Oysters and oyster reefs are important components in the rich and productive southeastern US marsh-estnarine ecosystems. In recent decades, ecological research has shown that these complex systems can be driven by external biotic and abiotic perturbations or internal system dynamics that cause the system to rapidly reorganize into another alternate state or regime. Such shifts may have happened on a much larger scale several thousand years ago along the southeastern coast of North America. Beginning about 4,500 B.P., the coastal Native Americans built complex structures or oyster shell rings on the landward side of the southeastern sea islands of South Carolina, Georgia, and Florida. The construction of shell rings is believed to symbolize the conversion of nomadic hunter-gatherers to coastal fisherfolk and is considered a pivotal stage in the evolution of preEuropean contact culture in the United States. But, by about 3000 B.P., the shell rings were abandoned and the Native Americans dispersed. With the objective of learning from the past to help manage for the future, the Fig Island and Sewee shell ring systems near Charleston, South Carolina are analyzed using ecological comparisons with modern oyster systems, published archaeological and geological data, as well as reverse engineering approaches. In just a few years, the Indians built the Fig Island 1 shell ring using over 1.2 billion oysters. Had these oysters not been removed from the system, they would have cleared or filtered a water volume the size of North Inlet estuary near Georgetown, South Carolina about 6 times per day. This exercise examines the evidence on how the prehistoric system might have changed or shifted in response to the massive removal of oysters to build shell rings and concurrent changes in the natural environment.

Anthropogenic emissions of carbon dioxide (CO₂) from fossil fuel combustion and deforestation are rapidly increasing the atmospheric concentration of CO₂ and reducing the pH of the oceans. This study shows that predicted near-future levels of ocean acidification have significant negative effects on early larval development of the Sydney rock oyster Saccostrea glomerata (Gould, 1850). CO₂ was added to seawater to produce pH levels set at 8.1 (control), 7.8, and 7.6 (actual pH values were 8.11, 7.81, and 7.64, respectively). These treatments represent present-day surface ocean pH, as well as upper (Δ pH ≈ -0.3) and lower (Δ pH ≈ -0.5) pH predictions for the surface oceans in 2100. With decreasing pH, survival of S. glomerata larvae decreased, and growth and development were retarded. Larval survival decreased by 43% at pH 7.8 and by 72% at pH 7.6. Antero-posterior measurement (APM) was reduced by 6.3% at pH 7.8 and 8.7% at pH 7.6, and dorso-ventral measurement (DVM) was reduced by 5.1% atpH 7.8 and 7.5% at pH 7.6. The percentage of empty shells remaining from dead larvae decreased by 16% atpH 7.8 and by 90% at pH 7.6 indicating that the majority of empty shells dissolved within 7 days at pH 7.6. Scanning electron microscope images of 8-day-old larvae show abnormalities on the shell surface at low pH suggesting (1) problems with shell deposition, (2) retarded periostracum formation, and/or (3) increased shell dissolution. Larval life-history stages are considered particularly susceptible to climate change, and this study shows that S. glomerata larvae are sensitive to a high-CO₂ world and are, specifically, negatively affected by exposure to pH conditions predicted for the world's oceans for the year 2100.

Natural variation in the physiological variables of the eastern oyster Crassostrea virginica from a tropical climate have until now been poorly documented. This study was conducted to characterize the influence of hydrological variables (salinity, temperature, nitrate, nitrite, ammonium, soluble reactive phosphorus [SRP], and soluble reactive silica [SRSi]) on oyster physiological variables (total hemocyte cells (THC), reactive oxygen intermediates (ROIs), agglutination, lysozyme, and protein concentration). Oysters were collected during 3 different months (April, August, and December) from seven sites in Terminos Lagoon SW-Mexico. The association of physiological variables with oyster condition index (CI) was also studied. The physiological variability explained by environmental variables was high (30.7%) when compared with the variability explained by the condition index (8.9%). The independent effect of salinity explained 69.7% of the total variability in the physiological variables (F-ratio = 3.4; P = 0.002, Monte Carlo test with 499 permutations). Protein concentration was significantly correlated with spatial salinity variation (r² = 0.89; H = 27.01, P < 0.0001). Site effects were salinity-protein discriminated (F-ratio = 3.406; P = 0.002). Temperature was not a significant variable in the oyster physiological variability. The oysters from marine freshwater transition zones were less affected in their CI and physiological parameters than oysters from permanent high (>28 psu) or low salinity conditions (<10 psu). This study represents the first step toward integrating specific C. virginica physiological information from tropical areas.

