The goal of this study was to determine: (1) the extent to which channeled whelks (Busycotypus canaliculatus) expressed biological rhythms in the field, based on catch data; and (2) the degree to which their daily activity rhythms in the laboratory are influenced by an internal biological clock versus exogenous environmental cues. In the field studies, a timelapse video system was used to quantify when whelks entered traps during deployments in the coastal waters near Cape Cod, MA (n = 23 trials). Most of the whelks observed entering traps did so during the night, shortly after sunset on the first day of deployment. There was also a tendency for whelks to enter traps more during high tides. In the first laboratory experiment, when whelks were held in flow-through seawater tanks receiving ambient seawater with prevailing environmental cues, 73% (8/11) expressed a tidal rhythm in both a light:dark cycle (13L:11D) and constant darkness (DD) conditions. In the second laboratory experiment, when whelks were tested in tanks held at a constant temperature and 11L:13D, 45% (9/20) were nocturnally active. When these same whelks were subsequently exposed to DD conditions, only 30% (6/20) expressed a circadian rhythm. In the third laboratory experiment, when whelks were held in 19-L (5-gallon) buckets, placed inside a larger holding tank, in an environmentally controlled cold room under 14L:10D illumination, 60% (6/10) of the whelks were nocturnal, but a circadian rhythm only persisted in 30% (3/10) of them in DD conditions. These data, taken together, indicate that, whereas this species likely possesses a circadian clock that plays a role in controlling their patterns of locomotion, prevailing environmental cues also have a large impact on their activity and catchability.

During live export, abalone are transported in air, exposing them to environmental hypoxia for extended periods. Hypoxia-inducible factor-1 (HIF-1), a fundamental moderator of hypoxia, activates a variety of genes in response to hypoxic stress, including inducible nitric oxide synthase (iNOS), which is involved in vasodilation, which ultimately can lead to improved perfusion. This study hypothesized that Haliotis midae, the South African abalone, recruits the under-perfused left gill during hypoxia via HIF-1 and iNOS induction whereas changing metabolic rates, transitions to anaerobic respiration and maintaining circulating oxygen by means of reverse Bohr shift that contribute to alleviating tissue hypoxia during 24-h air exposure. Haliotis midae were exposed to air for 24 h as a proxy for hypoxia and were reimmersed in water for 1 h for recovery before the HIF-1α protein expression, iNOS gene expression and ¹⁴C inulin space were measured in the gills. We also measured oxygen consumption rates, hemolymph D-lactate levels, pH, and PO₂. We found no evidence of HIF-mediated iNOS induction, but abalone hypometabolism and the presence of lactic acid in circulation during the short recovery indicate some reliance on anaerobiosis.

Developing methods for the cultivation of the pinto abalone, Haliotis kamtschatkana, has seen increased attention, both by groups using restoration aquaculture to reestablish endangered populations in Washington and British Columbia, and in the State of Alaska, where pinto abalone are viewed as a promising new species for commercial mariculture. To enhance the viability of cultivating H. kamtschatkana for commercial and restoration purposes, more information is needed on the optimal macroalgal diet that maximizes abalone growth and nutrition. This study compares the suitability of two commonly cultivated species of macroalgae as feed: Saccharina latissima (sugar kelp), a kelp with relatively low protein content, and Devaleraea mollis (Pacific dulse), a rhodophyte with comparatively high protein content. Fifty H. kamtschatkana specimens, with a mean shell length of 45.25 ± 4.26 mm, were collected from the wild and fed either S. latissima, D. mollis, or an alternating diet of the two for 28 wk. Feed consumption was measured weekly, whereas shell length and weight change were recorded every 2 mo. Despite consuming significantly more S. latissima than D. mollis (P < 0.001, H. kamtschatkana showed no significant difference in specific growth rate (SGR) (P = 0.775) or linear growth rate (LGR) (P = 0.746) among the diets. Feed conversion efficiency (FCE) was significantly higher for D. mollis than S. latissima (P < 0.001), although there was no significant difference in protein efficiency ratio (PER) (P = 0.129). Proximate composition analyses of abalone tissue showed no significant difference in protein, lipid, carbohydrate, or caloric content across macroalgae diets. Additionally, sexual dimorphism was observed, with females exhibiting significantly higher daily feed consumption (DFC) (P = 0.001), SGR (P = 0.003), and LGR (P = 0.001) than males. These results indicate that whereas both macroalgae species are suitable as feeds for H. kamtschatkana cultivation, the benefits of a D. mollis diet are less pronounced compared with other commercially cultivated abalone species. This study provides actionable insights for those interested in cultivating H. kamtschatkana for commercial or restoration purposes and adds to our understanding of an environmentally and culturally important species in the Northeast Pacific Ocean.

