Spawner sanctuaries, harvest-free areas planted with high densities of adult clams, are currently being used to restore self-sustaining populations of Mercenaria mercenaria (L.) to Great South Bay, New York. To evaluate and guide this restoration, we monitored the condition and spawning of clams transplanted from two source locations in Long Island Sound since April 2004. Transplanted clams were in relatively high condition and gonad ripeness at time of transplant, spawned the first spring and/or summer after transplant, reconditioned and spawned in subsequent years, but rarely reconditioned to as high of levels as when they were first transplanted. All populations exhibited similar annual patterns of condition and gonad ripeness: both peaked in mid to late spring, dropped steeply through summer with spawning, and they were lowest in fall. In some years condition increased during fall, and the higher the condition attained by the end of fall (mid-December) the greater the peak in condition the following spring. Across years and populations, condition at the end of fall explained ∼89% of the variance in spring peak condition. Consistent differences in condition through time among some populations suggested that location within the bay as well as clam size impact condition. Because of interannual and locational variability, long-term monitoring of this long-lived species is essential for determining factors affecting condition and reproduction, and the ultimate restoration of sustainable hard clam populations.

Bivalve larvae in mixed samples collected from the field have traditionally been identified through morphological differences among species. It is difficult, however, to use this method accurately because of overlapping size ranges and similar shapes of the larvae of many species. We used the molecular technique developed by Hare et al. (2000) to test the accuracy of morphological identification of Mercenaria mercenaria (L.) larvae from plankton samples collected from the Great South Bay and Coecles Harbor on Long Island, New York. We found that morphology is unreliable as the only means of identification for bivalve larvae in a mixed field sample, and a very high false positive rate of identification of M. mercenaria (100% of 71 larvae were misidentified). Morphological characteristics may be used to eliminate larvae from a field plankton sample, as the false negative rate for M. mercenaria was only 1.4% (n = 140). To determine larval bivalve densities accurately, other techniques in addition to those based on morphological characteristics, such as the molecular technique used in this study, must be used.

Monthly monitoring of the clam Venus verrucosa was carried out in the channel of Bizerta Lagoon (Tunisia) from September 2002 to August 2003. Approximately 100 individuals were collected on each occasion from between 7- and 9-m depth. Individual shell sizes (measured as the antero-posterior shell length) varied from 13.7–59 mm. Some specimens showed shell abnormalities that indicated a heterospecific association. The proportion of specimens affected by these abnormalities was high (38%) and a comparison of the relative growth of healthy and abnormal clams was made. The relative growth of shell thickness and weight parameters, were compared with the antero-posterior valve length measurements. We calculated regression equations for annual and seasonal changes in valve length with shell thickness (E/L) and with shell weight (W/L). Annual and seasonal assessments of relative growth (as compared with the antero-posterior valve length) in the two clam populations showed that growth was negatively affected in the abnormal population. Affected individuals contained more intravalve water than normal individuals. The different growth metrics all indicated that affected clams were less well developed than unaffected clams. The organisms living in association with Venus verrucosa have a negative impact on shell thickness, on shell dry weight and on biomass (as dry flesh). This biometric growth study indicates that hetero-specific associations stressed the studied affected clam population and retarded somatic growth. It is suggested that clam emergence, probably caused by adverse conditions, encourages the formation of unfavorable heterotrophic associations by invertebrate species.

To optimize the conditioning procedure to obtain better larvae with lower production costs, Ruditapes decussatus broodstock was conditioned at different periods during the year [October (C1), February (C2), and April (C3)] under two different controlled temperature regimes: a constant temperature (CT, 20°C) and a gradual increase in temperature from ambient to 20°C (GT). Samples (30 adult clams) were collected randomly every month from a control group and from each conditioning tank (three tanks for each temperature treatment). A section of the gonad-visceral mass was sampled for gonadal histology and the remaining tissue was used for biochemical analyses. Gonadal developmental stages were determined based on the classification proposed by Wilson and Seed (1974), and fertilized eggs were reared after the method of Walne (1966). In the three conditioning experiments fewer degree-days were required to successfully spawn clams in tanks with the gradual increase of temperature. Clams conditioned in October spawned in February, four months prior to spawning under natural conditions after 1,030 degree-days (D°) in CT tanks and 937.5 D° in GT tanks. Clams conditioned in February and April spawned after 410 D° and 470 D° when held at constant temperature respectively, whereas a gradual increase of temperature shortened this to 383 D° and 337.5 D° respectively. The most important difference between the two temperature regimes was the higher condition index of clams conditioned under the GT regime. The percentage of larvae that survived metamorphosis was higher in clams conditioned at GT, maximum survival ranged from 25% in C3 at CT to 40% in C1 at GT, except for CT tanks in C2 where it was less than 10%. Results showed that Ruditapes decussatus conditioned with a gradual increase in temperature, enhanced larval production and also reduced overall hatchery production costs.

