The rock scallop (also known as “donkey thorny oyster,” “spiny oyster,” and “thorny oyster”), Spondylus calcifer, is the largest member of any Panamic Province Spondylus and has played important economic, political, and cultural roles in coastal communities of the Eastern Tropical Pacific for thousands of years. Despite its importance, knowledge of its biology is scant. We assessed seasonal variations in shell and adductor muscle growth, longevity, reproductive age and period, and population sex ratios in the upper Gulf of California, Mexico, the northernmost area within the geographic distribution of this species. Information on shell growth and age was obtained via the use of stable oxygen isotope profiles of shell aragonite cross-referenced with mark recapture data. Spondylus calcifer forms white growth bands during winter and spring months. Shell growth accelerates during warmer months and diminishes during colder months. Likewise, the adductor muscle increases in size and weight during colder months, affecting fishermen's distribution of fishing effort. These seasonal variations in growth are likely a result of energetic shifts related to resource allocation pre and post reproduction, which takes place in July-August as water temperatures reach 28°C to 30°C. The species reaches sexual maturity between 2.5–4 y of age and can live to at least 12 y. Overall sex ratios consisted of 1:1 male:female, a population structure in accordance with previous reports for the southern Gulf of California. We discuss our findings in the context of management and conservation of the species.

The aim of the present work was to compare microstructure in strong and weak scallop Pecten maximus shells of cultured and wild origin using observations from scanning electron microscopy (SEM) and atomic force microscopy (AFM). The scallops representing the strongest and the weakest shells from each origin and age were selected for the microstructure observations. SEM observations showed various abnormalities of the microstructure, whereas AFM observations did not reveal any abnormalities of the nanostructure. The observed abnormalities were separated into two categories: irregularities and modifications. Irregularities were not directly linked to the microstructure and included bubbly sheets, bacteria, sponge, and hexagonal shapes on the inner layer. Modifications were directly linked to the microstructure and included irregular laths, crystal fragments, and severely modified granule layer covering the myostracal layer. Although irregularities were observed in samples of both cultured and wild P. maximus shells, modifications of the microstructure were observed only in those of cultured origin. Abnormalities were observed more frequently in four- and five-year-old scallop shells, whereas no abnormalities were observed in any of the shell samples from one-year-old scallops. These results suggest that abnormalities in scallop shells develop over time and that cultured scallops seem to be more at risk to develop modifications in microstructure compared with wild scallops. To be able to optimize conditions in aquaculture procedures, more investigation is needed on how the culture environment influence the biomineralization process in hard shelled molluscs.

To determine if population density in areas closed to fishing in Narragansett Bay is causing differences in the reproductive potential of the organisms, this study used two approaches to determine the reproductive condition of the animals. The first approach consisted in employing a gravimetric condition index (CI) to evaluate the general condition of quahogs from nine different sites, 3 sites open conditionally for fishing (conditional areas) and 6 sites closed to fishing. The second approach was a determination of gonadal index (GI) of a subset of the sample sites, by histological observation of gonadal tissue sections. Initial sampling included determination of CI only, and lasted from March 25 to Sep. 22, 2005. The subset of six of the sites was sampled the next year (2006), every three weeks from April 15 until Sep. 28 to determine CI and the gonadal index (GI). Results show that there is a significant difference between the CI of northern quahogs from conditional areas and quahogs from closed areas (P < 0.001). There is a significant difference in GI between sites at (P < 0.10). The GI in conditional areas was consistently higher than in closed sites indicating that maturation and reproductive stages are more prevalent in conditional areas than in closed sites. When sites were separated into three categories: conditional fishing sites; coves; and Providence River sites, the GI and CI of the conditional areas were always higher than the CI and GI of all the other sites. The coves had intermediate indices, and the Providence River sites always had the lowest indices. The results indicate that the populations of quahogs in the closed sites sampled are not completing the gonadal cycle as expected and that the reproductive capability of the quahogs in conditional areas is higher than those in closed areas. Possible explanations to this condition include lower water quality in the closed areas, low dissolved oxygen concentration especially during the summer, poor bottom conditions and high population density. Although, not one single characteristic of the environment is solely responsible for the reproductive condition of the quahog population, density appears to have significant effect.

A numerical bioenergetics simulation model based on the physiological processes affecting individual clams across a range of phenotypes describing a cohort has been developed and applied to the conditions in Great South Bay, New York. The clam population is relatively sensitive to food and to a lesser extent to temperature within this system. The timing of temperature and food in the spring, and more importantly in the fall, can increase population sensitivity beyond the effects of one factor operating alone. The effects of fishing on the stocks in proportion to the size structure present, and as directed fisheries on various size classes (littleneck, cherrystone, chowder) was simulated. Recruitment overfishing was responsible for the stock decline in the 1970s and 1980s, but the continued decline into the late 1990s and 2000s cannot be attributed to fishing alone. Recruit-per-adult declined after the mid 1990s. Modeled stock recovery times under constant environmental conditions are on order of 10–15 or more years depending on the exploitation rate. Under base conditions a proportional fishery that removes approximately 25% of the stock, or a littleneck fishery that removes approximately 37.5% of that size class annually would provide the best economic returns under constant average environmental conditions. Slightly less harvest would be desirable to avoid overfishing in years of less than optimal environmental conditions.