The day octopus Octopus cyanea Gray, 1849, is a large, muscular and robust octopod distributed across the tropical Indo-West Pacific. In Fiji and other Pacific Island Countries and Territories (PICT), it is an economically, ecologically, and socio-culturally important species, and supports a small, but high-value artisanal fishery providing a basis for coastal community livelihoods. Despite its importance, the presence of this species has not been confirmed in Fiji using molecular methods. To provide taxonomic verification and inform genomic stock assessment of the Fijian octopus resource, two mitochondrial barcoding genes (cox1 and 16s rRNA, n = 60), together with morphological assessments, were applied to specimens collected from six provinces in Fiji. In both reconstructions, all Fijian sequences resolved within broader clades comprising additional O. cyanea sequences sampled across the species distribution (cox1 688bp: n = 53; 16s rRNA 572bp: n = 10), with high node support (100%) and sequence identity matches (97%–100%), confirming their conspecifity. Morphological features of Fijian specimens (n = 79) confirmed to ranges reported for O. cyanea, including mantle length, head width, sucker counts on hectocotylized arm and ligula lengths (3.47–5.94 mm). With the resolution of species identity, species-appropriate stock assessment may now proceed, to inform sustainable and accurate fishery exploitation, catch reporting and management. The independent molecular barcoding and morphological characterization approaches used have high utility for octopus fishery characterization efforts in other PICT, which remain data deficient.

Gulf ribbed mussels (Geukensia granosissima) act as ecosystem engineers and reside within the marsh platform of saltmarshes across the northern Gulf of Mexico. With climate models projecting increasing temperatures, and more frequent and extreme heat events, these mussels face increasing temperature-related risks. Marsh surface and subsurface (5-cm depth) temperature was measured continuously in the summer of 2022 in south Louisiana Gulf ribbed mussel habitat at nine stations. Marsh surface maximum temperatures were 5°C higher and more variable than recorded water temperatures, exceeding 38°C for periods of up to 3 h which generally coincided with low tides and peak solar radiation. Marsh subsurface temperatures were cooler with a lower mean and maximum temperature compared with the marsh surface, but higher than adjacent water. In two laboratory experiments the acclimated and acute thermal tolerance of wild mussels collected from the saltmarsh where temperatures were recorded, were explored. G. granosissima survived more than 40 days of continuous exposure in the laboratory to mean daily temperature values recorded for the marsh and subsurface microhabitats (28°C–34°C) but their calculated median lethal time (LT₅₀) ranged from 35 to 56 days (36°C), to less than 3 days (40°C). Mussels acclimated to temperatures similar to long-term average water temperatures (28°C–32°C) and then exposed to maximum daily temperatures acutely experienced LT₅₀ of less than 6 days (38°C), <1 day (40°C), and of less than 5 h (42°C). For G. granosissima both their thermal tolerance and behavioral response likely contribute to their survival in the face of extreme heat events, and their resulting distribution across the marsh surface and subsurface. Overall, results indicate that ribbed mussels in coastal Louisiana may rely on their ability to migrate vertically and bury in the marsh to avoid extreme heat exposure (temperature, duration) that may be lethal. The ability of Gulf ribbed mussels to endure short-term thermal extremes may ultimately determine the mussels' use as a tool in marsh stabilization and coastal restoration.

