This study assessed the impact of an acoustic stimulus on the behavioral responses and physiological states of the large yellow croaker (Larimichthys crocea). The test fish, with an average body weight of approximately 352.81 ± 70.99 g, were exposed to one hour of acoustic stimulation at seven different frequencies: 100 Hz, 125 Hz, 160 Hz, 200 Hz, 500 Hz, 630 Hz, and 800 Hz. The aim was to delineate the specific effects of acoustic stimulation on the behavior and physiological indices. The results show that acoustic stimulation significantly altered the behavioral patterns of the large yellow croaker, predominantly manifested as avoidance behavior towards the sound source. At a stimulus frequency of 630 Hz, the test fish exhibited continuous irregular motion and erratic swimming. Physiologically, one hour of exposure to acoustic stimulation notably affected the endocrine system. The levels of Epinephrine and thyroxine were significantly elevated at 200 Hz, while the cortisol levels did not show significant differences. Additionally, the lactic acid content significantly increased at 800 Hz, and the blood glucose content peaked at 630 Hz. This study discovered that sound frequencies of 200 Hz, 630 Hz, and 800 Hz led to a significant increase in the levels of Epinephrine, glucose, thyroid hormones, and lactate in large yellow croaker, consequently affecting their behavior. The changes in these physiological indicators reflect the stress response of the large yellow croaker in specific sonic environments, providing crucial insights into the physiological and behavioral responses of fish to acoustic stimuli.

The construction of marine ranches can enrich and conserve the fishery resources and improve the marine ecosystem, which helps realize the sustainable utilization of these resources. Sebastes schlegelii is a major breeding and releasing fish species in the marine ranches of North China. Its behavioral characteristics can be understood better by researching its vocalization, which will provide data support for constructing acoustic taming marine ranches with S. schlegelii as the target fish species. However, there are few studies focusing on its sounds and behaviors. Therefore, based on the passive acoustic monitoring technology, the audios of underwater noises made by S. schlegelii were extracted using an AQH hydrophone. The high-definition internet protocol camera was used to monitor the behavior change of S. schlegelii. Then, by collating and replaying the collected audios and videos, the feeding behavior and biological noises of S. schlegelii were matched to analyze their relationship. Results are as follows: (1) The noise of chewing settling granular baits (Φ5.0 mm) has a main frequency band and sound pressure level of 2000~4500 Hz and 96.53 ± 0.65 dB, respectively; in this feeding process, the main frequency band and sound pressure level of the swimming noise are 25~400 Hz and 95.63 ± 0.38 dB, respectively; the values are 500~700 Hz and 97.34 ± 4.91 dB, respectively, for the noise of flapping the water with the tail. (2) The sound signals emitted by S. schlegelii are mostly presented as single pulses during normal habitation or ingestion of baits on the surface of the water tank. However, S. schlegelii will attack and fight against each other when scrambling for baits, during which these signals are presented as continuous pulses. To sum up, the vocalization of S. schlegelii is closely related to feeding activities, and the sounds produced under different behaviors have specific biological significance.

In this study, passive acoustic technology was used to obtain sound signals indicative of feeding in individual rainbow trout (Oncorhynchus mykiss). Feeding signals were separated from background signals to characterize their acoustic parameters, in order to quantify feeding activity. The audio and video data of rainbow trout during feeding were synchronized to determine the signal category and mark it, and the time-domain features and frequency-domain features of fish swallowing feed were extracted. This not only has important theoretical value for in-depth understanding of fish growth, reproduction, and other life activities, but also provides data support and technical recommendations for future research on this topic.

Xiangyun Bay Marine Ranch, in the Bohai Sea, China, is an important fishery resource area but has long been affected by eutrophication, habitat destruction, and overfishing. To support resource conservation and management, this study combined environmental DNA (eDNA) metabarcoding, acoustic survey, and a traditional net survey to assess fish resources. The traditional net survey collected 18 fish species (2143 individuals), with Speartailed goby (Chaeturichthys stigmatias) and Indian flathead (Platycephalus indicus) as the dominant species (~70% of total). An acoustic survey revealed that fish resource density in the reef area ranged from 6.05 × 10⁻⁵ to 9.38 × 10⁻⁵ ind/m², with vertical distribution concentrated in the 1–3 m water layer; strong scatterers (−47 to −42 dB) at 3 m depth indicated benthic large individuals. The eDNA analysis generated 1,091,731 high-quality sequences assigned to 39 fish species, with dominant species including Kammal thryssa (Thryssa kammalensis), Yellow-spotted slipmouth (Nuchequula flavaxilla), and Large-mouth naked goby (Gymnoglobus macrognathos). In conclusion, the acoustic survey demonstrates unique advantages in assessing spatial distribution of fishery resources, while eDNA technology serves as an effective supplement to traditional net surveys. Their combined application provides more accurate scientific evidence for the production management and sustainable utilization of marine ranches.

To evaluate the effects of swimming training on growth, swimming performance, and osmoregulatory-related indices in juvenile coho salmon, freshwater-reared fish were subjected to current of 1 body length per second (BL·s⁻¹) from December 2024 to April 2025. Fork length, body weight, condition factor, insulin-like growth factor-1 (IGF-1), and gill and intestinal Na⁺/K⁺-ATPase (NKA) protein abundance were measured monthly, and critical swimming speed (U_crit) was evaluated after one month of training. Trained fish showed greater fork length in March and higher body weight in March and April than controls. The condition factor was higher in trained fish in February and March, but declined during spring smolt development. Swimming capacity was enhanced by training, as indicated by significantly higher U_crit. Mean IGF-1 levels did not differ between groups, but IGF-1 correlated positively with body size only in trained fish. No significant training effect was detected for either gill or intestinal NKA protein abundance, although gill NKA increased significantly in April, likely reflecting seasonal smoltification. In addition, IGF-1 was significantly correlated with gill NKA in trained fish in March. Collectively, these results indicate that sustained swimming training improves growth and swimming performance and may enhance associations among measured physiological variables during smoltification in juvenile coho salmon.

Corrigendum: Study on feeding behavior and biological sound of Sebastes schlegelii