The Japanese Society of Fisheries Science Award:

　　Michiya MATSUYAMA

The Japanese Society of Fisheries Science Award of Merit:

　　Yoshihiro OCHIAI

Scientific Achievement Award in Fisheries Science:

　　Yoichiro KITANI, Naoyoshi NISHIBORI, Ryuichi WATANABE

Achievement Award for Young Scientist in Fisheries Science

　　Manabu TANIMURA

Technical Achievement Award in Fisheries Science:

　　Toshiaki ITAMI, Keiichi UCHIDA・Ryuichi HAGITA・Tohru MUKAI・Keiri IMAI・Kenichi SHIMIZU・Mitsuharu YAGI・Yuichi YAMANAKA・Takahisa MITUHASI・Atsuhiko ISOBE・Mao KURODA, Ko YASUMOTO・Mina YASUMOTO-HIROSE, Yoshihisa YAMAMOTO

　The alfonsino Beryx splendens is an important fishery resources in Japan but recently its catch has declined dramatically. To promote seed production of this fish species, we developed an extender solution for short-term storage of sperm. We diluted the semen in several solutions with different concentrations of salt, Ca²⁺, pH, etc. and examined the motility after storage in a refrigerator (4–5℃) for days or weeks. Slightly hypotonic NaCl solution with low concentrations of KCl and CaCl₂ at pH 7.5 efficiently maintained the viability of sperm with high percentages of motility. The addition of both glucose and glycine prolonged the storage period for sperm. By using the extender solution developed in this study, we kept the alfonsino sperm active for up to 81 days in a refrigerator with the swimming velocity of 69.0 µm/s and motility of 11.2%. The alfonsino sperm stored in this extender solution for 24 days retained fertilizing capacity.

　Food made by pickling pufferfish ovaries in salt and rice-bran is a tradition in Ishikawa Prefecture in Japan. The food is manufactured in two stages: curing in salt for a year and pickling in rice-bran for one or two years. Since pufferfish ovaries contain the potent neurotoxin tetrodotoxin (TTX), a toxicity test is implemented by mouse bioassay and only food that contains less than the quarantine limit (10 MU/g) are marketed. However, testing by instrument analysis is internationally accepted for inspections for marine biotoxins including TTX. In the study, we developed a pretreatment method for TTX suitable for instrument analysis in food containing a large amount of salt, and then used the method to assess the level of TTX in food. Our experiments revealed that an activated charcoal cartridge is useful as the pretreatment method for TTXs in pufferfish ovaries: the recovery test of TTX using the food was 90%. We used the developed method to assess the level of TTX in commercially available foods made using pufferfish ovaries.

　We recently reported that refrigerating yellowtail Seriola quinqueradiata fillets in oxygen-filled packs slowed down the decrease in redness while suppressing browning in dark muscle as compared to refrigerating the fillets in air-filled packs. To better understand this phenomenon, we stored cultured yellowtail muscles packed in oxygen and air at 10℃, and compared changes in the color variables (L^＊, a^＊ and b^＊), ultrastructure and cytochemical Mg²⁺-adenosine triphosphatase (Mg²⁺-ATPase) of the dorsal dark muscle. The dark muscle stored in oxygen exhibited significantly higher a^＊ values (redness) than those stored in air. No significant difference was observed in the collapse of Z lines and A and I bands between the oxygen and air-stored muscles. Ultrastructural disruptions of sarcoplasmic reticula and mitochondria were less pronounced when muscles were stored in oxygen than in air. Mg²⁺-ATPase activity was observed in the sarcoplasmic reticula, mitochondria and nuclear membranes of the dark muscles immediately after death. On day 2, faint Mg²⁺-ATPase activity was detected in the sarcoplasmic reticula and mitochondria of muscle stored in oxygen but was undetectable in those stored in air. These findings suggest that the maintenance of mitochondrial functional activity and preservation of the ultrastructure of the sarcoplasmic reticula and mitochondria are much better when muscles are stored in oxygen, consequently delaying the color deterioration of the dark muscle.

　Bleeding (or blood removal) is an important procedure to maintain the quality of fish during chilled storage. The bleeding level is commonly evaluated by analyzing hemoprotein content in fish muscles, but this requires time and effort. The development of a simple and quick technique for quantitatively evaluating the bleeding level in fish muscles is needed. Therefore, we investigated the relationship among visible light image analysis for measuring the change in blood vessel area, color measurement, and hemoprotein content in fish muscles. Horse mackerel Trachurus japonicus was bled by cutting three different locations to analyze hemoprotein content in its muscles. Cutting the gill was the most effective for reducing hemoprotein content in the fish sample compared to the other procedures. The hemoprotein content correlated with the blood vessel area (%) and L^＊, a^＊, and b^＊ values of the sample. Notably, hemoprotein content and the dorsal segmental blood vessel area (%) had a high correlation (correlation coefficient R＝0.96, coefficient of determination R²＝0.93). These results indicated that the blood vessel area (%) obtained by visible light image analysis can be used to evaluate the bleeding level in horse mackerel muscles.

　To understand the financial costs associated with fishery resource enhancement to inland fishery cooperatives in Japan, the annual reports of cooperatives throughout the country were analyzed for the fiscal years 2010 and 2017. The percentage of total fishery resource enhancement outlay to the total outlay of cooperatives was 35.8% in 2010 and 35.2% in 2017 on average. The percentage of obligatory fishery resource enhancement outlay, based on the Japan Fishery Act, to the total outlay of cooperatives was 27.6% in 2010 and 23.6% in 2017 on average. Some of the cooperatives are concerned that the obligatory fishery resource enhancement is a greater financial burden for the cooperative management. However, most cooperatives report only total fishery resource enhancement that is the sum of obligatory and voluntary enhancement outlays in annual reports, and the exact ratio of obligatory fishery resource enhancement outlay to total fishery resource enhancement is unclear. But in our estimation, the costs for total fishery resource enhancement amounted to about double the amount for obligatory fishery resource enhancement, 1.8 times in 2010 and 1.7 times in 2017. Over 84% of the cooperatives had fulfilled their obligatory fishery resource enhancement for six species—ayu Plecoglossus altivelis altivelis, whitespotted charr Salvelinus leucomaenis, masu salmon Oncorhynchus masou, rainbow trout O. mykiss, crucian carp Carassius spp., and Japanese eel Anguilla japonica.