variations in condition, reproductive activity, and biochemical composition of clams in created and natural conditions were compared from May 2000 to October 2001. Clams reared in the newly created and natural habitats had similar patterns and levels with respect to condition and tissue dry weight. Standardized animal condition and tissue dry weight of clams peaked in spring, when protein and carbohydrate reserves were at maximum levels, and declined progressively throughout the summer-autumn period to October, as a result of continuous spawning. Condition and tissue weight were quickly restored during the winter-spring period, concurrently with accumulation of protein and carbohydrate reserves. Similar biochemical compositions and reproductive cycles for the clam stocks in the two habitats are likely to be related to their similar environmental conditions, in particular food availability. Comparison of the isotopic signatures of T. philippinarum tissues and potential food resources suggested that food availability in the study area was mostly dependent on resuspension of microphytobenthos, along with seasonal dynamics of phytoplankton. These observations clearly show that newly created sandy habitats may provide habitat functions that enable Manila clams to have similar biological cycles to those in natural habitats.

The histochemical characteristics and ultrastructure of the mantle of Gomphina veneriformis, were described using light and electron microscopy. When the mantle was distinguished into marginal, middle, and apical zones, the marginal mantle was also divided into 4-folds (inner-inner, inner-outer, middle, and outer fold), making it similar to the typical marginal mantle of Veneridae. The mantle thickness displayed a trend of reduction from the marginal zone to the apical zone. However, epidermal thickness was the thickest in the middle zone, with a thicker epidermal layer in the outer epidermis than the inner epidermis. The inner epidermis of the transitional area between the marginal and middle mantle is a simple columnar layer with well-developed microvilli on the free surface. Although the outer epidermis is also a simple columnar layer, few microvilli are present. The inner epidermis of the middle and apical zone is simple cuboidal layer, whereas the outer epidermis is a simple columnar layer. Ciliated cells are columnar in shape, with development of microvilli and cilia on the free surface. In the apical cytoplasm, numerous mitochondria were observed along with granules of low electron density. The distribution of mucous cells was found to be higher in the marginal mantle than those in the apical mantle. The proportion of mucous cells in the inner and outer epidermis in the marginal zone was 20.3% and 2.8%, respectively, with a high ratio in the inner epidermis. The result of this study illustrates that there are three types (A, B, and C) of secretory cells in the mantle, all of which are unicellular glands. Furthermore, in type A cells, the most ubiquitous of the three types and a typical goblet cell, the mucous substance contained in these cells was a weakly acidic or neutral carboxylated mucopolysaccaride. A periostracal groove was located between the middle fold and the outer fold, where the periostracum originates. Intermediate cells and basal cells were observed in the transitional area between the middle fold and the outer fold. Intermediate cells are elliptical with numerous vacuoles of various sizes. Basal cells have microvilli on the free surface, and there are membrane-bound granules between the microvilli and immature periostracum. The periostracum, as it moves further from the periostracal groove, displays higher electron density and gets thicker. Mature periostracum is composed of a homogeneous layer and a fibrous layer. The homogeneous layer appeared darker than the fibrous layer because of higher electron density.

This paper describes morphometric relationships, and the timing of gametogenic development and spawning for the geoduck clam Panopea globosa (Dall 1898) from a population in the east central Gulf of California. Clams were collected monthly for a year (October 2004 to October 2005), and were measured and weighed to obtain morphometric relationships. Standard histological analysis and measurements of oocyte diameters were used to describe the timing of gametogenic development and spawning. Most morphometric variables were significantly correlated, however the coefficients of determination were generally low (<0.5) indicating high variation in measured traits. Early gametogenic development was observed in late summer/autumn when SST was high (∼30°C). Development increased as water temperatures fell with ripe individuals observed in early winter (∼20°C). Spawning occurred between January and February (winter), when SST were at their coolest (∼18°C). Cytological characteristics of the gonad and averages of oocyte diameters for the different reproductive phases were similar to other geoduck species previously described. Overall sex ratios were equal. This study is the first ecological study to be conducted for P. globosa. Given the development of fisheries for P. globosa and the interest in developing aquaculture for this species, the data provide valuable information for fisheries managers and aquaculturalists and represent the basis for further research on this species.

