外來種琵琶鼠魚生物學探討與可行去除法之建議研究

Abstract

近年觀賞水族業迅速發展，水族業者引進琵琶鼠魚，為水族寵物缸中清潔用魚種，有清道夫之稱，被棄養之後進入台灣河川，族群持續擴增，需進一步探討其生物特性，是否對本土魚種造成威脅。所以本研究收集各國外來水生生物入侵情形，整理各國對外來水生生物的防治方法，可做為去除琵琶鼠魚之參考依據，同時調查琵琶鼠魚的入侵途徑，及收集在台灣河川之數量及分佈範圍，並進行琵琶鼠魚之生物試驗，如成長、耗氧、排氨、耐溫、耐旱、耐饑餓、食性、抱卵數、物種競爭力與耐污力等，以評估琵琶鼠魚進入後對台灣河川生態的危害，並尋求最佳之琵琶鼠魚去除方式。結果得知本研究之河川中，僅發現一種琵琶鼠魚為Pterygoplichthys multiradiatus，尚無發現其他種類之琵琶鼠魚。雖琵琶鼠魚分佈範圍日漸擴大，但其分佈高度受到本身適應的溫度限制，故許多河川上游冬季都沒有其蹤跡，這也可能是北部琵琶鼠魚族群量比南部少的原因。由於琵琶鼠幼魚耐氧可達0.50 ppm以下(30℃)、耐旱可達4小時以上(成魚6小時以上)、耐饑餓更達1個月以上(成魚6個月以上)，故其適應力極高，當環境中食物缺乏時，可比其他魚類更容易存活。以顯微鏡觀察琵琶鼠魚腸內，有高比例的有機碎屑和藻類，但並無如小魚或蝦的生物體。本試驗中12隻琵琶鼠雌魚的抱卵數平均約6324顆但卵粒較小(<3 mm)。從琵琶鼠幼魚與鯉魚競爭試驗結果得知，琵琶鼠幼魚在體重6 g時，不容易與鯉魚競爭食物，與單養琵琶鼠魚的控制組之成長有顯著差異存在，但在琵琶鼠幼魚在體重16 g時，便容易與鯉魚競爭食物，使得與控制組的成長速率相同。本試驗也發現琵琶鼠魚耐污力大多比其他魚類強，所以在台灣河川中下游污染區域，琵琶鼠魚群量較多。對於防治琵琶鼠魚的方式，在人力機械防治方法，可利用1、人力捕釣丟棄，可利用流刺網收穫達到最大去除的效果。2、可舉辦釣琵琶鼠魚比賽，以獎勵的方式回收魚體。3、從琵琶鼠魚不耐低溫的特性，可利用在每年冬季，在河川以竹枰圈圍出一個區域，使用加溫棒提高水溫，應可吸引琵琶鼠魚前來，再一併捕捉丟棄。4、在化學防治方法，可尋找對琵琶鼠魚毒性較高的農藥如耐克螺，即選擇性農藥，合理的使用劑量來進行琵琶鼠魚的去除工作。5、在生物防治方式，可放流數量較多的原生魚種與之競爭，琵琶鼠幼魚競爭不過體型較大的魚種，可降低琵琶鼠魚族群量。6、利用特定的魚類寄生虫或是專一性細菌原的釋放。希望本研究能給予進行外來種管制者一些參考，提供台灣琵琶鼠魚的防治法，供相關單位採用。

It is generally known that exotic aquatic species could destroy the local ecological system and extinct the native species, while it became invasive species, due to its top predator or competition with native species. It is important to know their invasive routes and to understand their biological characters for the case eradicating management of these species. The objective of this study is to set up a model to control invasive species, especially the sucker catfish (Pterygoplichthys multiradiatus), and to investigate its impact on endemic organisms in Taiwan river. Therefore, biological aspects of the sucker catfish, such as growth, oxygen consumption, ammonia excretion, water temperature tolerance, drought resistance, hunger effect, feeding habits, fecundity, and competition with other fish were studied. Because the junior catfish can tolerate low oxygen concentration of 0.35 mg/L at 25℃, survive droughting over 4 hours, stand against hunger more than 1 month. The adaptive capacity of this sucker catfish is extremely better than other fishes. When the food is scarce in the river, it can survive longer than other fish, especially for the bigger sized catfish. From the intestines of this fish, high proportion of organic debris and alga was found, but no small fish or shrimp. In Competing with golden carp, junior sucker catfish (6 g), was not able to compete up with it, but this is not the case in larger sucker catfish (16 g). Furthermore, sucker catfish can tolerate high concentration of many chemicals, except for Niclosamide, a chemical can be used as selective toxicant. It is thought the population of the sucker catfish will expand and invade into the upstream section in Taiwan river, with an impact on the endemic fish species of periphyton and bottom feeder fish. The present studies also collected some elimination methods of invasive aquatic species in the world for reference, including the aquatic plant (Eichhornia crassipes), African giant snail (Achatina filica), Apple snail (Pomacea canaliculata), Black striped mussel (Mytilopsis sallei), Zebra mussel(Dreissena polymorpha), American crayfish (Procambarus clarkii), Sea lamprey (Petromyzon marinus), Ruff (Gymnocephalus cernuus), and North snakehead (Channa argus). This study offers and suggests different reasonable methods for eliminating the sucker catfish and restocking the native species to maintain its original ecosystem. Finally, the mode for eradication of invasive species which needs more cooperation efforts from different parties such as fish importer, fish farmer, public, institution, news medium, is sophisticatedly set up.