Larval food abundance is one potential cause of recruitment variation in benthic invertebrates, including bivalves. Bivalve veliger larvae can clear particles <~10 µm. However, the particle retention efficiency (PRE) of bivalve larvae differs among species, so is necessary to determine larval food abundance in nature. We investigated the PRE of larvae of the asari clam Ruditapes philippinarum, which recently has greatly decreased in numbers in Japan. Artificially hatched larvae from the umbo to the full grown stage were exposed to natural food assemblages. Larval clearance rates were determined for particles in 32 size ranges from 0.8 to 18 µm. We observed significant clearance of particles in the ~1 to 8 µm size range, with the highest clearance rates being on 1.4 to 2.0 µm particles. Larval ingestion of the natural food assemblages ranged from 50 × 10 2 to 120 × 10 2 µm 3 ind., which is below the hatchery food ration, suggesting larval food limitation in nature.

The eŠects of soaking conditions on released water of thawed jack mackerel Trachurus japonicus meat after soaking, freezing, and thawing were studied using a jack mackerel immediately after being killed. The water release rate for previously soaked thawed meat did not increase when the NaCl concentration of the soaking solution was 0.5 M or higher. When the NaCl concentration in the jack mackerel meat was 0.25 mol/kg or higher, the water release rate was not aŠected by moisture but showed a constant low value. In muscle homogenate, a rise in water-holding capacity matched the solubilization of myoˆbrils (Mf) by NaCl in the vicinity of 0.2 to 0.4 M. Glucose, which is not able to solubilize Mf, did not show improvement in the water-holding capacity. Therefore, it is suggested that a dissolution action of Mf by NaCl improves the water-holding capacity of the soaked, frozen, and thawed meat and suppresses water release.