We report for the first time annual gametogenesis in the Chinese anapella clam Coecella chinensis (Deshayes 1855) living on an upper intertidal sandy beach on the eastern coast of Jeju, Korea. Using histological methods, gonadal maturation, oocyte area in the follicle (follicle index, FI), and oocyte diameter were investigated. Gametogenesis began in the middle of April, when the sediment temperature was 13°C. Annual maximum oocyte size and FI peaked in July, when water temperature reached 20°C and sediment temperature reached 35°C. Subsequent spawning of C. chinensis occurred in August and continued until the end of September. Mean ripe oocyte diameter was 31.2 μm, which is comparatively smaller than that of other bivalves. Clams over 15.7 mm in shell length had mature gonads, indicating that this size is a biological minimum for reproduction. Annual sediment temperature fluctuation was positively correlated with condition and gonadal development (P < 0.01), indicating that cyclic changes in gametogenesis are in part governed by substrate temperature. The relatively smaller eggs observed here are believed to be a reproductive strategy of C. chinensis, an adaptive trade-off between reproduction and growth in the food-poor upper intertidal environment.

The Greenland smoothcockle (Serripes groenlandicus) has a circumpolar distribution in the northern hemisphere. Despite such a wide range and potential commercial importance, little is known about most aspects of the biology of this species. As part of studying the growth rate of this cockle species, we compared 3 methods that could be used to estimate the age of S. groenlandicus: (1) reading the external rings on the shell, (2) counting the growth rings on thin sections of the chondrophore, and (3) counting growth rings of whole shell sections. The chondrophore proved to be the best region to count the growth bands compared with the other regions in the cockle shell. Age bias plots and the coefficient of variation indicated that our ageing method represents a nonbiased and precise approach. This age method was validated by using Marginal increments Ratio method (MIR) to confirm that the growth bands are deposited annually. Marginal increments were significantly different between months (Kruskal-Wallis P < 0.001); a distinct trend of increasing monthly increment growth began in August. We estimated age in 425 cockles, which were collected from the Banquereau Bank (n = 240) and Grand Bank (n = 185). This data was used to determine the von Bertalanffy growth parameters for the 2 populations: L_∞ = 95.64 mm and 96.29 mm (Length), k = 0.21 and 0.17 and t_o = 0.97 and 0.33 for the Banquereau Bank and Grand Bank, respectively. There was a significant difference in growth curves between the 2 populations (Likelihood ratio test: X² = 33.40, P < 0.05). Minimum size and age at sexual maturity were 27.92 mm and 2.83 y for male tissues and 37.22 mm and 3.69 y for female tissues, respectively. This is the first time that age determination, growth, and minimum size of sexual maturity of the Greenland smoothcockle has been investigated.

Specific-pathogen-free (SPF) oysters (Crassostrea virginica) were set on shell and deployed on three oyster bars along a salinity gradient in the Patuxent River, MD, to determine growth, time to initial infection by Perkinsus marinus (causative agent for dermo disease), and subsequent mortalities. Initial deployment was in September 2000, during the second year of a 4-y drought. The salinity gradient experienced by these oysters during the drought was 4‰ to 6‰ above normal and provided ideal conditions for proliferation and dissemination of P. marinus. Oysters grew well during the first year, but mortalities rose rapidly during the second year, and reached 97% to 98% at all sites by the end of the second year. Although mean P. marinus body burdens reached levels of 2.3 × 10⁷ cells·g⁻¹ oyster tissue, MSX disease was also detected at both the lower and midriver sites in 2002, and was probably responsible for some mortalities at those sites. Due to extensive mortalities of the first deployment, we began to monitor a second group of oysters that had been deployed in May 2002. These oysters experienced a first year of extreme drought, followed by a freshet year during 2003. By the end of the study in November 2003, the overall growth of these oysters (64 mm) was similar to that observed for the first deployment (63 mm), but mortalities were much lower (maximum 58% at the downriver site and 0% at the upriver site). Perkinsus marinus infections in feral oysters, which were the probable source of infectious cells for SPF oysters, showed differences among sites before the drought and during the 2003 freshet year, but no site differences were detected during the 2000–02 drought years. Condition Indices (CI) differed between harvest and spawning seasons, and was greater at the upriver site than at the others during the drought. No site differences were detected for CI during the freshet. Results of this study showed that use of SPF juvenile oysters may not reduce infection and subsequent mortality by either dermo or MSX diseases when deployed during multiyear drought conditions, and the use of SPF seed in most areas when such conditions exist will not improve chances of survival. SPF juvenile oysters are more likely to survive and grow to market size if subjected to just one year of drought than oysters subjected to two years of drought, but their ultimate success will remain a function of the salinity regime they experience.

