Rotational harvesting of marine areas is a spatial fisheries management tool that aims to improve fishing sustainability (e.g., protect fishing resources whereas maintaining fishing yields). It consists of dividing fishing grounds into areas that are alternatively closed for a period. In November 2016, a marine rotational harvest area was implemented in the Bay of Seine (English Channel, French coast), one of the main king scallops (Pecten maximus) fishing grounds in Europe. The king scallop is the most valuable commercial marine species landed and sold in France. As this marine rotational harvest area was established, the biomass of king scallop in the Bay of Seine has multiplied by three times. Using a 30-y dredge survey time series, a general linear model was developed to assess the impact of this marine rotational harvest area on the rising biomass of king scallop in the Bay of Seine. This statistical analysis demonstrated the role played by rotational closure areas in improving P. maximus stock sustainability. The effect of this management tool was, however, dependent on the life stages of P. maximus, environmental conditions and fishing effort regulations.

The ribbed mussel, Geukensia demissa (Dillwyn, 1817), is an abundant bivalve in New England salt marshes and is a long-term integrator of anthropogenic nitrogen loading to a watershed. The response of G. demissa morphometrics, condition index, density, and nitrogen and carbon isotope values were examined at Spartina alterniflora (Loisel, 1807) creek edge, creek wall, and mudflat habitats from two pairs of nutrient-enriched and reference creeks at Plum Island Estuary, MA. Ribbed mussels from the creek wall had greater shell weight and condition index than mussels from the S. alterniflora creek edge or mudflat habitats. Ribbed mussel density was generally greater at the creek wall and unexpectedly greater at the unfertilized Nelson Creek than at the fertilized Clubhead Creek in 2013. Few G. demissa were collected from the mudflat in any creek. Ribbed mussels collected from creek wall habitat in fertilized creeks demonstrated lower nitrogen isotope values than reference creeks resulting from the fractional contribution of the nitrogenous fertilizer in the experimental creeks. Significant differences between carbon isotope values were inconsistent between the nutrient-enriched and reference creek pairs. Carbon isotope values indicated the main food source of G. demissa, a primary consumer, was phytoplankton. Despite significant differences in G. demissa nitrogen and carbon isotope values between enriched and reference creek pairs, the <2‰ difference indicates that moderate levels of nutrient enrichment may not have been sufficient to elicit a bottom-up response in the phytoplankton that transferred to the local mussels. This study highlights the temporal and spatial complexities between the response of primary producers to nutrient over-enrichment and the response of G. demissa condition and distribution in tidal salt marshes along the Atlantic coast.

ABSTRACT Understanding the dispersal dynamics of molluscan larvae is crucial for population structure analysis, population dynamics assessment, and effective management of exploited or declining species. Traditional methods of larval identification rely on morphological analysis, labor-intensive and costly. Alternatively, DNA analysis has been used for molluscan larval identification, but the quantification of larvae using molecular methods remains unclear. In this study, a molecular identification method for Semimytilus algosus larvae in field samples, along with a quantitative approach cross-validated with microscopy counting are presented. The quantitative proficiency of the method was evaluated using subsamples of known larval quantities, showing a high correlation between PCR results and larval count, but when blind field samples were quantified, the correlation was lower. Although this method may not replace larval counting by microscopy, it provides quantitative information about total larval DNA that could be considered in the future as a relevant predictor for settlement.

In the late 1940s and early 1950s Thurlow C. Nelson and Harold H. Haskin conducted a series of mark-recapture experiments to assess the growth of hard clams (Mercenaria mercenaria) on Delaware Bay mud flats adjacent to the Rutgers University Oyster Research Laboratory in Cape May County, NJ. Two specimens from these experiments were recovered alive on September 7, 1980. The growing shell margin of one of these clams (Specimen #1) had been notched with a hack saw between March and December 1947. The growing shell margin of the second clam (Specimen #2) had been notched with a small triangular file between March 1948 and December 1951. Examination of polished shell sections (cut along the axis of maximum growth) of specimens #1 and #2 revealed, respectively, 33 and 30 dark (translucent) bands within the postnotch regions of the outer and middle shell layer of each specimen. The presence of light (opaque) shell material in the outer and middle shell layers at the growing margin of each of these specimens is consistent with the observations of other workers that indicate the formation of dark (translucent) bands in this species during the winter months in certain coastal environments from the MidAtlantic region northward along the east coast of North America. The present study provides convincing evidence that alternating light (opaque) and dark (translucent) bands within the outer and middle shell layers of Mercenaria mercenaria from Delaware Bay, NJ mud flats reflect annual cycles of growth and can be used for estimating the age of hard clams from this region. It is believed that the present study represents the longest mark-recapture study of growth patterns within the shells on any bivalve mollusc.

