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Deep Water Surveys

rabbit fishThe recent Scottish deep-water fishery prompted Marine Scotland Science to undertake a new type of survey dedicated to deep-water species. MRV Scotia has now conducted three bi-annual surveys along the slope and shelf edge to the west of Scotland. The results of these surveys will form a new time series of data that will allow us to identify long-term trends.

Special Considerations for Deep-Water Surveys

The extreme environment requires special considerations for surveys:

  • The depth (and pressure) involved requires the fishing gear to be much larger and heavier than gear deployed on the continental shelf
  • Floats have to be specially strengthened to prevent implosion
  • Since deep-water species are depth dependent, hauls have to be made at a variety of different depths in order to sample the stocks currently being fished. The nature of the bottom slope along the shelf edge means five nautical miles on the surface may cover a shelf gradient of 1,000 metres

What the Surveys Tell Us

  • The survey time series being developed is not yet long enough to produce definitive results on the impact of the deep-water fishery but we do already know more about the fragile community in which these species exist. The surveys regularly catch more than 130 different species, as opposed to around 50 different species from surveys on the continental shelf. Scientists at Marine Scotland are beginning to understand some of the complex biology of these fish.