We examined the possibility that a nonnative oyster species would provide an ecologically functional equivalent of the native oyster species if introduced into the Chesapeake Bay. Habitat complexity and associated benthic communities of experimental triploid Crassostrea virginica and Crassostrea ariakensis reefs were investigated at 4 sites of varying salinity, tidal regime, water depth, predation intensity, and disease pressure in the Chesapeake Bay region (Maryland and Virginia). Four experimental treatments were established at each site: C. virginica, C. ariakensis, 50:50 of C. virginica and C. ariakensis, and shell only. Abundance, biomass, species richness, evenness, dominance, and diversity of reef-associated fauna were evaluated in relation to habitat location and oyster species. Although habitat complexity varied with location, no differences among complexity were associated with oyster species. Similarly, differences in faunal assemblages were more pronounced between sites than within sites. Our results show functional equivalency between oyster species with respect to habitat at the intertidal site and the low-salinity subtidal location. At subtidal sites of higher salinity, however, the numbers of organisms associated with C. virginica reefs per unit of oyster biomass were significantly greater than the numbers of organisms associated with C. ariakensis reefs. Multivariate analyses of data from subtidal high-salinity sites revealed unique communities associated with C. virginica treatments, whereas mixed-oyster species assemblages were functionally equivalent to monospecific C. ariakensis experimental treatments. Our study represents the first effort to quantify the potential habitat function of C. ariakensis, which has been proposed for an intentional introduction into Chesapeake Bay, and provides evidence of species-specific similarities and differences in reef-associated communities.

We describe oyster population trends in the Great Wicomico River, VA, from 2009 through 2009 using quantitative fishery independent survey data collected using a stratified random design. The seven public reefs examined cover a total of 2.8 × 10⁵ m² and vary in individual size from 1.36 × 10⁴ to 7.16 × 10⁴ nr. The river is functionally divided by a sand spit into upriver and downriver regions. Oyster densities on the upriver reefs were typically an order of magnitude higher than densities on the downriver reefs within the same time period. Throughout the system, the highest observed densities were coincident with high annual recruitment events (2002, 2006). Recruitment events were usually followed by high mortality, with small percentages of the population reaching ≥3 y of age. A predictive stock—recruit relationship is absent; rather, population demographics appear to be dominated by periodic high recruitment events. In the absence of seed removal, biomass maxima follow 1–2 y after recruitment maxima. Standing stock for the system varied between 1.56 × 10⁶ g and 3.63 × 10⁷ g in 2005 and 2006. Year-specific age-at-length relationships were estimated from demographics data. Length demographics were recast as age demographics to estimate mortality. Observed proportional mortality between young of the year and age 2 oysters was approximately 0.88 for the 2006-y class, which is slightly higher than the 0.62–0.71 observed for the 2007-y class. The ability to estimate age specific mortality accurately allows the construction of shell (habitat) budgets for the individual reef systems. The Great Wicomico oyster population appears to be maintained by episodic and extraordinary recruitment in the face of high mortality—the latter driven by disease (predominantly Perkinsus marinus) epizootics. The shell resource is modest, equivalent to little more than a monolayer several centimeters thick. Over short timescales (years), the available shell resource oscillates in concert with mortality. The shell accretion rate on upriver reefs is consistently 4–5 times greater than that observed on downriver reefs. Periodic modest shell planting has maintained the habitat base (the shell resource) throughout the system over decadal scales.

Subtidal eastern oyster Crassostrea virginica (Gmelin) cover large expanses of many Gulf of Mexico estuaries; however, few researchers have attempted to quantify the value of deep, open-water, subtidal reefs as habitat for fishes and crustaceans as a result of gear limitations. We developed quantitative sampling gear for live oyster reefs by slightly modifying an epibenthic sled. Gear comparison trials showed similar effectiveness among marsh edge, submerged aquatic vegetation, and nonvegetated bottom for both epibenthic sled types. We then quantified the density and community assemblage of nekton and benthic crustaceans on deep subtidal oyster reefs in Lavaca Bay, TX, and compared it with densities found in nearby marsh edge, submerged aquatic vegetation, and nonvegetated bottom habitats. We found significantly fewer nektonic and benthic crustaceans on nonvegetated bottom and oyster reefs than in marsh edge and submerged aquatic vegetation over all seasons and regions, and community analysis revealed similar differences among habitat assemblages. Using gill nets, the greatest catch of transient fishes and crustaceans were collected on oyster reefs and nonvegetated bottom. Although relatively low densities of small juvenile fishes were observed over deep oyster reefs, our community analyses and the high catch-per-unit-effort of large, transient species provide evidence that subtidal reefs are a critical habitat for numerous estuarine fishes and crustaceans.