We conducted a 36-mo study to determine the effects of environmental variables and proximity to infected resident oysters on Perkinsus marinus infection acquisition and progression in specific-pathogen-free (SPF) juvenile oysters in the Patuxent River, MD, a mesohaline tributary of Chesapeake Bay. Multiple deployments of experimental SPF oysters were made at four sites along the river's salinity gradient, with three sites adjacent to infected resident oyster populations and one site isolated by at least 5 km from known oyster populations. Experimental cohorts were analyzed for dermo disease at deployment (time 0), approximately 2 and 4 wk, and at subsequent monthly intervals, using quantitative whole-body-burden alternative Ray's fluid thioglycollate medium (ARFTM) assays. Some oysters in some experimental groups acquired P. marinus infections as early as 10 d after placement in dermo disease-enzootic waters, and infections were detected in all groups by 62 d postdeployment. In several cohorts, first infections were simultaneously detected among >62% of experimental oysters, reflecting epizootics within 8 wk of their exposures to local infection pressures. Threshold values of 12‰ for salinity and 24°C for water temperature influenced infection acquisition rates. Isolation of SPF juvenile oysters from known populations of infected resident oysters did not prevent or delay acquisition of dermo disease during drought conditions. Once initial infections occurred, infection prevalences and mean intensities increased over time in all experimental oyster cohorts.

The increase in disease related mortality has made managing oyster resources increasingly difficult. In Delaware Bay sustaining harvest requires specific information on growth rates of adult oysters on the different beds. We reviewed the literature and found such information, particularly that depicting oyster growth directly on subtidal oyster beds, lacking. We used three methods to determine growth of oysters on Delaware Bay seed beds: measuring the new growth at the lip of oysters retrieved from the bottom, tethering individually identifiable oysters on specially designed frames, and size-at-age information based on ages developed from check marks in growth lines in the oyster hinge. Measuring new growth on the lip of the oyster was not accurate. Use of the frames was exact but very labor intensive and only provided data for the one season. Use of the check marks in the hinge to estimate age provided a growth history, and was relatively accurate. Intensive harvesting of oysters appeared to significantly reduce the accuracy of all techniques. Based on literature values, it is difficult to determine latitudinal gradients in oyster growth, but these data indicate more rapid growth in the northern Gulf of Mexico than in other locals. In general, oysters in higher salinity portions of the Delaware Bay seed beds grew faster than those in the lower salinity regions.

Neutral red retention (NRR) assay was used to evaluate the effects of sexual maturation, spawning, and post spawning recovery on lysosomal membrane integrity in hemocytes of two size classes of Pacific oysters. Large (102.23 ± 1.79 mm in height and 24 mo old) and small (52.47 ± 2.08 mm in height and 14 mo old) oysters were divided respectively into two groups: Group H was fed a high quantity of microalgae (approximately 2 × 10⁶ cells mL⁻¹ at a rate of 1.0 L per oyster per day) to enhance gonad development, whereas Group L was fed a low quantity of microalgae (same cell concentrations but at a rate of 0.15 L per oyster per day) to minimize changes in their dry meat weight and NRR time. The results showed that prior to spawning the decrease in lysosomal membrane stability in Group H were negatively correlated with the changes in dry meat weight. After spawning, the dry meat weight reduced to a level that was not significantly different from their initial values on day 0. This indicates that prior to spawning the increase in dry meat weight mainly resulted from the growth of gonad tissue, and thus the stress experienced by the oysters during this period was mainly related to gametogenesis or its related metabolism and/or biological functions. The results also showed that spawning further impaired lysosomal membrane stability (P < 0.05). After spawning the NRR times remained at the lowest recorded levels for a period before recovering to levels corresponding with the water temperature in which the animals were maintained. The smaller oysters recovered from the stress of spawning much faster than the larger animals (P < 0.05). Prior to spawning the dry meat weights of large and small oysters increased by approximately 85% in the first 42 days, whereas during the same period after spawning they only increased slightly, suggesting that the available energy was mainly used to recover from the stress created by spawning.

