Daytime seine net sampling was conducted on three artificial sandy beaches（Inage, Kemigawa and Makuhari）formed on reclaimed land at Mihama, Chiba Prefecture, central Ja- pan, in September and November 2017, and May and July 2018. A total of 1091 individual fishes, representing 19 families and 23 species, were collected throughout the study period. Five species （Lateolabrax japonicus, Platichthys bicoloratus, Konosirus punctatus, Hypoatherina valenciennei and Plecoglossus altivelis altivelis）were dominant, accounting for 87. 4% of all individuals. Al- most all of the species collected were represented only by juveniles, suggesting that the artificial sandy beaches were used as an important juvenile habitat by a variety of fishes. Although no differences in total numbers of fish species and individuals, and species composition were found among the three beaches, the mean standard length of fish pooled for each species tended to be smaller on Kemigawa Beach than the other two beaches. This difference may be due to the pro- tected aspect of the former beach, resulting in relatively low wave activity, due to the construction of inwardly-curved groins on either side of the beach.
Occurrence patterns of the larval and juvenile Japanese whiting, Sillago japonica, were investigated in Tokyo Bay by monthly samplings using the following two types of gear: a small seine net towed at three tidal-flat stations around the river mouth of Tama-gawa River from May 2006 to September 2009; and a ring net towed at a station in the offshore water of the Tama-gawa River mouth from January 2006 to May 2008. Their functional development was also observed mainly by osteological characters on the basis of 111 cleared and stained specimens of 2.0-21.1 mm in body length（BL）. Specimens collected from the offshore water were 30 in number with 4.6 ± 1.6（mean ± SD）mm BL, ranging from 2.0 to 8.5 mm BL, and those from the tidal flats were 232 with 15.7 ± 5.6 mm BL from 6.1 to 49.3 mm BL. Based on the functional development of swimming- and feeding-related characters, the larvae and juveniles were divided into five and four developmental phases, respectively. Improvements of swimming and feeding functions observed at about 3 mm BL were considered to assist the early larvae in migrating shoreward, and the specimens of 6.0-8.9 mm size classes occurred in both the offshore and tidal flat stations. Thereafter on tidal flats, the number of individuals increased and reached a peak at about 15 mm BL, when the juveniles acquired functional swimming and feeding abilities. The juveniles > 15 mm BL decreased in number, and then those ca. 30 mm BL had scarcely appeared on the tidal flats. The Japanese whiting juveniles > ca. 30 mm BL in the innermost Tokyo Bay are most likely to move into deeper waters.
Larvae of Auxis collected around Tosa Bay from May 2002 to May 2018 could be distinguished into two types primarily by the pigmentation patterns on the caudal peduncle. Type-A Auxis larvae possess a row of pigmentation along the midlateral line in all larval stages, while type-B does not. Little morphometric differentiation was found until the flexion stage in both types, but at the postflexion type-A showed significantly larger head［36.8% BL(mean）］, larger mouth（24.1%）, shorter vent to anal-fin length（17.7%）and deeper body（27.8%）than type-B (34.8, 21.5, 19.0, 25.9%, respectively）. These observed differences indicate the validity of the pigmentation row in distinguishing Auxis larvae. Between the two types, type-B larvae（n = 795） were more abundant than type-A（n = 21）in Tosa Bay. Based on this distribution pattern and shallower body depth, type-B larvae could be considered as A. rochei and type-A with a deeper body as A. thazard.
This study used micro-acceleration data loggers to measure burst movements, such as feeding behavior, of smallmouth bass（Micropterus dolomieu）. Data loggers were attached to the dorsal side of seven bass released into Lake Kizaki, Japan, during summer 2007-2008. From 220.7 total hours of data, the burst movement rate was 0.7 ± 0.3 events/hour（mean ± s.d.）（range: 0.4-1.1 events/hour）. All bass showed burst movements during both daytime and nighttime, but four fish had higher event rates during the day. For two individuals, the mean event depth was significantly deeper during the daytime than the nighttime.