A defining characteristic of Japan's seafood consumption, which underpins traditional dietary cultures of the Japanese (Washoku), is the “diversity” cultivated through a long history of fully utilizing the vast array of seafood available across different regions and seasons. Sushi exemplifies this diversity through the simultaneous use of a variety of seafood. However, the fisheries production in Japan is facing an ongoing decline. The pronounced aging and depopulation of communities reliant on the fishing industry and decreasing fishery workers are of great concern. The fisheries sector continues to be perceived as emblematic of the so-called “3D industries”—dirty, dangerous, and demanding—leading to a scarcity of young workers.
A fundamental transformation of the fisheries sector is required to secure sustainable and stable seafood production. Considering the global trends, further development of Japan's aquaculture sector appears to be a viable option. However, given the Japanese consumer's traditional preference for a wide variety of seafood, adopting the “single-species mass production” model exemplified by Norway's salmon industry would not suffice. Japan must also promote “multi-species, small-lot aquaculture” to preserve the diversity of its seafood offerings. While single-species mass production offers cost advantages and competitive pricing, the establishment of economically viable multi-species, small-lot aquaculture will require innovative solutions, such as the development of highly efficient rearing technologies that reduce production costs, the cultivation of high-value-added species, and vertical integration of production, processing, and sales. Though this is an extraordinarily challenging task—easier said than done—it is nevertheless a critical mission for ensuring the sustainability of Japan's seafood production and preserving the country's world-renowned Washoku culture.
With the future development of Japan's aquaculture industry in mind, this special issue titled “Current Status and Challenges of Aquatic Food Production” presents expert contributions on several critical topics: challenges toward sustainable aquaculture production through resource recycling and interdisciplinary collaboration, efforts toward the complete aquaculture of eel, marine fish farming utilizing underground seawater, applications of genome editing technologies as a challenge for the future, and current and future perspectives on protein and lipid sources for aquaculture feed. Each contribution captures the unique characteristics of the Japanese aquaculture industry and provides concise summaries of current conditions and challenges for the future. This preface hopes that this special issue will offer valuable insights and contribute, even if in some small measure, to the future advancement of Japan's aquaculture industry.

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Aquatic food production is currently facing increasing challenges, and its sustainability in the future is in jeopardy. The issues surrounding aquatic food production include the growing pressure for increased production due to global population growth, particularly in developing countries, which will continue until the mid-2080s; population decline and aging in developed countries, leading to a reduced labor force; the evident limitations of biological and non-biological resources in aquatic ecosystems (with current production methods utilizing resources to their maximum limits); and the disruption of marine ecosystems caused by global climate change and ocean warming. To ensure the stable supply of high-quality, safe, and secure seafood in the future, it is essential to enhance production through innovative methods, actively conserve aquatic ecosystems, and develop resource-circulating production systems that reduce food loss, all of which must be realized through collaborative systems across various industrial sectors. Additionally, it is crucial to promote a shift in consumer awareness regarding seafood consumption. This paper discusses these issues and presents examples of practical measures being implemented, such as the technological development of full-cycle aquaculture of Pacific bluefin tuna (Thunnus orientalis) and mottled spinefoot (Siganus fuscescens) in Kindai University, as well as the growing trend of land-based aquaculture worldwide in recent years including completely closed circuit systems.