The blacklip rock oyster Saccostrea spathulata has been identified as a promising candidate species for commercial aquaculture, particularly in the tropical Asia Pacific region. Currently, however, commercial production is constrained by unreliable spat production in hatcheries, with low and variable settlement rates proving a major issue. Improving larvae settlement rates during metamorphosis is a critical step toward establishing a fledgling tropical rock oyster industry. To this end, the present study examined the effects of both salinity and epinephrine bitartrate exposure on oyster settlement, survival, and spat size. It was found that salinity, epinephrine dose, epinephrine exposure and their interactions significantly impacted both oyster settlement and survival. Notably, an epinephrine dose of 1.8 × 10^–4 M yielded the highest settlement rates (>30%) and was most effective at higher salinities (≥25). Survival was generally high (>75%), however, appeared to be favored by low salinities (10) and exposure to lower epinephrine dose. Finally, spat size was positively affected by increasing salinity and tended to decline with increasing epinephrine dose. Given the clear impact of the production variables reported in this study, it is envisaged that these findings can be used to enhance the production efficiency of cultured tropical rock oysters and thereby support this emerging aquaculture industry.

The blacklip rock oyster, Saccostrea spathulata, has significant potential to support oyster aquaculture development in the tropical Asia-Pacific region; however, hatchery production is currently constrained by the absence of a reliable broodstock conditioning protocol. This study aimed to investigate the effects of salinity and diet on blacklip rock oyster S. spathulata gonad development, as well as the subsequent ability to spawn, fecundity, and oocyte quality. Broodstock were conditioned for a period of 8–12 wk and sampled at regular intervals for histological analysis. Results showed that salinity has a significant effect on gonad development, with the greatest proportion of ripe broodstock produced at salinity 25. Gonad development was also dependent on diet. Broodstock fed a diet comprising 100% live microalgae (35% Chaetoceros muelleri; 5% Skeletonema costatum; 20% Tisochrysis lutea, 20% Pavlova spp.; 20% Tetraselmis chui) achieved greater condition indices than those fed a formulated diet and were brought into spawning condition within 5 wk. Further, female broodstock fed the live microalgae diet produced more, and larger eggs compared with those fed a full or partial formulated diet. Based on these results it is recommended to condition blacklip rock oysters at salinity 25 for a period of 5 wk, with a diet comprising live microalgae at a rate of 2–3.5 × 10⁹ Tisochrysis lutea cells^–1 oyster^–1 day^–1. This study provides the first method to condition blacklip rock oyster broodstock and removes a current bottleneck to hatchery production.

Genomic selection was conducted in the eastern oyster using a 66K single-nucleotide polymorphism (SNP) array to improve resistance to dermo disease caused by Perkinsus marinus. Oysters from a Florida wild population were divided into a training and a breeding population; oysters from the training population were challenged with P. marinus in the laboratory, separated into dead (“susceptible”) and alive (“resistant”) phenotypes, and genotyped with the array. A genome-wide association study identified no major loci for dermo resistance confirming the polygenic nature of the trait. Dermo resistance as measured by binary survival had an estimated heritability of 0.255 ± 0.115. Markers and associated genes were identified including some related to phagocytosis providing insights into dermo resistance. Markers were ranked according to their association with dermo resistance, and marker-sets were evaluated with five statistical models for prediction accuracy by cross-validation. The genomic best linear unbiased prediction model with the top 10K markers that produced the highest prediction accuracy was used to calculate genomic estimated breeding values (GEBVs) for genotyped oysters from the breeding population. The top 36 individuals with the highest GEBVs were bred to produce a genomic up-selected group (FLGS), and the bottom 39 individuals with the lowest GEBVs were bred to produce a down-selected control group (FLC). A phenotypically selected group (FLP) was produced using 46 survivors from the dermo challenge. When progenies from the three groups were challenged with dermo, FLGS showed a 20.4% increase in survival over down-selected FLC, whereas the survival increase in FLP was not significant. These results suggest that dermo resistance can be more effectively improved by genomic selection than phenotypic selection.