The freshwater gastropod, Bellamya purificata, is recognized for its ecological and economic importance. Nevertheless, the mechanism of shell color formation in the white shell of B. purificata remains unclear. This study aimed to investigate the molecular mechanisms underlying shell color differences by deeply sequencing the mantle tissue transcriptomes of blue-shelled and white-shelled B. purificata (BBPM, WBPM). Through bioinformatics analysis, genes were functionally annotated, and genes and metabolic pathways related to shell color formation were identified using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis. The results revealed significant differences in gene expression related to shell color formation. A total of 423 differentially expressed genes were detected, of which 224 genes specially were up-regulated in WBPM. Kyoto Encyclopedia of Genes and Genomes analysis of differentially expressed genes showed that the formation mechanism of the WBPM is related to tyrosine metabolism, tryptophan metabolism, arachidonic acid metabolism, the Notch signaling pathway, and porphyrin metabolism. The reduction in melanin synthesis and pigment deposition is likely the main reason for the white shell color formation in white-shelled snails B. purificata. The tyrosinase genes related to melanin synthesis and genes related to tryptophan metabolism significantly decreased in white-shelled snails B. purificata. Furthermore, reduced production of leukotriene C4 from arachidonic acid metabolism appeared to prevent pigment deposition, whereas endocytosis inhibited the Notch signaling pathway, further decreasing melanin synthesis. This study provides important information for understanding the mechanism of white shell color formation in B. purificata, laying a foundation for further research.

Obtaining basic life history information, such as age and size at maturity, for invertebrates subject to harvest is an important first step in assessing population status. In estuaries of the southeastern United States, the gastropod Cinctura hunteria (banded tulip, Perry, 1811) is regularly collected for the shell and aquarium trades; however, basic life history information is sparse. The objective of this study was to determine the growth rate of C. hunteria using three methodologies: population length-frequency, mark-recapture studies, and laboratory growth. Age and size at maturity were also verified through histological analyses. Monthly surveys were conducted from October 2018 to October 2020 at two sites in Tampa Bay, FL, within the core of the species' range. Two models were compared per methodology to define growth rate. First, population metrics were used to estimate von Bertalanffy growth parameters of asymptotic length (L_∞) and Brody's growth coefficient (K) using Gaussian mixture (GMM) and electronic length-frequency (ELEFAN) models. Next, mark-recapture and laboratory growth data were used to estimate L_∞ and K using a Bayesian Fabens method and the Wang growth model. The average estimated age at maturity for male and female C. hunteria was 2 y of age at similar but slightly larger sizes for females (42.2 mm) than males (38.2 mm). Based on the Tampa Bay populations studied, the GMM and BFa models were the most biologically plausible for maximum age and size and for predicting growth increments, and together had an average L_∞ of 81.3 mm and K of 0.112 y^–1. The mean shell length observed (51.6 mm) was estimated to be 3-y-old, the average maximum age observed on the reefs was estimated as 4-y-old, and typical individuals were estimated to contribute reproductively over two to three breeding seasons during their lifetime. Understanding the age and size at maturity of individuals and their potential reproductive contribution should be considered when developing and implementing marine life management practices and regulations.

Oyster shell is a critical component for restoring and enhancing oyster reefs. An oyster shell recycling program could partner with 10–40 restaurants to collect between 2,160 and 4,978 cubic yards of oyster shell over a 10-y period. Overall program costs, consisting of collection, storage, and administration, are estimated to range between $85,782 and $144,720 per year ($356–$604 per cubic yard of shell), depending on program participation levels and labor costs. These shells could be used to construct 15–36 acres of new oyster reefs that would be expected to yield ecosystem services annually. The estimated mean payback period of the program is 16–23 y, that is, it would take 16–23 y for the estimated mean cumulative value of these ecosystem services to exceed the mean estimated cumulative program costs.

ABSTRACT Eastern oysters (Crassostrea virginica) are well known for their tolerance of anoxic conditions. Earlier studies revealed biochemical and physiological changes during acclimation to anoxia and some reported the expression of anoxia-responsive genes. Studies summarized here reveal that extended valve closure, valve integrity (no holes), and heart rate reduction/ cessation appear to contribute to long-term anoxic tolerance of the eastern oyster. A single hole drilled into a valve compromised the oysters ability to survive under anoxic conditions. Mechanical and behavioral contributions to anoxic tolerance have not been well studied in bivalves.