This study analyzed the effect of water quality, different diets, and water temperature regimes in the conditioning and maturation of the Pacific oyster Crassostrea gigas. A recirculating aquaculture system prototype was used in this experiment and 2 different trials were performed. During the first trial, the effects of 3 different diets using different preserved concentrates of microalgae held at 20°C were tested: D1 (fed with Tetraselmis 3600), D2 (fed with Isochrysis 1800), and D3 (fed with a 50:50 mix of Tetraselmis and Isochrysis). During the second trial, 3 different temperatures regimes—T1, 16–24°C; T2, 20°C; and T3, 24°C (fed with preserved concentrates of microalgae at a 50:50 Tetraselmis and Isochrysis food ratio)—were evaluated. For each one of these treatments, 43 organisms were used and every treatment was done in triplicate. Seven samplings were completed in 72 days. During each sampling period, 9 oysters from each treatment were collected, and a gonad sample was obtained for histology analysis to determine gonad development. The results obtained in this study indicate that the recirculation system prototype was able to keep optimum water-quality parameters, and the nitrogenous components stayed below toxic levels (<0.2 mg/L). For the first trial, D3 showed gonad maturation at day 72, which was significantly different from D1 and D2 (P > 0.05). In the second trial, no significant differences were detected in gonad development among the 3 temperature treatments. Even when D2, T1, and T3 showed no gonad maturation, a trend was detected. Thus, it can be concluded that the combination of diet and temperature allows the manipulation of the gonad development of C. gigas, and that recirculation systems are an efficient tool to maintain appropriate physical—chemical and environmental parameters.

Since 1995, hatchery-produced juvenile oysters have been planted on numerous natural oyster bars in Maryland in an effort to restore degraded reefs. As part of the monitoring effort, 27 discrete hatchery plantings spanning 10 y of restoration were sampled during late summer and fall 2009. Oyster shell height, dry meat weight, shell weight, and clump height all increased significantly with age. Perkinsus marinus infections were low in all sampled populations, but increased with ago. These data enable estimates of growth and shell production rates, and highlight the low prevalence of disease in restored Maryland oyster populations. The longevity of these dense patches suggests that local metapopulation restoration may provide substantial ecological services. The trends presented in this study may provide valuable insights for refining management tools, adapting ongoing restoration, and improving population modeling efforts.

A commercial fishery for gcoduck Panopea generosa in Baja California began in 2002 and has since achieved landings comparable with those in Washington state and British Columbia, Canada, where geoduck fisheries developed in 1970 and 1976, respectively. This investigation was motivated to acquire the knowledge of population biology of P. generosa at the southernmost extent of its distribution that is required to establish a biological basis for fishery management decisions. This article was further motivated to assess the appropriateness of the current minimum legal size of 130 mm established by the Mexican fishing authorities. Morphometric relationships, age, and growth, and natural mortality of P. generosa were investigated with animals collected from Bahía de San Quintin and Islas Coronado, Baja California, Mexico, collected monthly from April 2008 through January 2009. Ages were obtained by counting growth bands in cross-sections of the shell hinge plate and utilizing cross-dating methods to increase accuracy. Individual P. generosa ages ranged from 3–96 y over both sites. Growth is rapid during the first 10 y and then slows for individuals older than 20–25 y. The asymptotic length was found to be 134 mm, the mean total weight was 764 ± 255 g, the Brody growth coefficient (k) was 0.191, and the natural mortality rate was estimated to range from 0.027–0.046, depending on the method used. These parameter values are similar to those of more northern populations of the same species. Because the proposed minimum legal size is close to the asymptotic length, and considering that geoduck size is difficult to determine before harvest, we suggest that the use of a minimum legal size is not an effective management strategy for geoduck clams.

Geoduck clams have become the most profitable emerging fishery resource in Northwest Mexico, with profits of more than US$30 million during the last few years. The fishery targets two species—Panopea glohosa in the Gulf of California and Panopea generosa on the Pacific coast of Baja California—but is managed indistinctively. Despite its growing importance, scientific research on the basic biology of the Mexican stocks has been inexistent until recently. A major gap in knowledge is the interspecific distinction in structural and functional biological attributes. Consequently, the aim of this article is to provide the biological basis of phenotypic (morphometric) and genetic distinction between P. globosa and P. generosa to assist in their management and conservation. We found that P. generosa from the Pacific coast of Baja California is significantly smaller than P. glohosa from the northern Gulf of California in shell length, width, and height (t-tests, P < 0.0001), and that shell width and height scale differently to length in both species. Multivariate analyses (multidimensional scaling) provided additional support (stress = 0.04) to the species and geographical distinction. Genetic data from the nuclear ribosomal DNA provided contrasting results between polymerase chain reaction— restriction fragment length polymorphisms and direct sequencing. Ribosomal DNA sequences revealed higher diversity (haplotype and nucleotide) in P. glohosa. Standing in sharp contrast with the low intraspecific divergence, was the very large genetic differentiation between species in excess of 20% corrected Kimura 2-parameter sequence divergence and accounting for 98% of the molecular variance of both species. This differentiation was found to be of consequence for novel methods of molecular species identification and for the interpretation of the phylogeography and evolution of Panopea in the North Pacific. The relevance of our findings goes to the heart of filling a major information gap pertaining to the distinction of both species. Scientific and lay stakeholders of these valuable resources need to ascertain and acknowledge this distinction to adopt sustainable management and exploitation practices.

