Bivalve molluscs represent a significant proportion of the diet of both Atlantic and Pacific walrus (Odobenus rosmarus rosmarus and Odobenus rosmarus divergens, respectively) and are pivotal to benthic–pelagic coupling and carbonate cycling in the Arctic oceans. The latter is of particular relevance in a period of seasonal ice retreat, freshwater release into associated surface waters, decreasing water pH, and possible undersaturation of Arctic waters with respect to aragonite. Using population estimates and predation rates for the walruses on bivalve molluscs, a conservative estimate of bivalve consumption in the regions of active walruses foraging is 2.0–3.0 × 10⁶ tonnes y^–1—a tonnage comparable to the landings for the largest U.S. commercial fishery, the walleye pollock fishery in the eastern Bering Sea. Predation loss to other apex predators such as bearded seals is discounted. Using production:biomass ratios comparable to other high-latitude bivalves, a conservative estimate of bivalve standing stock required to support walrus populations is 0.4–3.0 × 10⁷ tonnes. Whereas predominant clam prey species exhibit longevity in the 30+ y range, sampled populations in the Bering and Chukchi seas are dominated by small, often less than 1.0 cm individuals. Large clams are rare to absent in samples, suggesting either rapid turnover of the population with high predation balanced by high recruitment and/or a bias in sampling that discounts larger, more sparse individuals. Walrus grazing contributes up to 4.0–6.0 × 10⁶ tonnes y^–1 of carbonate to buffering of near-surface sediments in Artic regions. Accurate estimates of bivalve biomass and, thereby, the carbonate budget of Arctic shelf clam species, are critical to understanding the stability of associated continental shelf communities with continued warming of these high-latitude systems and their associated tendency toward aragonite undersaturation.

The reproductive strategy of Dosinia ponderosa at a site of the eastern coast of the Gulf of California, Puerto Libertad, Sonora is reported. Samples of visceral mass were taken from 30 clams that were collected monthly from March 2015 to March 2016, and the length and weight of the tissue without shell of each organism were recorded. Through histological analysis, the gonadal index were calculated, and the reproductive stages of the ponderous dosinia were determined. Six oocyte substages and five gonadal development stages for females and five for males are described. The sex ratio was 1:1, and no undifferentiated specimens were found. The sexual maturity phase was observed throughout the year, with two reproductive peaks in June–July and October–November. No correlation was observed between the reproductive activity and temperature or primary productivity.

The intertidal soft-shell clam Mya arenaria fishery in Maine is comanaged under a cooperative agreement, or shellfish ordinance, between coastal communities and the state. The ordinance, among other things, defines conservation tools that encourage communities to engage in activities with a goal to enhance local densities of 0-y class individuals of this infaunal bivalve. One method used by communities for over 75 y is referred to as “brushing,” which involves forcing dozens of the recently cut white spruce Picea glauca boughs (approximately 70 cm in length) vertically into the soft sediments of a mudflat so that 40–45 cm protrudes into the water column. Typically, multiple rows of boughs are deployed on flats in the spring before clam spawning where they remain through the fall after annual settlement and recruitment have ended. Brushing purportedly results in slowing down tidal currents and creating eddies that allow recently settled clams that otherwise are susceptible to bedload transport away from the flat to establish themselves in the vicinity of the boughs. During spring–fall 2019, a comparative field experiment was conducted at three intertidal flats within a 160-km stretch of the Maine Coast to test, for the first time, the efficacy of this traditional management tool versus another approach used to enhance local densities of 0-y class clams—predator-exclusion netting. At each flat, neither treatment enhanced densities when compared with controls of recruits of Mya as well as recruits of another commercially important infaunal bivalve that occurred at a single site, the northern quahog Mercenaria mercenaria. That is, neither bivalve responded positively to experimental additions of spruce boughs to soft sediments at any study site. Passive bivalve collectors demonstrated that both species settled into plots, ruling out recruitment limitation. Comparison of recruit densities between collectors and core samples from both brushed and netted plots demonstrated losses greater than 97% for Mya and greater than 93% for Mercenaria. Collectors also provided data on densities of recruits of the invasive green crab Carcinus maenas, which ranged from 1.2 to 13.9 ind. m^–2 across sites, and were 3–6× more abundant in collectors within plots with brush or netting versus adjacent control plots, suggesting that this predator selects heterogeneous versus homogeneous environments during its early life history. As green crab populations in Maine vary directly with seawater temperatures, and the Gulf of Maine is warming relatively rapidly, adding potential habitat for green crabs, such as brush, to intertidal flats should be discontinued in favor of more effective methods to enhance local densities of 0-y class individuals.

