Natural Propagation and Growth of the Endangered Japanese Bagrid Catfish Pseudobagrus tokiensis in an Ecological Test Pond

Abstract

The propagation and rearing of Pseudobagrus tokiensis were performed in an ecological test pond from 2004 to 2007 in order to collect baseline data for habitat restoration and restocking purposes. Over the four-year period of the study, spawning in P. tokiensis occurred between the end of August and September. Pseudobagrus tokiensis exhibited sexual dimorphism with respect to growth with males tending to be larger. In females, maximum standard length (SL) was approx. 150 mm and individuals 120 mm< were rare, while males with SL exceeding 200 mm, were often observed. The relation between SL and the mass of both males and females, could be expressed by y=0.133x^2.482 (R²=0.981) and y=0.0431x^2.775 (R²=0.948), respectively, the logarithms of which were significantly different (t-test, P<0.001).
Successful propagation of the catfish during the study period resulted in a remarkable increase in their numbers in the test pond. They can, to a certain degree, inhabit artificial, concrete-lined streams, provided that a stable supply of spring water can be ensured, large natural stones are arranged along the side walls, and variously sized pebbles are used to line the stream bottom.