The need for age determination for the proper management of octopus fisheries has directed research attention to the few hard structures in the octopod's soft body, beak, statoliths, and the vestigial shell. So far, none of these structures have proved reliable or practical for the purpose. Eye weight, pigment, and nitrogen content have been used successfully in age determination of vertebrates. Given the structural similarity of lenses between octopus and vertebrate, we explore the possibility of using octopus eye lens weight, diameter, and structural marks as age indicators. The lenses of 228 octopi were obtained from the commercial catch from Ancud and Quellén, in Chiloe, Chile. They were measured, weighed, and prepared for histological analysis of the concentric lines structure. The prehatching nucleus was identified, and the total number of lines counted. The lines start to form in the prehatching larvae. Lens diameter and weight showed a much smaller variation than body length or weight, with an apparent correspondence of size or weight classes of body measurements to a lens diameter or weight.

The current study was carried out to investigate the influence of water temperature on growth and activity of the digestive enzymes pepsin, trypsin, lipase, and amylase in common Chinese cuttlefish (Sepiella maindroni de Rochebrune). Triplicate groups of S. maindroni (weight ± SD, 4.08 ± 0.26 g; mantle length, 31.37 ± 1.04 mm) were reared at different water temperatures (16°C, 20°C, 24°C, 28°C, and 32°C). S. maindroni instantaneous growth rate (IGR), feeding rate (FR), food conversion (FC), and mantle length increase (ML) were significantly affected by water temperatures. Regression relationships between water temperature and IGR = -0.026T² 1.359T - 12.63 (n = 15, R² = 0.995); FR = -0.064T² 3.465T - 25.69 (n = 15, R² = 0.971), FC = -0.069T² 3.55T - 25.01 (n = 15, R² = 0.983); and ML = -0.238T² 12.27T - 123.9 (n = 15, R² = 0.992). The optimum temperatures for IGR, FR, FC, and ML were 26.13°C, 27.07°C, 25.72°C, and 25.78°C, respectively. Survival was greatest at 24°C and 28°C (>95%), and was significantly higher than other temperatures. Digestive enzyme activities were highest at 24°C or 28°C, and were significantly higher than at 16°C. In conclusion, the optimum temperature for growth of S. maindroni is 25–27°C based on IGR, FR, FC, and digestive enzyme activities at different temperatures.

Regardless of the high economic value and large geographical distribution of oysters, the current knowledge of oyster taxonomic relationships and systematics is still limited, particularly for flat oysters. In this study, the molecular cytogenetic characterization of mitotic chromosomes of the Provence flat oyster or dwarf oyster, Ostrea stentina, was performed through Giemsa staining, chromosome measurements, in situ restriction endonuclease banding, C-banding, fluorescence in situ hybridization with major ribosomal RNA genes (ITS1), and telomeric sequence (TTAGGG)_n. The karyotype (2n = 20) consisted of 6 metacentric (1, 3, 4, 6, 8, and 10) and 4 submetacentric (2, 5, 7, and 9) chromosome pairs. Chromosome treatment with HaeIII produced specific banding patterns for all chromosomal pairs, confirming the efficiency of this restriction enzyme for chromosome banding in oysters. Results for C-banding revealed the presence of heterochromatin in the telomeric regions of the short arms: on a large metacentric chromosomal pair and on a submetacentric chromosomal pair. In situ hybridization with telomeric sequence revealed bright hybridization signals in the telomeres of all chromosomes. The location of the major ribosomal rDNA (ITS1) displayed the presence of 2 signals: in the telomeric regions of the short arms of the largest metacentric chromosome and in a submetacentric chromosome. The cytogenetic data obtained was used to perform a comparative karyological analysis within the subfamily Ostreinae. It is also important to highlight that this type of work can provide new insights on major genomic changes at the chromosome level in the flat oysters.

The Solent, United Kingdom, contains a commercially fished, rapidly declining wild population of the protandric sequential hermaphrodite European flat oyster Ostrea edulis. The population has suffered repeated recruitment failures since 2007, suggesting a disturbance in reproductive processes. As part of an ongoing investigation into the causes of this population collapse, the reproductive status of 362 individuals sampled in 2009 and 2010 was determined by histological and visual examination. In both years, significantly more male-phase oysters than females were found (chi-square, P < 0.001). There was also a significant difference in the size distribution of male- and female-phase oysters (Mann Whitney U-test, P = 0.032), where the median of female-phase animals was 6.5 mm larger than that of males. Monthly analysis of gonad development between June 2008 and September 2009 showed that, despite the skewed sex ratio, the reproductive development in each gender was as expected, and animals were developing and spawning sperm and eggs, peaking toward the end of June.