The goal of this study was to evaluate the efficacy of phenotypic traits and two genetic assays to distinguish between Mercenaria mercenaria, an important aquaculture species, and Mercenaria campechiensis, a conspecific species that is partially sympatric, but that has not been successfully farmed. The objectives were to evaluate (1) four established diagnostic phenotypic traits (lunule shape, thickness of concentric shell ridges, prominence of anterior side of the concentric ridges, and presence of purple nacre inside of the shells) to distinguish between species, (2) size polymorphism of PCR fragments from four genes [16S rRNA, 18S rRNA, Internal Transcribed Spacer genes (ITS1 and ITS2)], and (3) PCR-restriction fragment length polymorphism (RFLP) on three of these genes (16S, ITS1, and ITS2). Phenotypic traits correctly distinguished two geographically distant conspecific populations (two locations in Maine for M. mercenaria and in Bradenton, FL, for M. campechiensis); however, among all other locations, both species had overlapping phenotypic trait values. Although PCR fragments were obtained for all genes tested, size polymorphism was not identified between the two species. Restriction enzyme digestion of PCR fragments resulted in diagnostic fragments distinguishing the two species for 16S, ITS1, and ITS2. Although phenotypic scores failed to delineate between the two species in most locations, PCR-RFLP results failed to identify hybrids in wild or hatchery samples. Further investigation is needed to apply the PCR-RFLP assays on known hybrid offspring from crosses of M. mercenaria and M. campechiensis. Results have elucidated the difficulties in confidently detecting hybridization in quahogs; however, determining effective methods for species identification and hybrid detection will be important to address issues such as the prevalence and distribution of hybridization in aquaculture and in wild populations, and to determin the presence of M. campechiensis which are currently difficult to find.

Both seagrasses and bivalves molluscs act as ecosystem engineers in marine systems by forming habitat or modifying environmental conditions. They also have the potential for reciprocal interactions when colocated, through a wide variety of potential mechanisms involving different directions in effect. Pathways mediated by biogenic structure could be facilitative through protection from predation or bioturbators, or by harboring beneficial interactors, or alternatively could result in competition for space or reduced food supply. Other pathways mediated by biological activity could positively link autotrophic roles of seagrass and heterotrophic roles of bivalves, but excessive organic matter production or nutrient release could be damaging. Published studies were compiled for a meta-analysis of field experiments testing bivalve response to seagrass (25 studies) and vice versa (11 studies), as well as for surveys of bivalves in and out of seagrass (39 studies). In experiments, seagrass improved bivalve survival, and bivalves at high cover reduced seagrass density, but seven other response metrics showed no consistent change. In surveys of particular bivalve species, densities were 1.6 times higher in seagrass than out of seagrass. This augmentation did not differ by body size but was especially pronounced in some functional groups, especially lucinid and solemyid bivalves harboring sulfide-oxidizing bacteria. Weak overall directional effects of colocation of seagrass and bivalves reflect weak effects in some individual studies, for instance because of low densities in soft-sediment systems, as well as strong but inconsistent effects because different pathways of interaction dominate. Therefore, generalizations about the outcome of interactions between these two ecosystem engineers when they are colocated cannot be made, although coexistence is typically enabled by weak or positive interactions. Further work is needed, especially outside of some well-studied regions, to explore the specific mechanisms and spatiotemporal scales enabling seagrasses and bivalves to coexist because there are many pathways at work.

