Sato Nobuhiko N, Kokubun Nobuo, Yamamoto Takashi, Watanuki Yutaka, Kitaysky Alexander S, Takahashi Akinori
Department of Polar Science, SOKENDAI (The Graduate University for Advanced Studies), Tokyo, Japan
Department of Polar Science, SOKENDAI (The Graduate University for Advanced Studies), Tokyo, Japan National Institute of Polar Research, Tokyo, Japan.
Biol Lett. 2015 Aug;11(8). doi: 10.1098/rsbl.2015.0358.
High levels of jellyfish biomass have been reported in marine ecosystems around the world, but understanding of their ecological role remains in its infancy. Jellyfish are generally thought to have indirect negative impacts on higher trophic-level predators, through changes in lower trophic pathways. However, high densities of jellyfish in the water column may affect the foraging behaviour of marine predators more directly, and the effects may not always be negative. Here, we present novel observations of a diving seabird, the thick-billed murre, feeding on fish aggregating among the long tentacles of large jellyfish, by using small video loggers attached to the birds. We show that the birds encountered large jellyfish, Chrysaora melanaster, during most of their dives, commonly fed on fish associated with jellyfish, and appeared to specifically target jellyfish with a high number of fish aggregating in their tentacles, suggesting the use of jellyfish may provide significant energetic benefits to foraging murres. We conclude that jellyfish provide feeding opportunities for diving seabirds by concentrating forage fish, and that the impacts of jellyfish on marine ecosystems are more complex than previously anticipated and may be beneficial to seabirds.
世界各地的海洋生态系统中都有关于水母生物量水平较高的报道，但对其生态作用的了解仍处于起步阶段。一般认为，水母会通过低营养级途径的变化对高营养级捕食者产生间接负面影响。然而，水柱中高密度的水母可能会更直接地影响海洋捕食者的觅食行为，而且这种影响不一定总是负面的。在这里，我们通过给鸟类佩戴小型视频记录仪，展示了一种潜水海鸟——厚嘴海鸦捕食聚集在大型水母长触须间鱼类的新观察结果。我们发现，这些鸟类在大多数潜水过程中都会遇到大型水母——黑色海月水母，它们通常以与水母相关的鱼类为食，并且似乎特别瞄准触须中有大量鱼类聚集的水母，这表明利用水母可能为觅食的厚嘴海鸦提供显著的能量益处。我们得出结论，水母通过聚集饵料鱼为潜水海鸟提供了觅食机会，而且水母对海洋生态系统的影响比之前预期的更为复杂，可能对海鸟有益。
