The fishing industry is one of the energy-intensive industries that emit large amounts of greenhouse gases through the navigation of ships and fishing operations, and there is a need for measures to reduce fuel consumption in order to mitigate the environmental impact of greenhouse gases. The author has been involved in research on reducing the environmental impact of various fishing sectors through improvements in fishing technology. In a series of studies on squid jig fishing, the changes in fuel consumption and catch amounts by employing light-emitting diode (LED) lamps were measured, and the adequate output of LED and the amount of fuel saved were examined by species and boat size. In a study of purse seine fishing with LEDs, the catch indicator that fishermen intend to shoot the net were identified. Also, the unmanned surface vehicle with underwater LED to assist purse seine operation was recently reported. In an offshore pair trawl fishing in the East China Sea, the modified trawl nets to maintain catches while reducing the resistance of the fishing gear during towing was tested, and these nets proved to reduce fuel consumption and maintain catches. The developed net is currently being used in industry. The valuable opportunities to verify hypotheses in the field of fishing were provided for this study, and I believe that the procedures were effective in terms of the speed and efficiency of the process from research to social implementation.

千葉県では2015年度漁期からノリの不作が続いており，この原因としてクロダイによる食害が疑われていた。そこで，本研究ではクロダイに対する網目選択性を推定し，クロダイ捕獲用刺網とノリ養殖網への侵入を防ぐための防除ネットの適切な目合を検討した。その結果，クロダイを捕獲するには100 mmと132 mm目合を組み合わせた刺網を使用し，ノリ網を保護するためには，53 mm以下の目合の防除ネットを使用することが効果的であると考えられた。

Using the effective diameter D20 used in Creager’s formula, which is most used to calculate hydraulic conductivity, we evaluated the lower limit of particle size in aestivation sites of Japanese sand lance Ammodytes japonicus (DUNCKER & MOHR). We investigated the relationship between the number of Japanese sand lance collected in their aestivation sites and the effective diameter D20 of the bottom sediment. As a result, the number of Japanese sand lance in the sites where the effective diameter D20 is 0.2 mm or less, where the water permeability drops sharply, was significantly reduced. This suggests that the grain size (pore size) must be large enough to ensure breathing during aestivation as a condition for the establishment of aestivation of in the Japanese sand lance. It was also shown that effective diameter D20 of 0.2 mm or greater, where the aestivation sites of Japanese sand lance are established, generally corresponds to 0.3–4 mm or greater in D50 (median diameter). which are the most used indicators of the grain size distribution of the bottom sediment.

The 2024 JSFE Spring Symposium, entitled “Marine Plastic Litter in Fisheries: Current Status and Future Prospects” was held on 26 May 2024. The preceding symposium (2021 Autumn Symposium on “Marine Plastic Issues and Measures in Fishing Industries” clarified the relationship between marine plastic pollution and fisheries, as well as matters that should be addressed in the fishing industry. Since then, various approaches have been developed to address the marine plastic problem related to fisheries. In this symposium, six speakers presented an overview of the recent domestic and international situation, research related to the collection of marine debris by fishermen, problems related to fishing gear such as ALDFG and countermeasures, and in particular, advanced efforts in fishing net recycling activities, as well as future issues. In the general discussion, the speakers and face-to-face participants engaged in a lively exchange of views on what is needed and what should be done to promote marine debris collection and fishing gear recycling by fishermen, while also taking questions from online participants. Many opinions were expressed that will lead to the next step, including the development of technology to separate fishing gear by material to facilitate recycling, and the branding of fishermen’s efforts to deal with marine plastic litter with the aim of raising awareness among citizens and consumers.

The issue of plastic litters leaked into the marine and other environment is of high international concern. Negotiations are currently underway to establish an international legally binding instrument, and fishing gear is being discussed as an example of plastic products that are directly used in the environment and thus have a significant impact. Ministry of the Environment Japan has been conducting surveys to understand the actual state of marine debris and other waste as foundational data for various policies. To implement these survey and monitoring methods more widely, various guidelines have been established, including the guidelines for coastal debris’ composition survey for domestic local governments, monitoring of ocean surface microplastics, and monitoring coastal debris using remote sensing technology. Additionally, to promote the collection and disposal of marine litters drifting in the ocean or accumulating on the seafloor, support is provided to fishermen and local governments through the establishment of specific subsidy scheme, the development of guidebooks or manuals, and the introduction of case studies. Furthermore, support is provided for the demonstration of alternative materials such as marine biodegradable materials and recycling technologies by the private sector.

