In order to clarify the effect of moon age on catch per unit effort (CPUE) of Japanese flying squid Todarodes pacificus in the squid jigging fishery, catch data of 30,178 operations conducted in the offshore area of the Sea of Japan from 2001 to 2020 were analyzed. A periodicity of approximately 29 days was detected in the time series of daily CPUE by a power spectral analysis. The relationship between moon age and CPUE was evaluated by the method of using the deviation between 5-day and 29-day moving averages of daily CPUE and by a generalized linear model. As a result, it was revealed that CPUE increased after a new moon, reached a maximum on the 6th day after a new moon and then rapidly decreased, reached a minimum on the 15th day after a new moon, and then gradually increased. The observed changes in CPUE were thought to be caused by changes in the length of time when the moon is up and the timing of moonrise and moonset during nighttime operation.

　Stock assessment of the golden threadfin bream Nemipterus virgatus in Japan began in 2021. To investigate the growth and maturation, we observed gonads and otolith annuli using 527 samples collected from June 2021 to August 2023. Occurrence of hydrated eggs in females and seasonal changes of gonadosomatic index (GSI) indicated that the peak spawning season was from June to July. Peripheral opaque zones in the sagittal otoliths were formed annually between May and September and opaque zones in otoliths were validated as a characteristic of age. The estimated ages ranged 0.92–6.5 years for females and 0.92–7.1 years for males. The von Bertalanffy growth equations were estimated as FL_t＝438.3 {1－e^{－0.491(t－0.187)}} for males and FL_t＝307.6 {1－e^{－0.640(t－0.000)}} for females (FL_t, fork length [mm] at age t [year]). Males were significantly larger than females at age 2 and above. It is suggested that males become mature at age 3 and above due to the elevation of GSI. Females were identified as mature at age 2 and above based on the occurrence of hydrated eggs.

　In the present study, we estimated certain population parameters of the blacktip grouper Epinephelus fasciatus and analyzed yield per recruit (YPR) and spawning per recruit (SPR) around the waters surrounding the Ogasawara Islands, southern Japan. The maximum age observed was 32 years old. The parameters of the von Bertalanffy growth equation for total length were estimated as L_∞＝368 mm, K＝0.159 year^－1, and t₀＝－0.967 year. The age at which the sex ratio reached 50％ by sexual transition from female to male was 10.8 years old, and the age at which 50％ of females reached sexual maturity was 7.0 years old. Males after sexual transition were mature at all ages. From 2015 to 2021, the number of E. fasciatus that were landed at the Ogasawara-jima Fisheries Cooperative Association was calculated to be 24,408 with an age composition ranging from 3–32 years old. Fish that were 6–14 years old constituted 75％ of the landings. The total, natural, and fishing mortality coefficients including both sexes were estimated to be 0.214, 0.078 and 0.136 year^－1, respectively. F_cur was higher than F_0.1 but lower than F_max and F_30％SPR. The increase in fishing pressure strongly affected the decrease in SPR of the males.

　The age and growth of the ark shell Anadara broughtonii in Osaka Bay were investigated by observation of the cross-sectioned shell and growth model estimation using samples collected from 2016 to 2022. The cross-sectioned shells showed a translucent zone each year from August to November, the period after reproduction that was estimated by seasonal variations of condition factor. In wild specimens, the translucent zone at age one was not always observed; the opposite was true in released specimens that had been cultured until juvenile. In addition, released specimens always had one or two more translucent zones than their actual age, which were possibly created by physical stresses at the time of release. Shell growth patterns were divided into four groups: (1) reproductive period including less-than-3-year-old specimens, (2) non-reproductive period including less-than-3-year-old specimens, (3) reproductive period including more-than-3-year-old specimens, and (4) non-reproductive period including more-than-3-year-old specimens. The ages were estimated to be from 1 to 8 years old. The age–length key showed that approximately half of the captured shells were estimated as 2 years old. For sustainable fisheries management, we propose to shift the main age of the fishery to 3 years old (i.e., setting the catch limit size to 70 mm or larger).

　Insufficient pigmentation in the muscle due to simple supplementation of astaxanthin to artificial diets is one of the problems for the aquaculture of sockeye salmon Oncorhynchus nerka. To develop an effective and practical method for improving pigmentation in the muscle of sockeye salmon, the effects of feeding Antarctic krill and supplementing lipid to an astaxanthin-supplemented diet were investigated. Feeding krill alone or combined feeding of both krill and an astaxanthin-supplemented diet improved the pigmentation in the muscle relative to feeding the diet alone. Supplementation of lipid to an astaxanthin-supplemented diet improved the apparent absorption of dietary astaxanthin, and improved the muscle pigmentation. However, muscle pigmentation by the astaxanthin- and lipid-supplemented diet was found to still remain at insufficient levels. Thus, further improvements in the absorption of dietary astaxanthin and deposition of absorbed astaxanthin are essential for the development of a practical diet for sockeye salmon aquaculture.

　Karenia mikimotoi red tides occur every year along the coast of Nagasaki Prefecture. The frequency of occurrence of K. mikimotoi red tide depends on each sea area. K. mikimotoi red tides were observed widely around Nagasaki in 2021. K. mikimotoi red tides were observed every year from late spring in Kujukushima and Sasebo Bay. In Kujukushima and Sasebo Bay, wintering cells were observed by winter investigation. The wintering cells caused the red tides in Kujukushima and Sasebo Bay. Red tides of K. mikimotoi in Omotaka, Tomie and Nomozaki were recorded for the first time in 2021. According to a particle tracking model, the red tides were advected from Sasebo Bay to Omotaka, Tomie, and Nomozaki and might increase in case of favorable meteorological conditions.

　Using a small, waterproof, and invasive prototype device, impedances at 154 different frequencies from 310 Hz to 1.5 MHz in 1.5 seconds were obtained from the head meats and dorsal meats of 278 farmed coho salmon, and the accuracy of K-value estimation was evaluated using a machine learning model. As a result, the coefficient of determination for the training data was 0.796 for the head meat and 0.789 for the dorsal meat, and the coefficient of determination for the validation data was 0.754 for the head meat and 0.773 for the dorsal meat. Using this method, it was possible to estimate the K-value of coho salmon with higher accuracy than before. It is considered that this method could be put to practical use in fisheries.

Erratum to "Search for a suitable diet for the culture of Monopylephorus rubroniveus"

Nippon Suisan Gakkaishi 2024; 90: 264-271. https://doi.org/10.2331/suisan.23-00041

Wrong : 　　267, Left　Table 4

　　　　Nutritional composition of experimental diet

Right : 　　267, Left　Table 4

　　　　Nutritional composition of experimental diet (dry weight, %)