Juvenile winged pearl oysters, Pteria penguin, were cultured for 6 mo in three commonly used culture units (panel nets, plastic mesh trays, and pyramidal pearl nets) at two dissimilar sites—Pioneer Bay (a coral reef environment in which P. penguin are naturally present) and Cape Ferguson (a coastal semiestuarine area with high levels of silt deposition)—to determine the effects of site and culture method on growth, survival, and fouling. Mean growth increases were recorded for the dorsoventral measurement (DVM), anteroposterior measurement (APM), shell thickness, and whole weight. At Pioneer Bay, five replicates for each of the three culture unit types were suspended at 3 m and at 6 m, and mean initial DVM was 28.0 ± 0.6 mm (n = 190). At Cape Ferguson, there were five replicates for each culture unit at 3 m only, and mean initial DVM was 28.0 ± 0.6 mm (n = 86). Mean growth increase at the end of the experiment for oysters at Pioneer Bay and Cape Ferguson, respectively, were 26.6 ± 1.0 mm and 32.6 ± 2.4 mm DVM, 29.6 ± 1.2 mm and 34.0 ± 2.9 mm APM, 6.7 ± 0.3 mm and 9.7 ± 0.5 mm shell thickness, and 16.5 ± 0.7 g and 23.0 ± 2.1 g whole weight. For all growth parameters, mean increase was significantly higher under high-turbidity conditions at Cape Ferguson (P < 0.05). Culture unit also affected growth, with oysters held in mesh trays showing significantly more growth at both sites (P < 0.05). Mean survival of oysters at Cape Ferguson (96.5%) was significantly higher than at Pioneer Bay (79.4%). Depth had no significant effect on growth, survival, or fouling. The results indicate that site selection and culture unit are important parameters for optimizing growth and survival during nursery phase culture of P. penguin.

The pearl industry in French Polynesia is based on exploitation of natural stocks of the blacklip pearl oyster (Pinctada margaritifera). It generates an annual turnover of €90 million. Improvements in pearl quality need genetic studies to improve the populations. This pearl oyster is a protandric species, in which the sex ratio normally is biased toward males. There is an increasing interest in gender control to find the mechanisms to augment female proportions for management purposes. This review summarizes information on exogenous and endogenous factors regulating gender in this and other bivalves, and concludes that P. margaritifera is a protandric hermaphrodite, developing as a male during the first 2 y, and without evidence of an effect from abiotic and biotic factors on gender during this phase. Later, pearl oysters progressively change to females, reaching a sex ratio close to 1:1 in specimens older than 8 y. At this stage, gender is apparently influenced by environmental parameters, but particularly by stress. Future research should seek to determine accurately the effect of temperature and food on sex ratios. Studies should be performed to characterize genes responsible for expression of gender. The use of hormones is a path that might be explored to influence the gender of pearl oysters.

A complete diallel cross between two geographically distant pearl oyster (Pinctada martensii) populations, an Indian cultured population (I), and a Chinese cultured population (C) was carried out, and the resulting progenies (II, CC, IC, and CI) were cultured and studied for more than 700 days. Shell height and total weight were measured monthly, and shell thickness was measured in the middle and at the end of the experiment. The results reveal that II grew fastest whereas CC grew the slowest. The growth rate of reciprocal crosses CI and IC exhibited no statistically significant difference, with both appearing to be intermediate between the parental species, but superior to the mid parent values. The morphological traits of parents were inherited differently by the two reciprocal crosses. The traits of large size and relative thinness of shell from the Indian population were largely transmitted to CI, whereas relative small size and increased shell thickness of the Chinese population were mostly inherited by IC. The two parental stocks, the Indian population and the Chinese population, were unsuitable for commercial production because of a relatively thin shell and slow growth, respectively, but the reciprocal crosses combined desirable traits of the parents and exhibited considerable potential for commercial production and pearl culture.

