Shellfish aquaculture in the United States contributes to the global seafood supply, provides habitat and restoration opportunities, and enhances the economic sustainability of coastal communities. Most marine aquaculture production (two-thirds by value) in the United States comprises bivalve shellfish (oysters, clams, and mussels). As the marine aquaculture footprint grows, so too does the potential for negative environmental and space–use interactions. To streamline shellfish aquaculture permitting, many states have developed web-based aquaculture map viewers to communicate critical regulatory, space–use, and natural resource information. In this study, 18 state-level shellfish aquaculture map viewers were reviewed for common design approaches, important data considerations, and useful tools and functions. Key characteristics of a successful shellfish aquaculture map viewer include a user-friendly interface, instructional guidance, the ability to assess both opportunity and risk, inclusion of authoritative data, and a long-term maintenance plan for the viewer and data. The most common design approaches reviewed were Esri Web AppBuilder and Google. Viewers ranged from having 3–27 layers, with “view orthoimagery” (94%) as the most commonly occurring function. This review provides valuable information on using map viewers and technological innovation to communicate shellfish aquaculture planning and permitting information to a variety of stakeholders.

Bivalve aquaculture accounts for 14%–16% of the average per capita animal protein of 1.5 billion people, supporting more than 200,000 livelihoods, mostly in developing countries. Massive mortality outbreaks of various cultured bivalves have been reported worldwide. Repeated episodes of mass mortality not only reduce the production and cause high economic losses but also have a negative impact on natural bivalve populations. The present article reviews the scientific evidence of mass mortality outbreaks of marine bivalve molluscs affected by extrinsic factors. It attempts to summarize the pertinent data published on specific research issues to improve understanding of the diverse factors. This helps to clarify the present state of research and to identify topics for future studies on bivalve mass mortality. It can be seen from the published data that bivalve mass mortality episodes are rarely caused by single factors but are more likely to be triggered by synergistic effects of two or more factors. Understanding these factors could aid in the development of good aquaculture practices and effective fishery management plans for bivalves.

The Atlantic sea scallop fishery is the one of the most valuable fisheries in North America. There is concern about scallops with low-quality adductor muscles, referred to as gray meats, impacting the fishery and the overall health of the stock because an apicomplexan parasite has been linked to gray meats and a mass mortality event that led to the collapse of the Icelandic scallop fishery. Yet, changes in scallop meat color have also been linked to the depletion of energy reserves in the adductor muscle following spawning. Seasonal scallop dredge surveys were conducted across Georges Bank, collecting data on scallop meat quality, scallop abundance, mortality, and reproductive cycles, as well as environmental parameters, including bottom depth and temperature. To investigate multiple causes for gray meats, a set of models were developed to examine the impact of biotic and abiotic factors on gray meat prevalence and meat quality of individual scallops. Model results indicate that different factors influence gray meat prevalence on the southern and northern parts of Georges Bank. In the south, location was a significant factor for predicting the presence of gray meats, highlighting Closed Area I where an outbreak of gray meats occurred after the area reopened to fishing. Yet in the north, reproductive stage was a significant factor, with scallops more likely to have discolored meats after spawning. Study results suggest that gray meats may be a symptom of poor condition that was caused by multiple factors and isolating a single cause may not be possible. Improved screening tests and continued monitoring of scallop health through targeted disease surveys is recommended.

Asian moon scallops (Amusium pleuronectes) were sampled by trawl vessels in the Beibu Gulf, South China Sea, from October 2014 to November 2015. Feeding habits and stable isotopic patterns of A. pleuronectes were examined using stomach contents and adductor muscles based on a conventional stomach analysis method and stable carbon and nitrogen isotope technology. The applicability of A. pleuronectes as a baseline indicator in marine ecosystems in the Beibu Gulf is discussed. The stomach content analyses indicated that A. pleuronectes mainly fed on Bacillariophyta (62%), a small quantity of Chlorophyta (8%), Pyrrophyta (8%), and Cyanophyta (6%). Species of Diploneis, Cyclotella, Pleurosigma, and Navicula played dominant roles in the stomach. The nitrogen and carbon stable isotope ratios were 6.41‰–12.80‰ (average 8.89‰) and –21.45‰ to –17.56‰ (average –19.54‰), respectively. Significant differences (P < 0.01) were observed among seasons in δ¹⁵N, with average values of 9.53‰, 9.80‰, 8.79‰, and 8.34‰ from spring to winter. The analysis of the feeding habits and stable isotopic patterns indicated that A. pleuronectes could be used as isotopic baseline indicators. It is recommended that A. pleuronectes can be used as a common isotopic baseline indicator for the ecology studies in the Beibu Gulf or even in the South China Sea because there is no standard baseline in this marine ecosystem.

