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Demersal Nekton

Demersal nekton are mobile animal species living near or on the seabed. Most species are widely distributed across the Atlantic. With different shapes and sizes, they have fascinating life histories and ecological adaptations. Some species, primarily fishes, are being harvested by deep-sea trawlers and longliners. However, most of the species have life history features that are incompatible with high exploitation rates.

  • Many are long-lived. (Some, such as the orange roughy, may live to be over a hundred years old, perhaps even more than 150 years)
  • Most deep-sea species mature late and have low fecundities; hence their reproductive capacity is limited
  • Growth rates tend to be slow and natural mortalities low

Much more information about deep-sea species is needed before researchers assume an advisory role for the management of deep-sea fisheries resources. Specific questions include: 

  • Do the members of given species inhabit different habitats at different ages?
  • Do fish seek out specific topographical features (near to currents, in the lee of geographic features etc)? 
  • What kinds of communities exist in areas of soft or hard bottoms? Are there latitudinal differences?

Aims

1. Analyse and describe demersal fish species composition in the three MAR-ECO Sub-areas, and provide material and supplementary data on any new species or new records.
2. Map and model species distributions, and compare these with patterns in adjacent areas of the North Atlantic.
3. Compare assemblage structure among different areas, including also
information from scattered seamounts and continental slopes on either
side of the MAR.
4. Relate the observed patterns to physical features, such as bathymetry and hydrography.

Hypotheses

  • On the basin-wide scale, the MAR has a fish fauna that is not a simple extension of that found on adjacent continental slopes.
  • At the scale of the ridge itself, climatically-induced latitudinal patterns in surface productivity may lead to latitudinal patterns in fish assemblage structure parallelling those along the continental slopes.
  •  At the scale of meso- or microhabitats, topography has the strongest effects on fish co-occurrence patterns, diversity, and abundance.

Strategy

Acoustic corridor and transect sampling in the three MAR-ECO Sub-areas, and also lander observations and submersible observations.

Technology

  • Hydroacoustics (using hull, vehicle and lander-mounted transducers, also multi-beam for habitat mapping).
  • Remotely Operated and Autonomous Vehicles (ROV "Aglantha", AUV "Hugin"), benthic landers.
  • Manned submersibles MIR1 and 2.
  • Depth stratified bottom trawl sampling, and sampling with static gears (longline, traps, trammel nets).

Schedule

Preparation of field work: 2002-2003, Sampling and observation at sea: 2003-2005, Analysis and dissemination, and provision of data to OBIS: 2005-2008.

Commitments

Ship-time on Icelandic, Russian and Norwegian vessels in 2003-2004, MIR submersible dives 2003, OASIS Project activities at Sedlo Seamount, IMR Norway internal gear grant, labour and other costs.

Partners

Principal investigators: Franz Uiblein (Austria), Ingvar Huse (Norway)

J. Galbraith (USA), Gui Menezes, Manuel Biscoito (Portugal), Sergio Iglesias, Pablo Duran Muñoz (Spain), Pascal Lorance, Sami Souissi (France), John D. M. Gordon, Monty Priede (UK), Maurice Clarke (Ireland), Peter Rask Møller (Denmark), Jakup Reinert, Eydfinn Magnusson (Faroe Islands), Thorsteinn Sigurdsson (Iceland), Odd Aksel Bergstad, Agnes Gundersen, Inge Fossen, Aage Hoines, Kristin Helle, Ingvar Byrkjedal (Norway), Uwe Piatkowski (Germany), Jerzy Janusch (Poland), Vladimir Vinnichenko, Andrey Dolgov, Alexei Orlov, Efim Gerber, Yuri Shcherbachev (Russia).

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