Ocean quahogs (Arctica Islandica) are long-lived bivalves. Distribution patterns and biology of ocean quahogs in the Mid-Atlantic Bight (MAB) off the east coast of North America are directly related to bottom water temperatures. We examined long term recruitment patterns for ocean quahogs across temporal (decadal) and spatial (latitudinal, bathymetric) scales using a spatially defined (Long Island Sound to Chesapeake Bay mouth) population encompassing a broad size (age) range of animals that had not yet recruited to the commercial fishery [<80 mm shell length (SL)]. An age-at-length relationship for quahogs less than 80 mm SL is described using a power function. Quahog age did not vary significantly with depth or region, nor were any interaction terms between age and length with depth or region significant. An age-length key was developed for ocean quahogs to generate age frequencies for each station. Principal components analysis (PCA) on the resulting age-frequency distributions standardized per tow enabled construction of characteristic age-frequency distributions for similar stations identified by the PCA factor scores. These characteristic age-frequency distributions identified quahog cohorts with modal ages corresponding to recruitment during the 1948–1950, 1954–1959, 1972–1980, and 1978–1983 time periods. Observed recruitment patterns in MAB ocean quahogs are strongly related to bottom water temperature patterns. Years in which the number of months with water temperatures averaging 6°C to 10°C exceeds the number of months with water temperatures less than 6°C by at least two months are also years that contribute strongly to the modal year classes in the population age-frequency distributions. In general, years with above average bottom water temperatures during January, February, and March tend to produce year classes that are distinct in the age-frequency distributions from the MAB quahog populations. The observed time series of quahog recruitment operates at a different time scale than stock surveys and most estimates of fishery dynamics. The 50–60-y lag between quahog recruitment to the benthos and recruitment to the fishery presents challenges for fishery forecasting in that changes in adult biomass and subsequent effects on stock-recruit relationships will only become evident on this time scale.

Four hundred years of commercial harvest of the oyster Pinctada mazatlanica in Pacific Panama were characterized by historical collapses and recoveries that finally ended in the 1940s; oyster populations have not recovered since then. This study provides a baseline and meta-analysis of current P. mazatlanica densities in Las Perlas and Coiba Archipelagos. We compared the oyster densities in relation to substrates and depths at 103 sampled sites using randomization techniques. Mean oyster density per site ranged from 2.8–238.9 ind·ha⁻¹ in Las Perlas and 6.0–263.9 ind·ha⁻¹ in Coiba. These values are one to three orders of magnitude lower than those reported for La Paz, Baja California (3,000–12,000 ind·ha⁻¹) and Costa Rica (24,200 ind·ha⁻¹) in recent times. Substrates within the archipelagos were diverse. We found an increasing trend of density variance when regressing log-transformed densities against substrates ordered according their increasing availability of hard surfaces. In Coiba, densities in substrates including rocks plus corals and sand were statistically lower in shallow than in deep waters, probably caused by harvest. The highest densities in Las Perlas occurred southeast of Del Rey and western Saboga islands. In Coiba, we found the highest densities in Ranchería Island and on the westernmost side of Coiba and Jicarón Islands. These data will help to define the environmental framework within which future research on this important species must be conducted and can be used to improve plans to address its management and conservation.

A population of European oysters (Ostrea edulis) was recently discovered off the eastern coast of Canada. The occurrence of this newly established population led various aquaculture stakeholders to consider this species commercially. To better assess recruitment capacity, the physiological quality of the adults, eggs, and larvae was described using glycogen and various lipid contents, including a TAG/ST ratio. Adults, early nonfeeding stages (eggs, pretrochophores, trochophores, veligers) and newly-released larvae were periodically sampled in the wild and/or the hatchery during the spawning period. The initial glycogen content was higher in wild oysters than hatchery-conditioned ones. The following larval stages showed higher lipid content in wild individuals as well. Spat collection in the wild was abundant. The free-living larvae, however, did not survive more than 10 days in the hatchery. TAG/ST ratios decreased during the veliger stage development and were lower when larvae were released from the paleal cavity of the female. The high spat collection observed in the wild suggests that observed TAG/ST ratios in early nonfeeding larvae are representative of a good larval quality. The physiological quality of the larvae in the wild seems to be good enough to allow larvae to settle in this particular environment.