The native Sydney rock oyster, Saccostrea glomerata, is under increasing threat from QX disease, competition with nonnative Crassostrea gigas and coastal development. Knowledge of the distribution and population structure of S. glomerata and C. gigas is essential if oysters and their ecosystem services are to be successfully managed. We determined spatial patterns of abundance, condition, and size-structure of S. glomerata and C. gigas, across two key habitats, mangroves, and rocky shores of the Hawkesbury River, a highly modified estuary 50 km north of Sydney. Sampling of five sites per habitat, spanning a 15 km stretch of river, revealed abundant populations of S. glomerata, averaging 514 ± 185 m^-2, in mangroves and on rocky shores. The native oyster accounted for 99% of all oysters sampled, with C. gigas found only at two of the five sites sampled within each habitat. Overall, rocky shores supported over eight times the oyster cover as mangroves. Among rock sites, live oyster cover and condition generally decreased with distance upstream. Although, at present, the Hawkesbury River estuary supports abundant wild oyster populations, ongoing monitoring of oyster populations is required to ensure that appropriate management strategies are established to ensure the persistence of this important component of the ecosystem. Our sampling of two key oyster habitats provides an important baseline against which future studies can assess change.

To understand possible reproductive interaction between Crassostrea ariakensis (Fujita, 1913) and C. sikamea (Amemiya, 1928), which coexist in estuaries of China and Japan, we conducted 2 × 2 factorial crosses between the two species. Asymmetry in fertilization success was observed, where C. sikamea eggs can be fertilized by C. ariakensis sperm, and the reciprocal cross resulted in no fertilization. Fertilization success in C. sikamea female × C. ariakensis male (SA) crosses was lower than that in the two intraspecific crosses and produced larvae that had similar growth rate as their maternal species during the first nine days because of maternal effects. After that, genome incompatibility casted negative effects on the growth and survival of the hybrid larvae. Most hybrid larvae died during metamorphosis, but a small number of spat survived. Genetic analysis revealed that the survived SA spat contained DNA from both species and were true hybrids. This study demonstrates that hybridization between C. ariakensis and C. sikamea is possible in one direction.

Perkinus marinus causes a devastating disease, known as Dermo, in the Eastern oyster Crassostrea virginica. Routine detection of the disease is traditionally accomplished by the use of the Ray/Makin assay, using Fluid Thioglycollate Medium (RFTM). A simple real-time quantitative PCR assay was developed as a diagnostic tool to detect and quantify P. marinus, to complement and serve as an alternate to the RFTM method. Using a dual-labeled probe approach, a sensitive assay was designed to accurately detect a range of one to several thousand P. marinus organisms present in oyster tissues. A simple extraction method was used to increase throughput of the assay. Cultured P. marinus cells were quantified prior to DNA extraction, generating a standard curve and allowing cell counts to be derived from PCR cycle threshold values. Direct comparison of the RFTM and real-time PCR methods was accomplished by using tissue samples from the same oyster for both tests. Plotting cycle threshold values against the known Mackin index value generated a standard curve with a coefficient of regression of 0.9. Our results indicate that correlations could be made between this molecular based approach and traditional methods, allowing results generated from the PCR assay to be easily translated into the understood Mackin scale.