The reproductive biology and glycogen content of a subcrenated ark shell Scapharca kagoshimensis (Tokunaga, 1906) in Ariake Bay were investigated from April 2004 to May 2005 in relation to environmental factors such as water temperature, salinity, and plankton settled volume. In the male, onset of gamete development was observed in April. The period of mature testis and partial spawning was from July to September, and the spent stage was first found in September. In the female, gamete development was first observed in April, and continued until July. The matured ovary was seen in July, and partial spawning occurred in August, and the spent stage appeared from August. The gonads could not be distinguished in both sexes from December to March. Spawning in both sexes occurred during the period of highest water temperature (>25°C). The condition factor index remained high (>28.0) from April to June and rapidly declined to 18.9 during June and July. Glycogen content gradually decreased from 43.1 mg/g to 20.1 mg/g from April to July 2004 and gradually increased from 34.1 mg/g in January to 62.6 mg/g in April 2005. These results suggested that S. kagoshimensis in Ariake Bay was characterized by a spawning period in summer, monocyclic gametogenesis throughout the year, and an inverse relationship between gonad development and glycogen content.

Eastern oysters were ecologically and structurally dominant features of the Chesapeake Bay prior to European colonization. Four centuries of harvest pressure, habitat degradation, and, more recently, disease activity have affected extant oyster population demographics. We compared population demographics and age-at-shell length relationships for modern mesohaline James River oyster populations with James River oysters collected in the years 1611 to 1612 by Jamestown settlers. Historic oyster collections made by hand included a more complete demographic than modern samples collected with patent tongs. Historic oysters had significantly faster growth rates than modern oyster populations. Modern oysters larger than 30–40 mm SL or age 1 grow more slowly than historic oysters of comparable ages. Unlike historic oyster populations, modern James River oyster populations are affected by Dermo and MSX. The downward trend observed in the modern age at length relationship (^{Fig. 4B} see later) between 1 to 1.6 y is probably related to the seasonal onset of disease with increasing temperatures. Observed changes in oyster demographics and growth rates across four centuries reflect changes in the environment as well as changes in oyster biology because of chronic pressure from two oyster diseases.

Severe over-fishing, habitat degradation, and recent disease impacts have devastated the eastern oyster (Crassostrea virginica) fishery in the Chesapeake Bay. Several restoration efforts are in progress, including the unconventional approach of seeding reefs with an aquaculture strain selected for disease resistance and fast growth in hopes of mitigating the negative effects of disease and low census numbers. Supplementation of four sites (The Great Wicomico, Lynnhaven, York, and Elizabeth Rivers) examined in this study totaled approximately 18,500,000 aquaculture oysters from 2002 to 2006. We collected locally recruited offspring (n = 6517) from 2002 to 2006 at these sites to determine if reproduction by the transplanted oysters produced detectable contributions to recruitment by examining the frequency of a composite mitochondrial haplotype that occurs at high frequencies in this aquaculture strain but is rare in wild Chesapeake Bay oysters. The estimated frequency of this haplotype in locally recruited oysters (average 1.4%, SD = 0.9) was compared with the average frequencies found in the hatchery produced (35.9%, SD = 12.8) and wild (1.2%, SD = 0.9) oysters, but we were unable to refute the null-hypothesis that population supplementation made no contribution to recruitment. We discuss five nonmutually exclusive explanations for the limited impact of supplementation, including unequal sex-ratio, predation, flushing, relative scale, and aquaculture selection. We argue that predation, relative scale, and aquaculture selection are the likely reasons for the limited contribution made by aquaculture oysters used for population supplementation.

In this study several parameters critical to the success of cryopreserving Sydney rock oyster (Saccostrea glomerata) larvae were investigated. They were: (1) cryoprotectants (10% dimethyl sulfoxide and 10% propylene glycol), (2) freezing protocols (with or without the seeding step), (3) larval concentrations (1,000, 3,000, 5,000, 10,000 and 30,000 individuals mL⁻¹), and (4) larval ages (6, 12, 24, 48, and 96 h old). The survival rates were determined as percentages of postthaw larvae performing active movements for the 6 and 12 h larvae or active cilia movement for the 24, 48, and 96 h larvae. Analyses showed that the difference in survival rates between different age classes was significant in all the experiments conducted, with the maximum survival rate being achieved in the 24-h-old larvae. When the freezing protocol without the seeding step was applied in 24-h-old larvae the postthaw survival rates of larvae cryopreserved with 10% dimethyl sulfoxide (93.1 ± 0.2%) were significantly higher (P < 0.001) than those with 10% propylene glycol (81.5 ± 0.4%). Differences in postthaw survival rates between different concentrations (1,000–30,000 individuals mL⁻¹) were not significant within each of the three larval age classes (6-, 12-, and 24-h-old) used.