This paper presents the findings of a research project aimed at developing experimental and analytical techniques to assess the sampling efficiency of towed gear utilized for the survey and collection of plastic debris from the seafloor. Towed gear is frequently employed for the purpose of surveying the current state of plastic debris on the seafloor. In the context of using fishing gear as a collection tool to determine the density of seafloor debris, it is essential to ascertain its sampling efficiency. In this project, four experimental methods for estimating sampling efficiency were proposed and subsequently implemented. Moreover, a variety of towed fishing gear exists, including otter trawl, beam trawl, dredge, and seine net. Each of these has distinct characteristics for collecting seafloor litter, influenced by the characteristics of the litter itself (specific gravity, shape, condition on the seafloor, whether buried or not, etc.). Dredges are capable of collecting plastic debris buried on the seafloor. However, plastic fragments can not only be caught on the codend, but also on the teeth of the dredge mouth and the mesh of the net. These factors must be taken into account when collecting benthic plastic debris with bottom trawls.

Marine plastic debris significantly impacts coastal landscapes, habitats, marine organisms and interferes with fishing operations. Our case studies in Nagasaki Prefecture investigate the amount of benthic marine plastic debris, assess the adverse effects on organisms, and the degree of these effects. In Tachibana Bay, a study using two bottom trawlers collected 523 pieces, 29.6 kg of debris for 6 months, of which 95% were plastic debris. Twenty-eight per cent of the plastic debris contained small marine organisms, which had all died and were small enough to pass through codend mesh. A positive correlation (p<0.05) was found between the number of plastic debris in the catch and dead organisms. The study on the impact of benthic plastic debris on the lobster gillnet fishing ground in the southern waters of Nagasaki revealed benthic plastic debris accounted for 93% of the total benthic debris, with 7–20% entangled in corals or oyster reefs. A long-term study on the eelgrass bed indicates that benthic plastic debris was considered to hinder leaf elongation and seed dispersal, while an underwater observation by the time-lapse camera and environmental DNA analysis indicated that eelgrass beds provide habitat for various marine organisms.

The issue of the increasing amount of plastic litter that is washing into the ocean has become a global concern, prompting international organizations and numerous countries to discuss potential solutions. In Japan, the Fisheries Agency of Japan (FAJ) is spearheading efforts to promote the proper management and systematic disposal of fishing gear in accordance with the “Guidelines for the Promotion of Systematic Disposal of Fishery Waste.” Additionally, FAJ is encouraging the collection of marine debris by fishermen and supporting the recycling of fishing gear and the development of biodegradable fishing gear.

Fisheries is an activity essential for humankind. This activity requires a biological rich ocean that can only be achieved and maintained through environmental protection. Therefore, the manufacture, marketing and use of fishing gear such as fishing nets—indeed, indispensable for fishing—has to be in line with the need to preserve the marine environment. Nowadays, the recycling of fishing nets made from nylon is already well developed in many countries around the world. Also in Japan, the recycling of nylon fishing nets is already well underway. However, the Japanese market for fishing nets has a specific characteristic, namely, that around 50 percent of it is made of net’s manufactured from polyester. Until recently, fishing nets made from polyester were thought to be unsuitable for recycling due to technological, cost and reuse unsolved questions. In order to overcome these pending questions and promote the reuse of recycled polyester fishing nets, an alliance of companies coming from different sectors was formed in Japan, aiming at giving an answer to the pending issues and, therefore, play a useful role for the Japanese fishing industry.

The Hokkaido Federation of Fisheries Cooperative Associations has been engaged in the recycling of nylon gill nets for a period of three years. This initiative has been undertaken with the dual objective of reducing the environmental impact of these nets and of reusing resources. The used gill nets are collected from fishermen in Hokkaido and subsequently supplied to a partner company, Suzuki Shokai Co Ltd., which has a recycling plant. However, the recycling rate of gill nets has been no more than 10% due to the necessity of separating the nylon netting from other materials for recycling and the additional cost associated with the collection and transportation of the nylon netting. In some instances, inadequate separation and the mixing of materials other than nylon, such as rope, during collection have occurred, which further increases the cost of separation and makes collection more challenging. We are working to address these issues individually to advance the recycling of nylon gill nets. In the future, we intend to conduct research on the recycling of various types of fishing gear, such as aquaculture baskets, ropes, and floats.