Research press release


Nature Communications

Ecology: Fishing disrupts crucial flow of nutrients in coral reefs



今回、Jacob Allgeierたちは、カリブ海において、漁獲圧が高く、その結果として大型の捕食魚類が減り、小型魚類が大部分を占めるようになったサンゴ礁と漁獲が禁止された海洋保護区にあり魚類群集が比較的無傷で残っているサンゴ礁の合計43か所をサンプルとして、魚類群集の栄養素貯蔵能力を調べた。その結果、体長の多様性が大きく、より上位の捕食魚の多い魚類群集で栄養素貯蔵能力(貯蔵能力と排出能力の組み合わせ)が高くなることが明らかになった。さらに栄養素貯蔵能力は、漁獲量の多いサンゴ礁の方が禁漁区のサンゴ礁より約40~46%低く、サンゴ礁付近の人口密度が高くなるにつれて低下した。


When humans remove fish - especially those higher on the food chain - from coral reefs, the key ecosystem-sustaining nutrients cycled by these fish are reduced by half. These results, published in Nature Communications this week, shed light on the costs of over-fishing not only for fish communities, but also for the ecosystem services that fish provide.

In coral reef ecosystems, fish act as an important ‘reservoir’ of nutrients, which could be lost when fish are removed from the system through fishing. Yet it has been unclear whether this effect might be driven by a loss of biomass, or instead by changes in fish community structure.

Jacob Allgeier and colleagues studied the capacity of fish communities to store nutrients across a sample of 43 coral reefs in the Caribbean. Some sites experienced intense fishing pressure (resulting in loss of large predatory fish and dominance of small-bodied fish) while other sites were located within marine reserves with prohibited fishing (resulting in relatively intact fish communities). The authors find that nutrient capacity (a combination of storage and excretion) is higher in communities of fish with a wider range of body sizes and with higher-level predators. Further, nutrient capacity was approximately 40-46% lower at heavily-fished reefs than those protected from fishing, and it declined with increasing human population density in the vicinity of the reef.

The results suggest that, in terms of their contribution to the flow of nutrients, not all species are equal; the loss of nutrient cycling after fishing is driven mostly by the selective removal of large, predatory fish species.

doi: 10.1038/ncomms12461

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