A sustainable fisheries model for the estimation of harvests of oysters, maintenance of cultch, and restoration of reefs has been applied across the northern Gulf of Mexico. Oyster density and size, and cultch density are provided from surveys by State agencies. The model simulates oyster growth and mortality, and cultch loss. Reef shell mass is increased when oysters die in place and diminished when oysters are removed by fishing. Harvest is estimated as sacks of live oysters that can be removed while retaining reef quality (i.e., reef cultch mass, oyster density). Application of oyster density and cultch density standards (OCS) for fishing at maximum sustained yield shows little sustainable harvest on Public Grounds in the northern Gulf of Mexico. Model heuristics focus discovery of negative and positive feedbacks to reef demise or persistence. Oyster reef dynamics are viewed as persistent processes within negative and positive feedback loops, and occasional shifts between them. A negative feedback loop is set up on poor-quality reefs. Lack of cultch and a paucity of adult oysters diminish recruitment and shell replenishment. In the absence of recruitment, natural shell loss ultimately drives the reef to extinction. A positive feedback loop is set up on reefs with adequate cultch and an abundance of oysters. There, oysters set, survive critical early stages in boxes and reef interstices, reproduce, grow to a large size, and die in place. Harvests on high-quality reefs beyond that which maintains reef cultch and spawning stock, and consequential recruitment failure cause a shift from a positive to a negative feedback loop. Likewise, restricting harvests and planting cultch on poor-quality reefs, together with successful recruitment, promotes a shift from a negative to a positive state. Results of no-net loss of cultch (NNL) and OCS simulations suggest two distinct management approaches. The NNL promotes the sustainability of reef shell and assumes that a stable shell bed promotes a stable living resource, whereas OCS explicitly promotes the sustainability of cultch and stock at msy (maximum-sustainable-yield). Furthermore, OCS, which incorporates optimal reef cultch and oyster density standards, provides restoration benchmarks. Achieving sustainability at msy will simultaneously promote habitat restoration, restoration of ecosystem services, and a sustainable oyster fishery.

Oyster population demographics are used to estimate shell standing stock (g m^–2) and rates of shell production (g m^–2y^–1) and loss by oyster, Crassostrea virginica, populations in both the Virginia and Maryland portions of the Chesapeake Bay. Source data are from long-term stock assessments whose footprints cover the majority of extant fished reefs in Virginia and a mix of fished and sanctuary reefs in Maryland. Individual longevity in extant fished populations is typically less than or equal to 5 y and truncated when compared with fossil C. virginica populations. Shell standing stock and productivity are maximal in year 1 or 2 of the progression of a year class through the population. Maintenance of the underlying reefs structure is dependent on regular shell input from mortality. The combination of truncated population structure and variable recruitment make shell addition temporally unstable. High turnover rates (≥30% y^–1) of the shell substrate pool in the oxic region above the sediment water interface are present. Reef accretion rates are generally less than the combination of sedimentation and relative sea level rise in most of the Bay system. Greater individual oyster longevity is required to ensure development of self-sustaining reef structures in the Chesapeake Bay.

Eastern oyster Crassostrea virginica populations have been declining steadily over the past several decades across the North American East coast. The Great Bay Estuary (GBE), located in New Hampshire, is experiencing this loss and restoration efforts have been put into effect. This paper characterizes larval abundances of settled spat and two early stages of C. virginica, D-hinge and veliger, in GBE from 2018 to 2020. Abundances are compared based on date of sampling, year, collection site, and the physicochemical data recorded on each sampling date. It was found that overall, D-hinge larval abundances have declined significantly from 2018 to 2020, whereas veliger abundances have remained steady or increased. Although the physicochemical factors are known to play a role in larval abundance, very little significance was found, suggesting future study may need to be modified to include a broader range of factors (e.g., more temporal sampling). This study indicates that both D-hinge, veliger, and spat settlement occur in GBE before sampling traditionally has started (June), suggesting an earlier than previously thought first spawn of C. virginica in GBE. This finding can be used to enhance restoration efforts as it suggests that spat brought in to augment current sites of active restoration should be released earlier in the season and that recruitment devices should be deployed before the previously thought first spawn of each season.