We describe the quantitative and qualitative histology and histochemistry for a tropical oyster, C. corteziensis sampled in a coastal lagoon in Northwest, Mexico. Males were larger than immature oysters, with females presenting intermediate values. In this species, mature organisms were found most of the year, and there were at least two strong spawning periods, one in summer and the second in autumn. The presence of mature oocytes most of the year did not allow for differentiation of an annual reproductive pattern using average oocyte diameter, as has been used in other species. There was a very short resting period in winter, particularly in December 2005, and by January to February 2006 postvitellogenic oocytes can already be found. Both sexes tended to have more lipids in the gonad tissue as maturation advanced, with an inverse correlation to carbohydrate in gonad and in vesicular tissue in females. No differences in lipids or carbohydrates content were found in digestive gland. A negative correlation was found between chlorophyll a content and gonad coverage area in males and females. Maturation occur at sea surface temperatures higher than 20°C, and spawning when temperature increases above 27°C.

Leucine aminopeptidase (LAP) belongs to a family of ubiquitous peptidases, with roles in growth and development, stress responses and adaptation to changing environmental conditions. The LAP gene was sequenced from a commercially important marine bivalve: the Pacific oyster Crassostrea gigas, and sequence polymorphisms were identified. This study identified 21 single nucleotide polymorphisms (SNPs), which would alter the encoded amino acid sequence, one 3 base deletion, one single base deletion, which would create a truncated protein (predicted to be nonfunctional), and a further 50 silent SNPs. The 23 polymorphisms altering protein sequence were found to occur in 34 different combinations, which we designated as 34 alleles: many more than the 6 alleles predicted previously by allozyme analysis. Predictions of protein structure and stability were used to identify which of the changes in the protein sequence are most likely to affect enzyme function. The sequence of the LAP gene noncoding regions was also analyzed and simple sequence repeats (microsatellites) were found in introns 1 and 9. The intron 1 microsatellite region was also found in another species of oyster: Crassostrea hongkongensis. We have demonstrated that the LAP gene region of the Pacific oyster, C. gigas is highly variable, and have identified new, potentially useful, genetic markers.

A molecular genetic identification key for nine species of Crassostrea oysters was developed based on restriction fragment-length polymorphism (RFLP) analyses of nuclear and mitochondrial DNA markers. Seven of nine species were unambiguously differentiated based on digestion of the ITS-1 nuclear marker with Hae III and Hinf I. Individual species exhibited one or two RFLP patterns for each restriction endonuclease, and only C. madrasensis and C. iredalei were indistinguishable electrophoretically. All nine species were unambiguously differentiated based on digestion of the COI mitochondrial marker with Dde I and Hae III. Species exhibited one or two RFLP patterns for each restriction endonuclease, and species pairs unresolved by the first restriction enzyme were completely resolved with the second. The resulting key distinguishes among many Indo-Pacific Crassostrea oysters that overlap across some or all of their ranges, and establish as an expandable framework for future additions of other species to the key.

Oyster reefs support a valuable commercial fishery based on the extraction of oysters from the biogenic reef matrix they form. This fact, combined with recent recognition of the many ecological services oyster reefs provide to estuarine ecosystems, has resulted in increased efforts to restore and/or enhance the spatial extent of oyster reefs. As part of a large-scale restoration effort in Mobile Bay, Alabama, we designed a field project to determine if the design and location across a bio-physical gradient of restored oyster reefs affect the recruitment of oysters and other sessile invertebrates. In January 2004, eight oyster reefs (625 m² each) were constructed in each of three areas of Mobile Bay (Cedar Point, Sand Reef, and Shellbank), which varied in water quality and spatial extent of existing oyster reefs. Four reefs were high relief (≥1.0 m vertical relief) and four were low relief (0.1–0.2 m). Semiannual quadrat surveys and monthly assessments of oyster survivorship were designed to evaluate oyster recruitment, abundance, and mortality as a function of reef elevation and location. The two most abundant sessile invertebrates found in the quadrat sampling were eastern oyster (Crassostrea virginica) and recurved mussel (Ischadium recurvum). Recurved mussels were abundant on all restored reefs, but densities did not significantly vary with location or reef elevation. Oyster recruitment and abundance varied by location (Cedar Point > Sand Reef > Shellbank). Oyster recruitment was also higher on high relief reefs compared with low relief. The pattern of higher recruitment of oysters at high relief reefs suggests that in locations where oyster mortality is high (i.e., Sand Reef) or larval supply is low (i.e., Shellbank), high relief reefs are an important design element in successful reef restoration.

