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In 1992, the UN banned the use of large‐scale pelagic driftnets on the high seas (UNGA Resolution 46/215). Three decades later, however, drift gillnets remain one of the primary fishing gears in the Indian Ocean, accounting for approximately 30% of tuna catches in this ocean. Recent estimates indicate that several million small cetaceans have been killed in Indian Ocean gillnets over the past few decades. National agencies and the regional fisheries management organization charged with managing tuna fisheries, the Indian Ocean Tuna Commission, have yet to effectively document the bycatch of small cetaceans in these fisheries. Here, we review current information on cetacean bycatch in Indian Ocean drift gillnets and propose potential solutions to this important conservation issue.

The Yujiang River, an important tributary of the Pearl River, flows primarily through Vietnam, Guangxi, and Yunnan in China. This cross‐border watershed supports a remarkable aquatic biodiversity, especially characterized by its unique fish species. In this study, we reported the length–weight relationships (LWRs) of 13 native fish species within the Yujiang River Basin (22.156N–24.353N, 105.845E–109.608E) sampled from July 2024 to February 2025. A total of 1967 fish specimens representing the 13 species were collected using drift gillnets of various sizes (mesh size: 10–70 mm; height: 2.0–5.0 m; length: 100 m). Nonlinear regression analysis yielded coefficients of determination ( r 2 ) ranging from 0.950 to 0.996 and the parameter b spanning 2.57 to 3.74. According to the records from FishBase database and other studies, the LWRs for these 13 fish species from the Pearl River are provided for the first time in this study. Among them, the LWR of Beaufortia granulopinna, Paranemachilus genilepis, Opsariichthys duchuunguyeni, and Sarcocheilichthys caobangensis are first reported in FishBase database. The maximum body length of Ancherythroculter lini is updated to 26.00 cm. Moreover, S. caobangensis is first reported in the Yujiang River Basin in this study. It is expected that the results of this study will provide a basic data for the study of fish ecology, fishery resource management, and hydroacoustic monitoring in Yujiang River Basin.

Invertebrate drift is a key process in riverine ecosystems controlling aquatic invertebrate distribution and availability to fish as prey. However, accurately quantifying drifting invertebrates of all sizes is difficult because the fine-mesh nets required to capture the smallest specimens clog easily, which reduces filtration efficiency and measurement accuracy. To address this problem, we developed a gas-powered pump system that delivers 20 m3/hour of river water through nested 80- and 750-μm-mesh nets suspended in the air. We compared 17 pumped samples with those obtained by adjacent, conventional deployment of a 250-μm drift net in a clear-water Alaskan river during both low and high flows. Our drift pump system sampled a geometric mean drift concentration of 467 invertebrates m−3 (maximum 5637 m−3) – eleven times the mean concentration of 42 m−3 estimated using the drift net. Invertebrates ≤ 3 mm long, primarily chironomids, comprised the entire difference between methods. Investigators for whom the drift of 0.5–3 mm invertebrates might be relevant (e.g., those applying foraging models for juvenile drift-feeding fishes) should consider using a pump or similar aerial filtration method to quantify small invertebrate drift, lest they underestimate it by an order of magnitude.

Fisherman in the Kotania Bay area of West Seram have utilized light technology to enhance the effectiveness of catching Amblygaster leiogaster since 1980. This study investigated the effectiveness of using LED lights as an attractant for catching A. leiogaster using surface gillnets in Kotania Bay, West Seram, Indonesia. The study involved five fishing trips during the dark moon phase in July and August 2024. The average total length and weight of A. /eiogaster caught using drift gillnets during the five trips were 20.9-22.0 cm and 90.5-112.7 g, respectively. The mode of the total length class was consistent across trips, but with slight differences between trips. This suggests that the population of A. leiogaster in the area may have similar sizes overall, but there might be variations in the distribution of sizes due to factors such as fish migration, spawning periods, and environmental conditions. Future research is needed to investigate these factors in more detail to gain a deeper understanding of the population dynamics of A. leiogaster in the area.