Progress in the Sydney rock oyster Saccostrea glomerata industry, through the adoption of oyster spat selected for faster growth and disease resistance, has been hampered by long-term variability in commercial hatchery spat supply. As part of a broader study to evaluate spat production impediments, the chronic toxicity of substances commonly used in bivalve hatcheries and the effects of handling procedures during early ontogeny (embryo to D-veliger) were evaluated. Among the substances tested, chlorine, Virkon S and Virkon S for Aquaculture (virucidal disinfectants, Antec International Limited, Suffolk, UK), bore water and stored rainwater were found to significantly affect larval development at practically/commercially-relevant concentrations. Toxicity was determined by quantifying embryo-larval development after 48 h exposure and three tests were performed for each substance or procedure. Concentrations of 0.83–1.66 mg L⁻¹ of chlorine in seawater and 0.05–0.5 mg L⁻¹ of Virkon S in seawater significantly decreased the normal development of embryos after 48 h exposure. An EC₅₀ value of 0.76–1.18 mg L⁻¹ for chlorine in seawater and 0.47–1.01 mg L⁻¹ for Virkon S in seawater was derived. The EC₅₀ value for Virkon S for Aquaculture was 0.99–1.12 mg L⁻¹ and this substance caused significant development problems for larvae at a concentration of 0.5 mg L⁻¹ in seawater. Tests that added stored rainwater to seawater had a significant decrease in the percentage of embryos developing to the D-veliger stage at concentrations greater than 1%, whilst no effect was detected at 0.1%. The EC₅₀ value for rainwater was 0.67% to 2.29%. Similarly, bore water added to seawater caused a significant decrease in the percentage of embryos to develop to the D-veliger stage at a concentration of 10% and no effect was observed at 1%. The EC₅₀ value for bore water ranged between 2.3 and 3.7%. Handling procedures for screening fertilized eggs did not significantly decrease development percentage after 48 h incubation time. Likewise, tests conducted with de-ionized water at concentrations up to 10% added to seawater did not significantly reduce the percentage of embryos to develop to the D-veliger stage after 48 h exposure. This study highlights the sensitivity of S. glomerata larvae to surfactants and disinfectants and identified contaminated water sources.

Estuarine acidification, caused by disturbance of acid sulfate soils (ASS) is a problem that affects many estuaries in eastern Australia. ASS outflows have low pH and elevated concentrations of metals, principally iron and aluminum. Most production of Sydney rock oysters Saccostrea glomerata occurs in estuaries along the Australian east coast and estuarine acidification has been implicated in localized declines in oyster production. Estuarine areas recurrently impacted by estuarine acidification have higher levels of oyster mortality and reduced oyster growth compared with sites that are not acidified. Two laboratory experiments were conducted to investigate reasons for poor oyster production at sites exposed to ASS-affected waters. Behavioral response, soft tissue lesions and filtration rates of S. glomerata when exposed to ASS-affected waters were examined. It was found that ASS-affected water altered oysters’ valve movements and significantly reduced filtration rates at pH 5.5. Acidic treatments (pH 5.1) containing 7.64 mg L⁻¹ of aluminum or ASS-affected water caused changes in the mantle and gill soft tissues after short-term (6 h) exposure. Degenerative effects were also caused by iron contained in ASS-affected water. Iron precipitates accumulated on the gills and mantle and were observed in the stomach, intestine, digestive tubules and rectum. Results from this study highlight the rapid deleterious effects of reduced pHs to oysters and the impacts of iron and aluminum contained in ASS-affected waters.

Estuarine acidification caused by outflows from acid sulfate soils (ASS), impacts many estuaries in eastern Australia. Affected waters are characterized by low pH and elevated concentrations of metals, particularly iron, aluminum, and manganese. The effects of low pH and elevated metals, associated with ASS-affected water, on adult Sydney rock oysters Saccostrea glomerata have not been previously studied in detail. Most production of Sydney rock oysters occurs in estuaries along the Australian east coast and has significantly decreased over the last 30 y. To investigate poor oyster production in particular areas of the Manning River, New South Wales, Australia, associations between ASS drainage water, estuarine acidification, and Sydney rock oyster survival and growth were studied. This involved a seven-month field study where water quality and oyster survival and growth was measured at seven sites differentially impacted by ASS-affected waters. Estuarine acidification on the Manning River followed periods of heavy rainfall and caused widely fluctuating pH levels, combined with low electrical conductivities and high concentrations of iron and aluminum at experimental sites selected to expose Sydney rock oysters to ASS-affected waters. Hydrologic characteristics and location of experimental sites controlled the extent of impact caused by ASS-affected waters. Sites exposed to ASS-affected waters had a significantly higher (P < 0.001) level of oyster mortality. Mortalities in small oysters were significantly higher (P < 0.05) than mortalities in large oysters. This was attributed to acid-induced shell degradation, which eventually caused perforation of the thinner shells of small oysters. Mortalities of small oysters increased after 42 days of exposure. ASS-affected waters also significantly reduced large and small oyster growth (P < 0.001). Growth of oysters improved and mortalities stabilized at sites impacted by ASS-affected waters in dryer periods because of the improvement in water quality.