The continued development of effective mark and recapture tools for marine invertebrates is required to better understand fundamental planktonic processes such as larval transport and mortality. Mass chemical marking methods provide researchers with the ability to mark large quantities of individuals at one time with reduced handling stress and costs. Although 3-day-old larvae of Crassostrea virginica (eastern oyster) have been marked with calcein (a fluorochrome dye) and recaptured, pediveligers have not been marked nor has mark retention through metamorphosis been verified. To track mark retention through metamorphosis, 12,000 pediveligers were marked for 24 and 48 h in calcein of 25 and 50 mg L^–1 concentrations, and mark retention was tracked every 7 days for 4 wk. Results indicated that calcein did not affect initial settlement rates, that the distinct bands on larval shells were visible after metamorphosis, that individuals marked as larvae were positively identified up to 4 wk postsettlement without sacrificing individuals, and that lower calcein concentrations than previously documented were effective. This study demonstrates that calcein is a reliable method for marking C. virginica pediveligers and suggests that relatively low concentrations of calcein can produce marks and could reduce costs and potential harmful effects.

The goal of this study was to initiate a program for producing Florida tetraploid founders to meet the needs of the fast-growing oyster farming industry in the Gulf of Mexico. The objectives were to: (1) produce chemically induced triploids originated from Florida wild stocks and (2) screen and identify triploid females for induction of tetraploid founders. By use of Florida wild stocks from different locations, chemically induced triploids were produced in three spawn groups. Compared with diploid siblings, triploids at juvenile stages did not show significant fast growth (shell metrics and body weight) in every group, but at 1-y-old in spawning season did show significantly faster growth (P < 0.0001) than their diploid siblings. Among triploids, the occurrence of female averaged 1.66% (43 out of 2,597 triploids), ranging from 0.68%, 1.2%, and 4.26% in the three spawn groups. Oocytes from these 43 triploid females averaged 214,715 per female ranging from <100 to 1,800,000. Flow cytometry analysis of gonad from the nonfemale triploids (n = 186) showed five types of ploidy composition. A majority of these nonfemale triploids (66.1%) showed 3n only, indicating no gametogenesis occurred, and other different ploidy compositions showed initiation of gametogenesis with different chromosome segregations. Tetraploid induction was conducted by fertilizing the oocytes from triploid females with sperm from diploid males followed by polar body inhibition. The fertilization varied greatly ranging from 12% to 91%, and survival to D-stage swimming larvae ranged from 0% to 24%. Ploidy of pooled D-stage larvae indicated a tetraploid composition ranging from 38% to 80%. Heavy mortality of putative tetraploid larvae occurred at about 7–9 days and juveniles (1, 3, and approximately 200) were harvested in three groups. Unfortunately, these juveniles were lost during a hurricane in October 2018 at the growout site of one collaborating farm before individual ploidy examination. Although no confirmed tetraploid founders were harvested, the occurrence and fecundity of triploid females were documented in detail, which should be useful for future development of tetraploid stock for oyster aquaculture.

The hemolymph acid–base status of Akoya pearl oyster Pinctada fucata martensii exposed to air at 20°C was investigated. Air-exposed Akoya pearl oyster showed a decrease in hemolymph pH from 7.568 to 6.825 after 24 h. The hemolymph total CO₂ concentration increased from 2.25 mM/L to 4.50 mM/L during 24 h of air exposure. The hemolymph CO₂ partial pressure (Pco₂) was calculated by rearranging the Henderson–Hasselbalch equation. The hemolymph Pco₂ increased from 1.0 torr to 14.8 torr, and bicarbonate ion concentration increased from 2.21 mM/L to 3.91 mM/L during 24 h of air exposure. The hemolymph calcium ion concentration ([Ca²⁺]) increased from 9.4 mM/L to 12.8 mM/L. These results indicated that Akoya pearl oysters showed hemolymph acidosis with partial metabolic compensation by mobilization of bicarbonate from the shell valve during prolonged air exposure. Immersion in seawater for between 4 h and 24 h decreased the effect of air exposure on hemolymph acid–base status, except for [Ca²⁺]. The hemolymph [Ca²⁺] of immersed Akoya pearl oysters was slightly higher than the initial level upon air exposure although hemolymph [Ca²⁺] had already decreased after immersion in seawater for 4 h and 24 h. The hemolymph acid–base balance of immersed Akoya pearl oysters recovered to the initial level after 4–24 h, even if the animals were exposed to the air for a prolonged time (24 h).