This study examined growth, gametogenic activity, condition index, as well as the relationship of the life cycle to environmental parameters of the Cortez oyster Crassostrea corteziensis, which was cultured for 25 mo in the lagoon of Las Guásimas (Sonora, Mexico). We used oocyte diameter and cytological characteristics of the gonad to determine reproductive stages in females and males. The condition index was used to describe the oyster's physiological health. Temperature, salinity, seston, and chlorophyll a, b, and c were recorded at the study site. The Cortez oyster had isometric shell growth, reaching 103.2 ± 1.82 mm height and 150.3 ± 4.98 g total weight. Data were adjusted to the von Bertalanffy growth equation (L_∞ = 132.2 mm and K = 1.08 y⁻¹), and survival was about 70%. This native species exhibited a distinctive gametogenic cycle, with the beginning and end of the cycle controlled by seawater temperature fluctuation (15–33°C), which once started, is continuous over a 9-mo period (March to November). Elevated temperature (>25°C) produced high gametogenic activity, exhibiting primary, growing, and mature oocytes, and partial spawning in April, September, and November. The peak spawning event occurred in August, when seawater reached peak temperatures of 31°C to 33°C, which was followed by a significant reduction of the condition index. During winter, storage of nutrients took place, and this appears to be used in the following season for gametogenesis. In general, the condition index was high throughout the study period. Energy for growth and reproduction came from phytoplankton blooms in summer and high concentration throughout the year of nonchlorophyll particulate organic matter. Observations show that this oyster is a protandrous species. High survival, elevated yields, and a long, continuous gametogenic cycle indicate that C. corteziensis has importance in aquaculture in Gulf of California.

Genetic variation was evaluated in populations of the eastern oyster Crassostrea virginica (Gmelin) from the coast of Veracruz, eastern Gulf of Mexico. We sampled six lagoons and analyzed variation at five microsatellite loci. Significant Hardy-Weinberg deviations occurred at all loci and were attributed to the presence of null alleles. We found no isolation by distance among the populations in these lagoons, but significant heterogeneity was observed among some adjacent lagoons, possibly reflections of geographical factors and local reductions in population size. Certain extreme north and south localities were not genetically different in terms of nonsignificant pairwise F_ST values. Gene flow is attributed to seasonal shifts in coastal currents, larval production throughout the year, human interference with the natural lagoon processes, and restocking efforts. The observed pattern of variation could be another example of chaotic genetic patchiness in marine organisms.

We evaluate a 54-y survey time series for the Delaware Bay oyster beds in New Jersey waters to identify the characteristics of regime shifts in oyster populations and the influence of MSX and Dermo diseases on population stability. Oyster abundance was high during the 1970s through 1985. Oyster abundance was low at the inception of the time series in 1953, remained low through 1969, and has been low since 1985 and very low since 2000. Natural mortality was low in most years prior to the appearance of MSX in 1957. From 1957 through 1966, natural mortality generally remained above 10% annually and twice exceeded 20%. Natural mortality remained well below 15% during the 1970s and into the early 1980s when oyster abundance was continuously high. The largest mortality event in the time series, an MSX epizootic that resulted in the death of 47% of the stock, occurred in 1985. Mortality rose again with the incursion of Dermo in 1990 and has remained above 15% for most years since that time and frequently has exceeded 20%. The primary impact of MSX and Dermo diseases has been to raise natural mortality and ultimately to cause a dispersed stock to retreat into its habitat of refuge in the moderately low salinity reach of the bay. The time series of oyster abundance on the New Jersey oyster beds of Delaware Bay is dominated by two regime shifts, the 1970 abundance increase that was maintained for about 15 y thereafter, and the 1985 abundance decrease that continues through today. These two regime shifts ushered in long-term periods of apparent constancy in population dynamics. The 1985 regime shift was induced by the largest MSX epizootic on record that produced high mortalities throughout a population distributed broadly throughout its habitat range after 15 y of high abundance. A putative new regime commenced circa 2000 as a consequence of a series of Dermo epizootics. Mortalities routinely exceeded 20% of the population annually during this period, with the consequence of a greater degree of stock consolidation than any previous time in the 54-y record. Extreme consolidation of the stock would appear to be a characteristic of the population's response to Dermo disease. The 1970–1984 and post-1985 regimes each were ushered in by a confluence of events unique in the 54-y time series. Each was characterized by a period of relative stability in population abundance. However, the stability in total population abundance belies a more dynamic process of stock redistribution during both time intervals, demonstrating that the appearance of constancy in stock abundance is not necessarily a result of invariant stock dynamics. Rather, the Delaware Bay oyster time series suggests that regime shifts delimit periods during which differential, often offsetting, local trends impart similar abundance levels, and thus constancy at the level of the stock masks substantive changes in local population dynamics potentially fostering future catastrophic changes in population-level attributes. Understanding such regime shifts will likely determine the success of decadal management goals more so than measures designed to influence population abundance.