Eastern oyster (Crassostrea virginica) populations are declining due to habitat degradation, overharvesting, and disease. One factor of potentially equal importance that has received little focus is the impact of food quantity and size composition of the seston supporting larval development, survival, and success at metamorphosis. Phytoplankton serve as a primary source of nutrition for oyster larvae; its size composition and content tend to fluctuate with environmental conditions. These fluctuations, in turn, may significantly impact larval performance. To investigate the potential of variations in the size composition of the seston determining the dynamics of larval performance, simulations are developed to project larval success in relation to variations in three size classes of planktonic food, <5, 5–20, and >20 µm. A biochemically-based larval performance model is implemented to track key outcomes, defined as the success rate at metamorphosis, mortality during development due to suboptimal food supply, and mortality due to egg quality characteristics supporting early development. The results support the potential of variations in the size composition of planktonic food as a key driver of outcomes, potentially explaining some of the well-described year-to-year volatility in recruitment. The results point to a number of key influences on larval performance including the critical need for sufficient availability of small food particles at the end of the trochophore stage, suggesting a potentially key match–mismatch point in larval development. The results point to the influence of larger food particles later in larval life in supporting increased size at metamorphosis and in reducing planktonic lifetimes, thereby reducing exposure to predation. Simulations also show the influence of egg size and larval physiology supporting increased survival when food size composition is suboptimal. Given the outcomes of this study, increased interest in the size-composition of seston in the field relative to larval performance metrics would seem warranted.

Chesapeake Bay has experienced nutrient-related water quality impairment for decades due to the discharge of nutrients (nitrogen and phosphorus) from human-related activities in the watershed. Water quality monitoring indicates a need for additional nutrient management. Oyster aquaculture has become a focus as an additional management strategy because oysters remove nutrients as they feed. Models can estimate oyster harvest and related nutrient removal, helping to develop comprehensive management plans that include oyster aquaculture. Water quality measures for at least 1 y are required as model inputs. Field sampling and laboratory analyses are time and resource-intensive. There is interest in finding less costly methods of data collection, or in using data already being collected for other purposes as model inputs.

Oyster reefs worldwide are experiencing a concerning decline, driven not only by overharvesting but also by parasites and diseases that threaten oyster and estuarine health. Here, the effects of the protozoan parasite Perkinsus marinus, which is known to cause dermo disease, were assessed after a 7-y gap in data gathering in a known infection center in the Gulf of Mexico: Galveston Bay (Texas). Eastern oysters (Crassostrea virginica) were collected from four sites across the bay from September to November of 2022 (a weak La Niña year) and 2023 (a strong El Niño year). Surveys revealed much higher infection levels (prevalence, infection intensity, and weighted prevalence) across almost all sites in 2023 compared with 2022. These high infection levels were likely driven by warm and saline conditions resulting from local droughts and potentially linked to large-scale climatic events. Parasite levels in 2023 resembled historical peaks reported in the late 1990s and early 2010s. High infections of P. marinus were also associated with poorest condition of the soft tissue and lower oyster quality, with temperature and oyster size as additional confounding factors. Given the potential for climate change to exacerbate conditions conducive to the reproduction of P. marinus, frequent monitoring is critical to understanding mortality trends associated with parasite outbreaks. This study provides information on recent parasite levels impacting oyster health and their links to local and large-scale climatic events to support scientists and resource managers in the restoration and conservation of estuarine ecosystems.

Mangrove clams of the genus Geloina primarily inhabit mangrove ecosystems and hold significant ecological and economic values. Accurate species identification among Geloina species is challenging because the members share similar morphological characteristics. In this study, a multivariate morphometric analysis of 13 conchological traits was performed based on a molecular systematic framework to find the differences between Geloina coaxans and Geloina erosa from four major mangrove areas on Hainan Island: Tielugang in Sanya, Dongzhaigang in Haikou, Qinglangang in Wenchang, and Hongshuiwan in Chengmai. Analysis of variance and principal component analysis revealed three traits (categorized as hinge teeth) with significant differences between the two species, which were then used for subsequent cluster analysis and discriminant analysis. Cluster analysis could clearly distinguish the two species. Although within the populations of G. coaxans, the one from Haikou exhibited the greatest morphological divergence from the other three populations. A discriminant function was established for distinguishing G. coaxans from G. erosa, with an overall discriminant accuracy of 87.9%. This study indicates that multivariate morphometric analysis may help identify the two species under a clear molecular systematic framework.