This study validated hand tong sampling as a cost-effective, quantitative alternative to “gold-standard” quadrat sampling facilitated by SCUBA diving. Side-by-side replicate sampling was conducted in six managed oyster habitat areas in Apalachicola Bay, FL, using hand tong and quadrat sampling approaches. Data were analyzed using cumulative population size distributions and conventional oyster fishery monitoring metrics. Cumulative height distributions and binned height data from all six sites demonstrated excellent agreement between quadrat and hand tong sampling approaches, with low D-statistics from Kolmogorov–Smirnov (K–S) test outputs across sampling sites, ranging from 0.06 to 0.16. Cumulative height distributions discerned from hand-tong sampling were indistinguishable from those derived from quadrat sampling at four of the six sampling sites (K–S test, P≥0.05). Median oyster heights were statistically indistinguishable between quadrat and hand tong samples at all sites (Mann–Whitney U-test, P>0.05). Mean oyster heights and the number of harvestable bags per acre were statistically indistinguishable between quadrat and hand tong samples at five of the six sites. Oyster counts per square meter and by size bin discerned by hand tong sampling and quadrat sampling were indistinguishable at four of the six sites. Overall, there was excellent fidelity of tong sample estimates compared with quadrat sample estimates, including detection of live oysters across size bins, when present. This study determined that standardized hand-tong sampling and quadrat sampling approaches produce functionally equivalent monitoring data. Hand tong sampling offers managers an additional tool to conduct oyster habitat assessments and monitoring under appropriate environmental conditions. Relative to quadrat sampling using SCUBA diving, hand tong sampling requires fewer trained personnel and has lower initial vessel and equipment costs, lower vessel and equipment maintenance costs, and fewer safety concerns. Together, these can facilitate the needed collection of more frequent and longer-term oyster monitoring data.

There is growing evidence on how shellfish aquaculture can provide beneficial habitats for marine communities, yet gaps remain about how farm attributes contribute to habitat usage. To assess how farm tending activities and the presence of biological fouling on farming gear impact habitat usage, point-of-view action cameras were used to document fish activity in and around oyster cages, floating bags, and a natural marsh habitat on an oyster farm in the Little Egg Harbor region of Barnegat Bay, NJ in 2019. A total of 27 species from 4 phyla were observed with five species; Atlantic silverside Menidia menidia, mummichog Fundulus heteroclitus, grass shrimp Palaemonetes spp., blue crab Callinectes sapidus, and feather blenny Hypsoblennius hentz; accounting for over 98% of the total observations. Significantly more individuals were observed in the floating bags than in the other two habitat types. Farm tending activities had an overall neutral impact on the number of individuals observed on the farm, with Atlantic silverside being the only species observed more during tending activities. The median time it took for a fish to return after a human disturbance was 1.07 min. The two gear types were colonized by different biological fouling communities, which provided species-specific benefits. Heavy fouling attracted more individuals to the floating bags, whereas fouling had little impact on the number of individuals observed in the oyster cages. These data support how shellfish farms and their attributes can provide habitat provisioning for local species and be used to inform management.

Tourists represent an emerging mass market for shellcraft in areas where the pearl oyster, Pinctada maxima, supports cultured pearl production. An analysis of purchase decisions related to half-pearl and mother-of-pearl shellcraft as souvenirs is now necessary to determine whether there is scope to increase half-pearl production with P. maxima. On such basis, this study created a task environment to generate data on half-pearl and mother-of-pearl shellcraft purchased as souvenirs by tourists at a popular coastal destination in Papua New Guinea. Data were generated by observing purchase decisions and then questioning consumers about how selected choice criteria influenced their decisions. In analyzing these data, it was found that 94% of interactions with the task environment (n = 142) resulted in a sale. A key finding was that purchase decisions were nonrandom with respect to the available products and mother-of-pearl earrings accounted for 66% of all sales, which was significantly more than expected (chi-square = 120.2, P < 0.01) and associated with strong preference (D = 0.71). Although preference for mother-of-pearl earrings does not negate the potential of tourism to create mass-market opportunities for half-pearls, it does highlight challenges in the realization of such potential. More broadly, the implications of purchase decisions are discussed and strategies to support expansion of half-pearl production with P. maxima are proposed.

The pearl oyster, Pinctada fucata, is typically cultured to produce marine pearls in China. Owing to the surgical transplanting of the pearl nucleus and the infection from various pathogenic bacteria, the mass mortality of cultured pearl oysters has frequently happened. Therefore, understanding the immune defense mechanism of P. fucata is crucial. Hepatopancreatic transcriptome analyses of P. fucata were performed before (0 h) and after (6 and 24 h) Vibrio alginolyticus infection to determine the potential early immune response against bacterial infection. A total of 48,175,132 clean reads were de novo assembled into 57,780 unigenes, of which 22,971 unigenes had annotations from the public databases. According to the clustering analysis, the 0 and 6 h groups had the greatest differences in gene expression patterns, but the patterns of the 0 and 24 h groups were similar to that of the 6 h group. In comparison with the 0 h control group, 16,442 and 10,415 differentially expressed genes (DEGs) were found in the 6 and 24 h groups, respectively. The identified DEGs were significantly enriched in those related to the immune system, immune diseases, or infectious diseases. Furthermore, the putative immune response genes of an early V. alginolyticus infection included API1, BPI, CD209, HSP90, TLRs, IAPs, caspases, and the calmodulin family. The findings contribute to the future study of the P. fucata molecular mechanism in defense against pathogenic infection and provide thorough information on the early immune response of P. fucata induced by V. alginolyticus.