The collapse of the native oyster Crassostrea virginica fishery along the eastern United States has prompted resource managers to consider introducing a nonnative oyster for restoration of the wild fishery and/or for culture as a nonreproductive triploid. Evaluation of the profitability of a medium-sized C. ariakensis culture operation (500,000 oysters per year on ∼3 acre lease), assuming constancy of present market price despite increased supply, indicated that grow-out over winter resulted in an estimated ∼27% to 29% return on the annual investment at salinities >10 ppt because survivorship was high and Polydora spp. infestation did not occur. The greater cost of a longer grow-out phase at intermediate (10–25 ppt) salinities compensated for slightly higher mortality rates at high (>25 ppt) salinity sites, such that profitability did not vary with salinity during winter. In contrast, operations in summer always lost revenue (−28 to −37% return on investment) because of higher mortality rates at high salinities and elevated Polydora spp. infestation rates at intermediate salinities rendering the blistered oysters unsuitable for the half-shell market. Solving both the Polydora and survivorship problems would suffice to render summer operations profitable. Purchase of larger (>25 mm SH) seed from hatcheries reduced the return on investment by ∼60% in comparison with purchase and further nursery rearing of smaller (3 mm SH) seed in 2-mm mesh bags at the grow-out site. Operations utilizing larger seed were, however, still profitable (11% to 12% return on investment) during winter grow-out, and are less risky than including a nursery phase. Although Polydora infestation did not occur during the winter, sensitivity analysis determined that culture operations are extremely sensitive to Polydora spp. infestation. For instance, our analyses suggest that operations with infestation rates greater than 54% would lose revenue. Therefore, growers must avoid extending production especially at intermediate-salinity sites where grow-out is slower into the summer months when Polydora spp. settlement typically occurs. Given the economic viability of culturing C. ariakensis oysters, the potential value of the aquaculture fishery must now be considered in a broader context of the economic and ecosystem risks and benefits associated with introducing a nonnative oyster versus not introducing but instead restoring the native oyster.

The reproductive cycle of a wild population of the oyster pearl Pteria sterna living in the Ojo de Liebre lagoon was analyzed from February 2001 to February 2002. The gonadic development was studied both qualitatively (through histological analysis) and quantitatively (through an analysis of the percent follicular area). P. sterna’s gonadic development consists of five stages (undifferentiated, developing, ripe, spawning, and spent). The percent follicular area turned out to be an adequate quantitative indicator of reproductive activity, with significantly higher values in the ripe months (August to September) and with a decrease directly related to spawning. The reproductive cycle of P. sterna is synchronic and is influenced by temperature and food availability. The reproductive season can be regarded to range from October to April, starting when temperature drops. The size at first maturity was determined at 117.1 mm SH and 106.6 mm SH for females and males, respectively. However, the smallest ripe female and male measured 73 mm SH and 26 mm SH, respectively, and both were undergoing the spawning phase. Differences in the reproductive cycle of P. sterna were found between the one reported here and reports for other Gulf of California's localities.

Shell closure and restriction of filtration are behavioral responses by which bivalve molluscs can limit exposure of soft tissues to noxious or toxic agents, including harmful microalgae. In this study, we assessed the clearance rates of five species of bivalve mollusc—the northern bay scallop Argopecten irradians irradians, the eastern oyster Crassostrea virginica, the northern quahog Mercenaria mercenaria, the softshell clam Mya arenaria, and the blue mussel Mytilus edulis—exposed for one hour to each of three harmful-algal strains: Prorocentrum minimum, Alexandrium fundyense, and Heterosigma akashiwo. Clearance rates of harmful-algal cells were compared with clearance rates of a benign microalga, Rhodomonas sp., and to a Mix of each harmful alga with Rhodomonas sp. Qualitative observations of valve closure and production of biodeposits were also assessed during the exposure experiments. Feces and pseudofeces were collected and observed with light and fluorescence microscopy for the presence or absence of intact, potentially-viable algal cells or temporary cysts. Results increase our understanding of the high variation between the different bivalve/harmful alga pairs. Responses of bivalve species to the different harmful algae were species-specific, but in most cases indicated a preferential retention of harmful algal cells, probably based upon different characteristics of the algae. Each shellfish species also reacted differently to the harmful-algal exposures; several remained open; whereas, others, such as oysters exposed to the toxic raphidophyte Heterosigma akashiwo, closed shells partially or totally. Similarly, production of feces and pseudofeces varied appreciably between the different bivalve/alga pairs; with the exception of softshell clams Mya arenaria, intact cells of most harmful-algal species tested were seen in biodeposits of the other four bivalve species. These results extend our understanding of the high species specificity in the interactions between harmful algae and bivalve molluscs and confirm that generalizations about feeding responses of bivalves to harmful algae cannot easily be made. In most cases, however, there was at least some ingestion of the harmful algae leading to exposure of soft tissues to the algal cells.

