RESTORATION IN THE ECO-CONSERVATION AREA OF THE GENTE RIVER OF PUNGITIUS SINENSIS

摘要

The Gente River, 3km in length and with a 5.1 m-wide bottom, is a drainage canal for thernfarming area. All its weeds-rampant soil riverbed was renovated in an eco-friendly designrnbetween 1996-2001. But the renovation made the flow velocity of the canal a little too high forrnthe propagation of Tomiyo, a tiny fish species (Pungitius Sinensis). To provide Tomiyo with arncomfortable niche to propagate in, an eco-conservation area was created halfway down thernrenovated canal in 2000. The area is a 100 m-long and 3.3 m-wide gravel-bottomed streamrnlaterally added to the main stream. This study was aimed at tracking how Tomiyo fared in thisrnnew environment.rnThe capture survey of Tomiyo was conducted in the quadrat section of the eco-conservation arearnfour times over a period of time 5 to 11 months after the completion of the area. The resultsrnrevealed that the population density of Tomiyo under the waterweeds ranged from 1.19 to 3.52rnfish/m. The marking survey was conducted six times over a period of time 18 to 47 months afterrnthe construction of the area. The results revealed that the population density of Tomiyo under thernwaterweeds ranged from 2.61 to 5.92 fish/m~2. Another capture survey (control) had beenrnconducted at five sections of the Gente River before its renovation. The result had revealed thatrnthe density of Tomiyo under the waterweeds ranged from 1.93 to 2.44 fish/m~2. The abovernsurveys of the density of Tomiyo differed from each other in the time spent, in the capturerntechniques and in the calculation methods. But they at least confirmed the following two facts:rn1) In the quadrat section, Tomiyo living under the waterweeds whose coverage rates were stillrnless than 50% showed levels of density similar to the ones in the pre-renovation stream.rn2) In the eco-conservation area as a whole, Tomiyo living under the waterweeds whose coveragernrates were around 70% showed levels of density far exceeding the ones in the pre-renovationrnstream.rnFrom these results we might conclude that the eco-conservation area serves well to preserve arngood enough environment for Tomiyo to propagate in.