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This study aimed to evaluate the effects of water temperature and catch frequency on biodiversity and distribution in the waters around Korea. We analyzed spatiotemporal catch data reported by fishermen and evaluated the fluctuations in the dominantly caught species based on the timing of the water temperature changes between 1999 and 2021. This study found an upward trend in the water temperature, and species diversity increased in the East, West, and South Seas after the water temperature changed. Relatively stable species diversity was maintained in the East Sea/Sea of Japan, although variability increased significantly in the West and South Seas. The distribution in the caught species showed that Octopodidae spp. and Ommastrephidae spp. were increasingly caught more consistently alongside Pleuronectidae spp. Moreover, this dominance was maintained even after the change in water temperature and was shown to be relatively less sensitive to water temperature changes.

Gizzard shads are facing a continual decline in population, necessitating the implementation of selective gear design for effective resource management. This study aims to prevent the bycatch of young gizzard shads, a non-target fish species, and to derive mesh sizes appropriate for fishery management. Experimental fishing (n = 11) was conducted by manufacturing gillnet fishing gear with different mesh sizes (50.5, 55.1, 60.6, and 67.3 mm) in the coastal waters of the southern Gyeongsang Province. Two methods were employed to estimate the appropriate mesh size of the shad gillnet as follows: firstly, by analyzing the selectivity curve based on body length data; secondly, by developing a complex machine learning model considering biological and economic factors. Model 1 was constructed using mesh variables to classify the score groups. As a result of this study, the total length with a 0.5 gillnet selection ratio. which was estimated to be 179.3, 195.6, 215.1, and 238.9 mm for the 50.5, 55.1, 60.6, and 67.3 mm mesh sizes, respectively. In Model 1, a mesh size of 57.85 mm or less was determined as the most appropriate mesh size. Therefore, considering both biological and economic aspects, shad gillnets should have a mesh size in the 50.5 to 55.1 mm range.

The installation of an egg collection net in the upper section of a Pacific bluefin tuna (Thunnus orientalis) cage (diameter 25 m × height 15 m) raises concerns regarding the potential compromise of cage stability due to the fine mesh size. This study addresses two primary questions: (1) How can the egg collection net be deployed effectively without undermining cage stability? (2) What are the effects of the egg collection net on the cage volume and shape under varying current conditions? To investigate these questions, a mass–spring interaction model was developed to simulate the contact behavior between net structures, and numerical simulations were performed under various current speeds and sinker weight conditions. The results indicate that optimal deployment is achieved when a sinker weight of 78.5 N per meter is applied along the lower perimeter of the egg collection net. The additional volume reduction induced by the egg collection net was minimal (0.01–0.54%), falling within the natural range of flow-induced fluctuations. These findings lay the groundwork for the development of more robust and efficient bluefin tuna aquaculture systems.

This study examined the post-surgery recovery of olive flounder (Paralichthys olivaceus) following tag insertion by analyzing behavior, heart rate, and wound healing. The experiments used 30 individuals (length: 38.67 ± 2.12 cm; weight: 742.48 ± 116.41 g). Heart rate was measured using a DST milli-HRT (Star-Oddi) bio-logger. To assess the influence of water temperature on the recovery process after surgical tag insertion, behavioral analyses, heart rate, and wound healing were conducted in two experimental groups: Experiment 1 (22 °C, optimal water temperature); Experiment 2 (28 °C, high water temperature); and control group (22 °C, non-operated fish). The experiment was repeated twice over a 7-day period for each experimental group. Compared to the non-operated fish, the operated fish exhibited stable levels after the 3rd to 4th day in Experiment 1. Statistical analyses based on heart rate in Experiment 1 indicated that the appropriate post-surgery recovery time point was approximately 3 days, representing the point at which behavioral fluctuations stabilized. In the case of Experiment 2, abnormal behavioral patterns (e.g., tilted swimming) and changes in average swimming time and daily heart rate were found to stabilize after 4 days post-surgery.

Traditional single-species fisheries management has proven inadequate for capturing ecosystem interactions, leading to a shift toward ecosystem-based approaches. In Korea, diverse small- and medium-scale with varying gear types, production volumes, and practices require management tools that address both ecological and industrial needs. This study developed a Gear-based Fisheries Management Index (GFMI) for 24 coastal and offshore fisheries in Korea. The framework, based on the “ideal gear attributes” defined by ICES, is structured around three objectives: gear controllability, environmental sustainability, and operational functionality. Sub-indicators and weights were derived through expert consultation using the Analytic Hierarchy Process and standardized with Z-scores from national statistics, including production volume, license numbers, and accident rates. Results show that in coastal fisheries, coastal gillnets (61.7) and coastal improved stow nets (60.7) recorded the highest scores, largely due to negative impacts such as bycatch, reproductive capacity, and gear loss. Coastal purse seines (40.9) received the lowest score, reflecting species selectivity advantages. In offshore fisheries, large bottom pair trawls (71.8) and Southwestern medium-size bottom pair trawl (69.3) ranked highest, indicating strong habitat impacts. While coastal improved stow nets, large purse seines, and large trawls performed well in operational functionality, high costs and efficiency constraints remain key vulnerabilities.

