The age and growth of northern quahogs Mercenaria mercenaria (=hard clam) from inner Tokyo Bay, central Japan, were investigated by observing the annuli in their hinge teeth. The ages in the shallow and deep areas are 2–9+ and 1–13+, respectively. Significant differences in growth between clams found in the shallow and deep areas were detected. The growth coefficient and shell length of clams of a particular age in the shallow area were greater than those in the deep areas. Northern quahogs in both shallow and deep areas were confirmed to spawn around summer. A larger gonadosomatic index and a higher proportion of spawning individuals were found in shallow areas. These results indicate that shallow habitats provide enhanced conditions for somatic development in northern quahogs in this region.

Owing to the high cost of microalgal production for bivalve culture, a need for alternatives to live microalgal diets exists, particularly in facilities where space and personnel required for live microalgal culture are limited. This study examined the feasibility of utilizing commercially available microalgal concentrates in place of or in addition to live microalgae as a feed for post set northern quahogs (= hard clams), Mercenaria mercenaria and sunray Venus clams, Macrocallista nimbosa. Clams were fed one of six dietary treatments for 6 wk, and growth, survival, and fatty acid (FA) profiles were evaluated. Treatments included two live microalgal diets Tisochrysis lutea and T. lutea + Chaetoceros neogracile, which served as controls for complete or partial replacements with two commercially available concentrate products, ISO 1800 and Shellfish Diet 1800. The production of both clam species was negatively impacted compared with the live microalgae controls when only concentrates were fed. Survival decreased by 29–33% for hard clams and 42–62% for sunrays; a similar decrease in the growth rate (25–34%, 42–62%) was seen for hard clams and sunrays, respectively. Survival was not affected by feeding the partial replacement diets; however, the growth of sunrays was negatively affected (32–38% decrease) compared with live microalgae controls. Clam tissue FA profiles generally reflected the FA profiles of the dietary treatment fed, yet production was decreased with complete replacement diets, suggesting nonnutritional factors as the cause for the poorer performance seen. These results suggest that a live microalgal diet may be able to be sufficiently replaced with up to 50% of the microalgae concentrates tested without affecting the production of hard clams. For both post set hard clams and sunrays, production will be decreased if the two concentrates used in this study are utilized exclusively.

Beaches along Cook Inlet, AK, historically supported commercial, sport, and personal use fisheries for the Pacific razor clam (Siliqua patula). In 2015, east Cook Inlet beaches were closed to sport and personal use harvests, however, due to low abundances of adult clams with concomitant decreases in average length and percentages of large-sized razor clams. Meanwhile, razor clams in west Cook Inlet have not experienced the same decline, and west Cook Inlet beaches remain open to harvest. The universality of the trends in east Cook Inlet suggests post-settlement mortality as a primary driver, but changes in source-sink population dynamics or oceanographic processes may also differentially influence productivity. Given the differences in productivity between east- and west-side beaches, a key question is the degree to which razor clams around Cook Inlet are genetically connected. To answer this question, RAD-seq was used to discover and successfully genotype 44,040 single nucleotide polymorphisms in 37–48 razor clams collected from 11 sites around Cook Inlet and one site on the Alaska Peninsula. Pairwise F_ST estimates indicated a lack of neutral population genetic structure across the sampled range, with no evidence of genetic isolation among samples, between east and west Cook Inlet, or between 2 y classes with sufficient sample sizes, and less than 0.1% of loci were deemed F _ST outliers. Despite the lack of neutral and putatively adaptive variation, these results provide insights into the biological and ecological processes that may influence dispersal, recruitment, and stock productivity among Cook Inlet razor clam aggregations. Moreover, the knowledge gathered can assist resource managers in evaluating harvest strategies for Cook Inlet sport and commercial razor clam fisheries and provides information salient to abundance and demographic survey design.

