Historical distribution of Arctic lamprey Lethenteron camtschaticum in Japanese rivers and its change estimated from fishery statistics and fishers’ local ecological knowledge

Abstract

This study identified the location and geographical characteristics of rivers where Arctic lamprey Lethenteron camtschaticum were captured in the past and present in Japan and evaluated the effectiveness of the local ecological knowledge (LEK) held by inland fishers for estimating species distribution. We collected information about fishery harvests for Arctic lamprey from fishery statistics published in the 1930s and directly from inland fishery cooperatives (FCs). The presence of a historical harvest and its southern limit were largely consistent between the two resources. The fishery harvest was historically distributed in relatively large rivers, with a low downstream gradient, along the Sea of Japan, and the southern limit was estimated to be in the range of 36.45–37.33° N. The number of active FCs decreased from a historical value of 59 to only 14 at present. The southern limit shifted further north to 43.13° N. The LEK from FCs provided sufficient information to estimate the spatial distribution within the local rivers and revealed that a decline in fishery activity had occurred in the upper reaches of rivers. Our data can be used as a baseline for the restoration of Arctic lamprey and to develop a monitoring tool to improve the conservation of inland biodiversity.