Oyster habitat restoration seeks to recover lost ecosystem services including increased provisioning of refuge and foraging habitat for fish and invertebrate communities. The goal of this study was to quantify the ecosystem service benefit of habitat provisioning in Ninigret Pond, RI, following oyster restoration. Four metrics were measured, abundance, biomass, species richness, and diversity, as well as isotopic composition in fish and invertebrates collected seasonally from restored oyster, aquaculture, and bare sediment sites, to examine whether the oyster habitat outperformed the bare sediment habitat. Sampling locations were chosen in Foster's Cove north and south, Grassy Point, South Sanctuary, and an Aquaculture lease; each had two restored oyster sites and one bare sediment site. Each site was sampled using a box trap, seine net, shrimp trap, and minnow trap. Oyster habitats had significantly greater metrics than did bare sediment habitats in some comparisons from the box trap and seine net samples. Restored oyster sites at South Sanctuary had lower metric values than the other oyster sites. Metrics from the Aquaculture sites were comparable to the Foster's Cove and Grassy Point restored oyster sites and often outperformed South Sanctuaryrestored oyster sites. Seasonally, spring and autumn samples tended to have higher abundance and biomass values than summer samples. Isotopic composition of five species occurring at both restored oyster and bare sediment sites demonstrated some differences in the trophic levels between species but not between habitat types. In Ninigret Pond, fish and invertebrate abundance, biomass, species richness, and diversity benefit from the use of oyster and bare sediment habitats. Coastal zone managers interested in restoring the ecological function of oyster reefs to support fish and invertebrate communities should consider strategically locating restoration projects within the mosaic of structured habitats and monitoring them for selected ecosystem services.

Local bay scallop Argopecten irradians populations are threatened or depleted in southwest Florida estuaries (Pinellas through Lee Counties) and in the Panhandle (Bay through Escambia Counties), and community-driven restoration efforts have been ongoing for many years. To obtain juvenile scallops for use in restoration, wild larvae (spat) were allowed to settle on suitable surfaces (settlement traps) at sites known to still have high larval supply. Traps used to harvest spat were constructed with enhanced surface area relative to routine monitoring traps. Enhanced traps resulted in 142 ± 317.1 (mean ± SD) spat per trap and a maximum of 2,321 spat on a single trap, whereas the routine traps resulted in 67 ± 146.7 spat per trap and a maximum of 726. Spat were harvested each winter (2008–2012) from either St. Andrew Bay or Tampa Bay and delivered to restoration sites where citizen-scientists or collaborators measured the growth (shell heights) and mortality (live count) of 25–50 scallops within 3–25 cages each month. Most cages were hung from their own dock or the dock of a partner organization. Scientists from the lead agency also measured growth of caged scallops. Thus, simultaneous sampling occurred across a large geographical range with varied organizations and skill levels. In the shortest trials, survival remained very high, and in most years involving prolonged efforts, some of the planted scallops survived long enough to reach a size where spawning likely occurred. A maximum survival period of 559 days and the greatest mean shell height (65.18 ± 2.48 mm) of caged scallops were observed in Sarasota Bay in 2012. The observed growth in restoration cages fit previously described patterns for Florida Bay scallops, reaching maximum sizes between 60 and 70 mm shell height in 1 y. Mean daily growth rates (mm/day ± SD) increased as latitude decreased: St. Andrew Bay, 0.15 ± 0.096 y; Tampa Bay, 0.21 ± 0.124; Sarasota Bay, 0.22 ± 0.134; Charlotte Harbor, 0.28 ± 0.112; and Pine Island Sound, 0.29 ± 0.086). Temperature, scallop shell height, and the number of days in captivity (a proxy for age) generally had only minor or no effect on growth rates. When combined, the process of collecting wild spat and growing those scallops in cages using volunteer networks offers the advantages of community engagement, relatively low costs, minimal technical skill requirements, and reduced threat of loss of genetic diversity.

