DAILY CHANGES IN THE CATCH OF PARAPRISTIP OMA-TRILINEATUM AT THE HOOKAND LINE FISHING GROUND OF TOSHIMA-FISHERMAN-UNION WITH THE SPECIAL REFERENCE TO WATER CONDITIONS OF UWA SEA, JAPAN

Daily catches of threeline grunt Parapristipoma trilineatum (CP) at th e Toshima hook and line fishing ground was studied during April 1988 a nd March 1989. Total catch (TC) and CP had seasonal changes; many fish were caught in summer and few in winter, and the PC/TC ratio exceeded 30% between May and September. Daily changes of CP were closely relat ed to the daily changes in the number of fishing boats that caught P. trilineatum (NFP) during June and September. Daily changes of CP and t he fluctuation of tide level in a day (FTL) were positively correlated during June and September except for August, and the same relation wa s found between NFP and FTL. Sudden poor CP was caused by poor NFP and /or great changes of water temperature (CWT). Sudden poor NFP was caus ed by heavy rain, high wind, public holiday and so on. The daily chang es of CP at the Toshima hook and line fishing ground were thus influen ced by the tidal cycle and the rapid changes of CWT, which were caused by kyucho.