The eastern oyster (Crassostrea virginica) is a vital species in the estuaries of the mid-Atlantic United States. Whereas their filtering activity and biodeposition play an important role in the ecology of these systems, the reefs they form are one of the few sources of hard bottom habitat for fouling organisms and are the foundation of a rich biological community. This species has experienced drastic declines throughout the mid-Atlantic region in the last two centuries due to overfishing, habitat loss, and disease. Much interest and effort is now focused on restoring this important commercial and ecological resource. Whereas oyster reef restoration is central to the recovery of this species and the habitat it creates, oyster aquaculture can provide many of these same services albeit on a smaller scale. This is a two-part study, assessing the macrofaunal communities associated with subtidal modified rack and bag aquaculture, conducted over the summer and fall of 2006. The first part of this study compares the macro-epifaunal communities associated with two oyster habitats: a created oyster reef and oyster aquaculture cages. Both habitats were sampled with lift nets and compared using two-way ANOVAs between habitat and time. Secondly, we compared the sediment composition and macro-infaunal communities below the oyster cages with a nearby reference area of open sand/mud bottom. A significantly greater (P < 0.05) total abundance and species richness was found in the oyster cages, but significantly greater (P < 0.05) species evenness was found on the reef with species diversity similar between habitats. The sediments below the oyster cages showed a slight but significant (P < 0.05) reduction in it's silt/clay fraction. The results of this study show that, this method of oyster aquaculture supports additional populations of ecologically and economically important macrofauna compared with a created oyster reef. Furthermore this study demonstrates that off-bottom oyster aquaculture operations in the mid-Atlantic United States are a beneficial addition to host estuaries and associated natural communities.

Because temperature plays an important role on progression and transmission of disease caused by Perkinsus marinus in the field, the effects of triclosan on the viability of P. marinus meronts (trophozoites) and oyster hemocytes were tested at a range of environmental relevant temperatures. Additionally, we examined the triclosan effect on reactive oxidative intermediate production (ROI) by oyster hemocytes and tested the efficacy of treating infected oysters with triclosan in eliminating/reducing P. marinus infection in a pilot experiment. When P. marinus cultivated at 13°C, 20°C, and 28°C was exposed to triclosan at corresponding temperatures, 2–10 μM triclosan killed 10–30% at 20°C and ≥40% at 28°C, but ≤10% at 13°C. When exposure of P. marinus cultivated at 28°C to triclosan at 26°C, similar mortality was noted as those recorded at 28°C. Treating hemocytes from oysters maintained at 13°C, 20°C, or 26°C with 2, 5, 10 μM triclosan at corresponding temperatures, killed 2% to 13% at 13°C and 6 to16% at 20°C. No mortality occurred in hemocytes exposed to 2–10 μM triclosan at 26°C. However, at the highest temperature and triclosan concentration tested (28°C, 10 μM triclosan), hemocyte mortality exceed 30%. Exposure of hemocytes to triclosan concentrations of 2–10 μM for 4 h at 4°C significantly reduced the ROI production in hemocytes in a dose-dependent response. Treating P. marinus infected oysters with 300 and 600 μg triclosan/oyster daily for 8 wk, significantly slowed the disease progression.

Refugia are increasingly being used to maintain and propagate imperiled freshwater mussels for future population augmentations. Success for this endeavor is dependent on good husbandry, including a holistic program of resource health management. A significant aspect to optimal health is the prevention or control of infectious diseases. Describing and monitoring pathogens and diseases in mussels involves examination of tissues or samples collected from an appropriate number of individuals that satisfies a certain confidence level for expected prevalences of infections. In the present study, ebonyshell mussels Fusconaia ebena were infected with a fish pathogenic bacterium, Aeromonas salmonicida, through their cohabitation with diseased brook trout Salvelinus fontinalis. At a 100% prevalence of infection, the F. ebena were removed from the cohabitation tank to clean tanks that were supplied with pathogen-free water, which initiated their depuration of A. salmonicida. Three samples (nondestructive fluid, mantle, hemolymph) collected using nondestructive procedures were compared with fluids and soft tissue homogenates collected after sacrificing the mussels for recovery of the bacterium during this period of depuration. Nondestructive sample collections, especially ND fluid, provide a comparable alternative to sacrificing mussels to determine pathogen status.

Indicator and some pathogen bacteria were investigated in both samples of Chamelea gallina and Donax trunculus collected from the northern coast of the Sea of Marmara Sea, Tekirdag, Turkey. Studies were carried out monthly from November 2005 to December 2006. The samples of C. gallina and D. trunculus which were collected from natural-growing areas by mechanical dredge implemented at approximately 5–7 m depth were examined for Staphylococcus aureus, Salmonella spp, Escherichia coli, fecal coliform and total coliform. The maximum levels (Most Probable Number: MPN) of E. coli, total coliform and fecal coliform were recorded in August in samples of C. gallina and D. trunculus. Salmonella spp. was found as positive in two samples of C. gallina and four samples of D. trunculus in the summer session. S. aureus was recorded as meanly between 12 CFU/ 100 g − 2.1 × 10² CFU/100 g in the all samples during the six months from April to October. Out of the total coliforms isolated, Citrobacter spp., Enterobacter cloaceae, Serratia marcescens, Proteus spp, non fecal E. coli, and Kebsiella pneumonia were identified as 38%, 25%, 16%, 10%, 9%, and 2% respectively. Whereas the effect of the clam types on distribution of bacteria has not been found to be statistically significant, it has been found to be significant with respect to seasonal distribution of bacteria. The highest bacteria values recorded were associated with local inputs and the increase of recreational activity in this area during the summer season.