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Japanese eel, Anguilla japonica, is one of the most important aquaculture species in Japan. From the past to the present, elvers for stocking of farms are completely dependent on the wild catch of glass eels, however the glass eel catch drastically decreased after the 1960s and has maintained extremely low levels since 2010. In this severe situation, development of full-life cycle eel culture was completed in 2010. This article reviews the history of the development of artificial seedling production techniques in the eel. Owing to the fact that eels do not undergo vitellogenesis, in other words, sexual maturation spontaneously in captive conditions, the early stage of studies was focused on inducing vitellogenesis. In 1973, Yamamoto and Yamauchi succeeded in inducing vitellogenesis and oocyte maturation/ovulation using weekly salmon pituitary (SPE) injections to silver eels, achieving the first production of eel larvae in the world. However, the rate of success in inducing oocyte maturation/ovulation by SPE injections alone was still very low. In 1985, a maturation-inducing steroid was first discovered, DHP, from masu salmon for the first time in vertebrates. DHP was found to be very effective in inducing oocyte maturation/ovulation in the eel also. The combination of weekly SPE injections and DHP injection at the final step enabled them to obtain fertilizable eggs in the 1990s. Since then, due to the higher availability of fertilized eggs, feeding experiments were carried out for the artificial eel larvae. After much trial-and-error, Tanaka developed an initial feed formulated based on shark eggs, for the artificial eel larvae, resulting in the first production of glass eels under artificial conditions in 2002. Using these eels produced in Tanaka's laboratory, the second generation of artificial produced eels was accomplished, closing the full-life cycle of the eels in 2010. However, commercial production of artificial eel seedling for aquaculture industries is still difficult because of the high cost of production compared to wild glass eels. At present, The Japan Fisheries Research and Education Agency is focused on developing the composition of the initial feed to improve growth speed and survival rate of the larvae, improving the rearing system specialized for mass-production of glass eels. These continuous efforts will allow the commercial production of glass eels, that are not dependent on wild glass eel catch, resulting in the protection of eel stock in the wild.

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Marine fish farming has been practiced in earnest since 1945 in Japan. The development of marine aquaculture began with the dike type fish culture, and then the small portion aquaculture, which made mass production possible. In recent years, although energy problems remain, the development of environmentally controllable land-based aquaculture technology and the ability to produce seedlings of a wide variety of fish species have led to the expansion of this new industry. On the Miho Peninsula in Shizuoka Prefecture, where Tokai University is located, seawater that has permeated into relatively deep strata can be extracted. The temperature of this underground seawater is constant throughout the year, and because it is oxygen-free, it does not contain larvae or parasites of various organisms. Therefore, it is possible to cultivate marine fish without the cost of temperature control, filtration, or sterilization. Therefore, it is possible to cultivate flatfish, trout salmon, mackerel, and other fish without the risk of Kudoa disease, Anisakis disease, and other organisms, at a low cost.

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Breeding is the collection of beneficial mutants. While breeding of crops and livestock has a history of more than 10,000 years, breeding of fish is still in its infancy. In fish, chromosome manipulation, gene transfer (transgenics), and drug-induced mutation have been used to modify the chromosome number and genome sequence in the past, but these techniques have not been able to produce superior species in a short period of time as planned.
Genome editing technology, which has been developed since 2010, has made it possible to create strains with desired traits in a short period of time. The authors have produced the world's first animal genome-edited food, the “increased muscle mass red sea bream”. The red sea bream is a strain in which the function of the myostatin gene was suppressed by deleting 8 or 14 nucleotides using genome editing technology, resulting in an increase in muscle mass, which is the edible portion. The red sea bream strain was established in only two years after the genome-editing process, and in addition to the increased muscle mass as originally intended, the feeding efficiency of this strain was improved. It was also confirmed that there were no changes in similar sequences in its genome other than the target sequence.
Thus, genome editing technology can be used to create fish strains with the desired traits in a short period of time. In other words, it has the potential to rapidly create strains that are beneficial to producers or consumers, or that match various aquaculture systems, and is expected to advance the aquaculture industry.

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World aquaculture production has been increasing year after year. Especially, the production of feed-feeding aquaculture, in which fish and shellfish are fed with aqua-feed, has increased significantly. In line with this increase, the amount of aqua-feed required has also increased. However, it is difficult to increase the production of fishmeal and fish oil, the main raw materials for aqua-feed, due to resource conservation of raw fish. In this paper, we discuss the direction that formula feeds should take in the future, taking into consideration the progress and challenges that have been faced by fish feed producers to date, as well as projections for the future. Namely, it is necessary to develop sustainable aqua-feed which have low fish meal inclusion, or no fish meal or fish oil.

