Abstract
Assuming negligible production of pseudofaeces, the amount of food filtered by the clam is equal to the amount of food ingested. The ingestion rate estimated as nitrogen per 1 m2 per h (F) was given in the following equation :
F=Σ7n=1(Fn·RT·Rs·Pn)·N
where ; Fn, filtration rate of a clam at L mm shell length at 15°C and 35 psu ; RT, correction coefficient for Fn at T °C ; Rs, correction coefficient for Fn at S psu ; Pn, clam density of 7 size classes and N, concentration of suspended particulate nitrogen (PN). L was given for the mean shell length of each size class. Filtration rate and effects of body size, temperature and salinity on the filtration rate were examined using the clam collected from Banzu tidal flat. Monthly changes of temperature, salinity, concentration of PN and clam density for the tidal flat were evaluated by analysis of available data. PN was calculated from Chl-a concentration and reported PN : Chl-a ratio.
The estimated ingestion rate was maximum at 300 mg-N·m-2·h-1 in August, and minimum at 19 mg-N·m-2·h-1 in February. From analysis of the results, it is suggested that both temperature and PN concentration affect significantly the seasonal changes of the rate, however, salinity has no detectable effect on them in Banzu tidal flat.