Perkinsus marinus is a lethal protozoan that impacts eastern oyster (Crassostrea virginica) populations along the eastern seaboard of the United States and the Gulf of Mexico. Despite the potential advantages of a chemical therapy to effectively treat P. marinus infected oysters for aquaculture and research, no such therapy exists. Given the close taxonomic and phylogenetic proximity of P. marinus to another protozoan parasite, Plasmodium spp., the antimalarial drug quinine was evaluated as a potential chemotherapeutic agent. A concentration of 50 μg/mL (0.13 mM) quinine HCl significantly decreased the viability of six geographic isolates of P. marinus after three hours in vitro. Although quinine HCl effectively decreased P. marinus viability, all concentrations tested decreased oyster hemocyte viability in vitro. Furthermore, concentrations below the effective concentration for P. marinus meronts were either lethal to infected oysters or had no observable effect on parasite infections.

Nine different species of oysters belonging to the genera Crassostrea, Saccostrea, and Ostrea occur naturally along Pakistan's coastline in the northern Arabian Sea. At the present time, no commercial harvesting or hatchery culture of oysters exists in Pakistan. The world's oyster aquaculture industry is seriously affected by diseases caused by parasites, such as Bonamia ostrea in the European flat oyster Ostrea edulis, and Haplosporidium nelsoni or Perkinsus marinus in the Eastern oyster Crassostrea virginica. Pathogens may be endemic or recently introduced and may cause epizootic mortalities and catastrophic economic losses. To evaluate if there are parasites or diseases in Pakistan's oysters that could limit prospective aquaculture development, histopathological analyses were performed on two oyster species, Ostrea nomades and Crassostrea belcheri. Oysters were sampled year-around, and fixed and processed for histology. Slides (217 cases for O. nomades and 76 cases for C. belcheri) were examined for the presence of parasites or pathological changes. Ostrea nomades was infected by a protozoan parasite, Nematopsis sp. Sneider, 1892 (Apicomplexa, Porosporidae), at 67% prevalence, and C. belcheri at 1.3% prevalence. Nematopsis spp. did not induce pathological changes in the oysters. Stegotricha-like ciliates (Thigmotrichida, Ancistrocomidae) were present in the stomachs of O. nomades with a prevalence of 1%, and 25% of C. belcheri presented ceroid deposits in their tissues. Historically, Ostrea and Crassostrea genera have been associated with epizootic diseases, but in the present samples, no known, economically important parasites or diseases were found. Absence of any pathology in these samples projects a positive future for oyster aquaculture in Pakistan. These oyster populations should be protected from nonendemic bivalve importations, which could transmit new parasites to these potentially susceptible, previously unexposed, native oysters.

The genotypic diversity of seventy-one Vibrio strains isolated from the culture of oysters and clams was analyzed by using ribotyping and sequencing of 16S rRNA gene. The combination of both techniques led to clustering, the separation of V. splendidus-related species and the identification of 91.5% of studied strains. New genotypic, phenotypic and biotypic information on V. tasmaniensis, V. kanaloae, V. pomeroyi, and V. neptunius was provided. Vibrio splendidus biotype 1 and Vibrio mediterranei were also identified. Different riboclusters of V. splendidus, V. tasmaniensis, and V. neptunius were obtained showing genotypic diversity of these species. A unique ribocluster in V. kanaloae, V. pomeroyi, and V. mediterranei was obtained. Venerupis rhomboides (P.) was susceptible to experimental infections with strains of V. kanaloae, V. neptunius, V. pomeroyi, and V. splendidus biotype 1. Mortalities of challenged clams and the isolation of strains from internal organs confirmed the presence of virulent strains among the isolates and pointed to the risk of molluscan culture outbreaks.

Suspended mussel culture entails loading high densities of juvenile mussels into mesh socks, and hanging them from floating longlines, often resulting in intraspecific crowding, reduced growth, and mussel yield. Despite this potential bottleneck in culture, there are few data on behavioral mechanisms that regulate juvenile density and growth rate. A field experiment was conducted with culture socks to examine the effects of stocking density (High ∼800 mussels/30.5 cm; Low ∼400 mussels/30.5 cm), blue mussel species (Mytilus edulis and M. trossulus) and environment on early development of the culture population. In situ photography and direct sampling were used to generate time series of mussel size, valve gape, siphon area, shell orientation, and emergence in experimental socks at a commercial farm in Ship Harbour, Nova Scotia, Canada. Moored CTD-current meters and water sampling were used to characterize the sites. Emergence from the culture socks required 1–2 mo, with faster initial emergence in M. trossulus. High densities generally did not affect mussel emergence rate or orientation, but higher current speeds produced a negative effect on M. edulis emergence rate. At the experimental densities used, emergence was complete and few mussels remained inside the culture sock. Nonetheless, interior mussels showed mechanical stress such as shell distortion and reduced growth compared with emerged individuals. Mussels exhibited largely horizontal orientation presumably in response to horizontal currents. Siphon area displayed a unimodal response with an optimum at the middle of the current speed range. No density-dependent effect on valve gape was detected, but a significant interaction between siphon area and stocking density suggests that optimal hydrodynamic response is sensitive to crowding. Growth of shell and tissue showed little negative density-dependence. Mussels are proposed to alleviate crowding via behavioral sorting. Although there is concern that growth studies of cultured mussels are often deficient because they use cages or other containers rather than socks, this study suggests that conditions of the sock environment such as crowding may be less important than macroenvironmental factors (e.g., current speed) in determining growth.