Growth of the lagoon cockle, Cerastoderma glaucum Poiret, was determined from samples collected seasonally from Keramoti lagoon in Greece in the northeastern Mediterranean. The three-dimensional almost “spherical” shell shape does not change throughout the life of the species. Foot length, flesh weight, shell, and total weight increased at a lower rate than shell size, whereas water content of the soft party decreased with growth. Condition index showed a strong seasonal variation. Flesh weight and flesh water content were among the body parameters examined that have a large influence on the physiological state of this bivalve. Burrowing ability of the species was examined in relation to type of sediment. Burial time was positively correlated with shell length in all types of sediment tested. C. glaucum is a substrate-specialist slow-burrowing species and it showed a clear preference for the sediment where it occurs naturally.

Analysis of bomb generated radiocarbon (¹⁴C) changes in a red abalone, Haliotis rufescens Swainson shell was used to evaluate age-at-length relationships derived from data from a previous multiyear, multisite tag-recapture study. Shell carbonate was extracted from four successive growth trajectory locations in a single shell with a maximum shell length of 251 mm. Extraction locations were based on Von Bertalanffy growth function (VBGF) predictions and chosen to span the initial rise of the ¹⁴C-bomb pulse that is known to have occurred in surface ocean waters during 1958 ±1 y in the northeast Pacific. The close temporal correspondence of the red abalone sample series to regional Δ¹⁴C records demonstrated the utility of the technique for validating age-at-length relationships for the red abalone. The findings provided support for a mean VBGF derived age of 32 y (range 30–33 y) for the specimen; however, the analysis of ¹⁴C data indicated that the specimen could be older.

Sea ranching of the saucer scallop Amusium balloti Bernardi, 1861 has recently been developed to compensate for the dramatic fluctuations in catch that naturally occur between seasons. Marking or tagging methodology is needed for this industry to evaluate the effectiveness of reseeding and to optimize spat deployment strategies. We tested the quality and longevity of fluorescent marks incorporated into the newly forming shell of 2–4 mm spat immersed in chemical solutions. Three chemicals, alizarin red S (ARS), calcein, and oxytetracycline hydrochloride (OTC) were tested in this study for mark quality, mark retention, and toxicity to scallops. Marks were identified and assessed for brightness using an epifluorescence microscope. Fluorescent marks were still visible after 10 mo of culture in our land-based system. Multiple marks were also produced on individual shells using OTC or a combination of calcein and OTC. This demonstrates the potential for specific “bar codes” to be used to distinguish between different cohorts or spat deployment strategies. Of the three chemicals, OTC was identified as the most useful chemical for industry, producing a bright mark and negligible mortality at 200 or 300 mg L⁻¹, which lasts for at least 10 mo in living scallops.

Changes in a common benthic community of mobile Japanese scallops Patinopecten (=Mizuhopecten) yessoensis and predatory sea stars under introduction of mariculture were assessed by comparing the distribution and abundance of each species, and the relationships between densities of these community elements in natural biotope and after twice-repeated seeding of young scallops on the bottom. Under mariculture, at high scallop density (up to 6 ind./m²), the scallop growth rates noticeably decreased. The density of the sea star Asterina (=Patiria) pectinifera markedly decreased, and its distribution was not dependent on scallop density both before and during mariculture. Mean sea star Distolasterias nipon density was also diminished, but aggregate response to high prey density increased. In contrast, the sea star Asterias amurensis density noticeably increased, and it positively correlated with scallop density before and during mariculture. The reduction of densities of sea stars A. pectinifera and D. nipon in mariculture conditions is likely to be explained by the increase in abundance of the large and mobile sea star A. amurensis as the competition for food resources seems to occur. Even big 2-y-old scallops (85.4 ± 1.5 mm shell height) at high density (>2 or 4 scallops per m², for different sea stars) attract such predatory sea stars as A. amurensis and D. nipon. The results indicate that seeding of young scallops on the bottom and especially reseeding markedly increase the attraction of the biotope to predatory sea stars for a long time.