Food sources of three filter-feeding bivalves from two habitats (intertidal oyster Crassostrea gigas, mussel Mytilus galloprovincialis, and subtidal cultured scallop Chlamys farreri) of Jiaozhou Bay (Qingdao, China) were determined by fatty acid and stable isotope analysis. Cultured scallop was characterized by significant diatom markers such as 16:1/16:0 close to 1 and high ratio of 20:5(n − 3)/22:6(n − 3), hence we assume that the scallop mainly feeds on diatoms. Fatty acid biomarkers specific to bacteria and terrestrial materials were also found in considerable amounts in scallop tissue, which suggested that there were substantial bacterial and terrestrial input into the food of the species. Intertidal oyster and mussel, however, exhibited significant flagellate marker, 22:6(n − 3), and lower level of diatom markers, which indicated that flagellates are also part of intertidal bivalves’ planktonic food sources; meanwhile, high level of Chlorophyta fatty acid marker, Σ18:2(n − 6) 18:3(n − 3), suggested that Ulva pertusa (Chlorophyta) seaweed bed supplied important food sources to intertidal bivalves. Additionally, result of stable isotope analysis showed that phytoplankton contributed 86.2 to 89.0% to intertidal bivalves’ carbon budget; macroalga U. pertusa origin source had a contribution of 8.7% to 11.0%, which indicated its role as an important supplemental food source to intertidal bivalves. From this study, it is concluded that the dietary difference of three bivalves probably relates to the different potential food sources in the scallop farm and intertidal zone in Jiaozhou Bay.

The Bay of Bizerta (Tunisia) has some sheltered rocky areas that support an important lithophagous fauna. The hard rocky limestone substrata in the bay showed a well-ordered mineralogical structure and the biomicritic matrix contained benthic Foraminifera and ostracod remains dating from Eocene. Monitoring the rocky benthic communities over a period of one year enabled us to study the behavior and the ecology of Lithophaga lithophaga and its associated fauna. The population of this lithophagous bivalve is threatened by unauthorized collecting and the rocky sites are seriously damaged by human activities. The number of individuals of L. lithophaga varies considerably, from one rock block to another, depending on the position and the shape of the substratum. This species usually dominates the zoobenthos community and the associated fauna comprises 29 species (between October 2002 and September 2003). This fauna consists of 8 faunistic groups (Bivalvia, Gastropoda, Polyplacophora, Sipunculoïda, Crustacea, Polychaeta, Echinoderma, and fish).

We describe a novel sensor based on fiber optic technology for fine scale (∼0.1 mm) laboratory measurements of valve gape in bivalve molluscs. We have illustrated the operation of this sensor by measuring valve gape in conjunction with depletion rate assays in the Eastern oyster (Crassostrea virginica, Gmelin 1791). The sensor is capable of accurate and repeatable measurements, with few of the drawbacks of other valve gape sensing methods (e.g., levers, strain gauges, electromagnetic sensors). This sensor technology can be applied to other systems requiring the measurement of axial distances while immersed in seawater or other harsh environments.

