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To improve breeding techniques for aquarium freshwater pufferfishes, hormone injection (hCG, 10 IU per g)-induced maturity and insemination of Auriglobus modestus from Thailand were undertaken, and morphological development of eggs and early stage larvae observed. Artificial insemination was performed two to five days after hormone injection. Although no fertilized eggs resulted from artificial insemination utilizing a wet (freshwater) method, an isotonic (sodium lactate ringer solution) method produced 458 fertilized eggs out of 787 eggs (fertilization rate 61.7%) spawned by one female, although only 8 larvae (1.7%) eventually hatched. Eggs were oval [long axis 2.05 ± 0.06 mm, short axis 1.68 ± 0.06 mm (n = 5)], translucent, demersal, and adhesive, and contained a number of small yellow oil globules. Oval eggs are unusual among pufferfishes, although common in the genus Chonerinos, an indication of the genetic closeness of the latter and Auriglobus, but also suggesting ecological similarity. The eggs hatched after 2 days, larvae one day after hatching [4.54 ± 0.34 mm NL (n = 9)] having a large yolk sac. However, the mouth remained unopened, the optic vesicle uncolored, and the pectoral fin membrane undeveloped, except for small knob-like rudiments. Seven days after hatching, larvae [5.22 ± 0.10 mm NL (n = 3)] had lost the yolk sac and acquired rudimentary soft rays in the pectoral, dorsal and anal fins. All larvae died after eight days. DNA barcoding comparisons (COI gene, 652 bp) of several pufferfish genera indicated a close genetic relationship of Auriglobus and Chonerhinos, being nested in the same clade.

An unusual instance of biting behavior by the pufferfish Arothron meleagris, possibly related to spawning behavior was observed during low tide of new moon spring tide while scuba-diving off the Maldives Islands. Multiple males were following, biting and clinging persistently to a female. Subsequent internet searches revealed that similar biting behavior was common among several congeners, possibly being a characteristic spawning-related behavior of the genus.

We investigated the hemolymph oxygen and acid–base status of akoya pearl oysters, Pinctada fucata martensii, exposed to air for a short time (4 h) to elucidate the acid–base balance and CO_2 dynamics. The hemolymph O_2 partial pressure (Po_2) in air-exposed akoya pearl oysters decreased from 88.7 torr (mean value) to 29.4 torr at 1 h, and the low Po_2 continued for the next 3 h during air exposure. The hemolymph pH decreased from 7.586 to 7.082 during air exposure for 1 h and reached 6.851 at 4 h. The hemolymph CO_2 partial pressure increased from 0.9 torr to 4.4 torr at 1 h and reached 7.3 torr after 4 h of air exposure. The hemolymph bicarbonate concentration and calcium ion concentration at 0 h (control) were 1.9 mM/L and 9.0 mM/L, respectively, and these properties did not significantly change during air exposure. From these results, it was determined that the akoya pearl oysters had hypoxemia caused by hypoventilation at an early phase of the short-term air exposure. The akoya pearl oysters inhibited the discharge of CO_2 by hypoventilation, and respiratory acidosis was caused due to the excessive accumulation of CO_2. Bicarbonate was not mobilized from the shell valve into the hemolymph during the short-term air exposure.

In aquaculture and fixed-net fishing, fishing nets need to be fixed in the water for a long period of time. Therefore, attached organisms such as shellfish, algae, and parasite eggs easily stick to the nets, making periodic cleaning indispensable. A common method is for divers to dive into the water and clean the nets directly with their hands. However, this method is dangerous because it can be fatal to divers due to high water pressure and low water temperature. Therefore, this study considered the possibility of using underwater robot to clean fishery nets in place of divers to avoid these dangers. A mobile mechanism that can move freely along the sides of fixed fishery net in the water has already been developed in this laboratory. In this study, we propose the cleaning system using autonomous robots that automatically cleans aquaculture nets underwater and the charging station using coils for wireless power supply. This robot and a charging station will be installed on the aquaculture nets, and the robot will be driven periodically to clean the nets underwater with less labor and in a safe manner.

Viral edema of carp (VEC) caused by the carp edema virus (CEV) causes economic losses for Japanese koi farms. In this study, we investigated the infectivity and pathogenicity of a domestic CEV isolate (genogroup IIa) in koi carp, common carp and goldfish. The challenge test consisted of 9 groups (n = 15):3 groups each of koi carp, common carp, and goldfish, at 15, 20 and 25℃. These groups were challenged with CEV (3.0×10^3 copies/µL) in duplicate. All koi carp died in the 15 and 20℃ groups, but all survived in the 25℃ group. The surviving koi carp in 25℃ groups showed high PCR positive rates of 66.7 and 73.3%, with VEC histopathological changes observed. For the common carp, 1 and 2 fish died in the 20℃ groups, but no deaths or VEC symptoms were observed in the 15 and 25℃ groups. In all common carp groups, PCR-positive fish were observed along with histopathological changes. For all goldfish groups, no deaths or VEC symptoms were observed. As with the common carp, PCR-positive fish were found in all goldfish groups, yet no VEC histopathological changes were detected. These results demonstrate infectivity of this CEV strain in koi carp, common carp, and goldfish, but low pathogenicity in common carp and goldfish.

Growth of immature Lates japonicus in eelgrass (Zostera japonica) beds of the Tomouchi River located at around 4.3 km upstream from the river mouth of the Gokase River, Kyushu Island, Japan was studied by the mark and recapture method and scale reading from September 1998 to March 2004. Newly occurring 0-year-old L. japonicus specimens of 13.9–78.0 mm SL (standard length) in Z. japonica beds of the Tomouchi River in August or September reached sizes ranging 58.8–125.7 mm SL by April and 203.4–232.8 mm SL between October and November of the following year. Monthly changes in specific growth rates of individuals demonstrated that rapid growth months of immature fish were limited to the period of high water temperature (22–28℃) from June to October. Also, it was supposed that the large-sized fish of the 0-year-old fish migrated away from Z. japonica beds after December, however a few fish remained in Z. japonica beds until the following November.