Clam landings have dramatically decreased in eastern Maine since 1982. Earlier studies demonstrated that densities of 0-y-old individuals of Mya arenaria L. were lower in Washington County on the eastern Maine coast than in Cumberland County on the southern Maine coast. Reduced juvenile recruitment could result from reduced larval abundances, high postsettlement mortality, or a combination of these factors. Attempts to assist recovery of populations experiencing reduced recruitment would vary depending on which combination of factors inhibited recruitment. In this study we measured initial settlement, short-term (<4 wk) postsettlement densities, and longer term (several months) postsettlement densities of 0-y-old juvenile M. arenaria in both eastern and southern Maine. Although there were seasonal and spatial differences, densities of juvenile clams were significantly greater in southern Maine over eastern Maine at each of these life history stages (initial settlement, and early and later postsettlement), generally by one or more orders of magnitude. These results suggest the low number of M. arenaria recruits in eastern Maine is a consequence primarily of reduced densities of larvae in near-shore waters rather than processes affecting postsettlement survival differentially between southern and eastern Maine. Because of the very low abundance of competent clam larvae in eastern Maine, restoration of clam populations there will require intensive efforts, such as seeding mudflats with hatchery-reared juvenile clams and managing subsequent clam survival.

This work describes for the first time the larval and postlarval development of the razor clam Ensis siliqua, and aimed to standardize the techniques for hatchery production of this species' seed. The larvae were obtained from the induced spawning of a group of broodstocks under controlled laboratory conditions. Five larval batches per duplicate were cultured to produce postlarvae for nursery culture. Unfertilized eggs of E. siliqua were brown and spherical, and measured from 76.9–99.3 µm in diameter in the different larval batches. Fifteen-day-old larvae settled when a size of 361.5–414.8 µm was reached. Larval survival ranged between 20.0–52.7%, with an average of 39.4%. Mortality was high from settlement until 1 mo of cultivation. The razor clam seed reached lengths of 20.9 ± 2.7 mm and 39.0 ± 4.0 mm at 3 mo and 6 mo, respectively. Substrate experiments during nursery culture showed that better survival was achieved when spat cultures were performed without substratum.

Relationships among shell shape, shell growth rate, shell thickness, and nutritional condition in the Manila clam (Ruditapes philippinarum) collected from various areas in Japan were analyzed to establish an easy and quick way of determining stock condition in a harvest area. There were significant local differences in “shell sharpness indices” (i.e., shell height and width relative to shell length) and relative shell thickness (i.e., shell thickness relative to daily shell length growth), which became insignificant after eliminating effects of nutritional level as determined by a condition factor for each individual, indicating that nutritional condition modifies shell shape, and therefore shell shape may be used as an index of nutritional condition regardless of locality. Individuals with a better nutritional condition had smaller relative shell thickness, and tended to have more elongate and flatter shells. Shell width relative to shell length was considered to be a better index of nutritional condition than shell height relative to shell length. Shell morphology also reflected moisture content of the flesh, which is an important measure of palatability. Shell length growth rate did not have a significant correlation with absolute values of shell thickness; however, it had a negative correlation with relative shell thicknesses and sharpness indices, indicating that faster growing individuals have relatively thinner and flatter shells. Thus, shell shape and thickness have been shown to be an indicator of growth rate and nutritional condition in R. philippinarum. Clam fishers and farmers may use this method to determine stock condition for making decisions, such as harvest timing, culling of excess clams, and translocation of clams to better locations for enhanced production.

The Humboldt Current System is a highly productive ecosystem that is subject to the dynamics of the El Niño Southern Oscillation (ENSO). El Niño (EN, the warm phase of ENSO) causes vital changes in surface water temperature, oxygen levels, and salinity conditions, which arc reflected in various responses of coastal pelagic and benthic organisms. For very shallow habitats such as sandy beaches, temperature and salinity are considered the principal parameters changing during strong EN. However, the mechanisms by which these changes effect change on the structure of coastal populations remains largely unknown. The surf clam Donax ohesulus is dominant on large sandy beaches of the Humboldt Current System. Its biogeographical distribution is largely influenced by EN-induced environmental changes. Despite the species' key role in the beach ecosystem, the effects of modified abiotic conditions on the meroplanktonic larval stages and threshold temperatures involved have not yet been investigated. After EN episodes, meroplanktonic larval stages play a crucial role in the medium- and long-term stability of shallow-water species. Thus, this study makes a first attempt to describe the ontogeny of D. ohesulus and examines the effects on development of EN temperature conditions (ENTC) in comparison with normal temperature conditions (NTC). Results indicate that early life history follows a pattern previously described for other donacid bivalves. Development, growth, and mortality of larvae were assessed during a 3-wk in vitro experiment, indicating that larvae reared under ENTC grew and developed faster in comparison with those reared under NTC; mortality was slightly higher under ENTC. During a 2nd experiment, larvae were exposed for 48 h to a distinct range of different salinities (35, 25, 15, and 5 ± 1) at 2 different temperatures (NTC and ENTC). At both temperatures, larvae suffered no mortality at medium and low salinity (35, 25, and 15 ± 1) but showed 100% mortality at very low salinity (5 ± 1) after 16 h at NTC and 32 h at ENTC. Activity of larvae was highest at medium salinity (25 ± 1) and lowest at normal salinity (35 ± 1). The results of this study indicate that early larval stages of D. ohesulus can cope with temperature and salinity changes induced during EN. Only extremely low salinity (5 ± 1) such as that observed close to river mouths may cause high mortality rates in D. ohesulus offspring.