Before collapsing, bay scallops (Argopecten irradians) supported commercial fisheries in Florida but, following decades of restoration efforts and management actions, still support a recreational fishery. Settlement was monitored along the west coast of Florida from 1992 through 2018, using collector traps. The primary environmental variables retained in the analyses included temperature, salinity, and red tide concentration (Karenia brevis). The settlement rate generally increased for the first days of trap deployment, then leveled off or declined. Settlement peaked when the average water temperatures were between 21°C and 23°C at four sites: St. Andrew Bay, St. Joseph Bay, West Coast, and Pine Island Sound, indicative of a fall peak in spawning. At the Tampa Bay and Sarasota Bay sites, settlement peaked when temperatures were around 16°C, indicative of winter spawning. At most sites, the highest peak in settlement occurred in association with declines in temperature of 10°C–15°C during the fall, with a smaller, secondary peak occurring with similar increases in temperature during the spring. Warming winter temperatures may already be negatively affecting the ability of the subpopulations to synchronously spawn, with unknown impacts to population dynamics. At all sites, settlement declined rapidly when salinity fell below 30 with little settlement occurring below 27, and approached zero when salinity fell below approximately 20. The occurrence of K. brevis exceeding 10,000 cells/L resulted in reduced settlement. In the core populations of West Coast and Steinhatchee, K. brevis was uncommon, and settlement resumed rapidly when blooms abated. For sites outside the core population, settlement was reduced for 2–4 y after red tides. Recovery of populations in these noncore sites probably relies on exogenous supply of larvae from the core. If blooms of K. brevis that penetrate the core region, as was observed in 2021, become more severe, more frequent, or have longer durations, the entire Florida scallop population could be endangered.

Populations of bay scallops (Argopecten irradians concentricus) in North Carolina (NC) declined precipitously following harmful algal blooms in the late 1980s and have struggled to recover. Following these harmful algal blooms, there was an increase in the frequency and magnitude of hurricanes and tropical cyclones in the 1990s, and a >30% loss of seagrass between 2006 and 2020 that further impacted the bay scallop populations. The last assessment of scallop density and distribution in multiple sounds in NC was performed in response to a 1987 red tide event. In the present study, 510 visual surveys of bay scallop densities and sizes in seagrass beds in southern Core Sound, Back Sound, and Bogue Sound, NC were conducted from May–November 2022. The mean scallop densities were 0.54/m² in Core Sound, 0.26/m² in Back Sound, and 0.19/m² in Bogue Sound. Using the healthy population density limits of bay scallops from Florida and New York to Massachusetts, a healthy density threshold of >1.0 spawning adult scallops/m² for NC was estimated. There was a positive relationship between seagrass density and scallop density, and as seagrass density decreased in the fall, scallop density also decreased. Bay scallops increased in size from May to August. In the fall there was a decline in the mean size as new recruits were added and a die-off of the adults occurred. Water quality appeared suitable to support healthy scallop populations at all sounds, consistent with previous observations in this system and others. The temporal scale of water quality sampling was not adequate to record short-term freshets that may have impacted scallop density. The information from this study can update the status of the bay scallop population in NC sounds, as well as inform management for the purpose of sustainable harvest or restoration.

The Florida bay scallop (Argopecten irradians concentricus Say, 1822) is a relatively short-lived species that resides in dynamic marine systems and is subject to multiple stressors, although the environmental drivers of bay scallop abundance along the Florida Gulf Coast are not well understood. The use of an ecosystem approach to fisheries management may be particularly relevant for short-lived species that are highly susceptible to environmental changes, but this approach requires an understanding of how environmental variables, such as salinity and temperature, may influence bay scallops throughout their range. This study was designed to identify the relationships between environmental variables and bay scallop abundance and to evaluate the relative effect of these relationships. Scallop surveys conducted in the spring and fall along the Florida Gulf Coast from 1992 to 2019 were compared with seasonal water quality parameters, streamflow discharge, precipitation, wind speed, and climate indices. The size and spawning success of the fall scallop population were negatively affected by relatively high Karenia brevis counts, low dissolved oxygen, and low phosphorus availability. During the period of early postsettlement growth in the winter, scallops were negatively impacted by salinities outside the range of 22–27 due to increased rainfall and low nitrogen availability. Finally, the factors that negatively affected juvenile scallop growth and survival in the spring included increased rainfall and wind speed resulting in relatively high turbidity and comparatively low chlorophyll a.