Real-time estimation of fish growth offers multiple benefits in indoor aquaculture, including reduced labor, lower operational costs, improved feeding efficiency, and optimized harvesting schedules. This study presents a low-cost, vision-based method for estimating the body length and weight of olive flounder (Paralichthys olivaceus) in tank environments. A 5 × 5 cm reference grid is placed on the tank bottom, and images are captured using two fixed-position RGB smartphone cameras. Pixel measurements from the images are converted into millimeters using a calibrated pixel-to-length relationship. The system calculates fish length by detecting contour extremities and applying Lagrange interpolation. Based on the estimated length, body weight is derived using a power regression model. Accuracy was validated using both manual length measurements and Bland–Altman analysis, which indicated a mean bias of −0.007 cm and 95% limits of agreement from −0.475 to +0.462 cm, confirming consistent agreement between methods. The mean absolute error (MAE) and mean squared error (MSE) were 0.11 cm and 0.025 cm2, respectively. While optimized for benthic species such as olive flounder, this system is not suitable for free-swimming species. Overall, it provides a practical and scalable approach for non-invasive monitoring of fish growth in commercial indoor aquaculture.

The consumption of aquaculture products and, in turn, the importance of the aquaculture industry are increasing with the depletion of global fishery resources. In the flow-through aquaculture systems used in Korea, olive flounders are overcrowded near the central outlet, causing stress, and the sharp central outlet hole injures the olive flounders. Therefore, in this study, we propose a central outlet cap that can prevent overcrowding and injuries in olive flounders near the central outlet in a flow-through aquaculture system. An L27(35) orthogonal array was constructed using five central outlet cap design variables, and computational fluid dynamics (CFD) analysis was performed for each experimental point. The pressure drop between the tank inlet and the central outlet was evaluated, and the experimental point with the highest pressure drop was identified. In addition, the internal fluid velocity of the experimental point with the highest pressure drop value was confirmed to be improved compared to the initial flow-through aquaculture system. The central outlet cap designed in this study is expected to be economically beneficial to aquaculture by reducing the overcrowding of olive flounder and preventing injury to olive flounder while improving the internal fluid velocity.

Abstract Efforts have been made to improve the prediction of implant treatment outcomes through biomechanical analyses using finite-element (FE) analysis. Particularly, a bone remodelling numerical model has been recently applied to forecast long-term stability. However, there is a scarcity of research on the long-term biomechanical stability of implant-supported bridges. This study investigates the impact of integrating a bone remodelling numerical model into FE analysis to evaluate the biomechanical stability of mandibular implant-supported bridges. To evaluate the impact of integrated bone remodelling, FE analyses were performed with and without a bone remodelling model. The bone remodelling model was implemented in Abaqus as a user subroutine, UMAT, used to define a mechanical behaviour of material. Cases were compared based on the number of fixtures used in the implant-supported bridges and the initial bone quality to assess risks in different treatment scenarios. The peri-implant bone density distribution ultimately showed higher values than the initial value after bone remodelling. The study analysed differences in microstrain proportions within the peri-implant bone, with and without bone remodelling, following simulated masticatory activity. Absence of bone remodelling consideration results in elevated microstrain, especially among elderly patients with fewer implants and in the second molar position. This omission leads to an overestimation of differences in high microstrain proportion based on implant position (senior, Group 1: 18.91%p) and number of implants (senior, second molar: 13.8%p). Initial bone quality has a significant influence on bone remodelling. The absence of long-term analysis exaggerates the risks for all considered cases. This study emphasizes the importance of incorporating bone remodelling considerations into the stability analysis of implant-supported bridges, particularly when they are used with fewer implants and for elderly patients. Graphical Abstract Graphical Abstract

Objectives This study aimed to investigate the strain in the bone surrounding dental implants supporting a 4-unit bridge and assess the role of excessive strain as a possible risk factor for implant related sequestration (IRS) or peri-implant medication-related osteonecrosis of the jaw (PI-MRONJ). Materials and methods A 3D-mandibular model was constructed using computed tomography and segmented it into cortical and cancellous bones. The 4-unit implant-supported bridges replacing the mandibular posteriors were constructed, and each featuring two, three, and four implants, respectively. The Young’s modulus was assigned based on the quality of the bone. A maximum occlusal force of 200 N was applied to each implant in the axial and in a 30-degree oblique direction. Results The maximum principal strain of the fatigue failure range (> 3000 µε) in the bone was analyzed. The volume fraction of fatigue failure was higher in poor-quality bone compared to normal bone and oblique load than in axial load. An increasing number of implants may dissipate excessive strain in poor-quality bones. Conclusions Occlusal force applied to poor-quality bone can result in microdamage. Given that unrepaired microdamage may initiate medication-related osteonecrosis of the jaw, long-term occlusal force on fragile bones might be a risk factor. Clinical Relevance When planning implant treatment for patients with compromised bone status, clinical modifications such as strategic placement of implants and optimization of restoration morphology should be considered to reduce excessive strain which might be associated with IRS or PI-MRONJ.

Peri-implant bone loss and bone quality significantly affect the biomechanical stability and long-term success of dental implants. This study used finite element analysis to evaluate the stress distribution and deformation behavior of implants and alveolar bone according to bone loss (0–5 mm) and bone quality (normal and low). A finite element model was implemented based on a three-dimensional mandibular model. The mechanical properties of each component were assigned, and finite element analysis was performed using a static occlusal load. The results showed that progressive bone loss increased von Mises stresses in the implant fixture and surrounding bone, and low-quality bone showed a significant vulnerability to stress concentration. The 2 mm bone loss model showed the maximum stress in cortical bone, and from 3 mm onwards, the stress decreased due to extensive loss of cortical bone. This may be because extensive bone loss causes the implant to lose interface with cortical bone and contact only with cancellous bone. This study confirmed that bone loss and the vulnerability of bone quality may potentially affect implant failure. Continued research is needed to suggest customized implants based on the structural vulnerability of alveolar bone.