Fisheries and Oceans Canada (DFO) and the Oweekeno Nation (ON) have undertaken a cooperative assessment of inshore Tanner crab, Chionoecetes bairdi, in support of developing a fishery for this species in Rivers Inlet, British Columbia (B.C.). This paper presents information regarding distribution, relative abundance, and biological characteristics of C. bairdi in Rivers Inlet. The results from exploratory trap and trawl surveys and a mark-recapture program carried out between January 2004 through March 2005 by DFO and the ON are presented. Trawling proved unsuccessful at capturing Tanner crabs. C. bairdi were found distributed throughout Rivers Inlet (except Fitz Hugh Sound), but were not overly abundant. Some areas supported more Tanner crabs than others; crabs were more abundant in Draney Inlet and Darby Channel. C. bairdi were found at depths ranging from 36–340 m with greatest abundance of males at 50–150 m and females at 100–200 m. Male C. bairdi ranged in size from 4–137 mm carapace width (CW). The mean size of 50% maturity is 94 mm CW for males and 81 mm CW for females. A twenty-percent growth rate was estimated for mature males. Our data show a small proportion of mature males molt throughout the year with a molt event possibly taking place in the spring or summer. Breeding in Rivers Inlet might occur in the fall with an egg-release period in the spring. Natural mortality (M) for male Tanner crabs was estimated two ways to be 0.69 and 1.12. Tagging showed that Tanner crab movements ranged between 39 and 4,592 m over a period of 7–422 days. Tanner crabs did not move between major areas within Rivers Inlet. The relatively small size of C. bairdi found in Rivers Inlet compared with those in Alaska, and the lack of significant abundance of legal male Tanner crabs, raises doubt whether a fishery for C. bairdi in Rivers Inlet would be economically viable.

Four formulated baits for the edible crab (Cancer pagurus L.), were developed. In all baits, fish skin and saithe were the main ingredients. Fish skin gelatin strengthened by the enzyme transglutaminase functioned as a binder in all baits. In Bait 1, a meal mixture (shrimp meal, kelp meal, fish meal) was added as attractant. In bait 2, protein concentrate (PC; 15% to 30% dry matter, on a dry matter basis >90% protein whereof >50% collagen/gelatin) was added as an attractant in addition to the meals mixture used in bait 1. Blue mussels (Mytilus edulis) and cod (Gadus morhua) roe were used as attractants in Bait 3 and 4 respectively. During three field studies, the perfomance of the formulated baits were compared with that of the most commonly used natural bait, chopped untreated saithe (Pollachius virens). Traps baited with baits 1 and 2 had a significantly lower CPUE compared with traps baited with natural baits, whereas traps baited with baits 3 and 4 had a significantly higher CPUE compared with traps baited with natural bait.

The size at onset sexual maturity in brachyurans can be evaluated considering different criteria, including growth allometry, gonad development stages, and presence of sperm in spermathecas or eggs in the abdomen. Morphometric aspects of males and the presence of eggs in females of P. patagonicus from the northern San Matías Gulf were respectively analyzed to determine its size at onset of the sexual maturity. Crab samples were obtained during a fishing experiment with traps (cubical, pyramidal, and conical, of similar internal volume), performed in the gulf during winter 2005. Also, the parasitism by a sacculinid rhizocephalan was analyzed to discuss possible effects on the reproductive success. All crabs caught were sorted by sex, carapace width (CW) and total weight (TW). Size frequency distributions were compared among sexes. Proportion of females bearing eggs were grouped into 16 size intervals of 5 mm to determine the size of first reproductive maturity based on a criterion of L_50%. In males, the allometric change of chela length was analyzed for this purpose. Only individuals exceeding 50 mm were caught. Of 807 crabs caught, 36% (289) were males and 64% (518) were females. The size frequency distributions differed significantly between sexes with males larger than females (K-S test). Relationships of total weight (TW) to carapace width (CW) were calculated for all reproductive types and compared by ANCOVA with the following results: parasitized crabs < females < females with eggs = males. The mean size at first maturity of females was estimated to be 87.66 mm. Size at maturity for male crabs could not be determined from morphometric data because there was no significant difference in the relationship of chela length and CW for juvenile and adult males. All parasitized crabs (73) were females, whose mean width and mean weight were significantly lower than those from nonparasitized individuals. Prevalence was 9% and the mean intensity was one parasite per host. The parasitized crabs resembled juveniles. The size at first maturity and the reproductive capacity of P. patagonicus could be affected by presence of the parasite, even producing significant interference at the population level. Parasitism by sacculinid must be monitored after the starting of an emerging fishery to assess the actual contribution of the reproductive stock.

The impact of meteorological factors on the condition of N. norvegicus caught for the live export market was assessed by correlating the mean wind speed and aerial temperature on the day of landing with the percentage of catch, on corresponding days, rejected for live transport. The study used the catch data from two Nephrops trawlers operating in the Clyde Sea area, Scotland. Results illustrated a large degree of variability in the condition of animals on arrival at the processing plant. Air temperature was the only meteorological factor, which significantly correlated with the morbidity and mortality of the catch. In one instance, mean air temperature on the day of capture had a significant negative impact on the health of the catch. This is the first study of its kind on the Nephrops fishery and although only a preliminary study demonstrates catch quality not only varies with the ambient temperature on the day of capture but also differs between trawlers. To conclude it is suggested that a larger study be commenced and a capture and post capture code of best practice be developed and used on all Nephrops trawlers.

