The contribution of hatchery-reared red tilefish released into the coastal waters of the Shimane Peninsula was assessed. Monthly surveys were conducted at Koizu fishing port from 2012 to 2019 to confirm the labeled red tilefish released into the coastal waters of the Shimane Peninsula. Labeled fishes were captured within 45 km of the release point, with 97% captured within 20 km of the release point. The number of labeled fish found was 123, 80 females and 43 males, with an annual bycatch rate of 0.12-1.01%. The estimated number of fish recaptured was 1,105 females and 681 males, for a total of 1,786 fish. The standardized accumulative recapture rate, calculated from the age composition of the fish recaptured and the number of fish released by year, was capped at 4.874% after age 9. The expected price of fish releases was 83.7 yen per fish as a direct effect and the ratio to selling price per seedling was 0.78. The mechanism of reproduction of red tilefish in this area will be an essential theme in the calculation of indirect effects in the future.

Octopus sinensis were mated, spawned, and hatched in an aquarium. Paternity was estimated by paternity testing to establish the reproductive ecology of the octopus. The durations varied in length: 8-140 days from the start of the mating test to the spawning of the female individual, 23-68 days from the start of spawning to the start of hatching of the paralarvae, and 6-24 days for the hatching period. The mating durations varied from 283 to 6277 seconds, and the number of male arch and pump movements varied from five to 25, showing differences by individuals. The paternity test confirmed the existence of multiple paternity in the octopus, while differences were confirmed in the proportions of each paternity in the hatched octopuses. In addition, many of the females used in the test had already mated with multiple males in natural waters and had stored sperm. Since there were no significant differences in the paternity ratio of the offspring octopuses on each hatching day, it is possible that the sperm of each male that mated with a female was well mixed in the female’s body, from mating to spawning.

For this study, we analyzed experiences of inland angling at nearby rivers or ponds for Japanese people during children and its transition using online survey with questionnaires given to Japanese adults. Results show that the most caught fish were Cyprinids, with angling using live bait collected individually as the most favored method. However, many respondents from the young generation chose fishing for alien species using lures. This trend was clearly observed in areas where salmonids are not familiar as a target for fishing. Most respondents went fishing during childhood with other children such as friends, brothers or sisters. Furthermore, most respondents were introduced to angling by other children. These results imply that angling for Cyprinids using live bait is most suitable for children. Furthermore, it is necessary that the rivers and ponds to which children can go fishing be prepared for enhancement of angling among children.

Gonadal maturation of 264 blacktip grouper Epinephelus fasciatus caught off Shima Peninsula, Mie Prefecture was histologically studied. These samples consisted of 230 female, 21 male, and 13 intersex individuals. The number of mature-stage females was high from June to September, especially from June to August, and the gonadosomatic index (GSI) was high in the same period. Although, males remained spermiated throughout the year, based on histology and GSI spermatogenesis peaked in July. From these results, the peak of the spawning season was estimated to be from June to August. From the relationship between standard length and GSI, the maturation length of females was considered to be about 170 mm standard length (SL). The maturation length of males was unidentified because all specimens were already spermiated. Since all specimens smaller than the smallest intersex (188 mm SL) were females and all specimens larger than the largest intersex (268 mm SL) were males, and the maturation length of females was smaller than the smallest intersex and male individuals, we conclude that this species shows a protogynous sex change and sex reversal was estimated to start about 190 mm SL.

Effect of the duration of plant-based starter diet (PD1) feeding in rainbow trout Oncorhynchus mykiss fry on the growth and biochemical parameters of juveniles fed again a plant-based grower diet (PD2) was examined. Three groups of swim-up fry were fed (1) a fishmeal-based starter diet (FD1) for 4 weeks, (2) PD1 for 2 weeks and then FD1 for 2 weeks, and (3) PD1 for 4 weeks, respectively. Thereafter, all the fish were fed a commercial fishmeal-based diet until 8 g BW, and then fed PD2 for 9 weeks in duplicate. Irrespective of the duration of feeding PD1 to the fry, juveniles having experienced PD1 exhibited advanced growth and feed efficiency ratio (P < 0.05) relative to juveniles without experience of PD1. Feed intake (% BW/day) of juveniles with experience of PD1 for 4 weeks was significantly higher (P < 0.05) than juveniles without PD1 feeding, and juveniles having experienced PD1 for 2 weeks showed an intermediate value. No marked effects of the first feeding diets were observed on the whole body proximate composition, blood chemistry, bile status, and nutrient digestibility in the juveniles. These results suggest that at least 2 weeks of first feeding of a plant-based diet to rainbow trout fry is necessary to improve the utilization of a plant-based diet in juveniles.

Blue sharks (Prionace glauca) are caught in many countries, but the body measurements data collected vary among countries and institutions. This paper examined if the logarithmic value model or the real value model is more suitable for estimating the body lengths of blue sharks caught in the northwestern Pacific Ocean, using the conversion factors from linear regressions between various body measurements. In addition, we identified suitable body measurements that can be used to estimate body lengths, which is important for stock assessment, based on their accuracy and convenience of measurement. Generally, the linear models using log-transformed numbers outperformed those that used real numbers. We considered the performance of each conversion factor and port sampling situation, and suggested that the pectoral fin anterior margin and length between the prior base from the 1^st to 2^nd dorsal fins were the optimal body measurements to measure. The findings of the present study can help incorporate the length and weight data of various body measurements and increase the amount of length frequency data available for stock assessments of this species.

In order to clarify the soaking effects of arginine and ornithine solutions to conchospores of Neopyropia yezoensis, the adherence strength for preventing losses and the growth for increasing yield of thalli were examined with laboratory culture experiments and field aquaculture trials, respectively. From the results of laboratory cultures, the adherence strength with soaking in ornithine for 1 hour or more were enhanced. From the results of field aquaculture trials, the enhances of the adherence strength and the growth promoting were showed with soaking in arginine and ornithine. Additionally, yields with soaking in arginine and ornithine increased by more than 10% per net a day. It was considered that the just once soaking in arginine or ornithine at the time of seedling collection, not only can contribute the enhance of the adherence strength for preventing thalli losses, but also can the increase of yields of lavers.

Food habits of juvenile rockfish (Sebastes cheni) were examined in the eelgrass (Zostera marina) beds restored in the nearshore area of Hinase, the Seto Inland Sea, to clarify whether these habitats can contribute to fish nurseries. Stomach content analyses showed that amphipods and calanoids were the most important prey for the juveniles, as in the case of the adjacent natural eelgrass bed. Furthermore, the genera of amphipods heavily consumed by the juveniles were almost the same as the genera predominant on the eelgrass blades. Therefore, we can conclude that these restored eelgrass beds function as a feeding habitat for juvenile rockfish.

The freshwater pufferfish Pao palembangensis was bred in captivity in order to advance breeding techniques for the species. Breeding occurred in freshwater under stable water temperature (25-26°C) and lighting (L12:D12) conditions, and a spawning bed comprising a stone pipe with a uniform internal surface suitable for establishing and guarding eggs set in a single layer. A pair of individuals spawned three times from June to August 2003, a single egg batch containing about one hundred 2.25 ± 0.01 mm diameter eggs. Hatching occurred 10 days after spawning, larvae being fed initially with Artemia larvae.