Dmrt genes encode a large family of transcription factors involved in sexual development. These genes have been well studied in various species. However, their expression profiles and functions in bivalves are still unclear. As an important member of the Dmrt gene family, Dmrt2 is controversial because of its role in sex determination and differentiation. In the current study, pmDmrt2 (Dmrt2 from Pinctada martensii) was screened from the male gonads cDNA library. The full length of pmDmrt2 cDNA is 966 bp, with an open reading frame of 836 bp (58–893), which encodes a peptide of 278 amino acids. This gene shows 36.2%, 35.9%, 34%, 33%, 32.7%, and 21.9% identity to Dmrt2 of zebrafish, clawed frog, chicken, house mouse, human, and sea urchin, respectively. Despite the low sequence identity, the highly conserved double sex and mab-3 domain was predicted to exist in pmDmrt2. Results from the reverse transcription—polymerase chain reaction indicate that pmDmrt2 is transcribed mainly in the male gonad, slightly in the gill, but not in other tissues. The gene is first transcribed in the early male gonads, and peaks in the mature male gonads. During transition from male to female, pmDmrt2 is gradually downregulated until it eventually becomes nonexistent in the mature female gonads. In situ hybridization analysis reveals that pmDmrt2 mRNA is localized specifically in the spermatogonia, spermatocytes, and spermatids in the male gonads. Our investigation indicates that pmDmrt2 might play a functional role during spermatogenic cell differentiation from spermatocytes and spermatids into sperm. Bivalves and mammals use at least several similar mechanisms to control sexual development.

In the Solomon Islands, there have been three periods of commercial exploitation of the silver (gold)-lip pearl oyster Pinctada maxima. The most recent ended in 1993, when export of all species of pearl oysters was banned to allow stocks to recover from overexploitation. In 2007, a nationwide survey was undertaken to determine the status of the population. Communities adjacent to former fishing grounds were interviewed about past and current fishing practices, and the abundance, size composition, and quality of P. maxima shells were assessed by drift diving. In total, 117 P. maxima were recorded, from 33 of 96 transects. When present, the mean density of oysters varied from less than 0.10–1.23 oysters/400-m² transect. Size structure was biased toward large individuals, with mean and median shell size for all oysters taken being 219 mm. There appears to have been little or no recovery of P. maxima stocks since their export was banned. The existence of small populations of large individuals implies persistent failure of reproduction, spat settlement, and/or recruitment during the past decade. Exploitation may have reduced the P. maxima populations to such an extent that their fertilization success has become susceptible to Allee effects. Recent poaching of shell reported by local villagers may have compounded slow or sporadic recruitment. If the stocks do eventually recover, management strategies that protect the recovered population will need to be implemented to prevent a repeat of the overfishing seen in previous harvest cycles.

Two species of mud crabs—the flat mud crab (Eurypanopeus depressus) and the white-fingered mud crab (Rhithropanopeus harrisii)—commonly inhabit subtidal oyster reefs in the Maryland portion of the Chesapeake Bay. Predation of juvenile Crassostrea virginica (spat) by mud crabs could be one of the major contributors to early juvenile spat mortality, hindering natural recruitment and restoration efforts in the Chesapeake Bay. The purpose of this study was to measure the number and size of spat preyed on by E. depressus and R. harrisii. Spat settled on oyster valves were placed in an experimental tank with one crab over a 96-h study period. Every 24 h, the number and size of spat scars were measured. E. depressus consumed nearly 40% of the spat offered whereas R. harrisii consumed less than 10%. E. depressus also consumed significantly more spat than R. harrisii within each spat size class (for all spat size classes, P < 0.0001). Although available spat sizes ranged from 1–29 mm, approximately 75% of spat preyed on by both species were less than 8 mm in size. Our data suggest E. depressus may have the potential to reduce spat survival significantly, with R. harrisii playing a minor role. Considering restoration strategies that reduce spat predation by mud crabs may increase the success of natural recruitment and restoring oyster populations.

Marine acidification will be an important environmental problem in the near future as a result of persistent emissions of CO₂ and dissolution into seawater. In this study, we found that calcification and respiration of the Zhikong scallop (Chlamys farreri) are likely to be severely affected by increasing acidification. Calcification and respiration significantly declined as pH decreased. The calcification rate decreased by 33% when the pH of water was 7.9 compared with a pH of 8.1, and decreased close to 0 when the pH was reduced to 7.3. CO₂ and O₂ respiratory rates were reduced by 14% and 11%, respectively, when pH decreased from 7.9 to 7.3. Increasing acidification also led to changes in the metabolic pathways of C. farreri. Under acidic conditions, proteins may replace carbohydrates as the metabolic substrate. The survival of C. farreri is likely to be severely threatened in the next few centuries.