Growth of pearl oysters, Pinctada martensii was studied from June 2003 to March 2005 in Li'an Lagoon of Hainan Island in China. Shell height (SH) and total weight (TW) were measured monthly and temperature was recorded daily. The growth of oysters is characterized by fast initial growth of SH in the first year, followed by rapid increase of TW in the second year. Growth of SH was influenced by temperature, showing reduced growth rate in summer, fitting the extended Von Bertalanffy model: y = 92.99(1 - e^{(-0.002070(t-13.63) 0.04164 sin(2π/365.25)(t-193.03))}) (y: SH in mm, t: time in day). Growth rate of total weight increased steadily, except during typhoons or spawning, fitting the logistic model: y = 53.63/(1 e^{-0.009770(t-463.33) 0.1938 sin(2π/365.25)(t-564.73)}) (y: TW in g, t: time in day). It is also established that in Hainan, most oysters were mature and suitable for pearl nucleus insertion after 16–20 mo of farming; hence to meet the implantation season in April to June, it is more advisable to conduct hatchery operation in autumn than in spring.

Using a combination of stereological and calorimetric methods, we studied reproductive effort of Pacific winged pearl oyster Pleria sterna during an annual cycle in Bahia de La Paz, B.C.S., Mexico. The relationship between changes in the volumetric fraction of germinal and somatic tissues (gonad, digestive gland, adductor muscle, and mantle tissue) and changes in their energy content was analyzed. These data were also correlated with changes in water temperature and availability of food (seston). Because P. sterna spawns several times a year, reproductive effort was estimated ∼400% in terms of energy increase from early development in October 2006 to the spawning occurring in January to February 2007. During this period, when water temperature was decreasing and seston concentration was increasing, P. sterna followed a conservative strategy for allocating energy from reserves previously stored in somatic tissues. In contrast, when productivity dropped in spring, the species followed an opportunistic strategy for sustaining gametogenesis from food energy. In decreasing order, total energy channeled for reproduction came from the digestive gland (23 KJ g 1), adductor muscle (19 kJ g 1), and mantle tissue (16 KJ g 1). Based on these results, we recommend that commercial pearl culture practices be conducted from mid-autumn (October) through early spring (April), when P. sterna is energetically more resistant to manipulation. An additional recommendation is to avoid grafting during the summer (June through September), when the species is energetically exhausted and highly vulnerable to manipulation.

Historically depressed bay scallop populations in North Carolina have retained some capacity to replenish themselves. However, continued abnormally high predation by cownose rays, and growing degradation of seagrass beds may limit bay scallop population recovery. We modified existing methods for protecting spawning adult scallops from cownose rays (stockades) and enhancing scallop set (spat collectors in the natural habitat and in managed shore-side ponds) to determine whether the population growth of bay scallops could be enhanced. We found, with one important exception, that spawner sanctuaries inside stockades could be used to concentrate and protect adult scallops during a time when they are susceptible to ray predation. Spat collector bags proved effective not only in gathering scallop spat but serving as nurseries for juvenile scallop grow-out. The results from our pond experiments were mixed: spat collector bags did not do well in the pond, but an alternative collector design holds promise for making shore-side ponds important sources for inexpensive scallop seed. The simple techniques examined in this study can be used to enhance the potential of bay scallop populations to recover from low abundances, and were applied successfully to enhance North Carolina bay scallops during the two years of this project.

During their escape response, scallops swim, using jet propulsion created by rhythmically opening and closing their valves. Valve closure is powered by the large adductor muscle that acts against the hinge ligament. We compared in vivo force production during escape responses and in vitro isometric contractions measured on fiber bundles from the sea scallop Placopecten magellanicus. The in vivo recordings quantify force development during tonic and phasic contractions and can assess clapping frequency. In vivo responses were measured at les Iles-de-la-Madéleine (QC, Canada) after which the animals were flown to Quebec City where we measured in vitro contractile properties of isolated adductor muscle at 5°C and 10°C. Interindividual differences in force production were positively correlated between in vivo and in vitro measurements. However, peak twitch force and peak tetanic force (N cm^-2) of the isolated fiber bundles were lower than the maximum phasic force measured in vivo. This difference is likely to reflect damage to fiber bundles during isolation and the mechanical arrangement of the adductor muscle that leads the force measured at the edge of the valve during the acceleration of the upper valve to be greater than that measured near the muscle in vivo. Our comparison of in vitro and in vivo force production by the scallop adductor muscle underscores the advantages of our simple, minimally invasive, in vivo method for assessing the capacities of scallop muscle in natural situations.

