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Fishing the ridge

Fisheries on the ridge: Prospects for fisheries on the seamounts, a russian study.

In the 60's-70's, large-scale fish scouting investigations were conducted by fishery researchers from the former Soviet Union around seamounts, in the world oceans.
The studies focused, in particular, on the biological resources around seamounts.(See map of known seamounts in the world's oceans.)

The results of 30 years of study show that there are concentrations of fishes around some seamounts, but that the difficult and complicated conditions of a seamount fishery, compared to comparable fisheries on the shelf or continental slopes, increases commercial risk for such a fishery.

Fish stocks around seamounts were found to be generally low. Large aggregations of fish were rarely seen in these areas. For the most part, each seamount needs to be considered individually as physical factors such as size, relief and depth, as well as water circulation patterns, vary for each seamount. The general biological productivity of each area varies also.

It is currently generally assumed that most fish species on the seamounts form local groupings. It is believed that these are resident groups and that these fish do not make long migrations. It is expected that the main stages of their life are restricted to just the one or perhaps several adjacent seamounts. Distribution variations and genetic exchange between the populations probably does occur, but only at early life stages due to passive drift of eggs and larvae. (Click for larger images of the fish and for their names.)

This assumption of local groupings has been confirmed by genetic studies with two common seamount species, the alfonsino and roundnose grenadier (Coryphaenoides rupestris).

This grenadier is a common species around the mid-Atlantic Ridge seamounts. It has also been indirectly demonstrated by the fact that areas that have been heavily fished have not re-stocked themselves. The highest catches were noted in the earliest years of the study. This underlines the vulnerability of these populations.

Researchers believe that this is particularly true for deepwater species with a retarded maturation and low fecundity.

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