This study investigated context-dependent characteristics of vocalizations in captive bottlenose dolphins (Tursiops truncatus) under different behavioral situations in Korea. The experiment was conducted on July 21, 2025, at the Whale Ecology Experience Center in Ulsan, Korea, involving four captive bottlenose dolphins housed together in a single tank. Four experimental conditions were established: (1) a normal condition without external disturbance, (2) a feeding condition in which a trainer threw food into the tank, (3) a training condition involving responses to trainer signals, and (4) a toy-provided condition. Dolphin vocalizations were recorded for a total of 90 minutes using an Aquafeeler IV A and AQH-200D hydrophone (10 Hz-200 kHz, sensitivity -220 dB re 1 V/μPa) while behavioral data were simultaneously collected using tank monitoring cameras. Acoustic analyses were conducted using PAMGuard software. A total of 197 whistles and 378 buzzes and burst-pulses were recorded during the experiment. In the normal condition, dolphins swam freely and predominantly produced whistles within a frequency range of 6.81-23.82 kHz. During the feeding condition, the production of whistles, buzzes, and burst-pulses decreased while click trains associated with food searching behavior were mainly observed, typically lasting 0.9-1.8 seconds. In the training condition, dolphins primarily produced buzzes and burst-pulses, often accompanied by low-frequency tonal components (1.55 – 8.13 kHz) in response to trainer signals. In the toy-provided condition, dolphins produced clicks associated with object exploration along with buzzes and burst-pulses ranging from 1.3 to 10.8 kHz. Whistles were most frequently recorded in the normal condition accounting for 72.5% of total whistle occurrences whereas buzzes and burst-pulses were most frequent in the toy-provided condition (51.1%). These results demonstrate that bottlenose dolphin vocalizations vary systematically according to behavioral context, suggesting that vocalization frequency and patterns should be useful indicators for inferring behavioral states and have potential applications in passive acoustic monitoring and biological monitoring technologies.

This study evaluated the effects of high-pressure shucking on the compositional quality and microbiological characteristics of raw oysters (Magallana gigas) in comparison with conventional hand shucking, and examined heavy metal contents in the pressure-transmitting seawater used during processing. Oysters collected from Tongyeong and Yeosu were treated at 200-240 MPa for 0-600 seconds. One-way ANOVA showed significant differences among treatment groups in moisture, crude fat, and crude protein contents whereas Dunnett’s test indicated that most high-pressure-treated oysters were not significantly different from hand-shucked controls. Initial total viable counts ranged from 2.77 to 3.46 log CFU/g and increased to 7.95-9.23 log CFU/g after 14 days of storage, generally remaining similar to or lower than the control. Coliform counts decreased under several pressure-time conditions, and Escherichia coli and Vibrio parahaemolyticus were not detected. Although Cu, Zn, Ni, and Fe increased in the process seawater, Cd and Hg were not detected.

This study evaluated the sensory characteristics of Pacific oysters, Magallana gigas shucked by high-pressure processing under various pressure – holding time conditions. Oysters harvested from Tongyeong and Yeosu aquaculture areas were subjected to seven high pressure processing (HPP) treatments consisting of combinations of 200, 220, and 240 MPa with holding times of 0, 60, 120, 180, 300, 420 and 600 seconds, using seawater as the pressure-transmitting medium. Manually shucked raw oysters were included as the control group. Sensory attributes, including color, shape, odor, salty taste, fishy taste, texture, and overall preference, were assessed by a trained sensory panel using a seven-point sensory scale. The results demonstrated that increases in pressure level and holding time generally led to a decline in several sensory quality parameters. In particular, treatments at 240 MPa or extended holding times resulted in decreased scores for color uniformity, odor acceptability, and texture firmness compared with the control. Conversely, oysters treated at 200 – 220 MPa with holding times up to 180 seconds showed sensory qualities comparable to manually shucked raw oysters. Among all conditions, treatment at 220 MPa for 180 seconds was considered an appropriate condition for maintaining sensory quality during high-pressure oyster shucking. Overall, these findings indicate that excessive HPP conditions may deteriorate the sensory properties of raw oysters whereas optimized moderate processing parameters can yield shucked oysters with sensory qualities comparable to manually processed products. This provides a scientific basis for determining appropriate industrial HPP conditions for oyster shucking applications.

