Spatial and size distribution and gonadal maturation of an alien species, channel catfish Ictalurus punctatus, in the Abukuma River system in Fukushima Prefecture, Japan
2018
Takasaki, K. (Fukushima Prefectural Inland Water Fisheries Experimental Station, Fukushima (Japan)) | Wada, T. | Morishita, D. | Sato, T. | Sakuma, T. | Suzuki, S. | Kawata, G.
During May 2015-November 2016, field surveys using various fishing methods (mainly gillnet and longline) were conducted at 13 sampling stations in the Abukuma River system of northeastern Japan to elucidate the spatial and size distributions and gonadal maturation of an invasive alien species, channel catfish Ictalurus punctatus. In all, 716 individuals (9.9-65.0 cm SL) were collected from the mainstream. Most of them were collected from two reservoirs (Shinobu and Horai hydroelectric dams) and its lower area located along the mainstream in northern Fukushima Prefecture. Results of gillnet surveys in Shinobu Dam showed that the catch per unit effort in 2015 and 2016 increased markedly compared with the reported value in 2008. Mature females with high gonadosomatic index were collected during May-June, the estimated spawning period. The results suggest the possibility that the channel catfish biomass in the Abukuma River system increased dramatically during 2008-2015 through successful reproduction in and/or around dam areas. Percentages of channel catfish individuals among all the fish specimens collected by gillnet and longline in Shinobu Dam were high (64.2% and 100%, respectively), indicating that suitable extermination methods should be urgently established.
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