Ecology of the oceanic rim: pelagic eels as key ecosystem components

摘要

Although 92 % of the total volume of the world's oceans occurs below a depth of 200 m, our understanding of deep-sea food webs lags far behind that of continental shelves. In particular, little is known about the exchange of biomass at the interface of continental margins and deep-sea ecosystems. Recent studies suggest that the transport of organic matter from continental shelves may influence deep-sea ecosystems more than previously thought. Here, we present results of a pelagic nekton survey along the southern slope of Georges Bank, NW Atlantic, a transition area between coastal and deep-sea environments. Specimens were collected as part of the Census of Marine Life program Gulf of Maine Area project. Macrocrustacea (primarily sergestid shrimps and large euphausiids) dominated the total nekton (all taxa) numbers and biomass. Of the 85 deep-pelagic fish species collected during this cruise, the slender snipe eel Nemichthys scolopaceus (Anguilliformes: Nemichthyidae) ranked first in biomass and second in abundance. Microscopic analysis of N. scolopaceus gut contents revealed a predominance of large euphausiid and decapod prey. Other abundant potential prey, such as zooplankton, fish, and cephalopods, were absent from the diet, suggesting discriminatory feeding. Considering the relative biomass dominance of sergestid shrimps, large euphausiids, and pelagic eels in this system, the ecological interaction described here likely represents a major trophic pathway in this and similar 'oceanic rim' ecosystems.