Two mass mortality events in 2016 and 2019 affecting the eastern oyster in the Mississippi Sound permitted an investigation of population dynamics during the collapse and recovery from systemic stressors capable of producing local extinction. In this study, metrics were reported as true population metrics with values included in proportion to the size class representation in the population. The approach was critical as trends in Dermo prevalence and weighted prevalence varied substantially between size classes, and this permitted elucidation of recovery trajectories not obvious from the population as a whole. The division of the population into larger and smaller size classes revealed a consistent differential in the time series for Dermo prevalence and weighted prevalence; these metrics did not return to levels observed before the 2016 mortality event in the 2-y interim between the 2016 and 2019 mortality events, and prevalence, in particular, remained low in the smaller size class. The time delay in the return of Dermo infection due to a substantial change in the size frequency of the population toward smaller initially uninfected animals is consistent with the differential in Dermo and young oyster cell doubling times and the required time delay, albeit relatively short, for transmission to occur. Gonadal thickness generally tracked with condition index and followed the expected seasonal cycle; any impact resulting from the 2016 mortality event on these metrics appeared to be inconsequential. The relationship between the adductor muscle diameter and shell height varied little over the time series and was much more stable than between the adductor muscle diameter and shell weight, suggesting a change in the oyster shell shape post-2016. By inference, shell weight is more variable among the three metrics in estimation of the condition index and standardization of other health indices. The ability to establish health metrics for both specific size classes and the population as a whole is essential to understanding the temporal impacts of a severe stressor or mortality event on oyster populations.

The eastern oyster Crassostrea virginica contributes important ecological and structural elements to estuarine ecosystems worldwide. Oyster reef persistence requires regular recruitment as well as growth by existing individuals. Saltmarsh tidal creek oyster population age structure and growth rates directly influence local benthic–pelagic coupling and biogenic habitat formation. Recruitment monitoring, substrate deployments (2017–2020), and field surveys (2018) were conducted in North Inlet Estuary, SC, to quantitatively describe oyster age–shell height relationships, population age structure, daily growth rates, and survivorship. Multiple recruitment events resulted in three to four cohorts each year. Oysters exhibited rapid shell growth but most died by the end of their second growth season after attaining shell heights of less than 100 mm. Daily growth rates immediately after recruitment (approximately 0.07–0.29 mm day^–1) and within the first 2 y (0.1–0.4 mm day^–1) allow maximum shell heights of 50–55 mm after to 6–8 mo, 80 mm within 1 y, and 140 mm within 1.6 y. Recruitment timing strongly influenced shell heights after 1 y, with July recruits approximately 33% larger than May recruits within the same year. The North Inlet oyster population age structure was dominated by oysters in their first (55%) or second (45%) growth season, with individuals less than 100 mm shell height composing approximately 99% of the population. Oyster survivorship beyond 2 y appears to be unusual. The opportunistic life history strategy used by North Inlet oysters incorporates multiple large recruitment events each year and rapid growth rates to offset short life spans so as to maintain reef populations and related ecosystem services.