Phenoloxidase (PO) is one of the most important factors in the bivalve immune defense system. In the current study, the PO of the scallop Argopecten irradians was purified from hemocytes using linear-gradient native PAGE combined with catechol and Coomassie brilliant blue staining. The results show that purified PO had a molecular mass of 555 kDa in native PAGE and 55 kDa in denatured PAGE. The analysis of the kinetics indicated that the K_m values of PO for L-DOPA, catechol, and hydroquinone were 0.51 mM/L, 0.23 mM/L, and 0.87 mM/L, respectively, which suggests that the PO was a type of p-diphenoloxidase. The PO had optimal activities at 40°C and a pH of 8.0, and its activity was greatly enhanced by Ca² and Mg² , and inhibited by Fe² and Mn² . In addition, the PO activity was inhibited by sodium sulfite, ascorbic acid, sodium diethyldithiocarbamate (DETC), cysteine, citric acid, and ethylenediamine tetraacetic acid disodium (EDTA). However, no inhibition was found when thiourea and sodium azide were used. Based on the inhibition that was induced by EDTA and DETC, we conclude that the PO of A. irradians was a copper-containing metalloenzyme.

Larvae of the northern Chilean scallop Argopecten purpuratus (Lamarck, 1819) can be produced in hatcheries in closed aquaculture systems (CAS), and then early juveniles transferred to the sea for further grow-out. A new scallop mass production method from larvae to early juveniles that applies recirculation aquaculture system (RAS) technology has been developed at Universidad Catolica del Norte. RASs might lose water by evaporation, which increases salinity. Water temperature will increase as well if it is not controlled. An experiment was performed to determine the effect of varying salinity and temperature over water quality parameters and scallop physiological processes. Feeding behavior of A. purpuratus was determined under CAS with daily water exchange for hatchery-produced juvenile scallops (mean shell height, 26.5 mm; SD, 1.9) reared at salinities of 34, 38, and 42 g/L, and temperatures at 16°C and 22°C. Weight-specific filtration rates (WFRs) were analyzed at day 12 and again at day 55. Scallops were fed Isochrysis galbana and Chaetoceros calcitrans (ratio, 1:1). Results shows that WFRs analyzed for a 24 h period had a tendency to be lower at 0 h than at 24 h, for both temperatures; WFRs were higher at 22°C than at 16°C. A significant positive regression was also found between final WFR and total ammonia nitrogen (both NH₃-N and NH₄ -N) levels. Results presented here should be interpreted with caution outside the shell height range of 26.5 ± 1.9 mm. These results are applicable to the management of A. purpuratus under controlled conditions, such as a RAS.

Sphaerids have adopted a variety of life strategies that have allowed them to show a cosmopolitan distribution. Among these strategies, those related to reproduction, such as sexuality (hermaphroditism), offspring incubation, fertility, number of generations per year, times an individual reproduces during its lifespan, among others, have been decisive with regard to its permanence in time and space, and to colonize and maintain populations in permanent or temporary freshwater bodies. The aim of the current study is to compare reproductive traits of 2 Musculium argentinum populations inhabiting different environments (stream and lake) to determine the potential influence of the environment on reproduction of these populations. During 1 y (October 2006 to 2007) monthly samples were taken at 2 study sites: Lautaro stream (38°32′ S, 72°27′ W) and La Poza, Villarrica Lake (39°16′27″ S, 71°58′54″ W). Sixty specimens were collected monthly from each population. Valve length of each specimen of the sample was registered to determine the size structure of each population. Fifty animals of known valve length were dissected to determine presence and number of brooding sacs in the inner hemibranches, number of embryos in each sac, and number of newly hatched clams. Ten specimens were processed for optical microscopy with routine histological techniques to characterize the gonad activity pattern. Results indicate that M. argentinum is hermaphroditic in both populations, with gonadal activity throughout the year, iteroparous, and with embryos in brooding sacs and newly hatched clams present year-round. These results indicate that differences in the environment did not produce major changes in reproductive strategies in both M. argentinum populations studied.

In this study, the influence of food availability on the gonadal development of the smooth clam Callista chione was analyzed for the first time. Callista chione adults were maintained for 60 days under controlled conditions with two different diet rations: a scarce diet (3% of dry weight of algae by meat dry weight per day) and a high diet (6%). The condition index, gonadal stage, and oocyte size were measured throughout the experiment. Maturation of gonad was achieved in both groups. Nevertheless, the condition index and oocyte diameter were significantly less in the scarce-diet group. These low values seem to be related to a loss in reserve tissue, not to the release of gametes. Thus, in food-limited conditions, the animals use the energy to mature instead of grow. Comparisons with animals from the field were made during all the study periods, and differences were found. In fact, these individuals were primarily in the postspawning stage, and the oocyte size was considerably smaller, coinciding with low chlorophyll a levels.