The scallop Argopecten purpuratus is a species of high commercial interest in northern Chile and Peru. Both natural and cultured populations are located in shallow bays which are periodically subjected to decreases in the levels of dissolved oxygen and to variations in the availability of food, due to upwelling events or large-scale oscillations such as El Niño–Southern Oscillation. The aim of the present study was to evaluate how the nutritional status of A. purpuratus juveniles affects their escape capacity (as a measure of their vitality) after exposure to hypoxia cycles such as those encountered in their natural environment. For this, three feeding levels were applied for 15 days: scallops fed with a mixture of microalgae equivalent to (1) 6% or (2) 3% of their body mass and (3) unfed scallops. Subsequently, half of the individuals in each treatment underwent daily hypoxia cycles for 7 days and the other half was maintained under normoxia. After this period, using their predator, the sea star Meyenaster gelatinosus, the scallops were induced to escape, and several escape response indicators were evaluated. In general, scallops fed with the highest microalgal ration (6% of scallop mass) showed the best escape performance in terms of the reaction time to the predator, total number of claps, and clapping time and rate, closely followed by scallops fed 3% of their mass. Unfed scallops showed the poorest performance in each of these escape parameters. These results were closely related with the carbohydrate content of the adductor muscle, with unfed scallops showing the lowest content. Hypoxia exposure resulted in a decrease in escape response, and unfed scallops were the most affected. Among unfed scallops, 40% of the individuals maintained under normoxia showed an escape response, whereas only 15% of those exposed to hypoxia escaped the predator. By contrast, and regardless of environmental oxygenation, more than 90% of individuals fed with either 3% or 6% rations escaped the predator. In conclusion, when scallops are under reduced nutritional state (due to low food availability), the cyclical hypoxic periods that they encounter in the natural environment can have profound effects on their vitality, making them more vulnerable against predators.

Overharvest of the once highly abundant northern quahog, or hard clam [Mercenaria mercenaria (Linnaeus, 1758)], has decimated local populations on Long Island, NY, and the ecosystem services they provide. Among the potential ecological consequences of the loss of hard clams, impacts on benthic community structure and function have not been well documented. This study took advantage of a large-scale hard clam restoration effort by The Nature Conservancy in Great South Bay, NY, to investigate these parameters. The benthic communities between areas planted with high densities of adult clams (i.e., spawner sanctuaries) and adjacent sites with no transplants were compared. In clam-stocked areas, there were greater trophic and taxonomic group densities, especially for some environmentally sensitive groups such as crustaceans, and increased species richness, which in turn altered community structure of the resident infauna. Differences between paired sites for macrofaunal diversity and community structure were also observed, likely reflecting larger scale differences in invertebrate communities. Minimal differences were observed in sediment porosity, carbon and nitrogen content, and total organic matter between adjacent areas with and without clams, although all of these parameters were significantly associated with community structure. Although shell density was significantly higher in clam-stocked plots, it explained little of the variation in macrofaunal composition on its own or in combination with other environmental parameters, but in combination with the living clams may have added enough environmental complexity to enhance densities of different trophic groups. Within the short period of 3 y, differences in the benthic community with the presence versus the absence of clams were already detectable. More long-term data incorporating the effect of processes at multiple scales are needed to gain insight into the complexity of rehabilitating coastal benthic environments following the removal of important species such as clams. The results of this work support the notion that M. mercenaria acts as an ecosystem engineer, modifying the environment by creating habitat and enhancing the abundance of other species.

The Manila clam (Ruditapes philippinarum) is one of the most important shellfish species cultured in China. The impact of disease on clam culture is becoming increasingly serious due to the deteriorated aquaculture environment. In July 2015, outbreaks of parasitic disease in the Dalu Island area resulted in death of Manila clams in large numbers. In this study, the parasite was morphologically characterized and its 18S rDNA was sequenced. Anatomical analysis of the infected clams showed that the parasites mainly distributed in the gonad tissue and those infected tissues could barely produce sperm or eggs. A BLAST search against the NCBI database using the 18S rDNA sequence showed that the parasite was 92% similar to the trematode Steringophorus margolisi (GenBank sequence AJ287578.1.1934). To investigate the infection mechanisms of this parasite, expression levels of the genes involved in reproductive processes (sodium–glucose transport protein, cytochrome P450 family 1 subfamily A member 1, lambda-crystallin, collagen alpha-1(IV) chain, inhibitor of apoptosis proteins, and 17β-hydroxysteroid dehydrogenases) were examined in infected and uninfected individuals, respectively. This study provides novel and preliminary data on the molecular mechanisms underlying the reproduction failure in digenetic trematode-infected Manila clams.