Stock–recruitment relationships (SRR) are used by many resource managers as a metric to evaluate stock reproductive potential and rebuilding capacity when harvested. This relationship is more evident in traditional finfish stock assessment models where larvae are frequently limited by the abundance of spawning adults, whereas invertebrate resources are much more confounding and often do not express a clear spawning SRR. Oysters in particular appear to be limited more strongly by post-settlement mortality as larvae are regularly demonstrated to be present in high abundance in response to timely shell plants; yet unexpectedly, a brood SRR appears to be present. Because of the unique life history of oysters which provide their own habitat through reef accretion, a posit is that the quantity and quality of such habitat are crucial determinants of recruitment to the stock, and habitat quality acts as a surrogate for brood stock in the stock–recruit relationship. An extensive dataset from Delaware Bay with a 65-y time series was analyzed to assess the relationship between available Crassostrea virginica natural reef materials and subsequent spat (<20 mm) settlement. Live oyster, box (dead and articulated valves), and cultch (disarticulated whole valves and shell fragments) surface areas were calculated for oyster reefs found in each of four regions oriented up-bay to down-bay within the survey area. Surface areas were standardized using RMA regressions which compared available surface area per shell type (live, box, and cultch) and the number of spat recruiting to each shell type. Standardized shell surface areas (i.e., effective surface areas) supported previous accounts that recruitment occurs with higher frequency on live oysters and boxes than cultch, and that excessive cultch availability does not always lead to successively high recruitment. Recruit density was found to not only vary by substrate type but also along a salinity gradient. In high salinity reefs, boxes function as high-quality recruitment substrate and cultch as low-quality substrate, whereas in low-salinity regions cultch is only slightly inferior to live and outcompetes box surfaces as a dominant recruitment substrate. Beverton–Holt and Ricker models were used to express the relationship between total effective surface area and recruitment; these models revealed that medium- and high-salinity regions produced higher recruitment rates than low-salinity reefs. Model steepness also increased at higher salinity, indicating that down-bay reefs responded more rapidly to a change in effective surface area than did up-bay reefs. Steepness was highest at the confluence of the medium-salinity and high-salinity reaches where larval supply provided by the down-bay drift of larvae from up-bay reefs was high, but salinity remained low enough to reduce biofouling and predation compared with the high-salinity region. Unlike the low-salinity region, the relationship between effective surface area and recruitment for the three down-bay regions exhibited compensation; recruitment did not rise linearly with effective surface area. In all four regions, however, recruitment was initiated on a reef at a nonzero effective surface area, an analogy to an Allee effect which existed in each case. By inference, reefs can die before effective surface area disappears.

The dark false mussel Mytilopsis leucophaeata is an invasive bivalve known from two locations in Rio de Janeiro (Brazil): Lagoa Rodrigo de Freitas and Lagoa de Marapendi. For a population biology study of this species, monthly collections were carried out at Lagoa Rodrigo de Freitas over a period of 2 y (March 2016–March 2018). High densities were registered in both studied years: 84,560 (±22,066) ind. m^–2 in the first year and 65,848 (±7,830) in the second year. Growth was lower for the first year (K = 0.4 for year 1 and K = 0.8 for year 2), whereas seasonal oscillation (C = 0.6) was of the same intensity in both years. The period of lower growth differed for the years, occurring in June (WP = 0.5) in the first year and in August (WP = 0.7) in the second year. The maximum and asymptotic lengths, longevity, secondary production, biomass, and turnover rate were higher for the first year; on the other hand, mortality was higher at the second year. Density of the invasive mussel was significantly and positively related with salinity (r² = 0.5547; P < 0.0001). In a general way, the second year of study seems to be a more adverse period for the population of the invasive mussel with reduced density, body sizes, life expectancy, secondary production, biomass, and higher mortality. Among environmental factors, salinity seems to exert the strongest influence on the regulation of population attributes.

Mabé pearl (half-pearl) culture provides rural livelihood opportunities in the South Pacific and is a low-tech alternative to capital and labor-intensive round pearl culture. The Kingdom of Tonga is unique among the pearl-producing countries of the South Pacific in focusing on mabé pearl culture using the winged pearl oyster Pteria penguin. The Tongan mabé pearl sector is developing rapidly and stimulated by routine supply of spat to mabé pearl farmers, from the government hatchery at no cost. It is likely that some level of cost recovery for spat supply will be considered as the sector strengthens, but information on hatchery production costs is limited. This study determined the costs of operating the government pearl oyster hatchery in Tonga and developed an economic model to assess the production cost of juvenile oysters. Modeling was based on a single annual hatchery run generating 6,600 oysters from the ocean-based nursery for delivery to commercial pearl farms. Estimated capital cost was USD 19,079 (excluding government buildings and chattels), and the major production costs were hatchery labor (37%), capital purchase and replacement (20%), and nursery labor (10%). Total annual costs for the pearl oyster hatchery were USD 13,263, equating to a cost of USD 2.01 per oyster supplied to farmers in Tonga. Given significant annual profits of around USD 9,338 that can be generated from 100 harvested oysters, there is justification for cost recovery. Results will be valuable to key stakeholders and have regional relevance for hatchery production of high-value aquaculture commodities.