The complete cDNA sequence of chaperonin-containing T-complex polypeptide 1-alpha (CCT-alpha) gene of the pearl oyster Pinctada maxima was determined using rapid amplification of cDNA ends technique and characterized with bioinformatic analysis. Its expression profile in different organs and under cold stress was characterized using real-time quantitative polymerase chain reaction. Results revealed that the complete cDNA sequence of P. maxima CCT-alpha has 1,803 base pairs (bp), including a 1,608-bp open reading framework that codes 535 amino acids. The protein has three conservative functional domains: equatorial, apical, and intermediate domains. The equatorial domain is 20 amino acids shorter than that of other species, and contains the three signature sequences of CCT family protein. The CCT-alpha of P. maxima has nine conservative ATP-binding sites and six protein-binding sites, and has high homology with Aplysia californica (80.7%), Delia antiqua (77.4%), Danio rerio (77.1%), Xenopus laevis (76.7%), Gallus gallus (76.4%), and Homo sapiens (75.4%). The CCT-alpha shows tissue-specific expression profile in P. maxima, with expression levels higher in gill, mantle, and adductor muscle than in hepatopancreas and heart. Cold stress markedly increased mRNA contents of CCT-alpha in the organs of P. maxima, but different organs showed distinct cold stress response pattern. Chaperonin-containing T-complex polypeptide 1-alpha transcription in adductor muscle, hepatopancreas, and heart increased at 2 h, and reached peak values at 6 h, maintained high levels at 12 h, and significantly decreased at 24 h. The product in gill and mantle decreased at 2 h, began to increase at 6 h, and showed a large increase at 12 h, but reduced to below the initial level at 24 h.

Bay scallops (Argopecten irradians), once a profitable fishery species in North Carolina, have declined in population size following harmful algal blooms in the late 1980s. To prepare for future scallop restoration efforts, appropriate survey methods should be identified to evaluate the status of the population with respect to managing harvest. The North Carolina Division of Marine Fisheries monitors bay scallop populations in seagrass beds using a scallop dredge, though it is still unclear what the current natural densities of bay scallops are. In this study, visual surveys in three time treatments (5, 10, and 20 min) were compared with dredging in terms of quantifying scallop density and the catch per unit effort (CPUE) in seagrass beds in Core Sound, North Carolina. There was no significant difference in scallop density and the CPUE among visual survey time treatments. Scallop densities observed during visual surveys were three times higher than densities using a scallop dredge; however, the CPUE was five times higher using a scallop dredge compared with visual surveys. If visual surveys indicate the true natural density of bay scallops in this study system, then the dredge sampling efficiency for evaluating bay scallop density was 33%. Dredging for bay scallops can uproot seagrass and displace juvenile bay scallops. Visual surveys provide a low-impact method for identifying the distribution and abundance of bay scallops in seagrass bed habitats.

Dredging for wild mussels Mytilus edulis Linnaeus, 1758 takes place in the marine protected areas (Natura 2000 sites) in Denmark. The fishery is strictly regulated to limit the impact of dredging to the benthic environment, and requires the use of modified lightweight mussel dredges. Nevertheless, the depletion of the benthic macrofauna associated with M. edulis beds after impact from such dredges is yet to be quantified. Here, dredging is shown to result in a significant decline in the density, species richness, and biological traits directly in the dredge track but no significant impact on the community composition. Species richness remained significantly affected 4 mo post dredging, although the positive trend after 4 mo may signal recovery. An effect of dredging was also detected in areas adjacent (approximately 5 m) to the dredge tracks, but needs further investigation to understand this impact. The results provide an estimate of benthic macrofaunal depletion in the dredge track as well as of the short-term recovery, which may be of use in the management of the fishery. Finally, it is suggested that species richness may be a more sensitive indicator than density in a eutrophic and species-poor system.

The Asian green mussel Perna viridis, was first detected in Tampa Bay, FL, in 1999 and quickly spread throughout the bay. The long-term population trend of P. viridis from 2002 to 2017 was assessed by monitoring settlement to collectors and bycatch of P. viridis in trawls in Tampa Bay. In addition, a suite of water-quality parameters and trends in predator abundance were modeled to evaluate the effects of these variables on P. viridis in the bay. Since 2002, settlement and bycatch of P. viridis in Tampa Bay has declined by 83% and 62%, respectively, in relation to nitrogen concentrations and productivity fluctuations limiting resource availability and energy acquisition in P. viridis. While Florida stone crab (Menippe mercenaria) landings, Atlantic blue crab (Callinectes sapidus) landings, and catch per unit effort of C. sapidus in fisheries independent monitoring trawls decreased throughout the study period, C. sapidus landings were the only biotic factor that was significantly related to P. viridis settlement. Temperature and salinity extremes, while not significant parameters in the models, likely negatively affected the distribution and persistence of P. viridis in the bay. Taken together, these findings suggest that conditions within Tampa Bay were not conducive to the large-scale dominance of P. viridis that was predicted when they were first introduced and they currently do not fit the definition of a problematic, invasive species. Conditions have been sufficient for this introduced species to remain established as a relatively minor constituent of the benthic community.