Geoduck clams (Panopea generosa Gould 1850) are large, deep-burrowing bivalves distributed from southeast Alaska to Baja California. This species supports a lucrative fishery in the states of Washington and Alaska, as well as in British Columbia, Canada, and geoduck aquaculture currently supplies approximately 30% of the market. To manage this species effectively, it is important to elucidate the population age structure. Geoduck ages are currently estimated by counting valve growth rings. We used bomb radiocarbon (¹⁴C) to validate geoduck age estimates derived from counts of growth bands in thin-sectioned valve inner hinge plates. Seven specimens with presumed birth years before, during, and after the bomb testing period (1957 to 1967) were sampled from the first 3–5 y of growth, and subsequently assayed for ¹⁴C using accelerator mass spectrometry. The ¹⁴C values from each of our specimens compared with reference ¹⁴C chronologies for the northeast Pacific were in accord at estimated birth years. The temporal concordance validates current age estimation methods, and provides a first record of marine bomb radiocarbon in Puget Sound.

Macrobenthic community changes were assessed in relation to different levels of fishing intensity following a before—after, control—impact experimental design with a control, a moderately impacted area, and a highly impacted area. Samples were collected before, immediately after, and 1, 2, 3, 7, 14, 30, and 120 days after fishing. Communities in fished areas showed short-term significant effects on abundance, number of species, biomass, and diversity 1–3 days after fishing, with fished areas presenting lower mean values than the control. The opposite pattern was found for the carnivore-to-suspension feeding ratio. The main taxonomic groups showed different responses to fishing. Only gastropod abundance and the abundance of the polychaete families Pectinariidae and Sabellidae showed persistent negative effects of fishing. The effects on these polychaete families confirms the sensitivity of sedentary and suspension feeders to fishing. Some variables presented slightly higher negative effects with fishing intensity, but differences were subtle. Between 30 days and 120 days, a period of storms occurred, resulting in a general decrease of biological variables in all areas. This decrease was usually more pronounced than after fishing. The general short-term effects of fishing observed may reflect the resilience of communities that are able to cope with frequent natural disturbance events.

The taxonomic status of the Chilean blue mussel Mytilus chilensis has been controversial for decades because of its phenotypic and genetic proximity to other species of the genus Mytilus from both hemispheres. This study reports the development of nine polymorphic microsatellite markers from the M. chilensis genome. The number of alleles per locus ranged between four and nine, and the observed heterozygosity ranged from 0.182–0.750 in a wild sample of 24 individuals from Caicaén (Chiloé Region, Chile). Lack of efficient amplification of many of these microsatellite loci in other Mytilus species suggests that M. chilensis is a valid, distinct species within the genus. These new markers would be useful in fine-scale population analyses of M. chilensis as well in the aquaculture management of this marine resource.

The experimental culture of Haliotis tuberculata coccinea is carried out at the Institute of Marine Science of Canary Islands (Gran Canaria, Spain) based on specimens captured in their natural habitat and conditioned as broodstock. In 2008, an outbreak of shell-boring polychaetes affected the culture. This study aims to identify some of the species of shell-boring polychaetes that affect H. tuberculata coccinea and, second, to assess the effectiveness of multiple mebendazole applications for the control of these pests. Mebendazole was applied as baths of Lomper (Esteve Laboratory, Barcelona, Spain) using the concentrations 6 mL/L, 8 mL/L, and 10 mL/L, with 0 mL/L as a control measure. Abalone were exposed to 3 mebendazole baths over a 3-day period (1× 3-h bath applied for 3 consecutive days), as recommended in the drug directions for human use. After each bath, the abalone were returned to their original culture tanks until the following day. After these 3 days, the abalone were kept in their original culture tanks for a term of 1 mo. Each month, as a result of the effect of mebendazole, moribund and/or dead polychaetes became detached from the burrows and were found at the bottom of the tank during the first 15 days after the baths of mebendazole were applied. The polychaetes expelled from the shells were counted, collected, and fixed in 10% buffered formaldehyde for subsequent identification. This process was repeated month after month until no moribund and/or dead shell-boring polychaetes were found after the application of the baths of mebendazole. The shell-boring polychaete species was identified as Polydora hoplura (Claparède 1870). The efficacy rate of Lomper was around 99% in all the concentrations tested when it was applied during a 7-mo term (each month, 1 bath was applied for 3 consecutive days), and abalone mortality was limited to highly infested animals only. Monitoring of abalone weight gain suggested that the mebendazole treatments did not affect growth significantly during the study period.