This study determined the appropriate pressure for high pressure shucking of oysters (Magallana gigas) according to size categories. One-year and two-year-old oysters harvested from Yeosu and Tongyeong coastal areas were subjected to high pressure treatments with pressure ranging from 180 to 240 MPa and holding times of 0 to 420 seconds. Results demonstrated that 100% shucking rates were achieved at 220 MPa with 120-180 seconds holding time regardless of harvest time and production area. K-means cluster analysis was used to classify oyster specimens into small, medium, and large size groups with mean shell heights of 69.0 mm, 86.6 mm, and 106.7 mm, respectively. The analysis revealed that shucking efficiency improved directly proportional to oyster size. However, the appropriate shucking pressures converged at approximately 220 MPa for all size groups, with small, medium, and large groups showing 218.9 MPa, 221.7 MPa, and 220.6 MPa, respectively, and no significant differences among groups. These findings suggest that the appropriate pressure for high pressure shucking processes be approximately 220 MPa regardless of harvest time and production area, providing foundational data for potential automation of oyster shucking processes.

This study aimed to measure the in-situ target strength (TS) of the moon jellyfish (Aurelia aurita) using a 200 kHz scientific echo sounder in a natural coastal environment. The acoustic survey was conducted in the coastal waters of Soho Port, Yeosu, Korea, from June 4 to 5, 2024. TS measurements were performed by installing the transducer in both horizontal and vertical orientations, and the TS distribution characteristics were analyzed. The measured TS values ranged from -89.8 to -64.8 dB in the horizontal direction and from -90.0 to -59.1 dB in the vertical direction, showing no significant difference between detection orientations (p<0.05). Additionally, a bell diameter-wet weight relationship for Aurelia coerulea was derived based on the specimens collected at the survey site. The empirical TS model proposed by Mutlu (1996) was applied to estimate TS values using the measured morphological data, and the results exhibited a similar trend to the field-measured TS distribution. These findings provide fundamental data for acoustic monitoring and stock assessment of jellyfish populations in natural environments.

This study investigates the opening force required for shucking farmed oysters to support the development of automated oyster-shucking systems. Oysters sourced from Yeosu and Tongyeong were tested for shell length, width, height, total weight, meat weight, and opening force. Results showed an average opening force of 8.1 kgf for one-year-old Yeosu oysters, 7.4 kgf for one-year-old Tongyeong oysters, and 8.7 kgf for two-year-old Tongyeong oysters, with correlations to shell width, height, and meat weight depending on production sea area and growing age. These findings highlight production sea area and growing age-based differences in oyster characteristics, contributing foundational data to advancing automation in oyster shucking.

Climate change has led to a significant increase in jellyfish populations globally, causing various problems. For power plants that use nearby seawater for cooling, the intrusion of jellyfish into intake systems can block the flow, leading to reduced output or even shutdowns. This issue is compounded by other small marine organisms like shrimp and salps, making it urgent to develop solutions to prevent their intrusion. This study addressed the problem using the BioSonics DT-X 120 kHz scientific fish finder to conduct preliminary tank experiments. We also deployed underwater acoustic and camera buoys around the intake of nuclear power plant, utilizing a bidirectional communication system between sea and land to collect data. Data collection took place from July 31, 2023 to August 1, 2023. While harmful organisms such as jellyfish and salps were not detected, we successfully gathered acoustic data on small fish measuring backscattering strength (SV). Analysis showed that fish schools were more prominent in the evening than during the day. The highest fish distribution was observed at 3:30 AM on July 31 with an SV of -44.8 dB while the lowest was at 12:30 PM on the same day with an SV of –63.4 dB. Additionally, a solar-powered system was used to enable real-time data acquisition from sea buoys with smooth communication between the land server and the offshore buoy located 1.8 km away. This research developed an acoustic-based monitoring system for detecting harmful organisms around the intake and provided foundational data for preventing marine organism intrusion and planning effective measures.