Lipid composition detected in juveniles of the carpet clams Paphia textile, and three feeding strains of microalgae were investigated. Lipids were extracted via the Folch method and analyzed through gas chromatography coupled with a mass spectrometry detector after methylation. The results demonstrated seven classes of lipids mainly alkanes and fatty acids (FA), accounting for more than 97% of the total lipids. Palmitic acid (C16:0), linolenic acid (C18:3n3), elaidic acid (C18:1n9t), linoleic acid (C18:2n6), and stearic acid (C18:0) were the characteristic FA in P. textile and Tetraselmis helgolandica. A large amount of PUFA precursors in the synthesis of T. helgolandica were identified, such as linolenic acid (18:3n-3) with a relative content of 14.37% and linoleic acid (18:2n-6) with a relative content of 9.56%. Although the composition of LCFA in P. textile was more similar to those in Isochrysis galbana and Chaetoceros muelleri, it was shown that T. helgolandica can also meet the lipid nutrition needs of P. textile with a high PUFA relative content of 42.19%, and it was an excellent diet for the juvenile carpet clam of P. textile. It is recommended to add a mixed diet of I. galbana and C. muelleri when feeding mainly T. helgolandica.

As invasive European green crabs (Carcinus maenas Linnaeus) continue to impact Gulf of Maine ecosystems and fisheries, harvesters and coastal resource managers are exploring strategies to mitigate the effects of this species. One option is to establish and promote a soft-shell crab fishery for this species; however, it can be difficult to accurately and consistently identify premolt crabs for harvest using external morphological cues alone. This study evaluated the application of several hemolymph indices as diagnostic tools for determining the molt stage in C. maenas. Captured crabs were tagged, measured, and held in individual compartments in a floating enclosure for up to 51 days. Hemolymph samples were collected twice per week from individual crabs (n = 126) and evaluated for hemolymph color, total protein (refractive index, RI), and calcium concentration. The resulting data suggest a positive relationship between these metrics: darker hemolymph samples had higher protein and calcium concentrations; crabs with darker hemolymph and higher initial RI were more likely to molt within 3 wk; and initial RI ≥9.5 resulted in a >50% chance of molting within 3 wk. In addition to improving our understanding of the biological underpinnings of molting in brachyuran crabs, these results provide practical information for creating an accessible molt assay tool (i.e., hemolymph color) that can be used by harvesters to further facilitate the development of a soft-shell crab market.

Screw pine (Pandanus tectorius) leaf extract (PLE) has been shown to improve the tolerance of the White-leg shrimp Penaeus vannamei to various biotic and abiotic stressors. This study was a continuum to highlight the remarkable effects of this coastal plant extract in safeguarding brine shrimp Artemia franciscana, an important larval live food organism in aquaculture, from lethal heat, acidity, and salinity stress assays. Axenic Artemia nauplii were used to examine the impact of abiotic stress on the organism without being affected by microbial contamination. This approach provides greater clarity into the detrimental impacts of these stressors and allows for a more precise understanding of the molecular responses of Artemia to PLE. Exposure to 1–6 g/L PLE for 2 h was nonlethal to Artemia nauplii, with 5–6 g/L PLE demonstrated the highest protection against all three abiotic stressors, where survival increased by at least 22% as compared with the nonPLE-exposed control. Comparative transcriptome analysis revealed that multiple genes related to chitin-based cuticle (insect cuticle proteins, chitin-binding domain type 2, and structural constituent of cuticle proteins), carbohydrate metabolism (alpha-amylase, dihydrodiol dehydrogenase, and V-type H+-transporting ATPase subunit C), and the stress and innate immune responses (spaetzle, C-type lectin, CD109, major facilitator superfamily proteins) were differentially expressed. This study highlights the functional roles of PLE as a potential antistress agent in mitigating stress caused by environmental factors in farmed shrimp, promoting better health and resilience during aquaculture.