1Fisheries Research Institute, Tokushima Agriculture, Forestry and Fisheries Technology Support Center, Hiwasaura, Minami-cho, Kaifu, Tokushima 779-2304, 2Graduate School of Intergrated Arts and Sciences, Minamijosanjima-cho, Tokushima 770-8502, Japan
Diurnal and seasonal behavior patterns of daggertooth pike conger Muraenesox cinereus were investigated in captivity using artificial burrows. Muraenesox cinereus, ranging 89-217 g in body mass, caught with a small-scale trawl were kept in three square tanks (1.6×1.6×0.6 m), 8 fish in each tank, with artificial burrows made of polyvinyl-chloride pipes (51 mm in diameter, 80 cm in length). The number of fish outside of the artificial burrows and the ones that passed under a standard line in one minute (=swimming index) were counted every hour from 14:00 to 13:00 on the next day in August, October and December, 2009 and February, April and June, 2010. The observations revealed that the fish swam only during the night, when the luminance was 0 lx. Both the number of fish outside of the artificial burrows and swimming index increased from April to August with the increase in water temperature and subsequently decreased with the decline in temperature. These results were in agreement with the diurnal and seasonal catch patterns of M. cinereus in the field.