Oyster population maintenance and growth require a sufficient larval supply competent for metamorphosis and settlement. Larval performance, in terms of growth, development, survival, and metamorphic success, determines the capacity for a larval cohort to effectively settle and establish into an existing population. Exogenous factors influencing larval development include temperature, salinity, food quantity, and food quality. A sufficient diet, composed of balanced protein, lipids, and carbohydrates to meet larval nutritional demands, is required to promote successful metamorphosis. To evaluate the influence of these exogenous factors on oyster settlement potential in Delaware Bay, a well-established biochemically based Crassostrea gigas (Thunberg, 1793) larval model was adapted to simulate Crassostrea virginica (Gmelin, 1791) larval performance under in situ environmental conditions measured during the 2009 to 2011 reproductive seasons at 10 sites across the salinity gradient of Delaware Bay. Variation in the initial egg size and lipid content, and larval food assimilation efficiency was incorporated into the model to represent potential within-cohort phenotypic variability. The middle portion of Delaware Bay along the New Jersey shoreline, bridging the 15-salinity line, generated the most successful larvae each year, whereas the low-salinity reach, on the Delaware side, and Nantuxent Point Reef had more variable success. Survivorship was a function of adequate temperatures and salinities, sufficient food quantity, and favorable food quality defined in part by the protein-to-(lipid-plus-carbohydrate) ratio. Most settlement was predicted by the model to occur between July and September of each year. To validate the model, estimated settlement windows were compared with calculated settlement windows derived from recruitment observations on yearly shell plants. Modeled and recruitment-derived settlement windows agreed well with each other and verified the capacity of the model to accurately forecast in situ larval performance. The oyster larval model, based on measures of lipid, protein, and carbohydrate, successfully passed an important field test, demonstrating the potential of such biochemically based models to reliably evaluate larval performance under real-world conditions.

Adductor muscle from Pinctada maxima and Pinctada margaritifera were analyzed for nutrient compositions. Both were characterized by relatively high-protein, low-lipid, and low-cholesterol contents. Palmitic acid and docosahexaenoic acid were the dominant saturated and polyunsaturated fatty acids, respectively, in both species. Amino acid compositions of adductor muscle from both species were characterized by a high abundance of glutamic acid, aspartic acid, and arginine, whereas cysteine, then tryptophan, were least abundant. Overall, these nutrient compositions are similar to those reported for other bivalve molluscs. The results are timely given the growing interest in pearl meat consumption and pearl meat farming.

Shrimp (Litopenaeus vannamei) were provided access to sea urchin (Lytechinus variegatus) egesta to investigate whether fresh egesta (containing an active microbiome) consumed alone or in combination with a commercial shrimp feed could influence growth, feed conversion, body composition, and survival of L. vannamei in co-culture. In an initial experiment conducted for 8 wk, shrimp were proffered a full or reduced ration (100%, 60%, and 20%) of commercial shrimp feed with or without access to sea urchin egesta serving as a source of supplemental nutrients and presumptive probiotics. Individual weight gain of shrimp provided sea urchin egesta only (10.37 ± 0.35 g) did not differ significantly from that of shrimp proffered a full ration of feed (9.46 ± 0.39 g) despite significant compositional differences. Consumption of sea urchin egesta combined with commercial shrimp feed resulted in significantly greater weight gain of shrimp when compared with shrimp proffered the same level of commercial shrimp feed only. The largest weight gains of shrimp were found for those groups fed rations of 60% and 100% and had access to egesta (14.09 ± 0.75 g and 14.72 ± 0.68 g, respectively). In the next experiment, shrimp were stocked at different densities (approximately 23, 45, 68, and 90 individuals m^–2) and were not proffered feed directly. All replicates were provided access to fresh sea urchin egesta produced by four urchins that were fed at a daily rate of 3% of the total initial group weight (140.4 ± 0.7 g) for 8 wk. The largest individual weight gain was found in the lowest density treatment (6.55 ± 0.38 g). Harvested biomass significantly increased as density increased, except for the highest density treatment. These results indicate that sea urchin egesta may provide some growth enhancement factor(s) to shrimp when proffered in conjunction with a commercial diet, and at a certain density of shrimp sea urchin egesta may actually serve as a nutritionally complete diet.