Spatial and temporal variations in the meat weight of sea scallops were examined in the Georges Bank fishery. From 1998–2007, 31 commercial scallop vessels supplied 145 dissections from the last tow of their fishing trip. During the dissection process we recorded the shell height, meat weight, sex, gonad weight, and visceral tissue weight. Meat weight was regressed against shell height (Ln(MW) = α β ln SH). Predicted meat weight varied by up to 29% for a 120 mm shell height scallop among months. Scallop meat weight varied by 31% for a 120 mm shell height scallop between areas in the same month. The Southern Flank of Georges Bank had a different pattern of monthly variation in meat weight, possibly because of a spring spawning event observed in the gonadal indices. These spatial and temporal differences in meat weight could affect harvest, and harvest rate, with a 22% difference in scallops harvested between June and October calculated from a hypothetical fishery. Understanding these spatial and temporal variations in the shell height/meat weight relationship is important for optimal harvest, especially if a fully rotational area management strategy is implemented.

Larval size and developmental rate can vary tremendously within and among cohorts because of genetics, environment, and maternal investment. This natural variation in larvae may have effects that span multiple life stages. Here we investigate the effects of larval size and developmental stage on the subsequent life stages of the commercially and ecologically important clam Mercenaria mercenaria. Fifteen days after fertilization, we divided larvae into two groups based on their developmental stage (umbonal or pediveliger) and recorded survival, size, and developmental stage of individuals over the next 4 months. Results revealed that after four months larvae that had only reached the umbonal stage by Day 15 were significantly smaller than those that had reached the pediveliger stage. These smaller and less developed larvae were less successful than the larger and more developed larvae across late larval and juvenile stages. In particular, smaller and less developed larvae were less likely to metamorphose, required more time to metamorphosis, and had lower survival and growth rates. These results suggest that natural variation in larval size and developmental rate can affect recruitment in a variety of ways: (1) Increased time to metamorphosis may increase the cost to larvae via predation or exposure to environmental stress, (2) Decreased proportion of larvae able to metamorphose may directly reduce the number of settlers, and (3) Decreased growth and survival rates for juveniles may reduce the number of new recruits. We also discuss the persistence of natural variation in larval size and developmental rate in light of the observed negative effects associated with smaller and less-developed larvae.

Donax hanleyanus Philippi, 1847 (Bivalvia: Donacidae) dominates fine to coarse sandy beach communities of the northern Argentinean Atlantic coast. The population biology of this intertidal wedge clam was studied by determining population structure, growth and production at the three locations Santa Teresita, Mar de las Pampas (both from December 2005 to December 2006) and Faro Querandí (from March 2005 to December 2006). Von Bertalanffy growth functions were established from length-frequency distributions using an asymptotic length (L_∞) of 44 mm and the growth constants (K) of 0.46 and 0.47 y^-1 respectively of Mar de las Pampas and Faro querandí. Compared with growth studies four decades ago, D. hanleyanus today is growing more slowly, but is reaching a higher maximum length. Longevity is estimated to be approximately five years. The present study confirms that the overall growth performance index is habitat-specific, grouping Donacidae into tropical/subtropical, temperate and upwelling species. The intertidal biomass of D. hanleyanus ranged between 0.04 and 1.32 g ash-free dry mass (AFDM) m^-2yr^-1. Individual production revealed the highest value at 30 mm length (0.16 g AFDM m^-2yr^-1) and annual production ranged between 0.08 and 0.99 g AFDM m^-2yr^-1, resulting in renewal rate values (P/) between 0.82 and 2.16. The P/ ratios of D. hanleyanus populations increased with decreasing latitude from temperate to tropical regions. Only at Santa Teresita D. hanleyanus was found living with the sympatric yellow clam Mesodesma mactroides. A significant negative correlation between abundances of both surf clams suggests that abundance peaks of D. hanleyanus are related with population crashes of M. mactroides. Spatial differences in abundance are significantly related to sand texture as confirmed by nonmetrical multidimensional scaling, but not to sea surface temperature. However, the decrease of D. hanleyanus seems to be principally related to human activities.