Concentrations of 29 elements were analyzed in the marginal area and central area of the shell nacreous layer of the winged pearl oyster Pteria penguin using a laser ablation inductively coupled plasma mass spectrometer. Color of the two shell areas was determined using the color parameter values of lightness, greenness/redness, and blueness/yellowness. It is shown that the concentrations of the elements and the nacreous color are different in the marginal area and central area. The concentrations of Mg, P, B, Li, Cu, and Mo are significantly correlated with lightness and differently distributed in the two shell areas (P < 0.05). The concentration of Na and Mg is significantly related to greenness/redness and differently distributed in the two shell areas (P < 0.05). The concentration of Na, Mg, P, B, Li, and Mo is significantly related to blueness/yellowness and differently distributed in the two shell areas (P < 0.05). The concentration of Mg significantly related to lightness, greenness/redness, and blueness/ yellowness and differently distributed in the two shell areas (P < 0.05). This study provides a new perspective to illustrate the mechanism of color change between the marginal and central areas.

The Omani abalone Haliotis mariae (Wood, 1828) supports one of the most valuable fisheries in Oman. It is specific to defined areas along the northern region of Dhofar in Oman. This study reviews the management of the Omani abalone fishery during the last 31 y, identifies the challenges encountered, and suggests solutions to overcome these difficulties. During the period 1988–2018, annual abalone landings ranged from 29 tonnes (mt) in 1999 to 149 mt in 2011, with an average of 53 mt. In 2019, landings 24 t (53 t whole weight) were reported to be the lowest in the last three decades and landed within 10 days of opening. The fishery generated 1.3 million Omani rials (3.38 million US$) (OR, where 1 OR = 2.6 USD) in 1993 and 8.2 million OR in 2011, with an average of 2.5 million OR (6.5 million US$). By contrast, the average annual price per kg was 50 OR (130 US$). The fishery was mainly managed in accordance with seasonal closures, which ranged from 6 mo to less than 1 mo; in one case, there was a complete suspension of fishing for 3 y. The number of fishers engaged in this fishery was not stable, and fluctuated between 1,450 in 1993 and 8,539 in 2014. The seasonal closures between 1988 and 2003 resulted in a gradual decrease in average landings, reaching 2%–45% at the end of the season, with an average of 27%. The percentage of divers who participated at the end of the season ranged from 9% to 90%, with an average of 47%. It is suggested that the government should conduct comprehensive research to assess the Omani abalone stock, population dynamics, and habitat, as well as the behavior of the fishermen. Furthermore, better data collection and monitoring systems should be established. It is strongly recommended that a “pulse fishing” or spatial-based or temporary marine-protected area fishing (zonation) approach that serves the objectives of stock and habitat preservation be implemented. Thus, the restoration of the Omani abalone fishery is achievable but will require long-term research efforts.

Direct measurements of ventilation rates in the marine gastropods Busycon carica, Busycotypus canaliculatus, Sinistrofulgur sinistrum, and Melongena corona were made. Ventilation in B. carica ranged between 3 and 186 mL min^–1; the rate in B. canaliculatus was 12–174 mL min^–1, and 0.6–42 mL min^–1 in S. sinistrum. There was no consistent relationship between the size of the animals and the ventilation rate. Ventilation rates for any individual were variable, and rates varied among individuals. The rates reported here are relatively low in comparison with those of cephalopods and bivalves, but not surprising as in nearly all gastropods, ventilation is tied only to gas exchange. In cephalopods, ventilation is also involved in locomotion, and in bivalves, a primary role of ventilation is feeding.