Failure of the Apalachicola Bay oyster population to recover since the 2012 fishery collapse, despite a decade of unprecedented restoration efforts and a fishery closure, indicates that the system has lost its former resilience, crossed a critical threshold between ecological steady states, and is experiencing hysteresis. This commentary contributes to the weight of evidence that reflects how accumulated system stressors led to reduced resilience and alterations in the ecological state of Apalachicola Bay. Discussion of resource exploitation, negative shell budget, salinity extremes, predator abundance, parasites, and disease underscore how these stressors accumulate over time to impact oyster populations and system resilience. Additionally, various interpretations of “resilience,” “exploitation,” and “restoration” have facilitated chronic resource over-exploitation and oyster habitat degradation in Apalachicola Bay. Within this context, a necessary cultural shift is described that reframes restoration and management goals to target healthy oyster habitat as the endpoint rather than using fishery metrics based on the number of harvestable oysters per acre. Failure to reframe restoration goals may be the cumulative result of resistance to accepting the presence of ecological state change, economic drivers overshadowing the weight of evidence, and outcomes not directly impacting decision makers.

The coastal fishing of the snail Titanostrombus galeatus is carried out in some coastal countries of the Tropical Eastern Pacific. In this study, the individual growth of T. galeatus that are fished in the community at Punta Maldonado was estimated. The size structure was made using the shell length (SL), and the growth parameters were estimated through the five Schnute cases, where cases 1, 2, and 5 describe asymptotic growth and cases 3 and 4 describe nonasymptotic growth. The male population was more abundant than the females, with 398 and 322 specimens, respectively, but the females were larger (198 ± 9.66 mm). In general, the average SL during the two sampling cycles was 196 ± 9.44 mm; this size was not significantly different between the first and second cycles (P = 0.98). Females had a greater range of SL (170–267 mm) compared with males (170–240 mm). The lengths of both sexes showed significant differences between months (P < 0.05). The multinomial analysis showed a multimodal SL distribution, with one to three modal groups for females and males. In growth, cases 2 and 5 were the ones that best describe the growth in females, in males the best were cases 5 and 2. According to the best case (case 2) in females, the growth curve is sigmoidal. In males, the best case (case 5) describes growth according to an inverted exponential curve. In relation to the estimated growth parameters, females showed faster growth than males, analyzed using Kimura's test. The present investigation is the first that reports the growth for both sexes of T. galeatus using the five cases of the Schnute model. The information generated can be used for management purposes, as this species is not currently regulated in Mexico.

In this study, the length-weight relationship (LWR) was determined for the marine gastropod and commercial fisheries species, Kellet's whelk (Kelletia kelletii), and possible site- and sex-based differences in the LWR were assessed. Data were collected from 761 Kellet's whelks (1.6–15.5cm shell length, 0.51–404g total weight) that were brought to port by commercial fishermen or collected using SCUBA from three regions across the US geographic distribution of the species: San Diego, Santa Barbara, including the Northern Channel Islands, and Monterey. Model fitting revealed a cubic function to represent the LWR of the entire dataset with strong explanatory power. The fitted model suggested the species demonstrates slightly negative allometric growth, indicating that shell length grows faster than the width of the organism. Whelk sex and collection site did not impact the LWR. The information from this study can be used to inform management decisions for Kellet's whelk conservation, aquaculture, and fisheries harvest and guide future research.