Growth curves of the geoduck Panopea globosa were compared from four zones in northwestern Mexico, with three zones in the Gulf of California (Guaymas, Puerto Peñasco, and San Felipe) and one zone on the Pacific Coast of the southern Baja California Peninsula (Bahía Magdalena). The curves were shaped using the von Bertalanffy growth model. The lengths-at-age data for each location were obtained from fishery-independent data at each location. The average asymptotic lengths of P. globosa were 114.4, 156.6, 161.5, and 168.4 mm in Guaymas, Puerto Peñasco, San Felipe, and Bahía Magdalena, respectively. The Kimura's likelihood ratio test was used as the goodness-of-fit trial. In comparison with geoducks from the other locations, geoducks from Guaymas, located on the central Gulf of California, were the shortest, with a significant difference in length from those at the other three sites. Geoducks from the upper Gulf of California (Puerto Peñasco and San Felipe) and Pacific Coast had no significant differences among them. Because the fishing management strategy for this species uses the minimum legal size (MLS), the MLS should vary regionally to promote sustainable use.

The present study was aimed at evaluating the histochemical distribution of alkaline phosphatase (ALP), nonspecific esterase (NSE), peroxidase (POD) and various types of mucous cells in the gill, mantle and hepatopancreas of the ark shell Scapharca subcrenata. The ALP activity was found in the epithelial cells (EP) of the gill filament and the mantle as well as in the basal lamina of the glandular duct in the hepatopancreas. The staining intensity of ALP in the mantle and hepatopancreas was stronger than that in the gill. The NSE activity was detected in the EP in the gill filament, mantle and hepatopancreas, with the hepatopancreas showing a stronger intensity than the gill. The POD activity was located in the EP of the mantle and glandular duct of the hepatopancreas as well as in the connective tissue of the gill. The mantle showed stronger staining intensity of POD than the hepatopancreas. The Alcian blue (pH 2.5) periodic acid Schiff (AB-PAS) histochemical results revealed four types of mucous cells in the gill, mantle and hepatopancreas. Type III cells (nPAS+AB+) and type IV cells (aPAS+AB+) were observed in the gill, mantle and hepatopancreas. Type I cells (PAS+AB–) were not detected in the hepatopancreas but were distributed ubiquitously throughout the gill filament and mantle. Type II cells (PAS–AB+) were not detected in the gill but were distributed ubiquitously in the digestive ducts of the hepatopancreas.

Small flat oysters of the genus Ostrea were collected from China, Japan, and the United States for identification and phylogenetic analysis. Fragments of mitochondrial cytochrome oxidase subunit I and 16S rRNA genes were sequenced in 57 specimens. Shell morphology and phylogenetic analyses identified four closely related groups in the Ostrea stentina/equestris/ aupouria species complex, supporting recent and ongoing speciation. Groups 1 and 2 are both O. equestris (Say, 1834), representing two divergent populations from the Asian Pacific and the Americas, respectively. Groups 3 and 4 are two separate species independent of O. equestris. Group 4 is O. stentina occurring in northern Spain, Portugal, Morocco, and northern Tunisia. Group 3 is a new species Ostrea neostentina sp. nov. found in southeastern Spain, eastern Tunisia, Hong Kong, and Japan. The occurrence of O. equestris in both Atlantic and Pacific oceans, from Argentina, Columbia, the United States, Gulf of California, Japan, and China to New Zealand, is unusual and highlights wide connectivity of Ostrea species as part of the marine ecosystem. This study provides the first record of O. equestris and O. neostentina sp. nov. along the southern coast of China and adds to the understanding of the diversity, global distribution, and evolution of Ostrea species.

