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   Alosa pseudoharengus (魚類) English 
生態 分佈 管理 影響 參考資料 聯繫


         一般影響

    在五大湖區勞倫森,灰西鯡的入侵已經導致一些魚類的豐度減少,例如翡翠夏納魚(Notropis atherinoides),黃鱸(Perca flavescens),深水杜父魚(Myoxocephalus thompsoni)和江鱈(Lota lota)。灰西鯡被懷疑會阻礙這些魚類繁殖,很可能會捕食其魚苗(Chuck Madenjian pers.comm, 2004)。
    佛蒙特州環境保護署(VTDEC, 2002)報告了多種影響。灰西鯡是非常有效率的浮游動物捕食者。他們會選擇性地吃較大的物種和一個物種中較大的個體,劇烈地改變浮游動物的大小,數量和群落結構。灰西鯡會與其他魚類競爭食物,進而將之競逐。灰西鯡會和其他吃浮游動物的魚類直接競爭,包括黃鱸(Perca flavescens)和彩虹胡瓜魚(Osmerus mordax),也會和許多食魚物種的幼魚競爭,如鱸魚等生命階段初期需依賴浮游動物的物種。灰西鯡會吃其他魚類的卵和幼體。灰西鯡會捕食黃鱸魚和湖鱒(Salvelinus namaycush)的幼體,似乎是造成這些物種死亡的一個重要原因。灰西鯡是導致陸封的大西洋鮭魚(Salmo salar)和湖鱒繁殖失敗的主要的原因。
    灰西鯡會有週期性的大量死亡。事件發生時,大量死亡的灰西鯡沖到海灘上,造成惡臭和公共健康問題。灰西鯡大量死亡後,任何利用灰西鯡族群作為主要食物來源的魚類,將難以找到足夠的食物。這將導致生長率下降,減少垂釣魚類族群。陸封的灰西鯡,硫胺酶量很高,主要吃灰西鯡的大西洋鮭魚和湖鱒,生產的卵會缺乏硫胺素,因而導致魚苗高死亡率(O’Gorman 和Stewart 1999)。



         地點特有的影響:
    Otsego Lake (United States (USA)) English 
    改變演化模式: Changes have taken place in Otsego Lake from the 1930s to present, at the trophic level. Prior to the introduction of the alewife in 1986 cisco (Coregonus artedi) was the dominant planktivore. Different patterns are observed in the pelagic flora and fauna under these two dominant planktivore populations. When cisco were the primary planktivores, claDOCeran size and biomass was significantly greater in the epilimnion (primarily Daphnia pulex) than in the hypolimnion (primarily Bosmina coregoni). Phytoplankton were dominated by net and large nannoplankton (>0.03mm), with cyanobacteria uncommon until late summer. Since alewife have dominated, Daphnia have become rare. Mean claDOCeran size in the epilimnion and hypolimnion (essentially all Bosmina) is much more uniform and reduced from prior size distributions. Phytoplankton abundance and mean summer chlorophyll has increased. The dominant algae are now smaller nannoplankton (<0.03mm) and cyanobacteria.

    改變自然底棲生物群落: Changes in Otsego Lake also include an increase in lake trout (Salvelinus namycush) and a decline in whitefish (Coregonus clupeaformis) and cisco numbers. The authors state that these changes have occurred in spite of significant efforts to reduce non-point source nutrient loading to the lake.
    Great Lakes (USA) (United States (USA)) English 
    捕食: Predates on the larval stages of Salvelinus namaycush and also causes diet mediated thiamine deficiency in larval stages of the lake trout causing death.



ISSG Landcare Research NBII IUCN University of Auckland