Bryozoan epibiosis on lobster hosts has rarely been reported. This study documents bryozoan fouling of the American lobster (Homarus americanus Milne Edwards, 1837) from the Connecticut portion of Long Island Sound, USA. A total of 168,664 lobsters were examined for epibionts from 2000 to 2013 following the lobster fishery crash in 1999. The lobsters were caught commercially for the State of Connecticut, Department of Energy and Environmental Protection lobster catch monitoring program. The lobster shell condition in four stages of its molt cycle was noted (i.e., from a soft new shell, hard new shell, hard shell, to ready to molt). Of the lobsters caught, 29% were fouled by epibionts. Of those, 88% were fouled by bryozoans, 20% by barnacles, 6% by tube worms, 3% by slipper shells, and <1% by mussels and sea squirts. The prevalence of fouling increased as time since last molt increased from <1% of soft new shells to 1% of hard new shells, 31% of hard shells, and 45% of those ready to molt. This prevalence of bryozoan fouling reported here was higher than that in other studies and may have been due to the poor health of the host lobsters and/or poor water quality.

There is considerable interest in improving hatchery production of the mud crab, Scylla serrata. Although some progress has been made toward identifying appropriate feeding protocols for live-foods, the density at which food is first provided to larvae varies greatly in practice. This study examined relationships between rotifer density and activity patterns of enzymes critical to digestion in S. serrata to evaluate feeding protocols from a nutrient utilization perspective. Activities of trypsin-like proteases, nonspecific esterases, and α-amylase were quantified to determine the response of newly hatched (Zoea I) larvae of S. serrata to rotifers provided at four different densities (i.e., 10, 20, 40, and 80 mL^–1) from first-feeding. Results showed that rotifer density significantly (P < 0.01) influenced total activity (mU larva^–1) patterns within 24 h of first-feeding for all the enzymes assayed. Based on these patterns, utilization of the associated macronutrients (i.e., protein, lipid, and carbohydrate) was presumably similar when larvae were provided with rotifers at densities of 10, 20, or 40 mL^–1 and increased when larvae were provided with rotifers at a density of 80 mL^–1. An optimal density at which to provide rotifers to S. serrata for first-feeding is likely to be >40 mL^–1. The comparative analyses of enzyme activities presented in this study represent an innovative approach to quickly (within 24 h) identify optimal food densities for larval crustaceans at first-feeding.

Shorebirds use a variety of intertidal estuarine habitats to rest and refuel during their seasonal migrations. Birds can be found foraging on mud or sandflats, aquatic vegetation, as well as intertidal areas developed for shellfish aquaculture. In Washington State, which contributes substantially to commercial U.S. production of the Pacific oyster (Crassostrea gigas), little research has been published about how aquaculture habitats are used by shorebirds relative to surrounding seagrass and mudflat. Using photographic sampling, shore- and waterbird use of mudflat, seagrass, and longline oyster culture habitats was studied on an oyster farm in Grays Harbor, WA. The effect of the tidal stage (ebb, dry, or flood periods) was also evaluated. Thirteen bird taxa were identified and analyzed for effects of habitat on community composition and total bird abundance, whereas the six most common taxa were used in an analysis of habitat type and tidal stage effects on taxon abundance. Of the six focal taxa, black-bellied plover, American crow, and dunlin (Pluvialis squatarola, Corvus brachyrhynchos, and Calidris alpina, respectively) responded significantly to habitat type—having positive associations with eelgrass and/or longlines—whereas dunlin, dowitcher, and gulls (C. alpina, Limnodromus spp., and Larus spp., respectively) responded significantly to tidal stage—having positive associations with the ebb or flood periods. Total bird observations varied by habitat and through the tidal cycle, where more birds were observed in eelgrass and during ebb and flood periods. There was no strong effect of habitat type on community composition when sampling across several months. Overall, all three habitat types were used by a variety of shore- and waterbird taxa, with no evidence of a negative effect of longline oyster culture on bird abundance.