In many molluscs, it has been found that Ca² signaling pathway is involved in the resumption of meiotic maturation in oocytes. To better understand the possible role of Ca² signaling pathway in regulating meiotic maturation in oocytes of the northern quahog Mercenaria mercenaria, free extracellular Ca² , A23187 (calcium ionophore), verapamil (calcium channel blocker), and trifluoperazin (calmodulin antagonist) were used to incubate oocytes or serotonin-induced oocytes by pharmacological methods. Results show that extracellular Ca² (50 ∼ 10 µM) and A23187 (1 ∼ 10 µM) can stimulate the meiotic maturation. In addition, verapamil (1 ∼ 100 µM) and trifluoperazin (10 ∼ 1,000 µM) could inhibit serotonin-induced oocyte maturation. Therefore, Ca² is essential for the reinitiation of meiotic maturation in oocytes of the northern quahog. Moreover, an increase in [Ca² ]i can promote meiotic maturation.

Owing to its extraordinary lifespan and wide geographical distribution along the continental margins of the North Atlantic Ocean, the ocean quahog Arcitca islandica may become an important indicator species in environmental change research. To test for applicability and “calibrate” the Arctica-indicator, metabolic properties of A. islandica specimens were compared across different climatic and oceanographic regions. Fully saline populations from Iceland to the North Sea as well as animals from polyhaline and low salinity, environments, the White Sea and the Baltic were included in the study. This calibration centrally includes recordings of growth-age relationships in different populations. Shells were used as age recorders by counting annual growth bands. As a result of this study, we propose a general respiration model that links individual metabolic rates of A. islandica from five populations: Norwegian coast, Kattegat, Kiel Bay (Baltic Sea), White Sea and German Bight (North Sea), to body mass, water temperature and site. Temperature exerts distinct site specific effects on respiration rate, which is indicated by Q10 values ranging from 4.48 for German Bight to 1.15 for Kiel Bay animals. Individual age, occurrence of apneal respiratory gaps, parasite infestation and salinity do not affect respiration rate. Respiration of Arctica islandica is significantly below the average of 59 bivalve species when compared at the same temperature and animal mass. This respiration model principally enables the coupling of A. islandica life history and population dynamics to regional oceanographic temperature models.

Cryptosporidium spp. are obligate intracellular apicomplexan parasites that infect epithelial cells of the gastrointestinal systems of a wide range of vertebrate hosts, including humans. Its importance as a serious public health threat was recognized only since the HIV pandemic. Because of the particular filter feeding behavior of bivalves, these marine organisms are susceptible to the accumulation of Cryptosporidium spp. oocysts from the environment and their retention for a certain time, acting as potential zoonotic reservoirs. To preliminary evaluate the presence of Cryptosporidium spp. oocysts in cultured bivalves from the Mali Ston Bay, Adriatic Sea, we have analyzed individuals from a black mussel (Mytilus galloprovincialis) population by immunofluorescence, over a one year period at four different locations. Overall one-year prevalence of the Cryptosporidium spp. was 16.8%, and was correlated with the presumptive number of E. coli in the shellfish and seawater and abiotic factors (temperature, salinity, oxygen), suggesting the necessity for the updating of existing sanitary control measures in Croatia.