Incidental mortality (bycatch) in gillnet fisheries is a major threat to many cetacean populations. Acoustic alarms or pingers are a widely adopted management tool used to deter dolphins and porpoises from nets; however, their efficacy is largely species- and fishery-dependent. As such, results from experimental trials may have limited transferability to poorly studied species or fisheries. Here, we investigated the effect of pingers on the behaviour of Burmeister’s porpoise Phocoena spinipinnis in the vicinity of the Peruvian small-scale driftnet fleet. Over a 4 yr period (2009–2012), 116 control (without pingers) and 94 experimental (with pingers) fishing sets were observed, and porpoise acoustic activity around nets was recorded using passive acoustic loggers (C-PODs). We modelled variation in detection rates as a function of pinger use and habitat covariates, and found that in regions of preferred habitat associated with cooler (17–18°C), shallow waters (within the 100 m isobath), the use of pingers lead to an 86% reduction in porpoise activity around nets. Our results suggest that pingers are likely to be particularly effective at deterring Burmeister’s porpoises from fishing nets, and given the vast capacity of this and other fleets in the region, may substantially reduce mortality. This study also emphasizes the potential of passive acoustic monitoring to determine the effectiveness of bycatch mitigation measures, both for species for which visual observations are scarce, and also in regions where gathering statistically meaningful bycatch rates is logistically challenging.

Recent years have seen the significant potential of Artificial Intelligence (AI) techniques in monitoring and managing ocean ecosystem. Among these, deep learning (DL) solution demonstrated considerable performance in forecasting drifter trajectory, which provide critical scientific support in a variety of ways. However, most existing DL methods still suffer from stability and accuracy problems, due mainly to the fact that they rely primarily on historical memory of tracking target, and that attention-introduced bias further limits their applicability. To address these challenges, this study proposes an innovative drifter trajectory prediction framework (DriftNet) based on newly designed 1) Target-Area Differential Attention (TADA) mechanism and, 2) Direction-Distance Loss function (DDL). For TADA, we constructed a tempo-spatial structure by combining the initial target position and surrounding environment features, then we introduced a Differential Transformer to the integrated features. DDL is an improved loss function to jointly optimize directional alignment and spatial displacement in drift trajectory prediction. Utilizing this model, a case study was conducted in the Taiwan Strait, and the results showed that DrifterNet improved drifter prediction accuracy by over 50% compared to the Lag-fjhyj operational model. This achievement indicates that DriftNet is not only able to better capture the features of target and surrounding area, but better integrate the interaction of timestamp data and spatial data, which further deepens our understanding of the interaction between time-domain factors and spatial-domain factors in maritime environment. This study presents a novel and effective solution for marine drift prediction, offering both theoretical insights and practical value for real-world ocean monitoring and emergency response scenarios.

To clarify the effect of the oceanographic conditions on the distribution of the neon flying squid Ommastrephes bartramii in the central North Pacific, we examined the mantle length composition, sex, maturity, and age in days of the squid caught from late June to early July during 2011–2019. Squid were collected using a non-size-selective research driftnet at seven sampling stations situated along 175° 30’ E and between 35° 00’ N and 45° 00’ N. The autumn cohort females were mainly distributed in the northern part of the study area, whereas the autumn cohort males and the winter–spring cohort squid were distributed in the southern part of the study area. The proportion of the autumn cohort males to the total males fluctuated annually. At the southernmost sampling station where the autumn cohort males were mainly caught, a strong positive correlation was observed between the mean sea surface temperature from mid-May to late-May and the proportion of the autumn cohort males to the total males each year. These findings suggest that the distribution of the autumn cohort males changed with oceanographic conditions, and high sea surface temperature before the survey period studied in subarctic waters caused a northward shift of the distribution of the autumn cohort males. In contrast, no strong correlation was observed between the distribution of the autumn cohort females or the winter–spring squid and oceanographic conditions probably because oceanographic conditions in their horizontal distribution ranges did not vary greatly among the survey years.