Substantial nutritional and energetic demands are associated with immune activation and the maintenance of an efficient immune system. One-year-old Chlamys farreri (Jones and Preston) scallops were maintained in lantern nets in different nutritional conditions (satiation and starvation) for 40 days. After the 40-day treatments, the condition index and the total hemocyte count (THC) decreased significantly in the starved group compared with the satiated and initial control groups. The percentage of phagocytic hemocytes also was significantly reduced with starvation. In contrast, no significant effect of starvation was observed on reactive oxygen species (ROS) production. The acid phosphatase (ACP) activities in cell-free hemolymph increased significantly in scallops in starved and satiated treatments compared with the initial control, whereas ACP activity in hemocyte lysate was significantly lower in the starved group. These results indicate that starvation stress compromises immunological activities of scallops.

Eight cases of disseminated neoplasia were found among 540 specimens of Mytilus edulis collected from an intertidal beach in Connecticut in western Long Island Sound. This was unusual, because disseminated neoplasia is very rare in M. edulis but causes epizootic mortalities in another mussel species, M. trossulus. According to histology, mussels showed a continuum of disease progression, from early stages with a few anaplastic cells around the stomach epithelium to more advanced cases with multiple foci of neoplastic cells in the tissues, finally to terminal cases with profuse infiltration of neoplastic cells in all tissues. Flowcytometric hemocyte analyses were performed to compare immune functions between neoplastic and healthy mussels. Circulating hemocytes from the neoplastic mussels showed significantly less phagocytosis and significantly more apoptosis than hemocytes from the healthy mussels. Hemocyte cell density measured by flow cytometry increased in the hemolymph with progression of the disease on histological sections. In situ hybridization was performed to detect apoptosis also on paraffin sections. There were more apoptotic neoplastic cells in the early stages of the disease than in the later stages. These observations suggest the need for further studies on apoptosis-regulating genes to explain differences in susceptibility to neoplasia of different Mytilus species, and the role of apoptosis in the progression of disseminated neoplasia.

Mussel cultivation is the most valuable sector of the bivalve aquaculture industry in the United Kingdom, and the largest mussel fishery in Britain is located in the Menai Strait, North Wales. The common starfish, Asterias rubens is highly abundant and widely distributed throughout British waters, affecting the distribution and abundance of prey species such as the common mussel, Mytilus edulis. This study investigates the potential influence of the Menai Strait mussel fishery on seasonal patterns of abundance, distribution, and migration of A. rubens, and aspects of their reproductive strategy. Starfish and mussel populations were surveyed and sampled monthly over a 2-y period using a visual survey technique and by trawling the seabed during the mussel harvest period. Maximum starfish density (40,586 ± 5,648 starfish·ha⁻¹) and percentage mussel coverage (∼40%) were recorded on a commercial subtidal mussel bed. Mussel density and starfish abundance increased seasonally between April and July and declined between September and March, with the loss of 1.7 × 10⁶ starfish attributed directly to the activities of the mussel fishery. Starfish migration onto subtidal mussel beds is deemed to be in response to the transplantation of high densities of mussels and trawling activity, and the reduction in starfish numbers over the winter a direct result of harvesting activities. Estimates of starfish reproductive condition determined from trawl samples collected during the same period suggest that starfish were aggregated and highly abundant at sites without mussel cultivation during their peak reproductive state. Asterias rubens migration into deeper water is believed to be in response to increasing seawater temperature where gravid individuals spawn in close proximity to improve fertilization.

Two stations northern Hurghada (Marine Biological Station and Ras El-Behar) were chosen during summer 2006 and winter 2007, to study and evaluate the compatibility of living bivalve assemblages on the living corals. Twenty-nine samples of hard corals contributed by living bivalves were collected using 0.25 m² aluminum square frame and were taken during daylight using SCUBA diving equipments. A total surveyed area of 132 m² and 534 bivalve individuals were counted from the studied sites and were associated with living corals, these individuals represented by 7 different families and 12 species. Pteriidae represented the highest individual numbers 229 (42.88%), whereas Veneridae recorded the lowest number 11 (2.06%). Electroma alacorvi recorded the highest presence 35.38% whereas Gefrarium pectinatum had the lowest value 2.06%. There was a high association and correlation between density and standard deviation of the bivalves. Mytilidae and Pteriidae have a wide and strong association with some corals (as Stylophora pistillata; Porites solida; Pocillopora verrucosa; Favites abdita; Favites fluxuosa; and Goniastrea pictinata; Acropora pharonis; Montipora venosa; Acropora humilis, Anacropora spinosa and Montipora spongiosa), whereas Pectinidae, Arcidae, and Tridacnidae have a low coral association. Electroma alacorvi recorded the highest density 6.79 individuals/0.25m² and a standard deviation ±2.41, whereas Barbatia setigera recorded the lowest density 1.9 individuals/0.25 m² (S.D ± 0.78). Sedimentation rate and the large coral coverage play a major role in the bivalve assemblages, density, and diversity where the highest coverage and dominance of Stylophora pistillata, Acropora spp., Porites solida, Favites spp., and Goniastrea pictinata were associated with high bivalve species density. Finally, the over-fishing activities, pollution particularly with oil and sedimentation are the major reasons for coral death causing absence of many bivalve species at Ras El-Behar.