The primary task of a selective breeding program to increase the production of Crassostrea gigas is the development of a new, fast-growing, and highly resistant oyster cultivar. Genetic parameters are the basic elements of such a program, which could better realize the intended program. In this study, a mixed-family approach combined with a partial factorial mating design was applied to obtain the experimental materials. Both genetic parameters and genotype by environment (G × E) interactions were analyzed with a mixed linear model and restricted maximum likelihood (REML) using the software package ASReml-R. The results showed the following. (1) the heritability of seven traits ranged from 0.19 to 0.43 for RS (RuShan) and 0.11 to 0.44 for KTD (KongTongDao). Except for the genetic correlations between shell width (SW) and other traits for KTD were not significant, the other genetic correlations between traits for RS and KTD were all positive and significant, 0.48–0.99 and 0.42–0.98, respectively. All phenotypic correlations between these seven traits for RS and KTD were significant and positive, ranging from 0.14 to 0.84 and 0.14 to 0.80, respectively. There is a high positive genetic correlation between the shell-closing strength (SCS) and adductor muscle weight (AMW), indicating that the selective breeding of SCS can play a synergistic role in the selection of AMW. (2) The significance of the genetic correlations between RS and KTD for wet weight (WW) and SCS were both less than 0.8, which meant that the effect of the G × E interactions should be considered. Therefore, G × E interactions had an important impact on the design of WW and SCS selective breeding. As a result, it could be set up for a site-specific breeding program for WW and SCS.

Temperature and salinity and their interaction exert a major control on the life cycle of the eastern oyster (Crassostrea virginica), affecting reproduction, development, growth, and mortality. Quantifying specific temperature and salinity relationships on oyster growth and mortality has, however, proven difficult, with data suggesting potentially region-specific responses. Legacy and recent data from field tray studies from public oyster grounds in Barataria Bay (BA) and Breton Sound (BS) were used to estimate growth and mortality rates as a function of temperature and salinity. Previous studies conducted in BA and BS reported differences in growth and mortality between the basins. In the present study, environmental conditions were synchronized to compare growth and mortality between basins at similar combinations of temperature and salinity. Results indicate that when temperature and salinity are the same (synchronized), seasonal oyster growth and mortality rates still differ between BA and BS. Given the same salinity and temperature conditions, differences in growth and mortality rates between estuaries may persist because of differences in other environmental conditions (i.e., food quality and composition, hydrology, site history, and salinity variation) or localized genetic adaptations to environmental conditions.

The study measured the mean and ranges of seasonal changes in whole body energetic values in two age groups of the Sydney rock oyster Saccostrea glomerata from the Clyde River, NSW, Australia. Oysters were collected over four seasons from two aquaculture-relevant age groups (24 and 36 mo) identified as key harvesting ages. Protein, lipid, glycogen energy equivalents, and electron transport system (ETS) activity were determined to identify seasonal changes in energy stores and consumption and to calculate cellular energy allocation. There were clear seasonal trends in energy changes, with glycogen and lipid energy equivalents highest in summer, decreasing to their lowest concentrations in autumn, and then slowly increasing through winter and into spring. Protein energy equivalents and ETS activity demonstrated an opposite trend, with increases in autumn and stable through the other seasons. Cellular energy allocation showed seasonal change, with highest values over summer, gradually decreasing in autumn and winter, and then starting to increase again in spring. These results indicate that seasonal changes in temperature, salinity, and food availability as well as reproductive cycles have a significant influence on S. glomerata energy storage and use. Developing an understanding of energetic responses in bivalves in response to environmental conditions can facilitate a more detailed understanding of growth potential and responses to aquaculture practices such as stocking density. As well, understanding natural energetic fluctuations allows a baseline for the assessment of other field-based stress responses such as anthropogenic contamination in S. glomerata.

Common-pool resources such as public oyster grounds are especially vulnerable to overexploitation and habitat loss. Like those elsewhere, oyster populations and habitat of Louisiana public grounds are in decline. To maintain reef habitat and increase oyster abundance, a sustainable harvest model is applied, which allows harvest above that required to maintain reef cultch stasis. The model is restrained to promote shell gain by limiting fishing by area, type (sack versus seed), effort, and season. Harvest quotas and cultch removal rates derived from shell-budget–based modeling are a foundation for sustainable management of public oyster resources.

Condition, growth, and reproductive indices of blue mussels (Mytilus edulis) grown in deep and shallow sites were studied from May to December 2016 in the South Arm region of Notre Dame Bay, Newfoundland. The region was shown to be characterized by a seasonal thermocline that formed in April and lasted to October annually, resulting in a cold-water deep layer (mean annual temperature: 4.36 ± 5.1°C) and a comparatively warmer surface layer (mean annual temperature: 5.81 ± 6.3°C). The deepwater culture sites extended into the cold-water layer and the shallow sites were typically in the warmer layer above. Mussels grown in shallow sites had longer and heavier shells than those from deepwater sites, likely linked to warmer surface waters. Both reproductive and physiological condition indices were high for mussels from both culture depths in May. Physiological condition declined for both deep and shallow cultured mussels from May through to August. Mussels from deep sites, however, had a higher overall mean dry tissue weight: wet tissue weight ratio for the study period. Reproductive indices, including measurements of reproductive output, declined for shallow mussels from May through to August, but remained high for deep mussels until August when a significant spawn occurred for mussels from both depths. In addition, mussels from deep sites were observed to maintain themselves in a prespawning ripe stage for a longer period than those from shallow sites. Variations in physiological and reproductive indices for mussels from each respective culture depth were thought to be linked to differences in the environmental characteristics of the deep and shallow water layers, including rate of temperature change and potential differences in phytoplankton quality and energetics. The additional data provided in the present study add to the current understanding of the effects of the deepwater environment on mussel reproduction patterns and its relationship to production meat yield. The data will help in highlighting the benefits of using deepwater sites leading to increased environmental sustainability for mussel culture in subarctic coastal environments such as those on the north coast of Newfoundland.