To fully understand the reproductive habitat of brown shrimp, Farfantepenaeus californiensis, this study analyzed reproductive dynamics of the stock in a semiarid coastal region of the Gulf of California. Monthly biological samplings were conducted simultaneously in a coastal lagoon and in adjacent marine waters from January through December 2002, during 5-d periods centered on full moon (full moon ±2 d). An Egg Production Index EPI was used to determine the reproductive period. The main reproductive period was from April to August in coastal waters and June to July inside the lagoon. The EPI was 10 times greater in coastal waters than inside the lagoon. We conclude that, contrary to what is generally believed, brown shrimp can mature and possibly reproduce inside the coastal lagoon, although the most important spawning habitat is coastal waters.

White Spot Syndrome Virus (WSSV) affects the penaeid shrimp culture industry, but the potential impact on the ornamental shrimp industry has not been studied. Therefore, experiments were conducted to determine the susceptibility of the ornamental peppermint shrimp Lysmata wurdemanni to WSSV. Litopenaeus vannamei, a cultured penaeid shrimp was used for comparison. Three experiments (two per os, one injection) were conducted. Adult shrimp were challenged in the first per os experiment, whereas juveniles were challenged in the remaining two experiments. In both per os challenges, shrimp (n = 15, 10) were fed WSSV infected L. vannamei tissue at 10% of their body weight. In the injection challenge, shrimp (n = 10) were injected with a 10⁻³ dilution of freshly prepared WSSV filtrate at 20 μL/g of body weight. Shrimp were individually housed, maintained at 25°C, and checked daily for mortalities. PCR was used to determine whether challenged shrimp were infected with WSSV. In all three experiments, L. wurdemanni appeared more resistant to WSSV than L. vannamei (40%, 0% mortality versus 60%, 100% mortality, respectively, because of WSSV). Results indicate that adult L. wurdemanni appear somewhat susceptible to the virus, whereas the juveniles appear refractory to the virus (40% versus 0% mortality), however as the adults and juveniles were collected from different geographical areas, genetic variation cannot be discounted. Although there are no reports to date of a natural WSSV infection in Lysmata or other ornamental shrimp species, the finding that adult Lysmata are susceptible to WSSV has implications for the ornamental industry.

In the early 1990s, the geographic range of the sea urchin Hemicentrotus pulcherrimus from the Sea of Japan increased from off southwestern Hokkaido to off northern Hokkaido. This was caused by episodic recruitment in 1989, 1990, and 1991. These recruitments coincided with high water temperature during the larval periods (March to May). In 1993, H. pulcherrimus, at a density of 2.4 individuals/m² derived from those three year classes, was found at a depth of 2–3 m in Tomari, where it had not been found in 1989. In Oshoro Bay, this sea urchin appeared dramatically in 1990, reached a peak density of 5.3 individuals/m² in 1992, consisting mainly of 1989- and 1990-y classes. The high-density level of >2 individuals/m² continued until 1998. Afterwards, no marked recruitment was found, corresponding to low water temperature in spring, and the density decreased markedly to 0.1 individuals/m² in 2005. High water temperature in the 1990s is more likely to be responsible for the reproductive success of H. pulcherrimus extending to the north. This study suggests the colonization and persistence of the population in the northern district over the species range in 1990s were closely related to the highest seawater temperature in the 20th century.

Dietary protein (<12% to 22%) and carbohydrate (9% to >25%) influences on the sensory characteristics of green sea urchin (Strongylocentrotus droebachiensis) gonads were examined in two feeding experiments, both lasting for 60 days. Gonad indices and sensory quality were evaluated, and were compared with those of gonads from wild sea urchins. Gonad growth was not significantly affected by dietary protein:carbohydrate ratio. Bitter taste was significantly affected by diet in both experiments, sweet taste was significantly affected by diet in only one experiment, whereas the taste attributes old/stale, metal/sour and aftertaste were not significantly affected by diet in either experiment. There was increased intensity of bitter taste with increased dietary protein, and the diet with the lowest protein concentration produced gonads not significantly different in taste from those of wild sea urchins. All sensory attributes related to texture (granularity, firmness, and melting) were affected by diet. Gonads from urchins given the diet with the lowest protein content did not differ significantly from those of wild sea urchins, but there was no consistent relationship between dietary protein and texture attributes.