Illex argentinus is known for spatiotemporally segregating into reproductive aggregations on the mid-continental shelf and slope off southern South America. In this study we found that the species also mates and spawns in San Matías Gulf, a coastal basin off northeastern Patagonia. Basing on the analysis of size and maturity structure of squids caught over a 28-month period in waters of the gulf, distinct demographic pulses were identified in the samples each year. Two of them were more consistent, one comprising small-sized individuals reaching full maturity in January to February (summer) and the other including larger individuals maturing between September and October/December (spring). Also, a less conspicuous group of mature individuals was observed in June/July (winter) of the last sampling year. So far, differences in the parameters of the size-at-maturity curves of these population components allow considering at least two stocks for management of I. argentinus in the gulf.

We analyzed the effect of outliers of the catch-per-unit effort on the catchability coefficient estimated by using a depletion model. When we used catch-per-unit effort in the Delury model, we observed a curve in the regression of depletion against time. When we then solved the model with a normal probability distribution, the catchability coefficient was poorly estimated. We improved the estimation of catchability using an algorithm that used a two-component-mixture probability distribution. The estimations for catchability (q) and recruitment (N ₀) were q = 0.41 × 10⁻³, N ₀ = 9.13 × 10⁶, and the estimated likelihood was 2.65 × 10⁴ using an algorithm of the normal probability distribution, whereas the estimations made using the algorithm of a two-component-mixture probability distribution were q = 0.23 × 10⁻³, N ₀ = 18.07 × 10⁶, and the estimated likelihood was 4.89 × 10⁶. The maximum likelihood estimated with the mixture-distribution algorithm was greater than the maximum likelihood estimated with the normal-distribution algorithm. We believe the two-component-mixture probability distribution fit the data better than the normal probability distribution. From this we determined the consequences on management when overestimations or underestimations of catchability are estimated.

A logistic regression model building approach was used to evaluate the association between the development of impoundment shell disease in an American lobster (Homarus americanus) storage facility, and prestorage physiological parameters (hemolymph total protein concentration, molt stage, sex, and shell hardness) and environmental factors (surface sludge accumulation). A total of 540 disease-free, winter-harvested lobsters from southwest Nova Scotia were tested prior to storage and then examined for signs of shell disease at 30, 60, 90, and 120 days of storage. Total protein concentration was the strongest predictor of shell disease, with the odds of developing shell disease ranging from 4.3–26.7 times higher for lobsters with low total protein concentration versus lobsters with high protein concentration, depending on the time point examined. Lobsters in the intermolt stage and removal of sludge from the surface of the lobster also emerged as important risk factors for shell disease development. These results reinforce the observation that the quality of lobsters entering an impoundment facility is critical and ultimately predicts the extent to which shell disease will develop.

An important part of quantifying predator-prey dynamics is to understand the contribution of various prey types to the predator diet. Although the role of juvenile penaeid shrimp as benthic predators is well established, recent research has indicated that penaeids are also capable of utilizing the energy available in zooplanktonic form. Yet the relative role of juvenile penaeids as direct zooplankton predators, capturing and consuming zooplankton from the water column—as compared with their role as benthic predators of animals that live on, or have fallen to, the bottom remains unknown. Two separate sets of laboratory experiments were conducted to determine the density-dependent predation rates of juvenile Litopenaeus setiferus feeding directly on (1) zooplanktonic prey Artemia salina in the water column and (2) benthic prey Mercenaria mercenaria in sediment. The average proportional mortalities for M. mercenaria (43% to 97%) were much higher than for A. salina (−10% to 28%). At low prey densities, proportional prey mortality increased with increasing prey densities for both M. mercenaria and A. salina, indicating a type III functional response by L. setiferus. A maximum consumption rate of 476 M. mercenaria/L. setiferus/hr was estimated in the benthic feeding experiments, whereas predator satiation was not observed even at the highest A. salina densities. High proportional M. mercenaria mortalities across moderate densities (1,000–2,500 m⁻²) suggest the potential for L. setiferus regulation of Mercenaria populations. Negative proportional A. salina mortalities at low and moderate densities suggest that L. setiferus are not efficient zooplankton predators. The variable consumption rates displayed by L. setiferus feeding on different prey types are a demonstration of their dietary plasticity as omnivores. Although L. setiferus are more effective as benthic predators, their ability to capture and consume prey from the water column suggests that zooplankton may be a viable alternative prey source when benthos are unavailable or inaccessible.