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Obesity is a global issue, with childhood obesity being a particularly critical concern. In 2016, the WHO published the Report of the Commission on Ending Childhood Obesity, urging countries to implement policy-level measures. Among the key factors contributing to obesity, food marketing has gained attention, with interventions such as pricing policies and advertising regulations being recommended. However, in Japan, these policies have not been sufficiently considered.
The impact of digital marketing has grown, with advertisements on social media platforms such as YouTube influencing children's food choices subconsciously. While television advertising has declined, online advertisements have increased, raising concerns about the promotion of unhealthy foods. Additionally, stealth marketing on social media has become a major issue, as food companies employ sophisticated advertising strategies that subtly affect children and their parents' decision-making.
To address this challenge, improving health literacy is crucial. Health literacy refers to the ability to obtain, assess, and apply health-related information, which is essential for making informed dietary choices and avoiding misinformation. However, health literacy education in Japan remains underdeveloped, particularly among young mothers, who often lack adequate knowledge regarding nutrition and food safety.
This paper emphasizes that combating childhood obesity requires not only individual education and guidance but also policy interventions such as food marketing regulations and health literacy education.

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There is a large demand for healthy foods due to an increase of health awareness, and various physiological effects, bioactive compounds and food materials are being investigated. We have researched the fruit of Viburnum dilatatum Thunb., called gamazumi, for many years. In China and Europe, the Viburnum genus is used as a medicinal plant, and there are various species in many countries. Sannohe Town in Aomori Prefecture began to cultivate V. dilatatum 27 years ago, and its fruit juice and processed foods have been developed. In this paper, we review the bioactivities and phytochemicals in the Viburnum genus in Japan and present our research and collaborative development with a regional community for creation of a local specialty.
Many compounds, mainly terpenoids, phenolics, and their glycosides, have been isolated from the Viburnum genus. However, most of these compounds have been found in the leaves and branches, and there has been little research on the fruit. Recently, physiological effects and bioactive compounds of the fruit have been investigated. We found antioxidant activity in the fruit of V. dilatatum first, and subsequently we have shown that V. dilatatum fruit has suppressing effects on the oxidative damage caused by stress and hyperglycemia, and α-glucosidase inhibitory activity. The active components are chlorogenic acids, anthocyanins, and quercetin, and in particular, cyanidin 3-sambubioside is a characteristic anthocyanin in V. dilatatum fruit.
With this investigation as a start, we have performed research and development to enhance the added value of this fruit, in collaboration with this regional community. We revealed the relationship between the seasonal progression of fruit ripeness, and antioxidant activity and phenolic compound concentration. As an outcome of these results, the procedure was established, which sets the date of harvest using brix as an indicator of ripeness. We have organized a research group to encourage collaboration between local companies, and they have developed new products such as jam, dressing, and sake from V. dilatatum fruit juice. We also developed the technique to separate the fruit flesh and peel, in which remained useful ingredients, from the pomace after squeezing out the juice, and succeeded in creating a new material. The powder of the flesh and peel, which is rich in polyphenols similar to the juice, has bioactivity and a high content of dietary fiber. Therefore, the powder has the potential to be a new functional food ingredient.
While the specialization of fruit has steadily progressed, farming and V. dilatatum fruit production are gradually decreasing due to aging and depopulation over the last 10 years. In order to keep up V. dilatatum fruit as a local specialty, we are challenged to solve issues such as work-saving mechanization in the squeezing process after harvest, and development of new uses with the regional community.

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Blackcurrant (Ribes nigrum) is produced in abundance in cool regions such as Poland, and in Japan, Aomori Prefecture is the largest producer. Blackcurrant contains various minerals, polyphenols, vitamins, and polyunsaturated fatty acids, but is especially rich in anthocyanins, mainly the following four types: delphinidin 3-glucoside, delphinidin 3-rutinoside, cyanidin 3-glucoside, and cyanidin 3-rutinoside. To date, a wide range of in vitro, in vivo, and clinical trials have shown that blackcurrant suppresses postprandial blood sugar, reduces lipid metabolism disorders, improves blood flow and vascular endothelial function, has antitumor effects, improves cognitive function, has phytoestrogen effects, improves osteoporosis, has beauty effects on skin and hair, and prevents aging odor. In this review, we will explain how blackcurrant took root in Aomori and introduce the various health benefits of blackcurrant that have been reported to date.

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