The triploid technology is a new frontier in shellfish aquaculture and has shown encouraging results in numerous shellfish species. We induced triploid larvae in the Yesso scallop, Patinopecten yessoensis, using hyperosmotic shock for the first time in this study. Different induction parameters, including salinity strength, treatment starting point, and the duration, were tested. The highest triploid ratio of D‐shaped larvae (72.12%) was obtained by 60 ppt salinity treatment for 20 min at the first appearance of zygote showing polar body II (PB2). A significantly faster growth rate was observed during the swimming larvae stage despite a decrease in the hatching and survival ratios. The triploid ratio decreased to 46.67%, and approximately 1.76 million triploid juveniles were harvested after 90 days of cultivation. The treatment parameters can be further optimized to improve the yield of Yesso scallop triploids.

Mytella strigata is a highly adaptable invasive alien species that has been established in coastal China since 2014. Mitochondrial DNA (mtDNA) is an important tool for studying the evolution and population genetics of invasive species. In this study, the mitochondrial genome of M. strigata from China was sequenced by Illumina high-throughput sequencing and characterized with 13 protein-coding genes (PCGs). By assessing the selective pressure of 13 PCGs, the nad2 gene had the fastest evolutionary rate and was finally selected for population genetic analysis. A total of 285 nad2 sequences from seven M. strigata populations in China were analyzed and showed obviously T-rich and C-rich characteristics. According to population genetic diversity analysis, all the seven populations had haplotype (gene) diversity (Hd) ≥ 0.5 and nucleotide diversity (Pi) < 0.005. Haplotype networks showed a “star” distribution. Population historical dynamic analyses showed that Fu’s Fs and Tajima’s D values of all populations were negative except the Qukou (QK) and Beihai (BH) populations. The Zhangzhou (ZJ) and Xiamen (XM) populations were unimodal while the other populations were multimodal. These results suggested that the population of M. strigata in China may have passed the bottleneck period and is currently in a state of population expansion.

Biological invasion is a primary direct driver of biodiversity loss. Recently, owing to exploitation competition with an invasive mussel, Mytella strigata (Hanley, 1843), there has been a drastic decrease in the population of native Perna viridis (Linnaeus, 1758) in several western Pacific regions. In the present study, intestinal microbiota, metabolome, and key digestive enzyme activities were compared between the two competing mussels, M. strigata and P. viridis, to elucidate the differences in intestinal microbiota and metabolic points. We observed that Proteobacteria, Firmicutes, and Bacteroidota were the three predominant bacterial phyla in the two species. The relative abundance of Bacteroidota related to carbohydrate-degrading ability was significantly higher in M. strigata than in P. viridis. Compared to P. viridis, different metabolites including maltose and trehalose were enriched in M. strigata. Lastly, higher carbohydrases activities of alpha-amylase, cellulase, and xylanase were observed in M. strigata than in P. viridis. These differences might play an important role in the adaptation process of M. strigata to the new environment. This study provides important basic knowledge for investigating the competition between M. strigata and P. viridis in terms of food resources utilization.

The marine economy has become a new growth point of the national economy, and many countries have started to implement the marine ranch project and made the project a new strategic industry to support vigorously. In fact, with the continuous improvement of people’s living standards, the market demand for precious seafood such as fish, sea cucumbers, and sea urchins increases. Shallow sea aquaculture has extensively promoted the vigorous development of marine fisheries. However, traditional diving monitoring and fishing are not only time consuming but also labor intensive; moreover, the personal injury is significant and the risk factor is high. In recent years, underwater robots’ development has matured and has been applied in other technologies. Marine aquaculture energy and chemical construction is a new opportunity for growth. The detection of marine organisms is an essential part of the intelligent strategy in marine ranch, which requires an underwater robot to detect the marine organism quickly and accurately in the complex ocean environment. This paper proposes a method called YOLOv4-embedding, based on one-stage deep learning arithmetic to detect marine organisms, construct a real-time target detection system for marine organisms, extract the in-depth features, and improve the backbone’s architecture and the neck connection. Compared with other object detection arithmetics, the YOLOv4-embedding object detection arithmetic was better at detection accuracy—with higher detection confidence and higher detection ratio than other one-stage object detection arithmetics, such as EfficientDet-D3. The results show that the suggested method could quickly detect different varieties in marine organisms. Furthermore, compared to the original YOLOv4, the mAP75 of the proposed YOLOv4-embedding improves 2.92% for the marine organism dataset at a real-time speed of 51 FPS on an RTX 3090.

In this study, the complete mitochondrial genome of Modiolus comptus was determined and annotated for the first time. The 15,591 bp circular genome has a base composition of 24.3% A, 38.6% T, 12.5% C, and 24.5% G, demonstrating a bias of higher AT content (63.0%) than GC content (27.0%). The mitochondrial genome contains 12 protein-coding genes (PCGs), 20 transfer RNA genes (tRNA), 2 ribosomal RNA genes (12S rRNA and 16S rRNA), and one control region. All genes of M. comptus were encoded on the heavy strand, except trnT(ugu) gene. The whole mitochondrial genome of M. comptus and 21 mitogenomes of other Mytilidae species were used for phylogenetic analysis. The result indicated the newly sequenced species had the closest relationship with Modiolus nipponicus (MK721547) and was clustered within the clade of genus Modiolus.