A video survey was conducted from August 10–14, 2009, to estimate sea scallop density, abundance, and size distribution on Platts Bank, Fippennies Ledge, Jeffreys Bank, Jeffreys Ledge, and Cashes Ledge in the central Gulf of Maine. Of the 298 km² surveyed, 134 km² (45%) had scallops present. Scallop density was estimated using only stations containing at least 1 scallop. High densities of small scallops occurred on all but Jeffreys Bank, where no scallops were observed. Densities ranged from 1.56 scallops/m² on Jeffreys Ledge to 4.70 scallops/m² on Platts Bank, equaling an estimated abundance of 470 million scallops. Less than 1% of scallops were larger than 100 mm. Explanations for the lack of large individuals may include sporadic recruitment, high natural mortality from predation, or environmental influences. If these scallops were to survive to harvestable size (approximately 102 mm), they could provide an important commercial resource worth approximately USS124 million.

In the Queensland, Australia, scallop fishery, the scallop catch is graded at sea using a specially designed grading machine called a “tumbler.” Experiments were conducted to determine the effect of repeated trawl capture, grading, and discarding on the survival of sublegal saucer scallops Amusium balloti. Scallops were caught within an area closed to commercial fishing and known to contain dense scallop beds. The trawled scallops were randomly divided into 2 groups, tumbled and control, and subjected to up to 4 tumbles and/or trawls before being caged for 2.5 days adjacent to the trawl grounds. Increased levels of both trawling and tumbling were found to decrease significantly the survival of sublegal scallops. Although 83% of scallops survived repeated intensive trawling (4 consecutive tows), survival fell to 64% when scallops were also graded using a commercial tumbler. Survival was high for both tumbled and control sublegal scallops after 1 trawl (97% and 98%, respectively).

The adequacy of empirical estimates of natural mortality (M) for the Patagonian scallop Zygochlamys patagonica (King & Broderip, 1832) is assessed against a direct estimate based on catch-at-ago data obtained from fishery research surveys and auxiliary information on fishing effort exerted by the commercial fleet. Based mostly on growth parameter information resulting from the von Bertalanffy equation, we obtained empirical estimates of M based on formulas commonly used in fisheries assessment and quantified variation in their estimates though parametric bootstrapping. The modal values of direct estimates of M was 0.38/y, with a 95% confidence interval in the range 0.09–0.77/y. Estimates obtained with empirical models were close to direct estimates. In particular, a model developed for invertebrate species (Arce's model) was very close both in point values and variability. Our results suggest that for this species, the empirical estimates, which are easily obtainable and broadly used in many fisheries, can be reliably used when no other estimates are available. However, we contend that in other cases their use should be limited to species when the performances of empirical methods were compared with direct evaluations of M.

The concentrations of selected trace metals were measured in commercially harvested New Zealand scallop species: Chlamys delicatula (queen scallop) from the Otago Coastal Shelf and Pecten novaezelandiae (dredge scallop) collected from 6 sites around the South Island, New Zealand (Titirangi Bay, Collingwood, Milford Sound, Breaksea Sound, Paterson Inlet, and the Chatham Islands). Bivalves were dissected into individual parts, the tissues lyophilized by freeze-drying, and then digested by heating with concentrated HNO3 and H2O2. The resulting solutions were analyzed by inductively coupled atomic emission spectrophotometry to determine the Cd, Cu, Zn, and Fe concentrations. For P. novaezelandiae, the trace metals in whole body tissues were site-specific with mean values ranging from 18–59 µg/g dry weight (dwt) for most sites and high Cd in scallops collected from the Chatham Islands (mean, 332 µg/g dwt). Cu concentrations were low, 6–11 µg/g; average concentrations of Zn ranged from 57–127 µg/g, and mean Fe values ranged from 197–2,324 µg/g. For C. delicatula the whole body tissue concentrations for Cd were 65 µg/g; for Cu, 6 µg/g; for Fe, 49 µg/g; and for Zn, 50 µg/g. The Cd concentrations were highest in digestive gland > gills > adductor muscle (striated and smooth) > gonad ∼ mantle. Particularly notable was the average Cd level of 3,985 ± 1,108 µg/ g dwt in the digestive gland and viscera of P. novaezelandiae collected from the Chatham Islands. The highest average Cu level was also measured in the digestive gland of both species. A higher average Fe level was measured in the gills of P. novaezelandiae (2,374 µg/g) compared with the gills of C. delicatula (133 µg/g). Trace metal concentrations in the scallop tissues did not correlate with any known environmental contaminants. Preliminary biochemical measurements using salt precipitation and dialysis indicated variable proportions of Cd bound to a protein with a molecular weight greater than 3,500 Da, depending on the scallop species and collection site. The Cd concentrations in P. novaezelandiae may be influenced by the Subtropical Convergence, with low Cd in areas more remote from this global oceanic current and highest values for samples from the Chatham Islands located within it. It was concluded that some scallop tissues may be useful as biomonitors for specific metals and that the characteristic metal signatures would be useful for fisheries management and compliance purposes in identifying scallops from various areas.

