Abundance & Distribution Discovery

New information on the distribution of deepwater grenadiers along the Mid-Atlantic Ridge raises questions about spawning and recruitment and could have implications for management of commercially important species.

Species of the family Macrouridae, the grenadiers, are widespread throughout the deep ocean environments of the world from the continental slopes to the abyssal plains. These distant relatives of cod are relatively common in some deep ocean environments and may even hold dominant roles in these ecosystems. As important members of bottom-dwelling fish communities along the Mid-Atlantic Ridge, grenadiers are some of the most abundant demersal fishes in the deep North Atlantic Ocean. Some species such as the roundnose grenadier (Coryphaenoides rupestris) are even important targets in commercial fisheries.

Research conducted by the Mid-Atlantic Ridge Ecosystem (MAR-ECO) project of the Census of Marine Life has now suggested that we know too little about these widespread, and in some cases relatively common, fish. Observations with manned submersibles, Remotely Operated Vehicles, and autonomous baited landers with cameras showed that grenadiers were present at all depths along the Mid-Atlantic Ridge. Trawl surveys conducted at depths ranging from 985 to 3461 m collected numerous species from up to 9 genera. Analysis of these specimens and the data associated with their collection has revealed that their distribution is likely structured by depth and, in some cases, latitude. However, despite this information, some characteristics of these fish remain unclear.

For instance, it is known that most grenadier species produce free-floating eggs and that their juvenile stages are mesopelagic. This raises the question of how recruitment to the Mid-Atlantic Ridge functions and how these eggs and juveniles are not swept away from the ridge by currents. Understanding these key issues associated with their life cycle is critical to managing those grenadier species that are targeted by fisheries. The roundnose grenadier has been fished consistently by large industrial trawlers along the Mid-Atlantic Ridge since the 1970s. This calls into question the success of management endeavors in light of the lack of understanding about their life-cycle.

This research has brought to light how little we may know about these fish species despite the fact that they are fairly common in the world's deep oceans. Because they are important ecosystem components and, in some cases, important fisheries products, concern for their conservation has been expressed by the International Council for the Exploration of the Sea. As a result, the North East Atlantic Fisheries Commission has introduced precautionary measures to control harvest of grenadier stocks until more information is available.



What: New information on the distribution of deepwater grenadiers along the Mid-Atlantic Ridge raises questions about spawning and recruitment and could have implications for management of commercially important species.
Who: MAR-ECO Scientists --> O.A. Bergstad, A.S. Hoines, A. Orlov, T. Iwamoto, J. Galbraith, I. Byrkjedal, and F. Uiblein
When: 2004
Where: Mid-Atlantic Ridge, North East Atlantic Ocean
How: Specimens collected via bottom trawl at depths ranging from 985 to 3461 m.
Reference: These results have not yet been published.

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