Color is an important indicator in evaluating the quality of pearls. Despite the well-developed technology of pearl production, evidence for what determines pearl color is largely absent. In the present study, a 2 × 2 complete double-row implantation experiment was conducted using the purple and white strains of mussels of Hyriopsis cumingii in three different aquaculture environments. The effect of purple and white strains of mussels on seedless pearl color was analyzed using a mixed linear model. The results showed that the effect of the donor mussel, which provides the mantle tissues, on seedless pearl color was significant (P < 0.001), whereas neither the strain of the host mussel nor the aquaculture environment had a significant influence on pearl color. The estimated values for the effect of the donor mussel on pearl color parameters CIE L*, a*, and b* were –9.35, 2.49, and 3.33, respectively. This study provides direct evidence that the color of a seedless pearl is mainly determined by the donor mussel, and both the host mussel and the aquaculture environment have a negligible role in the determination of pearl color.

Knowledge of squid early life history is relatively poor despite its importance for fisheries management. The longfin inshore squid Doryteuthis pealeii (Lesueur, 1821) is a commercially important species harvested extensively along the northeastern United States continental shelf. To understand the effects of fishing and environmental variability on D. pealeii in an inshore spawning ground (Nantucket Sound, MA), egg deposition and embryonic development were monitored in situ at commercial fish weirs in spring and summer 2008 to 2016. Logbooks were maintained in which catch (including the presence of egg masses) and effort data for each weir were recorded daily. Seawater temperature was recorded using data loggers affixed to the weirs. Newly deposited egg masses were transferred to a mesh enclosure on an opportunistic basis and placed immediately adjacent to the weir to permit semiweekly retrieval and sampling. Samples (five randomly chosen “fingers” excised from a mass) were chilled and transported to a nearby wet lab for microscopic examination to determine embryonic development stage. Hatch timing was determined via direct observation of paralarvae emerging from egg masses and development time was calculated as the number of days between egg mass deposition and hatching. The timing and duration of egg mass deposition varied between years. Embryonic development time of 15 egg masses ranged from 12 to 34 days and generally decreased at warmer temperatures. In situ observations were consistent with the findings of laboratory studies of D. pealeii and other loliginid squids.

The jumbo squid Dosidicus gigas was recently claimed to be an iteroparous species with ovaries returning to an immature, resting stage after spawning. Analysis of the data and figures presented in two recent articles revealed that this claim was based on misinterpretation of histological information and that Dosidicus is not iteroparous. Having consensus on the reproductive strategy of Dosidicus is important for the management of fisheries for this species.

The eastern elliptio Elliptio complanata is a species of freshwater mussel common to streams and rivers of the Atlantic Coast. Egg fertilization, larval brooding, and glochidial release are reported to occur within a period of several weeks during early to midsummer. In this study, mussels were exposed to manipulated photoperiod and water temperatures to prolong the availability of glochidia for use in artificial propagation and research. Brooding mussels were collected from Pine Creek, Tioga County, PA, in late December and were housed in groups subjected to one of four environmental treatments: natural temperature and photoperiod, 6-wk delay in natural conditions, 12-wk delay in natural conditions, and natural temperature and photoperiod with a winter low of 10°C. Reproductive activity was monitored for 1 y. Mussels subjected to natural conditions released mature glochidia between 16°C and 19°C with a photoperiod of 15 h of light. Temperature and photoperiod delays of 6 and 12 wk delayed reproduction proportional to the treatment, and constant 10°C winter low temperatures slightly shifted the timing of glochidial release. Survival during the study was high (96%–100%). Data indicate that the seasonal availability of E. complanata glochidia can be extended 3-fold using photoperiod and temperature manipulation.