We propose the release of ready-to-set pediveliger larvae as a restoration strategy for bivalve shellfish. In this study, bay scallop (Argopecten irradians) larvae were released within two West Florida estuaries (Pine Island Sound and Boca Cicga Bay) currently closed to scallop harvest and where local scallop populations arc severely depleted relative to historical abundances. Populations in both estuaries appear to have limited larval supply and show no tendency toward natural recovery after decades of decline. Larvae were either released into enclosures or free released on four separate dates in each estuary. On a given day we used 1, 2, 3, or 4 enclosures per site; multiple release sites; and multiple releases within a year. Assessments were made via several methods, including larval recruitment to collectors, juvenile quadrat surveys, adult timed surveys, and adult transect surveys. In Pine Island Sound, following the initial larval releases in 2003, an isolated recovery in adult scallops was observed at the release site in 2004 followed by a massive resurgence in the local population in 2005. This population declined dramatically in 2006, however, and had completely collapsed by 2007. In Boca Ciega Bay, the series of larval releases did not immediately produce any detectable scallop patches, but the combined releases did immediately precede a population resurgence to levels greater than had been observed in the past three decades. Scallop abundance increased 10-fold at 10 stations in Boca Ciega Bay from 2007 to 2008. In both Pine Island Sound and Boca Ciega Bay, the increases in scallop populations were probably the result of successful survival, growth, and reproduction of the released larvae, followed by successful recruitment and growth of the subsequent generation.

Tools of histochemistry and digital image analysis were used to quantify changes in the coverage area of lipid droplets (lipid content) of oocytes of the penshell Atrina maura during oogenesis and to determine its relation to changes in water temperature and seston content. These data led to calculating a lipid index as a criterion of gamete development and quality. Gonads were collected monthly for 18 mo and prepared for histochcmical processing with Sudan Black B for identification of lipids. Finished slides were digitized for determining stages of oogenesis and variations in the size of oocytes. Two periods of greatest reproductive activity occurred during the study, with a lower peak from November through January (∼15°C; 26 mg/g) and a major peak from April through June (∼20°C; 25–40 mg/g). Oocyte area significantly varied during the stages of active development (516–2,743 µm²), ripeness (1,073–2,930 µm²), spawning (145–2,939 µm²), and atresia (331–2,001 µm²). Lipid incorporation into oocyte cytoplasm followed a clear seasonal pattern, peaking again in winter and spring. Temporal variations in the lipid index and its relation to oocyte diameter were irregular, but also peaked in winter and spring. Histochemistry and digital image analysis resulted in reliable methods for estimating oocyte development and quality in this species, and can certainly be applied in studies of reproduction of other bivalve, invertebrate, and vertebrate species.

In this study, our objective was to understand life history attributes of Mytella charruana, a newly introduced species to the southeastern Atlantic coast of the United States, that would enable its survival in the introduced range. We therefore addressed the following questions regarding the range of salinities in which M. charruana can survive: First, in what range of salinities is survival possible for M. charruana if slowly adjusted to test salinities? Second, in what range of salinities can these mussels survive when experiencing rapid changes of salinity? Third, in what range of salinities can M. charruana survive with temporary, rapid changes of salinity (6-h duration)? We tested survival in salinities ranging from freshwater to hypersaline conditions (0–45 ppt) and determined whether mussel size affected experimental results. All experiments examined survivorship of mussels by increasing or decreasing the salinity from the field value under laboratory conditions. Mortality in each tank was recorded daily for 43 days for the gradual adjustment trials, and 12 days for permanent and 6-h shock trials. Large M. charruana (20–54 mm) survived best in salinities from 2–23 ppt, with 100% mortality at 0 ppt and 45 ppt with gradual adjustment. Small M. charruana (3–19 mm) survived in a wider range of salinities (2–40 ppt) with gradual adjustment to new salinities. However, survival of both large and small mussels was significantly lower in permanent shock trials at salinity extremes. Six-hour shock trials had no effect on survival at any of the test salinities (0–45 ppt) for both large and small M. charruana. Overall, the data indicate that these mussels could invade a wide variety of saline environments with significant freshwater or saltwater input.

The reproductive biology of a population of the edible muricid Trophon geversianus inhabiting an intertidal rocky shore in Golfo Nuevo (Chubut, Argentina) was studied regarding the seasonality of oviposition and oviposition induction under laboratory conditions. Sex ratio in the population differed from 1:1 (female biased). The mean shell length was 22 mm for males and 24 mm for females, although the females presented significantly larger maximum sizes. No external sexual dimorphism was evident, whereas the female snails differed internally by the presence of the albumin and capsule gland and by gonad color. Although the population under study inhabits an area with marine traffic and a concentration of 1.9 ng Sn/g, it did not present signs of imposex, in contrast with other sympatric species. T. geversianus presented a marked reproductive seasonality during the study period. Oviposition started in May and concluded in November, when hatching of crawling embryos was registered up to January. This seasonality coincided with changes in water surface temperature, ambient temperature, and photoperiod. Reproductive activities were registered when the environmental stress was minimum. In the aquarium, each female laid an average of 12 egg capsules (range, 6–26) per oviposition event, and needed a total of 25 h (range, 12–57 h) to complete attachment of a single egg capsule. Data presented here could be useful for culture of the species.

