The narrow-clawed crayfish (Pontastacus leptodactylus) is a native Eurasian species of significant ecological importance and increasing commercial interest, representing a promising species for freshwater aquaculture development. Although the species demonstrates broad physiological tolerance to varying environmental conditions, its intensive cultivation remains limited by persistent biological constraints, including high juvenile mortality, cannibalism associated with asynchronous molting cycles, and vulnerability to crayfish plague caused by Aphanomyces astaci. Building on recently published comprehensive accounts of the biology and distribution of the species, this review focuses specifically on nutritional optimization and technological integration as pathways for overcoming these key production constraints. Recent advancements in sustainable aquafeed formulations are evaluated, with particular emphasis on the substitution of fishmeal with alternative protein sources, including insect-based meals and microalgae, alongside the application of prebiotics, synbiotics, and functional feed additives to modulate gut microbiota, enhance antioxidant capacity, and improve stress resistance. Environmental management strategies, including habitat enrichment, stocking density optimization, and photoperiod manipulation, are further examined for their roles in reducing agonistic interactions and improving animal welfare under intensive culture conditions. The epidemiology of A. astaci is further discussed within the context of biosecurity strategies aimed at protecting both aquaculture systems and native freshwater biodiversity. In addition, the potential contribution of nutritional conditioning to host immune resilience against pathogen exposure is discussed as an underexplored but promising management strategy. Overall, current evidence suggests that the long-term scalability of P. leptodactylus aquaculture depends on the adoption of recirculating aquaculture systems, biofloc technology, and genomic breeding tools, integrated with optimized nutritional and welfare-oriented management strategies, to achieve sustainable intensification and commercial viability.
Compliance with the United States Clean Water Act requires states and municipalities to reduce nitrogen (N) pollution and document the effectiveness of mitigation efforts. Oyster aquaculture is a cost-effective and sustainable approach to N removal; however, direct measurement of oyster N content is time-and resource-intensive. Meanwhile, existing predictive models are either broadly general or developed for specific regions outside of Massachusetts (MA). Consequently, the MA Department of Environmental Protection (DEP) requires site-specific measurements. In this study, oysters from 21 southeastern MA estuaries were analyzed as a case study to quantify region-specific relationships of N content, calculated as both mass and percent of whole oyster dry weight, in relation to oyster size, deployment method (surface versus bottom), and water quality metrics. A nonlinear model was used to estimate oyster N mass from shell height (SH), whereas a stepwise linear regression model was used to identify tissue weight, shell weight, water column total N, and oyster deployment method as significant predictors of percent N content. A potential benefit of regional models is to provide a better fit to local data than a general model that incorporated data from across a broader range (e.g., in the present case North Carolina to Maine), particularly for the upper range of oyster SH. These region-specific models enable municipalities to estimate N removal from harvests without laboratory analyses, supporting state level DEP-approved nutrient crediting.
Swollen-siphon disease has caused significant mortality in snout otter clams (Lutraria rhynchaena), a valuable aquaculture species in Vietnam, yet its causative agent remains unidentified. In this study, integrated transcriptomic and metagenomic data were analyzed to investigate host molecular responses to the disease and to further re-evaluate its microbial basis. The authors conducted a controlled disease-challenge experiment, demonstrating the presence of a transmissible pathogenic agent and a significantly higher mortality rate in the experiment group, up to 100% by day 6 postinjection. Transcriptomic profiling of siphon and body tissues from diseased (n = 4) and healthy clams (n = 4) identified 508 differentially expressed genes (DEG), including 308 upregulated and 200 downregulated in diseased samples. Upregulated DEG such as cd109, chit1, and duox2 indicate enhanced innate immune responses against microbial pathogens, whereas downregulated genes, including hsp70, hsc70, and hsp68, suggest suppressed stress responses. Gene ontology enrichment revealed activation of immune signaling and suppression of energy metabolism and muscle contraction. The analysis of metagenomic data identified viral communities dominated by Heunggongvirae, Monodnaviria, and unclassified viruses. Although potential pathogenic taxa were detected, their role in disease etiology needs to be further investigated. The transcriptomic profiling presented in this study provides insights into host-pathogen interactions underlying swollen-siphon disease in snout otter clams, supporting future studies on disease etiology and epidemic control.
