How do teraponids utilize the reflective sandy beach?

Occurrence patterns of the larvae and juveniles of two teraponid fishes, Rhynchopelates oxyrhynchus and Terapon jarbua, were examined in a reflective sandy beach in Tateyama Bay, Central Japan. Samplings were done at the shoreline and offshore areas of the sandy beach. A small seine net (1 min mesh size) was used for the samplings and two sampling strategies were adopted: 1) semi-monthly daytime samplings carried out at the shoreline and the offshore areas from April 1999 to March 2001 and 2) day-night samplings carried out with tidal rhythms at the shoreline area in July and September 1999. Additionally, visual observations were also conducted in a shallow water zone (< 20 cm depth) to substantiate sampling data. The two teraponid fishes occurred mainly in the summer from July to September. Specimens of R. oxyrhynchus < 15 min SL made up 76.5% of the total catch and they were at postflexion larva and juvenile developmental phases. The occurrence patterns of R. oxyrhynchus were not related to diel/tidal phases. Visual observations showed that only T. jarbua occurred in shallower zones (< 10 cm depth), where they formed small schools when they were in the juvenile and young developmental phases (10 - 30 min SL). These results suggested that R. oxyrhynchus larvae/juveniles utilize the shoreline area as a nursery ground for a short period of time. On the other hand, the shoreline area would not be a suitable nursery ground for T. jarbita but the juveniles/ young utilized the shallow water zone as a habitat.