Kagawa Prefectural Fisheries Experimental Station, Takamatsu, Kagawa 761-0111
For catch forecasts of halfbeak Hyporhamphus sajori, I examined the relationship between catch per unit effort (CPUE: kg day-1 boat-1) of halfbeak and their mean standard length (SL: mm) or the number of recruits of Japanese anchovy Engraulis japonicus in eastern Hiuchi-nada, the Seto Inland Sea. SL in a mixture of normal distributions was estimated with the non-linear least squares method on the length frequency composition. SL in one-year-old males and females ranged from 185.6 to 217.9 and from 194.2 to 228.4, respectively. The catch was mainly composed of one-year-old fish. CPUE fluctuated between 65.1 and 261.1. SL at one year of age was negatively correlated with CPUE. The positive correlation between CPUE and the number of recruits of Japanese anchovy was significant. The multiple regression equation using CPUE (y) as the outcome variable and SL at one year of age of female fish (x1) and the number of recruits of Japanese anchovy (x2: hundred million) as the predictor variable was y=780.82-3.37x1+0.30x2 (n=6, r2=0.98, p<0.01).