We examined specimens from the winter–spring cohort of the neon flying squid Ommastrephes bartramii caught off the coast of northeastern Japan in early summer and the following winter for mantle length, sex, maturity, and age to determine their hatching dates as well as their growth and migration patterns. Squid specimens were collected with a research driftnet in July 2018 in the northwestern Pacific and by squid jigging off the coast of northeastern Japan in November 2018 and January 2019. The ages of 300 specimens were estimated from statolith increment counts and used to back-calculate hatching dates. Hatching dates ranged from September 2017 to July 2018. The peak hatching dates varied with the survey season, even for the same winter–spring cohort. Squid caught in July 2018 hatched mainly from February to April, while those caught in November 2018 hatched mostly during April and May and those caught in January 2019 hatched principally during May and June. This pattern indicates that squid migrate among fishing grounds and that stocks are gradually replaced by late-hatching squid.

River flow alterations caused by dams have introduced many ecological problems, in particular a decline in aquatic species such as fishes. One compensatory measure is to create a hydrological process similar to the natural state with regard to the survival requirements of the fish. In recent years, the Three Gorges Reservoir (TGR) has introduced man‐made flood by ecological operation experiments to facilitate spawning of the four major Chinese carps in the Yangtze River, China. To investigate the fish spawning activities and their responses to the TGR operation, eggs from the four major Chinese carps were sampled using conical drift nets in the middle mainstream of the Yangtze River, May to July in 2012 and 2013. Spawning timing, location, and scale of the four carps were studied and compared between the 2 years; key hydrological and environmental factors associated with spawning were determined by principal component analysis and stepwise regression analysis. Two factors were significantly positive when correlated with egg abundance: one was increasing rate of the river flow (flood amplitude), and the other was river transparency; only one factor, starting of the river flow (flooding occasions), was significantly and negatively correlated with the time of spawning. Comparison of egg abundance in one flood pulse response to different operation rules showed that flooding made by an ecological operation induced a larger scale of spawning than a conventional operation. The study implied that suitable flood conditions could produce a successful spawning event, and that the occasion and pattern of the flood process might result in different responses in fish spawning. Further research is required to develop more scientific monitoring designs in order to obtain accurate field data for both biotic and abiotic factors, and explore new research methods for egg abundance estimations combined with particle experiment and hydrodynamic modeling. This work is fundamental to improve the strategic decisions on reservoir operation and river management.

Understanding the feeding ecology and habitat use of vulnerable shark species is crucial for effective conservation. This study focuses on two large filter-feeding sharks, the megamouth shark (Megachasma pelagios) and whale shark (Rhincodon typus), in Northwestern Pacific waters. Stable isotope analysis (δ13C and δ15N) was conducted on white muscle samples (n = 91) of M. pelagios and fin clips (n = 90) of R. typus, collected via large-mesh drift nets and set nets in Taiwanese waters. In this study, we investigated feeding strategies, ontogenetic dietary shifts, habitat use, and isotopic niche variation in both species. For R. typus, the observed positive correlation between δ13C and δ15N supports the previously proposed active suction filter feeding, as well as implying both a diet with an increasing proportion of higher trophic level prey and an ontogenetic shift. In contrast, M. pelagios displayed a negative correlation, consistent with a previous study associating such patterns with primary or secondary consumers, further aligning with its reported planktonic prey dominance. Both species had increasing δ13C with growth, signifying a shift to nutrient-rich habitats. Only R. typus exhibited ontogenetic diet changes (δ15N). SIBER (Stable Isotope Bayesian Ellipses in R) analysis revealed distinct feeding strategies and habitat use between the two species, potential sexual segregation, and wider isotopic niche widths for males in both species. The findings underscore the importance of considering species-specific behaviors and sex-based differences in conservation strategies.