Ammonia is a toxic metabolite of protein catabolism that can limit growth and health of aquatic animals. This study investigated the effect of dietary protein level on the average total ammonia (TAN) and free ammonia nitrogen (FAN) concentrations in a serial-use raceway used to farm South African abalone, Haliotis midae Linneaus. Three isoenergetic diets contained 33% (P33), 26% (P26), and 22% (P22) protein. Biomass of abalone was 7.6 ± 0.1 kg/300-L tank (45–55 g/abalone). TAN and FAN concentrations were significantly correlated with dietary protein (P) (P < 0.0001) and flow index (FI; as measured by liters per hour per kilogram; P < 0.0001), and could be estimated using the models TAN = 9.73 P – 110.3 log (FI), and FAN = 0.132 P – 1.10 log (FI). Mean FAN concentration in the P22 and P26 treatments was 67% and 41% lower, respectively, than in tanks fed the P33 diet. Because this species can grow well on low-protein diets, it is hypothesized that a reduction in percentage protein will improve the carrying capacity of serial-use systems. The models estimate to what extent discharge of nitrogen could be reduced through lowering the protein level in the formulated diet.

The nervous system of the female spotted Babylon, Babylonia areolata Link 1807, consists of left and right pairs of buccal ganglia, pedal ganglia, cerebral ganglia, pleural ganglia, and parietal ganglia, and a single left-side visceral ganglion. Each ganglion has an outer cortex and an inner medulla. The outer cortex contains three cell types: neurosecretory (NS) cells, neurons (NR), and neuroglia (NG). The medulla consists of NG and nerve fibers. The ultrastructural studies of the NS cells in each ganglion demonstrate that the buccal, pleural, and pedal ganglia contain neurosecretory granules (NSg) type I and II cells. The NS cells in the cerebral ganglia are NSg types I, II, and III, whereas in the parietal ganglia their NSg are types I, II, III, and IV. Furthermore, the NS cells of the visceral ganglion are of NSg types I and III. The different structures of NSg in the NS cells in the ganglia indicate that they may produce different neurosecretions.

In this study we describe the feeding biology of the exotic predatory whelk Rapana venosa from the Río de la Plata when offered representative coastal bivalves from both soft and hard bottoms. Furthermore, we estimate daily consumption rates using two mussel species commonly found on local rocky outcrops and artificial reefs. R. venosa gastropods (n = 21; shell height (SH), 45–117 mm) were obtained by trawling in the Río de la Plata, and were kept in controlled laboratory settings. To describe its feeding behavior, 10 potential prey species were offered to the gastropods, including Mactra isabelleana, Erodona mactroides, Pitar rostratus, Donax hanleyanus, Mesodesma mactroides, Mytilus platensis, Brachidontes rodriguezi, Mytella charruana, Amiantis purpurata, and Crassostrea gigas. All prey species were consumed. The empty shells left after consumption frequently showed broken shells and rasp signatures on the edges, suggesting a prey attack by marginal chipping or a similar mechanism. This common pattern was not observed in A. purpurata or C. gigas. To explore potential effects of size on feeding behavior, the gastropods were separated into three size classes and offered M. platensis, B. rodriguezi, and M. charruana mussels. Small, intermediate, and large gastropods (SH <60 mm, 60–90 mm, and >90 mm, respectively) consumed comparable mussel size ranges. Small gastropods fed on prey sizes up to 30% larger than their size, whereas large gastropods consumed the largest mussel offered (SH, 78 mm). To estimate daily consumption rates, the 21 gastropods were fed with M. platensis and B. rodriguezi in individual tanks for 12 days. They ate 1.45 ± 0.67 SD mussels and 0.68 ± 0.65 g/day per gastropod. The proportion of tissue wet weight consumed did not change with prey species, but varied among the size classes of R. venosa. Small (<60 mm) and intermediate (60–90 mm) gastropods consumed a similar proportion of prey tissue (up to 12% of their tissue wet weight). In contrast, large gastropods (>90 mm) ate up to 5% of their tissue wet weight. This work is the first report of R. venosa feeding behavior and daily consumption rates in Argentina. The gastropods succeeded in attacking and feeding on a broad variety of local bivalve species characterized by noticeable differences in shell shape, size, and life habits.

Mussel die-offs have been noted in recent years in Pickwick Reservoir, Tennessee River, Alabama. The primary affected species was Fusconaia ebena, but also affected to lesser degrees were Ellipsaria lineolata, Quadrula pustulosa, and Quadrula quadrula. These events were characterized by large numbers of empty shells—fresh-dead and live individuals that were presumed to be diseased because of weak and slow valve closure responses to external stimuli. Anecdotal evidence suggested the possible involvement of an etiological agent, such as a bacterial pathogen. The die-offs have occurred in Pickwick Reservoir (river miles 236–256) in sequential years during the past approximately 10 y. These timeframes have coincided with reduced basin inflows and warmer water temperatures. The majority of the moribund and freshly dead F. ebena were females possibly predisposed to infection and disease from ongoing reproductive activity. Affected and healthy-cohort mussels were collected to characterize the bacterial flora prior to, during, and after a July 2006 die-off, and during a subsequent die-off in September 2008. The numbers of total bacteria from both the 2006 and 2008 die-offs were significantly greater from the diseased specimens. For example, from the September 2008 die-off, the mean count from diseased F. ebena soft tissues was 9.75 × 10⁶ cfu/g, which was more than 100 times greater (P = 0.025) than the mean from healthy cohorts (6.74 × 10⁴ cfu/g). The predominant bacteria from affected F. ebena from July 2006 were Hafnia alvei and Aeromonas sobria, whereas from September 2008 the predominant bacteria were Enterobacter spp., Aeromonas schubertii, Aeromonas veronii bv. veronii, and Aeromonas veronii bv. sobria.