The population structure of the blue crab Callinectes sapidus was examined in the Maryland Coastal Bays (MCB) from 2014 to 2016. Crabs were sampled from April to December of each year. Size–frequency distributions showed a strong seasonal cycle, with small crabs being abundant in April, increasing in size through September, with adult crabs observed in the highest proportions from August through October of each year. A subsample of crabs was assayed for hemolymph ecdysone concentrations to examine molting patterns in field-collected blue crabs. Molting was observed throughout the sampling season, peaking in April for immature crabs, with lows in all size classes occurring in October. The mean size at maturity (L₅₀) for females collected in this study was 116 mm carapace width (CW), which is comparable to that reported for the lower Chesapeake Bay (CB) and suggests crabs in the MCB are not significantly smaller as previously thought; however, large crabs (>127 mm CW) appear to make up a smaller proportion of the total population in the MCB than in CB. Ovigerous females were observed at two distinct locations depending on the season, with 13/15 (86.7%) in southern Chincoteague Bay in April and May and 24/41 (58.5%) nearest to the Ocean City Inlet in July and August, indicating two potentially distinct spawning grounds and periods. This work suggests that blue crab reproductive success and general population trends are similar across both systems, with fishing pressure or disease in the MCB potentially explaining the low abundance of adult male crabs.

Culture data representing 96 observations of larval survival for the blue crab (Callinectes sapidus) over the time period 2008–2019 were examined to determine factors relevant to larval health and survival. The study spans years before and following the Deepwater Horizon (DWH) oil spill in the northern Gulf of Mexico (GOM). Variability in survival of cultured larvae was high over the study period, despite attention to water quality standards and consistent culture protocols. Generalized linear models were constructed using the pre/postspill factor, several covariates, and individual crabs as subjects to predict the 96 larval survival observations from cultures representing 25 individual spawning female crabs. Survival decreased with age of the culture and nitrite concentration as covariates for both zoeal and megalopal stages. Notwithstanding effects of the two covariates, prespill survival was substantially higher than postspill survival for both zoeae and megalopae. Mean prespill survival values of 13.2% and 21.5% were notably higher than mean postspill survival of 4.7% and 11.2% for zoeae and megalopae, respectively. Postspill studies in the northern GOM found widespread evidence of PAH contamination associated with the DWH event in coastal biota, including wild-caught blue crab megalopae. The co-occurrence of oil and larvae offshore coupled with the oiling of megalopal settlement habitats, juvenile maturation habitats, and barrier island spawning areas suggest there was a high potential for PAH exposure to blue crab populations at all life history stages. Based on published data and known exposure mechanisms, plausible pathways exist for carryover effects of oil on developing larvae. Although the history of contaminant exposure to spawning blue crab females was unknown, the pattern of larval survivorship concurs with published environmental impacts and suggests that bioenergetic effects associated with PAH exposure may have affected maternal crabs or embryos during embryogenesis.

This study was conducted to assess the status of small-scale artisanal sea cucumber fishing around the islands of Phu Quoc, Nam Du, and Hai Tac, located in Kien Giang Province, Vietnam. A total of 90 sea cucumber fishers were randomly interviewed from October 2018 to March 2019. Results indicate that most fishers (96.7%) consider sea cucumber fishing as an extra income and use simple fishing methods such as diving (free diving and snorkeling), gleaning, and scoop nets. Catch composition (% whole wet weight) comprises five species, of which low- and medium-value species are most commonly harvested, including Holothuria leucospilota (39.5%–58.2%) and Stichopus spp. (29.7%–48.4%), followed by Holothuria atra (7.3%–10.9%) and two high-value species that are rarely found, that is, Holothuria scabra (2.6%–6.6%) and Holothuria nobilis (1.2%–1.6%). Current catch rates for an average fishing trip are 25.8–37.6 kg wet weight per diver, which has declined by 60%–95% over the past 10 y, indicating heavy overexploitation. Currently, the exploitation of sea cucumber in Kien Giang has encountered some difficulties, such as unusual weather, the drastic depletion of high-value stocks, and unstable selling price. This information will be useful for further research related to planning effective management programs for sea cucumber fisheries in the region.