The main objective of this study was to allocate and evaluate the most optimum condition to prepare the chitosan and chitosan nanoparticles that will, subsequently, give the best physicochemical characterization regarding the nanoparticles' size and surface morphology. Chitosan from the exoskeleton wastes of Procambarus clarkii with degree of deacetylation 87% was extracted. Viscometry indicated that the obtained chitosan had a low molecular weight that can be useful in many applications. Chitosan nanoparticles were prepared by using different concentrations of chitosan and the polyanion sodium tripolyphosphate (TPP). For the determination of the optimum condition for the prepared chitosan nanoparticles, three different ratios of chitosan to the polyanion TPP were used, 1:1, 3:1, and 1:3. A novel nanoparticle system composed of low molecular weight chitosan was successfully prepared by the ionotropic gelation technique under an aqueous-based condition. The physicochemical characteristics of chitosan and chitosan nanoparticles were elucidated by Fourier-transform IR spectroscopy, nuclear magnetic resonance spectroscopy, elemental analysis, scanning electron microscopy, transmission electron microscopy, and zeta potential. The best physicochemical characteristics were obtained by adding chitosan to TPP in a ratio of 1:1. The small particle size and narrow range distribution of the obtained chitosan nanoparticles may increase their chance for easy and efficient manipulation for several applications in various fields. In addition, the obtained positively charged chitosan nanoparticles can be used for the delivery of negatively charged compounds.

In recent years, the total quantity of abalone produced on farms worldwide has increased significantly, although abalone fisheries have declined. Production from fisheries has decreased from almost 20,000 metric tonnes (mt) in the 1970s to only about 6,500 mt in 2016/17. Over the same period, farm production has increased from negligible quantities in the 1970s to about 160,662 mt in 2016/17, the vast majority being produced in China (139,697 mt) and South Korea (16,042 mt). Illegal exploitation, particularly in South Africa, Australia, New Zealand, and California, is still a major problem reaching an estimated 7,000 mt in the 2016/17 period. A positive development that partially counteracts the illegal exploitation has been the establishment of restoration and ranching operations in various countries around the world. Taking all sources of abalone into account (fished, farmed, and illegal), it is estimated that in 2017, the total availability of abalone to the world market was 174,162 mt.

Microorganisms and parasites are some of the major threats to aquaculture, including abalone culture worldwide; however, few reports concerning these microbes and parasites in abalone have been published. Moreover, several studies were conducted to determine the microbial load and degree of parasitism in abalone of other species but not the abalone Haliotis asinina of the Philippines, particularly in Palawan. This study was conducted to assess the abundance of microorganisms and microparasites in the cage-cultured abalone. The microbial abundance was determined by dilution plate count technique. Slide sampling and scoring was performed using methylene blue and acetocarmine stains to determine the abundance of microparasites. Results revealed that fungi have the highest total abundance among the four functional groups of microorganisms present in abalone. The Gram-positive bacteria had the highest abundance in the digestive tract (178 × 10³ CFU/g). Actinomycetes had the highest abundance in the gonad (35 × 10³ CFU/g). On the other hand, fungi had the highest abundance in the gills (198 × 10³ CFU/g) and in the mantle (95 × 10³ CFU/g). The highest abundance of microorganisms was found in the digestive tract of abalone. Microparasites such as trematodes, nematodes, copepods, and protozoans were found in cage-cultured abalones. Among these microparasites, trematodes were found abundant in the gills, whereas protozoans were abundant in the stomach of abalones.

This study was conducted to isolate, test the antimicrobial potential, and characterize bacterial isolates from the gut of Haliotis asinina collected from cage culture and wild population. Isolation was performed using dilution spread plate method and antimicrobial property was determined using streak plate method against nine test microorganisms. Results showed that of the 29 isolates from the cage-cultured samples, five isolates showed the presence of antimicrobial property against Escherichia coli, Staphylococcus aureus, Bacillus cereus, Bacillus subtilis, Bacillus megaterium, Pseudomonas aeruginosa, and Candida albicans. Among the 30 isolates from the wild-caught samples, six isolates showed the presence of antimicrobial potential when tested against E. coli, S. aureus, B. cereus, B. subtilis, B. megaterium, and C. albicans. None of the isolates inhibited Aspergillus niger or Aspergillus flavus. The bacterial strain coded C28, isolated from cage-cultured abalone, and that inhibited the most test microorganisms was subjected to cultural, morphological, and physiological characterization. It was characterized as a bacterial strain closely related to the genus Pseudomonas. The results suggest that bacteria in the gut of H. asinina have potential antimicrobial properties where bacteria related to Pseudomonas spp. are present.