Mussels of the genus Mytilus are ecologically and commercially important worldwide, and they form hybrid complexes where their distributions overlap. Allozyme and nuclear markers have been used to investigate their genetics over many years, but successful development of reliable highly valuable microsatellite markers has lagged behind other shellfish species. We have developed and characterized ten novel microsatellite loci that amplify reliably for the blue mussel Mytilus edulis. The number of alleles among 30 individuals from a wild population (Menai Strait, North Wales, UK) ranged between 9 and 29 and the observed heterozygosity between 0.300 and 0.954. Significant heterozygote deficiencies against the Hardy-Weinberg model were observed at 6 out of 10 loci. Analyses using MICRO-CHECKER suggested the presence of null alleles at 8 out of 10 microsatellites with estimated null allele frequencies ranging from 0.105–0.305. The 10 newly developed microsatellites will have value to discriminate between Mytilus species, to support studies of introgression and hybridization and to strengthen and improve the available genetic linkage map.

The sea urchin Paracentrotus lividus was grown on commercial mussel long-lines with the blue mussel, Mytilus edulis, at a farm in Loch Beag, on the west coast of Scotland, to investigate if enhanced sea urchin survivorship and performance (somatic and gonadal) resulted from sea urchin-mussel co-culture system. The sea urchins were fed four diets including: two class sizes of Medulis, (1) large mussels (31.16 ± 5.25 mm shell length), (2) small mussels (18.47 ± 4.86 mm shell length), (3) the kelp Laminaria spp. and (4) no additional feed. The experimental period lasted for 12 mo. No significant difference was observed in survivorship among treatments, ranging from 95.8% to 100%. Final test diameter, linear growth rates (LGR) and specific growth rates were significantly greater for the sea urchins fed the kelp diet compared with sea urchins fed either of the mussel diets and given no additional feed. No significant difference in growth rates was seen between the sea urchins fed the two size classes of mussel. A seasonal variation in growth rates was observed for all the treatment groups with a greater LGR in September to November 2005 compared with January to March 2006. Sea urchins fed on kelp showed significantly greater gonadal growth than the other treatment groups and no significant difference was observed between the sea urchins fed the two size classes of mussel. Gonad coloration in the sea urchins grown on the kelp diet was acceptable or excellent. Minimal roe material in the other treatments prevented color assessment. The results show that P. lividus exhibits high survivorship and linear growth rates when grown on long-lines used for commercial mussel cultivation, even at this northerly latitude. The results suggest that Laminaria spp. is a superior food source for P. lividus compared with the mussel M. edulis, however, a preharvest diet would have to be used to increase roe content prior to harvest even when fed a diet of Laminaria spp. The co-culture of sea urchins and mussels could potentially be implemented globally, wherever rope-grown mussel culture is practiced and sea urchin hatcheries are present. This would enable mussel farms to diversify in the production of a second commercially valuable product, with minimal requirement for new equipment or infrastructure, and would reduce the pressure on the already depleted wild stocks of sea urchins.

The processes of gametogenesis and maturation in broodstock of the scaly-type pen shell Atrina pectinata, in suspension culture were studied throughout the year. Gametogenesis in both sexes was initiated in February, when the water temperature was lowest. Gonad development and subsequent maturation occurred from March to September as the water temperature and food density increased. Spent gonads were found in October. Analysis of oocyte diameter frequencies in females just after spawning suggested that pen shell females spawn repeatedly during the breeding period. A number (1.6%) of hermaphroditic animals were also identified. Glycogen contents gradually decreased during the vitellogenic and mature stages. These results suggested that gonad development of pen shells in suspension culture was characterized by annual synchronicity in males and females, a spawning period from May to September resulting from monocyclic gametogenesis throughout the year, and an inverse relationship between gonad development and glycogen level. This study provides basic information applicable to mariculture of pen shells for commercial production.

Laboratory experiments were conducted to identify settlement cues of larval top shell Turbo cornutus on the articulated coralline alga Marginisporum crassissima. Fragments of M. crassissima strongly induced the larval settlement of the top shell. The settlement percentage of the larvae on ethanol-killed fragments of M. crassissima was significantly lower than on intact algal fragments, even though algal morphology did not differ between live and dead fragments. When the densities of diatoms on algal surfaces were altered by soaking the algal fragments in a germanium dioxide solution or a modified Jørgensen medium, neither treatment (increased or reduced diatom densities) affected the larval settlement percentage on M. crassissima. Similarly, reducing bacterial densities with antibiotics did not affect the larval settlement response to the treated M. crassissima. Top shell larvae were induced to settle by crude extracts of crushed M. crassissima but not by seawater where fragments of M. crassissima were immersed. These results suggest that the main cues inducing larval settlement of T. cornutus are chemical compounds derived from the alga, which have poor water solubility; algal morphology, and surface biofilms did not directly contribute to settlement by top shell larvae.