Farfantepenaeus paulensis postlarvae were reared at different stocking densities during the nursery phase in a biofloc technology (BFT) culture system without water exchange. An experimental system comprising a 70-m³ macrocosm tank containing shrimp cultured in the BFT system at 300 shrimp/m², with a productivity of 2.7 kg/m² was used, which supplied twelve 0.5-m² tanks at densities of 500, 1,000, 1,500, and 2,000 shrimp/m² through pumping. The experiment lasted for 30 days. The water was recirculated 48 times a day from the macrocosm to the microcosm tanks. The growth rate, final weight, survival, and productivity of the shrimp were analyzed. There were no significant differences in the water quality parameters among treatments because the water input and output from the macrocosm tank to the experimental units was constant. There were also no significant differences (P > 0.05) in survival. However, the final weight and productivity were significantly different (P < 0.05) among treatments. The treatments with the lowest stocking densities were associated with the highest weights, whereas the treatments with the highest stocking densities presented the highest productivities. The study demonstrates that the use of a BFT culture system may enable the culture of this species at high stocking densities in nurseries. The results also demonstrate the possibility of using a high stocking density for commercial culture and restocking programs.

In this study, postlarvae of the fleshy shrimp Fenneropenaeus chinensis “Huanghai No. 2” (a new shrimp variety bred in China) were fed with white spot syndrome virus (WSSV)-toxic bait with amount of 25% of the total shrimp body weight and were evaluated WSSV loads at different postinfection periods (i.e. early, peak and late periods). A total of 83 of 4,424 shrimp (1.88%) survived at the end of the experiment, which lasted 358 h, 662 h, and 232 h in 3 ponds, respectively. The WSSV loads were 8.8 × 10⁴–1.5×10⁵,4.4×10⁵–1.2×10⁶, and 8.5×10⁵–4.6×10⁶ copies/ng DNA, respectively, averaging 9.5×10⁵ copies per anograms DNA of all sampled shrimp (n = 229). The viral loads in the shrimp that died during the late postinfection period were significantly higher than in those shrimp that died during the early and peak periods (P < 0.01). The viral load in surviving shrimp was 2.2×10⁵ (n = 44) copies/ng DNA. Among the surviving shrimp, 18.2% (n = 8) had a viral load greater than 1.0×10⁴ copies/ng DNA and 52.3% (n = 23) had less than 100 copies/ng DNA. Based on these result, the range of 7.0×10⁴–10⁷ copies/ng DNA is suggested to be the lethal amount for shrimp death caused by WSSV. These results could be an important reference in an advance warning of a WSSV outbreak in the culture process of these shrimp, and could provide valuable information in further selective breeding of WSSV-tolerant or -resistant varieties of F. chinensis.

In decapod crustaceans, chemical cues are usually detected by antennal and antennular setae. Different types of setae have been identified in various decapod species. In Lysmata shrimp, aesthetascs have been identified to be responsible for distance sex pheromone detection, whereas some other nonaesthetasc setae can detect contact sex pheromones. In this study, the morphology of antennal and antennular setae in six species of Lysmata shrimp was examined using scanning electron microscopy. The number of nonaesthetasc setae was counted and compared among the species with different social environments. Four types of antennal and antennular setae were identified, and their morphology was similar in all the Lysmata species studied. No sexual dimorphism was found in the morphology of setae. The total number of nonaesthetasc setae increased with shrimp size, whereas the density of nonaesthetasc setae did not change with growth. In general, the number and density of nonaesthetasc setae was greater in pair-living cleaner shrimp than in group-living and low-density peppermint shrimp, indicating that contact sex pheromones may be more important in pair-living species. Among peppermint shrimp, there were no significant differences in the number and density of nonaesthetasc setae between group-living species and low-density species, which suggests that social environments may not be the only factor that is related to the higher setae number and density in pair-living species.

