颱風降雨與橫向構造物障礙之有無對山區溪流水生物影響探討

The Impact on the Aquatic Species of Stream with/ without Check Dam Obstruction and Typhoon Rainfall

胡通哲(Tung-Jer Hu)

《濕地學刊》 2卷2期 (2013/07) Pp. 25-40

摘要

本文針對具有橫向構造物與沒有橫向構造物障礙的溪流，進行魚類與水棲昆蟲調查結果的探討，並探討大型颱風降雨對山區溪流水生物的影響，分別選取蘭陽溪的兩條支流－多望溪、田古爾溪，兩條溪匯入蘭陽溪的的會流口接近，上游皆源自太平山。多望溪有三座高壩，代表具有橫向構造物阻礙生物通道的溪流，田古爾溪雖然曾建造防砂壩，但在二十餘年以前已被土砂掩埋，已是洄游性魚類可自由上下的生物通道。調查結果卻顯示多望溪雖然上游樣站受防砂壩阻隔，只有3種魚，但在颱風過後卻保有一定程度的魚類數量，即使是強降雨引發土石運移，魚類數量恢復快，但上游的魚種受到防砂壩影響而往上游遞減的情形。田古爾溪的強降雨導致樣站棲地常被上游沖刷而下的大量土石覆蓋，魚類調查數量稀少，雖然上游樣站有2站次紀錄的魚種高於多望溪，但大部分情形魚類數量、種類皆低於多望溪，且有33%（13／39）站次的調查是完全沒有調查到魚類的情形。在颱風降雨影響下，設有防砂壩的溪流，雖然阻礙洄游性魚類上溯，但或有魚類避難的功能，而山區溪流若沒有避難空間，魚類族群量、水棲昆蟲數量直接受到強降雨的影響。

關鍵字

颱風降雨 ； 生物整合指標 ； 棲地 ； 生物通道

並列摘要

This study discuss the impact of heavy typhoon rainfall on the aquatic species (fish and aquatic insects) with/without transverse obstruction. We choose Dongwang stream and Tianguer stream as our field site. These two streams are the tributaries of Lanyang stream. For Dongwang and Tianguer stream, the flow juction place of Lanyang stream is very close for each other and the headwater zone is the same (Taiping mountain). In Dongwang stream, there are three check dams higher than 6 meters, it means the stream had obstruction to intercept the bioconduit for up-migrated fish species. In Tianguer stream, there were two check dams exist about twenty years ago, but the dams had burried by massive sediment. So Tianguer stream had the free-moving bioconduit for migrated fish. The field data show the species of upstream site of Dongwang stream have few fish species, but the habitat can remain some extent of fish population after heavy typhoon rainfall hit and sediment cover. The fish population recover sooner than another stream after debris disaster in Dongwang stream. For Tianguer stream, the habitat usually was covered by massive sediment caused by heavy rainfall. In most records of Tianguer stream, the fish species and population was less than Dongwang stream. Only two times, the species of Tianguer stream was more than Dongwang stream. To count the times that no fish recorded, the probibility was 33% (13/39). Although, the mountain stream with check dam may decrease the opportunity of freshwater fish up-migrating. It may let the fishes have refuges to avoid high speed flow during flood period. If the stream there were no refuge, the fish and aquatic insects population need to bear the impact of heavy rainfall.

並列關鍵字

Typhoon rainfall ； Index of Biotic Integrity ； Habitat ； bioconduit