Meat yield, expressed as the ratio of somatic tissue weight (flesh or meat weight) to total weight, is extensively used in the Atlantic Canadian mussel culture industry as a measure of product quality and market suitability at harvest. Atlantic Canadian mussel populations typically exhibit high genotypic variability with stocks at most sites consisting of mixtures of Mytilus edulis, M. trossulus, and their hybrids in widely varying proportions. In this paper, we examine relationships among genotypic variability, shell and somatic tissue weight, and their effect on measurement of meat yield. We further compare these relationships in populations grown from indigenous seed collection with those derived from transferred seedstock, and across different year classes within sites. Within 10 of 13 samples, M. edulis were greater than M. trossulus in shell length. Within all samples, weights of somatic tissue (flesh weight) and shell varied significantly with shell length. M. edulis typically had greater flesh and shell weights than M. trossulus. Hybrids tended to have intermediate values. Similar genotype-dependent relationships between shell weight and shell length occurred in all year classes taken from the same site. However, flesh weight relationships with shell length were inconsistent among year classes. Within-sample genotype-dependent relationships between flesh weight and shell length evident in indigenously-reared populations did not always persist in transferred populations. Meat yield was not significantly related to shell length. Meat yield was significantly greater in M. trossulus than in M. edulis in 12 of the 13 samples. Similar within-sample relationships between meat yield and genotype were evident among year classes and between indigenously-reared and transferred populations with M. trossulus having greater meat yields than M. edulis. Averaged over all samples, mean meat yield in M. trossulus was 7.4% greater than in M. edulis. Possible industry implications of these genotype-dependent differences are discussed.

Abalone meat has long been held in high regard for its unique sensory properties of texture and flavor, as well as its appearance. From a physicochemical viewpoint, the concentrations of certain free amino acids (especially glycine and glutamate) and the nucleotide AMP have been implicated as major factors characterizing the taste of abalone, and there seems to be a strong interaction (synergism) between them. The texture of abalone meat is related to the distribution of protein within the foot, and there is a good correlation between the collagen content and the toughness of abalone. These physicochemical factors, which largely define quality, may be influenced by species, season, diet, physiological condition and genetic factors. Protocols for handling and transport, and processing also influence quality; lactic acid is considered a useful post-mortem indicator of “freshness” in abalone meat. This review focuses on the abovementioned physicochemical factors and their link to abalone quality, and briefly discusses market related aspects and objective methods used for assessing quality attributes in abalone.

The occurrence of newly settled postlarvae (<500 μm of shell length [SL]) and subsequent growth and survival of the abalone, Haliotis diversicolor, were observed from 2001–2004 at two stations in the rocky shore of Nagai on the coast of Sagami Bay, Japan. Seawater temperature, current velocity, and distance of the weekly stone movement were monitored at both stations to determine factors affecting survival and growth of postlarvae. There were newly settled postlarvae in August and September of 2001, October 2002, August 2003, and September 2004. A total of 6 cohorts were identified between 2001 and 2004. Initial density of each cohort was generally higher at Station 1 than Station 2, but recruits at Station 1 had greater mortality than Station 2. Results from measurements of the physical environmental factors suggested that higher mortality rate of postlarval and juvenile H. diversicolor at Station 1 were produced by greater water turbulence and stone movement caused by storms. Growth rates in the first month after settlement varied between cohorts (35–62 μm SL day⁻¹), and growth rates were slower for cohorts settling later in the spawning season and experiencing lower water temperature. The timing of typhoon-triggered spawning in H. diversicolor population was also suggested to be an important factor affecting growth and survival of postlarvae and early juveniles, along with their subsequent recruitment. The cohorts from 2001–2004 attained 17–40 mm SL in about one year after settlement. To estimate the size and age at the first stage of maturation, the increase in shell length and gonad development of a single cohort from 2001 were measured. This cohort attained 30–55 mm SL and showed high gonad index at 22 mo after settlement, indicating the first stage of maturation of H. diversicolor is achieved at age 2.

A computer simulation was conducted to study the effects of densities, abundances, and aggregations of adult abalone populations on the fertilization success (amount of fertilization per spawning female). Impacts of densities were examined by having different numbers of adult abalone in spawning grounds of the same size. Impacts of abundances were studied by having different numbers of adult abalone in spawning grounds of different sizes with constant densities. Impacts of aggregations were investigated by having different spatial distributions for adult abalone with constant densities and sizes of spawning grounds. The fertilization success increased with the adult density, and the rate of increase in the fertilization success decreased with increasing densities, exhibiting a typical Allee effect. If the density remained the same for a single population, changes in the adult abundance had minimal impact on the fertilization success unless the abundance was really low. Adult aggregation would only considerably increase the fertilization success at relatively low adult densities. The fertilization success was greater for a large population than the combined fertilization success for two smaller and isolated populations with the summed abundance of the two small populations equivalent to the abundance of the large population.