Ventless trap surveys are becoming an increasingly common method to estimate American lobster (Homarus americanus) population structure and abundance. These surveys typically consist of strings of conventional commercial vented traps set alternately with experimental ventless traps, which lack escape vents and, as a result, capture higher proportions of sublegal-size lobsters. To determine how accurately ventless trap surveys reflect lobster populations on the seafloor, lobster density, size distribution, and sex ratios observed from scuba transect and tagging surveys were compared with ventless trap survey catches at 17 locations that varied by average temperature and dominant substrate. Diver surveys indicated that higher lobster densities were associated with increasing substrate complexity and constant temperature. Trap catch per unit effort increased with substrate complexity and decreased with increasing water temperatures. Comparisons of survey methods suggest ventless trap surveys overestimate average carapace length and proportion of males, and that selectivity and catchability varies with respect to substrate and temperature. To avoid violating the assumption of constant sampling of the population, time-series data based on relative abundance estimates generated from ventless trap surveys should consider stratification by substrate and temperature. To account for potential geographical variability in the relationship between trap catches and lobster density, further consideration and development of spatial and temporally specific calibration studies are required prior to assigning stock assessment parameters confidently based solely on existing trapping techniques.

The presumption is that egg quality influences larval survival and that egg size influences egg quality. Thus, larger eggs should be favored by selection. Counterweighing the tendency for egg size to increase is the number of eggs that can be produced if egg size remains small. We examine how egg size and egg number counterbalance in Crassostrea oysters, resulting in an average egg size near 50 µm. Simulations imposing a diversity of ranges in larval survivorship—from little advantage for large eggs relative to small eggs to a great advantage—yield some anticipated outcomes in which genotypes generating larger eggs are favored. In other simulations, however, genotypes generating smaller eggs became increasingly common. In these cases, egg size declines, as does the likelihood of survival of individual larvae: the antithesis of expectation. Few simulations identify preferred egg sizes near the size typically observed, suggesting that, under most field conditions, a selective advantage exists for smaller or larger eggs than those typically spawned. However, the extremes in egg size are rarely advantageous. Most simulations resolve an optimal intermediate egg size. Thus, observed egg size is a balance between the chanciness of larval survival enhanced by the production of a larger number of eggs and the genetically predisposed, but environmentally modulated, individual probability of larval survival that is a function of egg size, with environment determining the optimal size. The 50-µm size observed likely represents the median outcome of a range of larval survivorship probabilities, each selecting for relatively larger or smaller eggs, imposed stochastically over multiple generations. In this scenario, each year the population is pulled toward smaller or larger egg sizes, but in the next year the impetus is independent of the previous year. Reduced generation time, by disease or fishing, modifies the extent, but not the direction of trend. Thus, environmental stochasticity retains preeminence in stabilizing a balance between the probabilities of survival modulated by egg number and by egg size. The influence of shortened generation time—by disease, for example—is unlikely to be manifest in a modification in egg size and hence egg number.

Catch-per-unit-effort (CPUE) is frequently used as a measure of relative abundance in fisheries stock assessment. Determining reliable estimates of species-specific CPUE is more challenging in multispecies, rather than single-species, fisheries because identification of appropriate effort data for each species is often difficult. Divers in the South Australian abalone fishery can harvest blacklip (Haliotis rubra) and greenlip (Haliotis laevigata) abalone simultaneously, but report only a single value for daily fishing effort. This is problematic because total allowable commercial catches are set for each species following species-specific stock assessments in which CPUE is a key index of relative abalone abundance. To provide an evidence-based approach to the identification of the most appropriate CPUE estimation method for ongoing assessment of the fishery, we assessed six diverse CPUE estimation methods for estimating annual, species-specific CPUEs using 30 y of data. The candidate CPUE estimation methods yielded relative CPUE time series with similar temporal trends throughout the 30-y period. These relative CPUE estimates each had low coefficients of variation and were highly correlated with one another, requiring consideration of other factors to determine a preferred method. Using a catch-weighted estimate of CPUE (CPUE_wt) overcomes many of the problems associated with using the other five methods tested. Specifically, CPUE_wt (1) weights each daily catch and effort objectively; (2) removes the need to “subset” the data subjectively, which ensures that data availability and representation are not reduced by arbitrary rules; and (3) is relatively simple to explain to stakeholders and can be applied consistently to greenlip and blacklip abalone at multiple spatial scales across the fishery. Although the requirement to estimate species-specific catch rates in mixed-species dive fisheries is rare, our analyses demonstrate that CPUE_wt could provide a robust measure of species-specific CPUEs across other diverse multispecies fisheries.