The eastern oyster (Crassostrea virginica) is the only oyster species farmed in the Canadian Maritimes. Although current production is limited to diploids, the development of triploid production is becoming increasingly urgent as industry expansion becomes constrained and emerging diseases threaten production. Although tetraploid methods for triploidy production are well established and are the standard production technique, establishing tetraploid lines is time-consuming. Given the urgency to produce triploids, the objective of this study was to establish an effective protocol to produce triploid eastern oysters using hydrostatic pressure shock as a short-term alternative to tetraploid methods. This study followed a factorial design and focused on three key parameters: postfertilization time of pressure initiation [13 and 14 min postfertilization (mpf)], pressure shock duration (10 and 12 min), and pressure intensity (9000 and 9500 PSI). To inform the factorial design, observations of polar body extrusion were made with oysters spawned during early, mid, and late natural spawning season. In addition, a preliminary experiment suggested that pressure intensities below 9000 PSI yielded low triploidy induction. Although a maximum triploidy of 83% was achieved with a 13-mpf initiation time, 10-min duration, and 9000 PSI, no triploids were detected by day 15, suggesting complete mortality. Furthermore, by day 15, overall survival in pressure shock treatments was 0.11% compared with 9% in diploids, which survived beyond metamorphosis. Consequently, the results indicate that hydrostatic pressure shocking is not a viable method to produce triploid eastern oysters on an industrial scale under the tested conditions. As such, the Canadian industry should redirect resources to exploring alternative induction methods, such as chemical or thermal shocking in the short term, and tetraploid and disease-resistant lines in the long term.
Shellfish farms manage and control biofouling through regular gear and shellfish cleaning practices. This forms a major part of operational costs and often meets negative public perceptions of work-related noise. Growers are therefore seeking solutions to reduce effort, maximize profit, and improve social carrying capacities for aquaculture. An emerging solution is to integrate sea urchins (SU) with shellfish and use their grazing activity to feed on and reduce biofouling. A small-scale study was conducted to assess the feasibility of integrating the native and unexploited Atlantic purple SU (Arbacia punctulata) with eastern oysters (Crassostrea virginica) in a Rhode Island farm. To evaluate whether this approach could be viable under real farm conditions, low (one) and medium (three) stocking densities of urchins integrated with 25 oysters (71.84 mm shell length) per bag over a 2-mo period were tested. These conservative densities were selected to assess the practical feasibility for this farm and site and to enable direct comparison with stocking levels used in previous urchin and bivalve co-culture studies. Urchin grazing removed 50%-90% of biofouling mass on gear surfaces and 60%-90% from shellfish surfaces at low (1 urchin bag-1) and medium (3 urchins bag-1) urchin inclusions, respectively. The most effective reduction was seen when 3 SU bag-1 were integrated with eastern oysters (C. virginica), which fully prevented the shell burrowing worm, Polydora sp., from occupying and damaging shells. Oyster growth and survival were not compromised and were of a similar shell cleanliness as the baselines, which had been cleaned through regular farming practices, further emphasizing biofouling control success. The trial was largely left unattended, and under normal farm workflow conditions without SU, these oysters would have been removed from bags, tumbled clean, air dried, and then redeployed into bags at least three times. This work highlights the potential for A. punctulata to mitigate biofouling and reduce farm-related effort through co-culture with eastern oysters, with state growers wanting to adopt this approach. Recommendations for next steps toward industrial feasibility include scaling up these approaches using higher oyster production numbers and determining seasonal effectiveness of biofouling mitigation.