We analyzed the decline in the abalone harvest of two species Haliotis fulgens and H. corrugata, from one region composed of six study zones along the Baja California peninsula, Mexico. Survey data from 1991 to 2001 were used and density estimations with a Δ-distribution were computed. The results showed a dramatic decline in density (kg/10 m²) for both species. The decline in densities of H. fulgens and H. corrugata is consistent with a pattern observed since 1975. The current condition of the abalone stock is an example of an uncontrolled fishery. An increase in fishing effort or harvest rate must be avoided because we do not know the equilibrium density of these populations.

Controlled feeding experiments with juvenile abalone Haliotis discus hannai were performed to evaluate the suitability of stable isotope analyses for diet inference. Juvenile abalone were divided into five size groups with distinct isotopic ranges caused by different dietary regimes before the experiments. Three different foods were provided for 42 days: a benthic diatom Cylindrotheca closterium (BD), a macroalga Laminaria japonica (MA), and a formulated pellet (FP). For the FP diet, the smallest juvenile group [8.3 mm in mean initial shell length (SL)] showed significant changes in carbon and nitrogen stable isotope ratios from the natural diet within approximately 1 wk. Using final tissue-diet isotopic differences in the two largest juvenile groups for the FP diet, the fractionation values were estimated as 1.6‰ and 2.2‰ for δ¹³C and δ¹⁵N, respectively. An exponential decay function of the change in δ¹³C with time indicated that the shortest period to complete equilibrium fractionation was >120 days. Given the estimated fractionation values, the major diets of juvenile abalone (1.9–6.9 mm in SL) in the field were inferred to be benthic microalgae and several red macroalgae.

The aim of this work was to investigate the seasonal variability in the biochemical composition in both sexes of Loligo forbesi, (Streenstrup 1856) in two locations in Egypt: the Mediterranean Sea off the coasts of Alexandria and north of the Gulf of Suez. The study is also aimed to document for the first time the fatty acids composition in both sexes in each location. There was a significant difference in the seasonal variations of total protein (P = 0.0001), total lipids (P = 0.036) and total carbohydrates (P = 0.009). Also, there was a significant difference in total lipids (P = 0.008) between sexes. Total lipids and protein declined from spring to summer and then increased in fall before they decrease again in the winter in males and females. Meanwhile, the concentration of total carbohydrates in females decreased from spring to fall then increased slightly in winter. There was a negative correlation between Gonado Somatic Index and Nidamental gland Somatic Index and each of total protein and lipids in different sexes (P = 0.01), which was not the case with total carbohydrates (P = 0.1). Seasonal fluctuations in biochemical content were attributable to the reproductive state of the animal. Although there was no significant difference in either total saturated lipids or total unsaturated lipids among the two sexes or between the two locations (P > 0.05), variations were observed in some fatty acids. The most predominant saturated fatty acid was palmitic acid (C16:0), comprising 68% to 73% for both sexes and locations. Most of the monounsaturated content was present as Cis-Pentadecanoic (C15:1) and palmiboleic (C16:1). Omega 3-poly-unsaturated fatty acids, which include linolenic, EPA, and DHA comprised ∼80% of total polyunsaturated fatty acids.

Populations of Strombus galeatus Swainson 1823 have been severely overfished in Pacific Panama. In this study, we assessed the status of the S. galeatus population in Las Perlas and Coiba Archipelagos. Average densities per site were dismal: 0.45 ± 3.8 ind·ha⁻¹ and 6.0 ± 18 ind·ha⁻¹ in Las Perlas and Coiba, respectively. In Las Perlas, low densities occurred on the southwest coast of Del Rey, the south coast of Chaperas, and Bolaños, whereas intermediate densities were found on the eastern coast of Saboga. In Coiba, high relative densities occurred only on the west coast of Coiba Island and at the north and south of Bahía Damas. Environmental variability and depth did not explain the differences found between densities nor the low abundances in the archipelagos. Shell length of S. galeatus from Coiba ranged from 91.0–213.3 mm (156 ± 22.2 mm). We fitted a von Bertalanffy growth model to juvenile data using the following parameters: L _∞ = 315 mm, K = 0.029 mo⁻¹, and t_o = 0.5 mo. The model suggests that 27–28 mo are required (on average) before the outer lip begins to form. Two years after the enactment of Decree No. 159 in September 2004, which banned the Strombus fisheries in Panama for five years, the conch populations in Las Perlas and Coiba have not recovered. The Las Perlas population is recruitment limited and we recommend that a program of law enforcement and monitoring should be implemented immediately to protect this species, conducive to increase spawning and settlement in nursery grounds.

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

Population structure of Dungeness crab (Cancer magister) from British Columbia was evaluated from a survey of variation of eight microsatellite loci in eight populations. Genetic differentiation among the populations surveyed was observed, with the mean F_st for all loci 0.031 (SD = 0.007). The Alison Sound population in the British Columbia central coast displayed less genetic variation and was distinct from all other populations in British Columbia, with pairwise F_st values >0.12, over 20 times the differentiation in other comparisons. The results were consistent with a high level of retention of larval crabs within Alison Sound, owing to reduced water exchange between the sound and adjacent waters. There was no evidence for an isolation by distance model of population structure of Dungeness crab in British Columbia, but there was some indication of differentiation between a west coast Vancouver Island population and a population adjacent to the southern Strait of Georgia.