Pacific abalone Haliotis discus hannai is one of the most economically important marine shellfish and is mainly distributed in the cooler seas of northern China. The molecular reactions that occur in this species under high temperature conditions have not been determined. To understand the molecular mechanisms of this species under heat stress, transcriptomic analysis of the hepatopancreas was performed at 33°C (22°C was used for the control) for 1 h on an Illumina HiSeq 2500 platform (pooling of six animals into single RNA-sequencing libraries). The results showed that 17,852 unigenes were annotated. In all, 8,532 genes were significantly differentially expressed in the test group compared with the control group, including 4,788 upregulated and 3,744 downregulated genes. Enrichment analysis identified some noteworthy GO terms (cellular process and response to stimulus) and pathways (protein processing in the endoplasmic reticulum (ER) and apoptotic signaling pathways), and these were further analyzed. Analysis showed that genes indicative of mitochondrial damage were upregulated; DNA damage formation, and fatty acid and amino acid synthesis increased; fatty acid decomposition reduced; and misfolded proteins accumulated in the ER, and the unfolded protein response and ER-associated degradation were triggered to relieve ER stress. In addition, the apoptotic pathway was activated; however, some genes associated with anti-apoptosis and molecular chaperones were upregulated to maintain homeostasis after heat stress. These data provide an increased understanding of the heat stress mechanisms in Pacific abalone.

Pacific abalone (Haliotis discus hannai) is an economically important species of sea snails found in China. Live abalones sold in domestic markets are sealed in insulated containers for transportation over extended periods of time (6–24 h), during which this species may experience stressful conditions and spoil. This study assessed the survival rate and weight loss rate (WLR) of abalone under various treatments to determine the optimal packaging transport conditions. Specifically, temperature, supplemental humidity and oxygen, and air exposure during simulated live transport were investigated. Results revealed that the survival rate increased significantly after cold-water shock and humidity control, whereas oxygen supplements did not have a significant effect. In addition, WLR significantly increased over time (P < 0.05). An additional experiment was conducted to investigate the stress response caused by air exposure. Hemocyte parameters, including total hemocyte count (THC), hemocyte mortality, and reactive oxygen species (ROS), were estimated for 2, 6, 12, 24, and 30 h after air exposure at different temperatures. Results revealed that THC significantly decreased after 30 h of air exposure at 5 and 10°C, and after 24 h of air exposure at 20°C. Hemocyte mortality and ROS significantly increased, peaking after 30 h at 5 and 10°C, followed by a gradual decrease over the subsequent 24 h recovery period. THC and ROS levels remained higher than the control levels by the end of the recovery period. The parameters investigated in this study could serve as indicators for the effects on the functional immune response and physiological stress of abalone during live transportation.

The Pacific abalone Haliotis discus hannai is a valuable food resource in China. Understanding the early development of this species will allow cell fate tracking and may help to guide artificial seeding. Scanning electron microscopy (SEM) was used to examine the morphologies of the major life stages of H. discus hannai from artificial fertilization to the juvenile stage (23 days postfertilization). The results represented the first comprehensive SEM micrograph record of early development in the Haliotidae. Special attention was also paid to shell formation in H. discus hannai, as these results might help inform biomineral-related research.

High-density abalone farming is restricted by the carrying capacity of water bodies where abalone is farmed. An analysis based on the cobweb model under restriction of environmental carrying capacity suggests that a disequilibrium in abalone market is likely to occur, caused collectively by the market failure due to the interaction of environmental carrying capacity restriction, externalities, and market condition. Where the equilibrium output represented by the junction of supply curve and demand curve exceeds the maximum sustainable output, externalities and limited carrying capacity will lead abalone market to an unstable state where the rise of equilibrium price and the deterioration of environment quality will reinforce each other and produce a positive feedback, i.e., an increase in price is likely to cause a corresponding decline in production, which, in turn, lead to a further increase in price until the industry runs into collapse.

Around the world, abalone species are a highly valuable marine resource. In recent years, abalone fisheries in the Northeast Pacific have suffered massive mortalities because of environmental factors. Aquaculture has been proposed as a solution to stop the collapse of this multimillion-dollar resource. Moreover, it has been shown widely that coculturing two or more species can increase the productivity of the resources cultured. The aim of this study was to test whether the growth rates of the green abalone Haliotis fulgens would increase when cocultured with the warty sea cucumber Apostichopus parvimensis. Growth rates of juvenile abalone increased by 29% in the presence of medium densities of A. parvimensis; however, coculture settings are not common in the Northeast Pacific. To our knowledge, this is the first coculture reported of these two species. Thus, these findings provide relevant information to promote innovative strategies for sustainable production of food.

