Size-selectivity of hole on tubular-pot for white spotted conger eel Conger myriaster in the adjacent sea of Korea

摘要

This paper describes size-selectivity for white spotted conger eel Conger myriaster of the holes on tubular-pot from which inner-water is discharged. Fishing experiments were carried out in the adjacent sea of Pusan, Korea in 1990, using pots with 6, 9, 12, 15, 18, and 21 mm hole-diameters. Selectivity parameters and split parameter of the SELECT model were calculated using the estimated split model and the equal split model, respectively. From the values of AIC )Akaike's Information Criterion), the equal split model was selected. Size-selectivity of the holes in the pots was expressed with logistic curve like mesh selectivity. Holes of larger diameter increased the allowance of conger eel escaping. The 50 percent selection length (L_50) of conger eel in the equal split model were 181, 244, 298, and 350 mm of hole diameter 9, 12, 15, and 18 mm, respectively. The values of L_50 for 15 and 18 mm hole-diameter were larger than the total length of the conger eel with cross-sectional diameter of its body equal to the diameter of the hole. This implies that conger eel have a high-ability of escaping through narrow holes with smooth body-surfaces. Holes of appropriate diameter on a pot would be useful as an escape vent for protecting conger eels of smaller than marketable size.