Increased production of eastern oysters (Crassostrea virginica) will be needed to meet consumer demand for seafood. To meet this demand for seafood in the face of disease and climate change, selective breeding has been proposed as a solution. This study evaluated the phenotypic traits of survival, growth, yield, and disease acquisition of four wild eastern oyster (C. virginica) populations and two commercial lines from the Northeastern United States at a Rhode Island growing site. This study also investigated the genetic parameters of genetic difference between subpopulations (F_ST), inbreeding (F_ROH), runs of homozygosity, proportion of polymorphic loci, and heterozygosity in these populations. Shell height varied between populations (48–79 mm) as did survival (18%–68%) and yield (3,744–27,085 mm). Prevalence of the protozoan diseases Dermo and MSX was high between populations, and intensity for both diseases varied between populations. All populations had a similarly high proportion of polymorphic loci (0.88–0.99) and moderate heterozygosity (0.29–0.31). The commercial lines, however, did have a significantly longer percentage of the genome in a run of homozygosity (ROH), a greater number of ROH, and higher F_ROH. Pairwise F_ST values varied (0.01–0.08), with the wild populations being more genetically similar to one another than to the commercial lines which were also genetically distinct from each other. This analysis provides an example of how phenotype and genotype information could be analyzed to inform the selection of founders for a breeding program.

ABSTRACT The hepatopancreas is an important tissue involved in various biological metabolism for molluscs, but its responses to salinity have not been well evaluated. In this study, the dynamic changes of antioxidant, immune function, and apoptosis in the hepatopancreas of Hong Kong oyster (Crassostrea hongkongensis) under high salinity (30 and 35) stress within a 7-day period were analyzed. The data showed that high salinity stress could lead to DNA damage in Hong Kong oyster hemocytes, resulting in an initial up-regulation followed by a decrease in the expression of enzyme-related genes (SOD, GPX) and immune-related genes (SABL, galectin, C3) in the hepatopancreas. Meanwhile, some apoptosis-related genes (Casp-2, P53), heat shock protein-related genes (HSP90), and osmotic pressure-related genes (NaK, CLC7) maintain high expression levels. Correlation analysis indicated that DNA damage showed a negative correlation with the mRNA expression of Casp-3, Casp-2, Casp-8, P53, SABL, galectin, C3, HSP90, HSP70, Na/K, and CLC7, with the negative correlation being particularly strong for the mRNA expression of HSP90 and Na/K. The results enhance the current understanding of the molecular mechanisms of salinity stress responses in Hong Kong oyster.

Microbial communities associated with marine invertebrates play a key role in the health and functioning of their host. In decapod crustaceans, the microbiome is heavily implicated in both disease prevention and pathogenesis, among other functions. Despite this, the microbial communities of most decapod hosts remain largely unexamined, including those of the commercially and ecologically important California spiny lobster (Panulirus interruptus). This study uses 16S rRNA amplicon sequencing to investigate the composition and diversity of the microbial communities associated with internal tissues and external surfaces of California spiny lobsters from San Diego County, CA. Results show that P. interruptus harbors diverse, tissue-specific microbial communities, including many taxa not yet reported from other decapod crustaceans. Notably, members of the genus Aquimarina, a bacterial genus associated with lobster disease, were common on the surface of the carapace, though the functional role of this organism in the P. interruptus microbiome is unclear. Overall, these results act as a baseline for further investigation of the microbiomes of other populations of the California spiny lobster, especially given the presence of multiple clades known to harbor invertebrate pathogens.

The green sea urchin (Strongylocentrotus droebachiensis) displays diverse behavioral responses to chemical and tactile stimuli. These responses are often observed as part of its voracious foraging behavior and have been less documented for their covering behavior, which is known to occur during and outside of foraging. Despite widespread knowledge of aggregative foraging, change in urchin behavior in the presence of conspecifics (i.e., in an aggregation), or under cover, is unclear. Studies were conducted to examine two areas: (1) the impact of competitive (=aggregated) versus noncompetitive (=isolated) urchins on foraging behavior and (2) how cover availability impacted that behavior. Sea urchins competing with conspecifics were generally faster at reaching food than isolated ones. When the cover was available, isolated urchins often did not move toward the food item in the time allotted. These results indicate the importance of considering the conspecific environment in urchin behavioral studies, which may have implications for the planning of urchin aquaculture systems.