A growing body of research on calcifying marine invertebrates suggests that ocean acidification will have deleterious effects on development and various physiological processes in these organisms. In laboratory experiments designed to mimic seawater chemistry in future oceans, we examined the effect of pH reduction, driven by the carbon dioxide (CO₂) acidification of seawater, on larvae of the red abalone, Haliotis rufescens. Following development under CO₂-acidified conditions, we measured 2 indicators of physiological response to low pH in 4 stages of larval development: (1) tolerance of acute thermal challenges and (2) quantitative real-time polymerase chain reaction-determined expression of 2 genes involved in shell formation (engrailed and ap24). The results showed that low pH (pH 7.87 vs. pH 8.05 for control treatments) had a significant effect and decreased larval thermal tolerance for some developmental stages (pretorsion and late veliger), but not for others (posttorsion and premetamorphic veligers). In contrast to the thermal tolerance data, decreased pH did not affect the expression pattern of the 2 shell formation genes in any of the abalone larval stages. The results indicate larval stages were differentially sensitive to low pH conditions and this variability may play into the resilience of individual species to withstand environmental change in the longer term.

Red abalone, Haliotis rufescens (Swainson), were tagged and recovered for growth and movement studies in northern California. Tagging and recoveries were conducted at north Point Cabrillo and south Point Cabrillo from 1971 through 1976 (no tagging or recoveries at south Point Cabrillo in 1973 and 1974), at Van Damme State Park from 1973 through 1975, and at Stornetta Ranch and Pedotti Ranch in 1975 and 1976. Von Bertalanffy growth curves were fit by area and year. Growth was found to vary by year and by study site. Fitted L_inf range was from 184–232 mm, and age at legal sport size ranged from 8–20 y. The fasted growth rates were observed at north Point Cabrillo.

In Baja California, Mexico, pink abalone (Haliotis corrugala) banks have been found to be heavily infested by endolithic (boring) organisms, which damage the shell, reduce individual growth, and, in many cases, prevent the abalone from reaching the minimum legal size of capture (140 mm). Thus, the accumulation of endolithic borings has a negative impact on the fishery. Infested shells have a different appearance from healthy shells, decreasing their ornamental value. As the size of the muscle scar of pink abalone increases with age, we assume that endolithic infestation affects individual growth and produces adults of a smaller size than normal. The correlation among the degree of muscle scar development, shell length, and percent coverage by endolithic borings was determined. We identified five stages of muscle scar development and found a significant correlation between scar stages and percentage of endolithic boring coverage and shell length. This correlation may be an indication of the profound effects that drilling organisms have on abalone growth rates. Determining the proportion of the population unable to reach the minimum legal size of capture resulting from endolithic borings will be useful in species management. It would also be useful to assess whether global warming favors greater damage to abalone shells by boring organisms and to estimate the possible consequences for the fishery.

This study evaluated the effect of different diets on the feeding, growth, and proximal composition of Octopus mimus. Animals were kept under controlled conditions in the laboratory for 3 mo and fed ad libitum with monodiets of the molluscs Eurhomalea lenticularis and Tagelus dombeii, and the crustacean Mursia gaudichaudi. The specific feeding rates (SFRs) of O. mimus were significantly greater in individuals fed with M. gaudichaudi (1.70% body weight per day), whereas the greatest specific growth rates (SGRs) were obtained in individuals fed with T. dombeii (0.26% body weight per day) and E. lenticularis (0.15% body weight per day). The weight increase of O. mimus was affected by the treatments, and the greatest increase throughout the duration of the experiment was observed in octopuses fed with E. lenticularis (0.12% per individual). Although the gender of the animals did not directly influence SFR and SGR, males had a greater weight increase, probably because some females laid eggs during the experimental period. The quantity of macronutrients in the different treatments was not clearly reflected in the growth parameters of O. mimus, because a high protein content (i.e., M. gaudichaudi) did not necessarily give a greater growth rate or a greater weight increase. It is necessary to consider the quality of each of the dietary components, because the changes observed in the tissue composition of O. mimus are related to the feeding levels and variability in growth.

To provide morphological bases for functional studies, the development of the photoreceptor cells in the retina of the cuttlefish Sepia esculenta from newly hatched juveniles to the adults was examined by light and electron microscopy. Four layers were distinguished in the retina: the rhabdomeric layer, subrhabdomeric layer, inner segmental layer, and plexiform layer. With the development of the retina, the structure of the plexiform layer becomes stronger. Morphometric data on the rhabdomeric microvilli from the newly hatched to the adult retinas arc presented. The thickness of the rhabdomeric layer and the total surface area of the rhabdomeric microvilli present beneath a unit surface area of the retina show an exponential increase with developmental days; the diameter of the lens shows a linear increase with days. The results of our research show that the visual acuity and sensitivity of S. esculenta continuously increased with development.