The gonadal cycle of Tegula eiseni (Jordan, 1936) was determined on monthly samples (25–30 organisms) collected from a population in Bahía Asunción, B.C.S., from January 2006 to December 2006. The results of the histological study indicate that both males and females show stages of gametogenesis and gonad maturation throughout the year and only two major spawning events: one in spring and another in fall. The species behaved as a partial spawner, and only at certain times was total spawning observed in females. Maturation and release or spawning times seem to be closely related to seasonal temperature rises and abrupt changes in surface sea water temperature, which occur at brief intervals for several days at certain times of year.

Consumer aggregations have the potential to drastically change the distribution and availability of resources. One form of aggregation observed in marine benthic invertebrates is the feeding front: a dense band of consumers that travels in a directional manner through a food patch, leaving a cleared area behind it. By artificially creating spatial heterogeneity in the distribution of a filamentous green alga, the formation of a feeding front of periwinkles Littorina littorea was induced on a rocky intertidal shore. The position of the front, the density of snails that comprised it, and the movement of individual snails in and around the front were monitored over a period of 14 days. During that period, the front advanced at an average speed of 2.25 cm d-1 and the density of snails in the front varied between 10 and 24 snails 100 cm-2. Temporal variation in snail density was negatively correlated with wave action. Snails on the trailing edge of the front or on bare rock behind the front exhibited directional movement towards the front, but snails in the front moved shorter distances than those on bare rock. These results support previous findings of resource-dependent movement as a causal mechanism of front formation in marine benthic habitats.

Haliotis iris is a species of abalone common on rocky reefs in southern and central New Zealand. This study examined the poorly understood feeding habits and preferences of H. iris in a series of laboratory experiments. Generally, H. iris consumed the blades of brown algae over red and green algae. However, when upright whole plants were given to H. iris, the highly preferred kelp Lessonia variegata was consumed in lower proportions than the less preferred but more accessible red alga Gigartina circumcincta. H. iris were less capable of reaching the blades or consuming the stipe of L. variegata, which has a stipe of ∼100–350 mm high. H. iris consumed greater amounts of drift over benthic L. vareigata. Water movement appeared to inhibit the active grazing of H. iris, but not the drift-trapping behavior, resulting in lower overall feeding rates for abalone under conditions of higher water movement. Abalone consumed fresh and aged algae equally. We conclude that H. iris feeds primarily on drift algae because preferred food sources are more accessible as drift than as attached macroalgae, and because this may be a more successful foraging strategy in the high flow environment this species commonly inhabits.

The understanding of genetic connectivity among populations is important for the management of fisheries, particularly in overexploited benthic species such as the pink abalone Haliotis corrugata, which might have limited dispersal because of a short-term pelagic larval stage. Eight microsatellite DNA loci (Hco15, Hco16, Hco19, Hco22, Hco47, Hco97, Hco194, and Hka56) from specimens caught at five locations from the northeastern Pacific of Mexico and the United States were examined. H. corrugata showed a low to moderate genetic diversity. Most loci from the five sampling sites were in Hardy-Weinberg equilibrium, except for Hco47, which showed null alleles. Hierarchical AMOVA from seven loci showed highly significant population divergence between San Clemente Island and the Mexican locations (F_ST = 0.021, P < 0.001) but not among Mexican subpopulations. The prevailing explanation for such divergence is the historical isolation by distance, but the presence of an oceanographic barrier (Southern California Eddy) and the insufficient mix between waters masses from both regions could preserve genetic differentiation.