The abalone Haliotis asinina is among the highly valued aquaculture commodities in the Philippines. But, the production of abalone in general has declined primarily because of unregulated exploitation. Predation, both in the wild and in grow-out cages may also contribute to the decrease of abalone production. As there has been no record on the predation of H. asinina in the past, this study is the first to gather information on the predators of this species, taken from the perspective of local fisherfolks. Four sites in Palawan Island, the Philippines, identified to have active gathering of wild abalone were sampled. Descriptive survey method with a semistructured questionnaire was used to interview local fisherfolks regarding their knowledge on predators of abalone. A total of 84 respondents were interviewed of which 53 have observed actual predation of abalone. Twenty-five species of predators composed of fishes, crustaceans, molluscs, an octopus, and a sea turtle have been identified. Of this, four species, namely, the fishes Cyclichthys orbicularis and Diodon liturosus, Octopus sp., and the crab Charybdis feriata were consistently observed in the four sites based on the synthesis of data obtained from the fisherfolks. Most respondents suggest that aquaculture is an essential way to increase the abalone production. The information herein serves as baseline information to develop appropriate design and management of culture facility to minimize predation and to maximize the survival of cultured abalone. Further study on the ecology, particularly the actual observation of predation and its effects, is recommended.

Nearshore kelp forest ecosystems are highly vulnerable to climate change and ocean warming, which can alter community dynamics and change the trajectory of species recovery in unpredictable ways. Abalone (Haliotis spp.) populations in the Southern California Bight (SCB) are still recovering from a combination of overfishing and disease, despite the closure of the fisheries 20 years ago and active restoration programs for abalone species in the region. For this study, abalone recruitment and sea urchin populations were surveyed in artificial habitats (16–22 m) across a spatial and temporal climatic gradient in southern California from 2010 to 2017 to inform the development of climate-ready abalone restoration programs. The SCB encompasses warm and cool islands, and experienced two periods of ocean conditions—cool (2010–2013) and warm ocean conditions (2014–2016). Dive surveys of the artificial habitats revealed that juvenile abalone recruitment remained low during the study period, suggesting that recovery is slow. Warm-water years favored recruitment of juvenile pink (Haliotis corrugata) and green abalone (Haliotis fulgens), with the highest abalone recruitment observed at Catalina Island. Endangered white abalone (Haliotis sorenseni) were not observed despite placing the artificial habitats in suitable deep rocky reefs, which is further evidence supporting their endangered species status. The coolest site, San Diego, had little abalone recruitment, with a few juvenile red abalone (Haliotis rufescens) and threaded (Haliotis kamtschatkana) abalone present. Sea urchin abundance and diversity increased during the warm period, with the largest increase at Catalina Island. During the warm period, Coronado sea urchin (Centrostephanus coronatus) increased in abundance, coincident with a decrease in the commercially valuable temperate red sea urchin (Mesocentrotus franciscanus). Potential shifts in the sea urchin assemblage to warm-water sea urchins may negatively impact recovering abalone populations and the red sea urchin fishery. Climate-ready abalone restoration will require ecosystem-based monitoring, tracking on not only abalone recruitment but also sea urchins, algal abundances, ocean temperature, and kelp forest communities as climate change may lead to complex and unexpected ecosystem interactions.

Extreme environmental events that trigger mass mortalities are making fisheries management more challenging. Catastrophic events can have unforeseen impacts on fished resources outside the scope of fishery models and management plans. Mass mortality events (MME) that rapidly reduce densities can decrease the productivity of Haliotis spp. abalone and other benthic free spawning marine invertebrates that require minimum densities for reproductive success. Density-based indicators using fishery-independent measures of density on the fishing grounds serve as an important alternative source of information for management. In northern California, this approach is used to manage the recreational red abalone Haliotis rufescens fishery using densities at key fished sites to guide management. In 2011, a harmful algal bloom (HAB) impacted the southern region of the fishery providing a test of the density-based indicators. Surveys following the HAB revealed a 35% decrease in average density in the southern portion and a decrease in the fishery overall. Empirical fishery-independent density surveys could be used in a range of fisheries for detection of impacts from nonclimate-related stressors such as overfishing and pollution as well as climate-related stressors such as warming, acidification, hypoxia, and disease bolstering climate-ready management. Ecosystem indicators may also be used as early indicators of future changes to productivity. As climate change is predicted to increase the intensity and frequency of MME, managers will need to use sensitive indicators to inform effective climate-ready management responses.