Claw morphology and prey consumption rates of two estuarine crab species were compared: the introduced European green crab, Carcinus maenas, and the native Dungeness crab, Cancer magister. For crabs of similar weight, both the crusher and cutter claws of C. maenas were larger and exhibited higher mechanical advantage values of the claw lever system than C. magister. The mechanical advantages of C. maenas crusher and cutter claws are 0.37 and 0.30 respectively versus 0.25 for the claws of C. magister. To evaluate the feeding rates of similar-size crabs of each species on prey varying in shell thickness, we conducted laboratory feeding trials. Each crab was offered thin-shelled mussels (Mytilus trossulus, 30–40 mm) or thicker shelled native oysters (Ostrea lurida, 40–50 mm), and the number of consumed prey items was recorded. When offered mussels, subadult C. magister ate significantly more prey per day (7.2 prey/day) than adult C. maenas (5.4 prey/day). However, when crabs were offered harder shelled native oysters, C. maenas, with their more robust claws, were more capable of crushing them than C. magister, with their more delicate claws. Although C. maenas is competitively dominant to similar-size juvenile C. magister, the per capita feeding rate and predatory impacts of these 2 species depends on prey type.

Knowledge of the brown crab's (Cancer pagurus Linnaeus 1758) tolerance to emersion related to air temperatures and duration is scarce. In the current study, the condition of the brown crab was examined during emersion in laboratory experiments simulating dry storage and transport at air temperatures between 2–20°C. Samples of hemolymph were taken at different intervals simultaneously as the crab was classified using a vitality index based on behavior and responses. Individual variances in hemolymph pH, total ammonia (TA), lactate, and glucose were large; but, in general, pH decreased and TA and lactate increased during emersion, most at the highest temperatures. When hemolymph samples were grouped according to vitality index, deterioration was found for pH, TA, and lactate as the vitality dropped, whereas no trend was found for glucose. Vitality of crabs was reduced during emersion, with the greatest reduction being crabs exposed to high temperatures. To secure strong and healthy crabs, exposure at 20°C and 15°C should not exceed 5 h and 10h, respectively. For crabs exposed at 10°C and 5°C, emersion for 36 h and 72 h, respectively, did not seem to have negative consequences for the animals. A general increase in vitality occurred when crabs were reimmersed. Delayed mortality occurred for weak and moribund crabs, highest during the first 24 h of reimmersion, and continuing over the next day, suggesting that such crabs should not be transported in the live value chain.

Little information exists on the effects of lobsters that have been v-notched. To help analyze the results of the North Cape restoration program, which released 1.248 million v-notched females, a controlled v-notching laboratory experiment was conducted to determine whether mortality, shell disease, and the rate of notch loss differed between groups of notched and unnotched lobsters. Results from a 2-y tank study indicate that v-notching did not have a significant negative impact on survival or disease susceptibility. After the first molt since being v-notched, 97% of lobsters were harvestable (according to southern New England lobster management definitions at the time of the restoration effort); 59% of lobsters had v-notches less than 6.35 mm (1/4 in); and 84% of the lobsters exhibited visual setal hairs in the notch. Digital images of v-notches were analyzed to examine repair rate of v-notches per molt. Notches were examined in relation to 2 v-notch depths that have been considered by southern New England lobster fishery managers: 6.35 mm (1/4 in) and 3.18 mm (1/8 in). Of lobsters that molted once, the mean and median v-notch depth was less than 6.35 mm (1/4 in). All of them still had v-notches greater than 3.18 mm (1/8 in). Of the lobsters that molted twice, 100% had v-notches less than 6.35 mm (1/4 in), whereas only the 25^th percentile had v-notches less than 3.18 mm (1/8 in).

The Asian shore crab Hemigrapsus sanguineus is the principal invasive crab in many intcrtidal habitats on the east coast of the United States between Cape Hatteras and Maine. Previous work has described general aspects of mating for the genus Hemigrapsus; however, there has been no explicit study of mating behavior in H. sanguineus, and there has been little consideration of how this behavior might influence the success of H. sanguineus as a bio-invader. The objective of our investigation was to document the mating behavior of H. sanguineus under laboratory conditions and compare this pattern of behavior with that of other species of Hemigrapsus. Our observations show that mating in H. sanguineus was always initiated by the male and that both the male and female had calcified exoskeletons at the time of copulation. Small males were sometimes successful in securing mates, even in the presence of larger males. However, the male was larger than the female in 67% of the observed copulations. Duration of copulation in H. sanguineus was relatively long compared with other species of Hemigrapsus, and averaged ∼30 min. H. sanguineus differs from other species of Hemigrapsus in terms of positioning during mating. H. sanguineus typically used a vertical position relative to the substratum, with both crabs standing and facing each other, ventral surface to ventral surface. This position facilitated some degree of mobility in the copulating pair. Females were receptive to copulation within a few days of larval release, and were also capable of storing sperm and producing at least 2 broods from a single copulation. Mean incubation time of newly extruded eggs was around 16 days, and females often produced a second brood within a few days of larval release. Thus, an individual H. sanguineus could produce 2 broods within 40 days and presumably additional broods with subsequent copulation. This pattern of reproduction provides enhanced fecundity relative to co-occurring native species of crabs.