Climate change may affect crab populations via thermal effects on embryo development and hatching. To test this, we measured the duration of development and hatching for the embryos of 11 blue king crabs Paralithodes platypus held at 2.3 ± 0.45, 4.3 ± 0.31, and 6.1 ± 0.61°C. Embryo area, length, and width, eye length and width, and percent yolk were measured biweekly from digital images, and hatching larvae were collected daily from individual crabs. Data were compared between eggs of identical age (weeks since fertilization). Temperature did not have a significant effect on embryo measurements, but did affect development indices (percent yolk and eye size). Hatching was significantly delayed at colder temperatures with about a 46-day difference from 2.3°C to 6.1°C. Length of development was related to temperature via a power function, and ranged from 410 ± 8 days at 6.1°C to 434 ± 11 days at 2.3°C. Length of hatching increased from 40 ± 4.6 days at 2.3°C to 55 ± 6.2 days at 6.1°C. A model for predicting hatching dates from an eye index was developed using a quadratic equation. Embryo development at 4.3 and 6.1°C was arrested between weeks 35 and 50; this evidence, plus other behavioral observations, suggests that crabs may be able to adjust development rates to partially compensate for temperature changes.

During trap-fishing investigations on the crab Cancer johngarthi along Baja California peninsula's southwestern coast, Baja California Sur, Mexico, conducted between 2002 and 2006, information was gathered to assess fishing efficiency in terms of the number of crabs caught per trap during one hour of operation (catch per unit of effort, CPUE = c/ht). As a result of vessel operation issues, some trap lines were abandoned, whereas vessels returned to land for repairing, and because the effective fishing time for these traps was significantly longer than normal, the information so obtained was regarded as reflecting the potential effect on fishing of traps lost during fishing operations (ghost fishing). Of 651 line sets analyzed, involving 45,152 traps, 77% had effective fishing times below 60 h, 14% between 70 and 150 h and 9% between 150 and 5,500 h. There is an exponential reduction in CPUE with increasing fishing time that could be associated to trap saturation. The number of crabs per trap also decreased with immersion time, fitting a power function. After 1,000 h of immersion, each trap may contain 7–18 crabs. Four hundred traps were lost over the course of 14 fishing trips. However, because the fishery is in the early development phases, the implementation of measures to avoid or restrain ghost fishing is deemed convenient.

Field investigations were performed to find out if trap catch could be an alternative to diving to harvest green sea urchins (Strongylocentrotus droebachiensis). Laboratory experiments in y-maze tubes showed that starved sea urchins responded on tree different baits in about one minute, but they did not discriminate between offal of fish (saithe), sea urchin fodder, and lamina of kelp. The trap catch investigations were performed at 0–2.5 m depth in Ytre Kårvika in Troms County and 2-m depth at Hjelmsøya in Finnmark County in autumn 2002 and summer 2003, respectively. Repeated catches 12 times at the same area in Ytre Kårvika showed higher catches at the last six drags than the first six during one month of fishing. In the Hjelmsøya area highest catches were found in barren grounds with high densities (50–80 individuals m⁻²) of sea urchins, whereas in kelp beds the sea urchin catches did not exceed catches if baits were not used. Offal of catfish and cod heads caught higher catches than sea urchin feed and lamina of kelp. Ring traps (diameter 45 cm) caught better than dropnets, and dropnets caught better than box traps. The 13 drags with the best catches out of 41 drags caught in mean 1.43 kg trap⁻¹ day⁻¹. Probably during the highest catches, the ring traps were saturated. These traps caught 1.23% of the sea urchin resources in the area per day. Estimates show that an area can be harvested for 41–165 days until it is cleaned, depending on the densities of the resources and the harvesting strategy chosen in the estimates. The traps caught sea urchins with low gonad indices, and the sea urchin industry has to feed them to increase the gonad content before they can be equipped.