In this study, the seasonal distribution was surveyed using acoustic in the coastal waters around nuclear power plants. Acoustic surveys were conducted in June, September, December 2022, and March 2023 in the coastal waters of Uljin-gun. According to the results of this study, zooplankton were distributed at the depths from 0 m to 50 m in the waters around nuclear power plants. Zooplankton appeared in summer (June), autumn (September), and spring (March). In the survey area, fish were distributed at the depths from 25 m to 190 m, appearing in the summer (June), autumn (September), winter (December) and spring (March). The SV of zooplankton appearing in the survey area ranged from -98.0 dB to -78.0 dB, and it exhibited a one-class in the frequency distribution of SV. The SV of fish appearing in the survey area ranged from -36.0 dB to -35.0 dB and -98.0 dB to -53.0 dB, and it exhibited two-class in the frequency distribution of SV.

This study developed and evaluated a load cell-based automatic weighing system for the automated harvesting of laver (Porphyra tenera) in seaweed aquaculture. The current manual harvesting process was compared with the load cell-based automated system, and quantitative measurements of time, distance, and weight were conducted. The results demonstrated that the load cell-based system reduced the unloading time and increased the throughput compared to the manual method. In addition, statistical analysis confirmed that there was no significant difference from the mean in the weight measurement obtained using the load cell-based system. Based on these findings, the load cell-based automatic weighing system holds potential for efficient production and transactions in laver cultivation, contributing to cost reduction and improving the quality of life for aquaculture workers.

Laver aquaculture, which occupies a large proportion in the aquaculture industry in Korea, is still highly dependent on human labor. Therefore, it is necessary to study the development of an automatic system to improve the working environment and increase the efficiency of aquaculture production systems. The purpose of this study is to evaluate the economic feasibility of an improved system in a study for the loading-unloading and automatic weighing systems in laver aquaculture industry. Economic analysis of the developed unloading and automatic weighing system were implemented under various conditions to calculate more accurate benefits and costs. As a result of this study, the economic feasibility was found to be very high in the three models: net present value (NPV), benefit-cost ratio (B/C), internal rate of return (IRR). Moreover, the results of sensitivity analysis showed that the economical efficiency of the automatic loading, unloading, and weighing system in laver aquaculture was very high.

Sensory evaluation of shucking pressure, pressure holding time, seeding method, difference in full shucking rate in the aquaculture area and shucking oyster was performed using an ultra-high pressure oyster shucking machine. The reaching time for each target pressure is 2.2-2.4 MPa/sec in the range of 180 MPa to 240 MPa. had a rate of pressure rise. There was a difference of 0.5-1.7℃ in the range of 24-27℃ in the seawater temperature before and after the pressure treatment inside the pressure vessel, but there was no specific increase or decrease in seawater temperature. When only the shucking pressure is increased without the pressure holding time, the critical shucking pressure at which the oyster shell is opened and the flesh is peeled in the range of 200 to 220 MPa. When the critical shucking pressure is reached, the oyster sample in the closed vessel is expected to be shucked by about 40%. If there is no pressure holding time when judged only by full shucking, an increase in pressure of about 1.5 MPa is required to further shuck 3% of the oyster population. The oyster samples cultivated in the south coast of Korea were subject to full shucking under the conditions of 220 MPa shucking pressure and two minutes (120 seconds) of pressure holding time, and the difference in the pressure of the oysters according to the oyster seeding method and the farming area was minute. Finally, the condition of 220 MPa of shucking pressure and three minutes of pressure holding time was the best at 1.52 when the result of the sensory evaluation performed manually was set to 1.0. Next was 1.4 under the conditions of 220 MPa of shucking pressure and one minute of pressure holding time (60 seconds), and 1.3 under the condition of 220 MPa and two minutes of pressure holding time (120 seconds). Therefore, it is considered that the most desirable shucking conditions, considering the efficiency and sensory evaluation results, are the conditions of 220 MPa shucking pressure and two to three minutes of pressure holding time.