Harvesting the mesopelagics - ecological and management implications
Informations
- Funding country
Norway- Acronym
- -
- URL
- -
- Start date
- 1/1/2018
- End date
- 12/31/2021
- Budget
- 967,026 EUR
Fundings
| Name | Role | Start | End | Amount |
|---|---|---|---|---|
| Marine Resources and the Environment (MARINFORSK) - call 2016 | Grant | - | - | 967,026 EUR |
Abstract
The main aim of HARMES was to increase the knowledge about mesopelagic organism abundance, diversity and ecological roles, thereby facilitating the management of a potential fishery and add to the overall management of the oceans. Several regions of the North Atlantic have been studied and major differences in physical structure, nutrient content, phytoplankton bloom dynamics have been revealed leading to phenological differences at higher trophic levels. Mesopelagic biomass and vertical distribution were very different among regions, probably related to epipelagic productivity and light regimes also governing active carbon vertical flux. Over the course of the project we concluded that abundance estimation of the mesopelagics was best done with submersed acoustics and echo-counting. The method has been published in peer reviewed journals. One uncertainty with the method is avoidance of the acoustic platform at depth, which we are now working to quantify. New developments of non-graded trawls have been used to improve abundance and biomass estimates of mesopelagic organisms and their size and weight. It is shown that the use of traditional pelagic trawls results in highly skewed size and weight distributions as well as biomass estimates. We have also been working with new optical methods to obtain vertical distributions from trawl samples. This has proven difficult due to organisms not being transported continuously to the back of the trawl, and we are still working on that. The model, NoBa Atlantis, was used to explore the combined effect of climate and fisheries. In these simulations, a harvest of the mesopelagic layer, both fish and zooplankton, were initiated using a fishing mortality at the maximum sustainable yield. The resulting mortality of mesopelagic fish might be on the lower side (F=0.15) and will be further investigated in future projects.