It is widely accepted that the identification and management of abalone populations is critical for the ongoing sustainability of the fishery. However management of the endemic blacklip abalone throughout the Australian states generally occurs over large spatial scales and in some instances, across morphologically different populations on a finer scale. In this study, we use molecular techniques to show that blacklip abalone from seven sampling sites (of which four sites were characterized by stunted abalone growth patterns) in South Australia were genetically homogenous. Ten microsatellite loci and five composite restriction fragment length polymorphisms from the ND3/COIIImtDNA region showed high levels of genetic diversity across the collections, irrespective of growth characterization. Both molecular techniques also revealed a concordant outcome; no significant hierarchical variance was detected across geographically close, yet morphologically different collections (microsatellite φ;ST = 0.002; mtDNA φ;ST = -0.010). Pair-wise F_ST estimates were also low and often negative for the microsatellites (F_ST = -0.002 -0.007) and mtDNA markers (F_ST = -0.023-0.011). Our current findings support the hypothesis that blacklip abalone sampled here from “stunted” and “non-stunted” collections in the southern zone of the South Australian fishery are genetically similar.

The profitability of octopus ongrowing remains limited because low cost artificial diets have not yet been effectively developed. Therefore, alternative, low cost diets are worth exploring. In this study, we have investigated the growth and mortality of octopuses fed strictly on mackerel (Scomber colias), a low cost fish, readily available in the Azores Archipelago. Different weight classes (150–300; 300–600; and 600–1,000 g) were maintained at two stocking densities; 5 versus 12 individuals (ranging between 0.38–2.72 kg m^-3). The trial lasted 72 days and was performed in an open system composed of large rectangular tanks. Each individual was tagged, and growth was followed weekly. Mean instantaneous growth rate (G) varied between 0.67 and 1.47 (% increase in body weight day^-1), depending on initial body size. Survival was 100% for octopuses held in tanks at low density. On the other hand, increased aggressive interactions in high density tanks resulted in higher mortality rates (MR), especially for the smallest size class (MR = 66.7%). The results of this study suggest that with a monodiet of mackerel, subadult octopuses of 300 g can reach commercial size (750 g) in 2.5 mo. However, high mortality under elevated stocking densities will hinder commercial profitability with such diet. A proposed approach to increase survival would be to periodically supplement the monodiet with crustacean flesh.

The gamete-specific effects of UV radiation on fertilization in the invasive freshwater zebra mussel (Dreissena polymorpha) are addressed. Both eggs and sperm of zebra mussels were highly sensitive to UVB. Sperm irradiated with 118 mJ/cm² UVB showed decreased fertilization rates when inseminating nonirradiated eggs. Sperm binding was unaffected; however, acrosomal integrity and sperm incorporation into the egg cytoplasm were reduced by UVB irradiation. There was a decrease in first zygotic cleavage. The level of UVB needed to inhibit fertilization was lower than that required for inhibition of sperm motility. UVB-irradiated eggs also showed reduced function when inseminated by nonirradiated sperm. UVB-induced damage in eggs most commonly resulted in a stoppage or delay of meiosis. The levels effective in killing zebra mussel larvae should be sufficient to inhibit fertilization.

A high-salinity embayment located near Beaufort, North Carolina was surveyed to create a bathymetric profile of the main basin. To examine population dynamics and habitat use within the embayment, over 3,000 blue crab locations, sex, size, and egg stage were recorded during nocturnal low tides. Males and females partitioned habitat, with males concentrated in the shallower upper portion of the embayment, and mature females concentrated near the deeper mouth of the embayment. Juvenile females were predominantly found in shallower areas within mature male habitat. Location of ovigerous crabs varied with egg developmental stage. Crabs with late-stage eggs were found closest to the mouth of the embayment, and 92.9% (156 of 168) of ovigerous crabs left the embayment before larval release and may not have returned. Because the embayment is homogenous at 35 psu, a salinity gradient is not the primary mechanism underlying this segregation. We hypothesize that tidal activity rhythms and microhabitat selection contribute to the observed spatial patterns.