Populations of the green spiny lobster Panulirus gracilis (Streets 1871) have sustained increasing harvesting pressure in Pacific Panama for decades, but basic information about their biology and ecology in the region is scarce. This study provides baseline data for the densities and biometrics of P. gracilis in Las Perlas and Coiba Archipelagos. The number of surveyed lobsters in both archipelagos was surprisingly low (85 in Las Perlas and 67 in Coiba), and average densities were dismal (4.1 ± 8.8 ind. ha⁻¹ and 5.3 ± 7.6 ind. ha⁻¹, respectively). Saboga and San Jose Islands had the highest relative densities of P. gracilis in Las Perlas, whereas intermediate relative densities were found only on Coiba Island in the Coiba Archipelago. Lobster density was not associated with either substrate or depth. In Las Perlas, female carapace length (CL) was 40–95 mm and that of males was 25–100 mm; in Coiba, female CL was 45–124 mm and male CL was 45–121 mm. In Las Perlas, the smallest lobster with eggs had a CL = 65 mm and a tail length (TL) = 120 mm, whereas the smallest in Coiba had a CL = 60 mm and a TL = 81–115 mm. We recommend implementing: (1) the minimum capture CL as the average carapace length at which half of the lobster population from Coiba is adult (CL = 84 mm; TL = 112–155 mm); (2) a fishing season no longer than 6 mo; (3) management decisions involving local fishermen and native peoples; (4) marine reserves or no-take areas (NTA); and (5) long-term monitoring plans, as the best current options to insure the survival of P. gracilis in the region.

A rapid polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) analysis was designed to examine genetic differentiation of some penaeid shrimps. Three hundred and fifty-six bp of cytochrome-b gene, a specific part of mitochondrial genome, was amplified with PCR to figure out differences between shrimp species Penaeus semisulcatus, Penaeus kerathurus, Parapenaeus longirostris, and Metapenaeus monoceros. PCR products were digested with different restriction endonucleases (DdeI, MboI, MboII, and MseI.). None of the tested enzymes, alone, was able to distinguish between the four shrimp species, but with the combination of the results of two digestions, all of the species could be differentiated. It was shown that PCR-RFLP method can be used to expose fraudulent substitutions of processed shrimps prior to marketing.

Sea urchin hatchery techniques are well established, but cost effective grow-out strategies are still under development. Juvenile green sea urchins (Strongylocentrotus droebachiensis) with a test diameter of less than 15 mm are vulnerable to predation when released into the wild and mortality can be high; therefore a protected nursery phase is required. This study investigated the feasibility of a cost effective on-bottom nursery cage system to provide protection at this stage. Wild-caught juvenile urchins (average diameter 7.93 ± 0.65 mm) were held in specially designed high-density polyethylene (HDPE) mesh tubes, 50 per tube, at two lease sites in Penobscot Bay, ME. Replicate tubes were placed on 3 bottom types (mussel, cobble, and ledge) at the Sloop Island site and on cobble bottom type at the Job Island site. Groups of urchins were counted and measured 5 wk, 3 mo, and 6 mo after placement to gauge handling mortality, growth, and survival. Handling mortality after 5 wk was 5% with no significant difference between treatments. Final survival indicated that cobble bottom type supported the highest survival at Job Island (89%) and Sloop Island (71%), followed by Sloop mussel (59%) and Sloop ledge (56%). After 6 mo the average diameter reached 11.08 ± 1.49 mm. Final average test diameter was significantly larger at Sloop ledge (12.17 mm) and Sloop mussel (12.58 mm), than at Sloop cobble (9.83 mm) and Job cobble (9.66 mm). These results suggest on-bottom culture through the critical nursery phase is technically feasible and may represent an economical way to rear hatchery produced green sea urchin seed to the “planting out” size.

Management of the Nova Scotia sea urchin fishery includes several unusual features: one license per fishing zone, fishers increase resource yields over natural levels by controlling the sea urchin-macrophyte cycle, fishers scale fishing effort to market demand, fishers map the resource in their zones, a reference point for good resource management based on a conspicuous habitat feature, an audit of zone management success, and low ongoing input from the management agency. The low mobility of sea urchins and the opportunity for the diver-harvesters to observe the resource directly make this fishery a good candidate for management by fishers. Variable sea urchin growth and reproduction on a small spatial scale and the high cost of stock surveys by diving make the fishery less suitable for government regulation. Fishing zones were allocated based on the length of feeding fronts (i.e., the deep edge of the macrophyte beds where sea urchins aggregate and where most harvesting occurs). Fishers and government jointly developed enhancement techniques to increase the length of feeding fronts. The reference point used to measure a fisher's success at managing the stock was based on the depth of these feeding fronts.