Spawning season of Strongylocentrotus intermedius in Hokkaido is classified into the 3 types, Sea of Japan, Funka Bay, Sea of Okhotsk, and Pacific Ocean. To clarify the type in Pacific Ocean, northern Honshu, we calculated seasonal gonad indices (gonad wet weight/body weight × 100) monthly and plotted the gonad development process from histological observation of Strongylocentrotus intermedius collected at depths of 0.5–1.0 m in Hirota Bay, Iwate Prefecture, from September 2005 to November 2006. The gonad indices showed a seasonal cycle: they reached peaks of 20.7–23.5 from September to October, when the gonads were in the maturation stage. They fell sharply to 1.9–3.4 in November, corresponding to the spent stage. They remained low until February, when the gonads progressed to recovering stage. They rose again with water temperature in March; the gonads were in the growing stage during March to May. In June, premature gonads appeared, and dominated in September. Spawning was vigorous in October as the water temperature fell from 20.0°C to 13.0°C, coinciding with that in the Sea of Japan off Hokkaido.

Growth and natural mortality rates (M) of the red sea urchin (RSU), Strongylocentrotus franciscanus, were estimated based on tetracycline tagging studies and abundance surveys in Queen Charlotte Islands (QCI), Price Island (PI), Alert Bay (AB), and Tofino, British Columbia. Growth was modeled using the Tanaka function and logistic dose-response function and was variable between locations. The growth rate of the RSU remained constant or even increased in the first few years, before declining with test diameter or age. The RSU appeared to be a slow growing and long lived species. Growth for the RSU to recruit into the fishery, at a test diameter of 90 mm, took about 10 and 14 y in QCI and AB respectively, and about 18.5 y in PI and Tofino. Growth rates seemed to be correlated with population density. RSU density was the lowest in QCI, and lower in AB than in PI or Tofino. M was estimated by comparing the survey-derived density of the RSU with the expected density calculated using the growth function and the densities in the previous survey years. The estimated mean M was about 0.08 y⁻¹ in PI and Tofino, 0.12 y⁻¹ in QCI, and 0.21 y⁻¹ in AB.

Domoic acid (DA) is a potent toxin produced by bloom-forming phytoplankton in the genus Pseudo-nitzschia, which is responsible for causing amnesic shellfish poisoning (ASP) in humans. ASP symptoms include vomiting, diarrhea, and in more severe cases confusion, loss of memory, disorientation, and even coma or death. This paper describes the development and validation of a rapid, sensitive, enzyme linked immunosorbent assay test kit for detecting DA using a monoclonal antibody. The assay gives equivalent results to those obtained using standard high performance liquid chromatography, fluorenylmethoxycarbonyl high performance liquid chromatography, or liquid chromatography—mass spectrometry methods. It has a linear range from 0.1–3 ppb and was used successfully to measure DA in razor clams, mussels, scallops, and phytoplankton. The assay requires approximately 1.5 h to complete and has a standard 96-well format where each strip of eight wells is removable and can be stored at 4°C until needed. The first two wells of each strip serve as an internal control eliminating the need to run a standard curve. This allows as few as 3 or as many as 36 duplicate samples to be run at a time enabling real-time sample processing and limiting degradation of DA, which can occur during storage. There was minimal cross-reactivity in this assay with glutamine, glutamic acid, kainic acid, epi- or iso-DA. This accurate, rapid, cost-effective, assay offers environmental managers and public health officials an effective tool for monitoring DA concentrations in environment samples.

Freshwater mussel conservation efforts by many federal and state agencies have increased in recent years. This has led to a greater number of stream surveys, in which mussel die-offs involving high numbers of dead and moribund animals are being observed and reported with greater frequency. Typically, die-offs have been incidentally observed while research was being done for other purposes, therefore, accurate mortality data have been difficult to obtain. Specifically, seasonal die-offs were noted in localized areas of the Clinch and Holston Rivers, Virginia, and to lesser degrees, in neighboring rivers in this geographic region, including southeast Virginia. The observed mussel species affected were primarily the slabside pearlymussel (Lexingtonia dolabelloides) and to lesser extents, the pheasantshell (Actinonaias pectorosa), rainbow mussel (Villosa iris), and the endangered shiny pigtoe (Fusconaia cor). To determine if a bacterial pathogen might be involved in these recurring mussel die-offs, this study examined characteristics of the indigenous microbiota (bacteria) from healthy mussels from sites on the Clinch and Holston Rivers where die-offs were previously observed. These baseline data will allow for recognition of bacterial pathogens in future mussel die-offs. Means for total bacteria from soft tissues ranged from 1.77 × 10⁵ to 3.55 × 10⁶ cfu/g; whereas, the range in means from fluids was 2.92 × 10⁴ to 8.60 × 10⁵ cfu/mL. A diverse microbiota were recovered, including species that are common in freshwater aquatic environments. The most common bacterial groups recovered were motile Aeromonas spp. and nonfermenting bacteria. Flavobacterium columnare, a pathogen to cool- and warm-water fishes was recovered from one specimen, a Villosa iris from the Clinch River.