1Hokkaido Research Organization Central Fisheries Research Institute, Yoichi, Hokkaido 046-8555, 2Field, Science Center for Northern Biosphere, Hokkaido University, Hakodate, Hokkaido 041-8611, Japan
We aimed to estimate the size selectivity of the shrimp pot for the northern shrimp Pandalus eous by the SELECT analysis method. Comparative fishing experiments were conducted by using shrimp pots of different mesh sizes (bar length: 13.99, 15.30, 16.84, and 19.13 mm) with control pots of 5.33 mm. We obtained size selective curves for non-ovigerous and ovigerous shrimps. The carapace lengths of 50% of the non-ovigerous shrimps caught (L50) with mesh sizes of 13.99, 15.30, 16.84, and 19.13 mm were 20.10, 22.75, 26.25, and 28.64 mm, respectively. The carapace lengths of ovigerous shrimps caught with a mesh size of 19.13 mm were significantly different from those of shrimps caught with a non-selective mesh size of 5.33 mm. Therefore, mesh size of less than 19.13 mm was nonselective for ovigerous shrimps. The L50 of ovigerous shrimps caught with a mesh size of 19.13 mm was 25.74 mm. The percentage changes in the total catch and income were calculated when mesh sizes of more than 15.30 mm were used: they decreased by 11.8% and 9.5%, respectively, when the mesh size was modified to 16.84 mm, while they decreased by 31.2% and 27.8%, respectively, when the mesh size was modified to 19.13 mm.