Data sets on the natural dynamics of beach ecosystems arc scarce and fragmentary. Such data arc necessary for implementing more efficient monitoring programs that quantify the dynamics of key ecological attributes on sandy beaches. This article contributes to the bioecology of ghost crabs from subtropical Praia Brava, Itajaí, Santa Catarina. Ocypode quadrata occurs in sandy beaches along the tropical-temperate western Atlantic, from Rhode Island (US) to Rio Grande do Sul (Brazil). During 14 consecutive months, a total of 649 specimens were captured: 255 females (39%), 241 males (37%), and 153 juveniles of undetermined sex (24%). Highest densities were recorded in June and November, with a total of 1,900 burrows distributed along the beach (56.95%) and dunes (43.05%). Sixteen natural diet items were identified for this crab, with a larger participation of Apis spp. (38.97% of relative volume). In the local food web, the ground-burrowing owl Speotyto cunicularia was the main crab predator. This article indicates that the ghost crab represented the second most consumed food item of the owl (29.24%), only surpassed by rodent remains, which occupied 50.32% of its stomach volume. The natural diet and the main predator of the ghost crab had not been observed along the coast of Brazil. Knowledge of natural diet is fundamental for understanding distribution patterns, migrations, and molting cycles. Further information on population structure (abundance peaks in spring and summer; a negative allometric growth pattern), spatial distribution (predominance of females in August and May, and of males in July; size of specimens increases toward higher intertidal levels), sexual proportion throughout the year (reproduction is continuous), form and disposition of burrows (reduced abundance toward the higher tidal levels), and relative importance for the diet of the main predator (both predator and prey arc nocturnal) may be used as instruments for evaluating the occupational impact and for conserving natural dune and beach environments along sandy beach ecosystems. In conclusion, ghost crabs provide an alternative source of food for the ground-burrowing owl, a predator that may represent an important population controlling factor, other than the human-induced impacts on sandy beaches. Although burrowing crabs are the most conspicuous and ecologically important invertebrates of intertidal beaches along tropical and temperate regions, factors that regulate abundance arc still controversial, whereas the biotic community interactions in sandy beaches remain barely known.

Given that sea urchins eggs and larvae have been proposed as putative prey in marine larviculture, broodstock rearing conditions must be optimized for this purpose. In the current study, adult sea urchins Paracentrotus lividus were reared in 400-L tanks for 5 mo under 4 stocking densities (100, 200, 300, and 400 sea urchins/m² of tank base area) to determine their effect on spawning performance and fertilization rate, and on broodstock month relative growth. For all stocking densities, more than 60% of sea urchins induced to spawn released a large number of gametes (more than 200 × 10⁶ spermatozoa or more than 500 × 10³ eggs per spawning). The percentage of males with large emissions was higher at a density of 300 sea urchins/m². Irrespective of broodstock stocking density, fertilization rate was always higher than 90%. Lower relative growth was recorded with densities of 300 sea urchins/m² and 400 sea urchins/m² compared with 100 sea urchins/m². We conclude that under the rearing conditions adopted in this study, captive P. lividus broodstock can be at least reared up to 400 sea urchins/m² without impairing reproductive performance.

The sea urchins Paracentrotus lividus and Arbacia lixula were collected monthly for 1 y in the southern coast of Spain, and their gonad fatty acids were analyzed to evaluate seasonal variations. The gonad fatty acids of A. lixula significantly differed from those of P. lividus, probably because of substantial differences in diet. In both sea urchins, seasonal changes were mainly characterized by the marked decrease of the major polyunsaturated fatty acid 20:5n-3 in summer and early autumn, and the opposite increase of 20:1n-11, 18:1n-9 and the principal nonmethylene-interrupted diene 20:2Δ5,11. Arachidonic acid showed the lowest levels in winter, increasing in April through May, and remaining at relatively high levels until the end of the year. Saturated fatty acids were less affected by seasonality, although they tended to decrease with advancing maturity of the gonad and to increase after spawning. These seasonal changes are discussed in relation to the annual reproductive cycle and to fluctuations in seawater temperature.

The triangle sail mussel (Hyriopsis cumingii Lea) is the most important mussel species exploited for commercial freshwater pearl production in China. However, little is known about the genes that arc involved in pearl formation. A complementary DNA library from mantle tissue of Hyriopsis cumingii was constructed to identify the genes required for pearl formation. A total of 5,019 expressed sequence tags (ESTs) were sequenced, which resulted in the identification of 620 contigs and 1,151 singletons. BLAST analysis showed that nearly half (44.7%) of these unigenes were homologous to the known genes and 55.3% were genes with unknown functions. Based on the sequence similarities, 29 genes were putatively involved in pearl formation. These EST data provide the basis for future studies of the molecular mechanisms underlying pearl formation.