Gastropods of the family Cymatiidae are a major predator of cultured pearl oysters, causing significant mortality in ocean culture systems. Improved knowledge of factors influencing cymatiid predation on pearl oysters is required to develop effective management strategies for these predators. This study determined whether size of the cymatiid, Gutturnium muricinum, is a significant factor influencing mortality of cultured Akoya pearl oysters (Pinctada fucata), and whether predation by this cymatiid on bivalve species in an ocean culture system is nonrandom. A single G. muricinum was capable of causing significant mortality in pearl oyster stock after a 6-wk culture period, with morality influenced by predator size. Oysters housed with a large (shell length: 55.0 ± 3.3 mm) G. muricinum experienced significantly greater mortality (23.3 ± 6.3%) than those in nets with a small (shell length: 37.8 ± 2.1 mm) individual (11.1 ± 0.6%). The presence of G. muricinum also had a significant impact on pearl oyster growth, but growth was not influenced by predator size. When presented with both Akoya pearl oysters and Hyotissa hyotis as potential prey items, cymatiid predation was nonrandom. Cymatiids preferentially preyed upon H. hyotis, that experienced 45.5 ± 12.4% mortality after 6 wk of ocean culture whereas, in the same nets, none of the Akoya pearl oysters were killed. Based on these results, various management strategies are discussed, and further research avenues identified.

The bacterium Vibrio parahaemolyticus (Vp) causes gastrointestinal illness in people, generally through the consumption of undercooked or raw seafood. It is a major concern in the oyster industry, especially as the raw oyster market gains in popularity. As a result, a network of adaptive regulations is triggered during times when Vp risk is high (i.e., during warmer temperatures) and reporting requirements to track confirmed infections. A survey of three main stakeholder groups—managers, growers, and restaurants/retail locations—estimated the costs of these regulations for the Washington State oyster industry to quantify their economic burden. Study participants requested that these costs be categorized by actual dollars spent and labor hours needed, and then again by whether those expenses were part of Vp prevention efforts or as the result of a traceable illness. The survey revealed that prevention efforts cost an average $0.45 per dozen oysters landed and a traceable case costs an average of $61,880 for 2019. These costs are largely borne by growers in the form of fixed costs and therefore, there is also an economy of scale at play. The discussion then focuses on how these costs may apply to future management plans and farm budgets, as well as other geographies.

Little has been published about the interactions of metals and parasites in economically important aquaculture species, particularly shellfish. Metal bioaccumulation and parasitic diseases could vary in different species depending on temperature changes and other environmental factors. Most studies conducted on endoparasites, such as acanthocephalans, cestodes, nematodes, and trematodes, indicate that only cestodes and acanthocephalans could absorb heavy metals successfully in their hosts, and that only adult worms could be used as indicators of environmental pollution. In Artemia parthenogenetica, cestodes increased resistance to arsenic (As) pollution and temperature changes; and infection was associated with improved antioxidant defense system without oxidative damage. The most serious parasite of Penaeus spp. is Enterocytozoon hepatopenaei (Microsporidia: Enterocytozoonidae). Apostome ciliates are negatively impacting Pandalus borealis of the northeastern United States (Synophrya sp. that causes “white eggs” or Black Spot Gill Syndrome) and Penaeus spp. from the South Atlantic and Gulf of Mexico (Hyalophysa lynni that causes shrimp black gill). In freshwater fish, the larvae of the nematode Eustrongylides spp. Jägerskiöld, 1909 (Nematoda: Dioctophymidae) absorbed lead (Pb), mercury, and cadmium, when the metal levels were close to zero in water and sediment. The concentration of Pb in the larvae was approximately 17 times higher than in the fish. Like the antioxidant defense reactions in the parasitized A. parthenogenetica exposed to As, an improved antioxidant defense system may be available in parasitized fish, limiting oxidative damage caused by metals. This study presents baseline concentrations of 30 metals in wild Penaeus vannamei Boone, 1931 from Ecuador and other species, as well as the current taxonomy for selected shellfish species and their parasites. Research is needed to assess the relationship of metals in parasites and host tissues, and oxidative stress in shellfish. The tools of One Health including molecular ecology, population genomics, proteomics, and epigenetic epidemiology should be used to detect parasites and environmental pollution indicators that could threaten aquatic species from freshwater and marine ecosystems, particularly considering climate change and pollution threats.