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MARINFORSK-Marine ressurser og miljø

Harvesting lower trophic levels - Ecosystem effects and trade offs

Alternative title: Høsting på lavere trofisk nivå - økosystemeffekter og avveininger

Awarded: NOK 3.4 mill.

Project Manager:

Project Number:

234341

Application Type:

Project Period:

2014 - 2017

Location:

Partner countries:

Due to an increasing demand for raw materials for feed production, there is an increasing pressure to expand harvesting of zooplankton. Presently, harvest of krill in the Antarctic and a small-scale fishery of copepods along the Norwegian coast exist, but these fisheries are likely to be expanded in the future. Zooplankton plays a key role in the ecosystem as both grazers and prey, and thus acts as a link between phytoplankton and zooplanktivor fish. Given the expected desire to harvest more zooplankton, it is important to start building up our knowledgebase of how such harvest affects other parts of the. The overall goal for HALO was to quantify how harvesting of organisms at lower trophic levels will influence the dynamics of the ecosystem in the Norwegian Sea. The project used an ecosystem model to assess the feasibility of harvesting at lower trophic levels, as well as studying potential effects on higher trophic levels, with focus on the already commercially exploited fish stocks. In HALO, two new modules to an existing IMR ecosystem model was developed. One of the modules is on mesopelagic fish, and is made to resemble the Glacier Lanternfish, as this is the dominant species in the Norwegian Sea. The entire life cycle is modelled from eggs to adult individuals, and two-way coupled to the existing Calanus module. This means that the spatial distribution of copepods will affect food uptake rates for mesopelagic fish, as well as consumption of copepods from mesopelagic fish will affect the local densities of copepods. We are thus now in a position where we can study their predator - prey interactions. Temperature, light, water currents and zooplankton biomass is continuously input from the ecosystem model and used to calculate variables such as consumption, respiratory, reproductive, mortality and behavior of the mesopelagic fish. The second developed module is a "fishing boat module." In this module, catch of selected organisms are simulated based on information such as boat speed, fishing ports, freezing capacity, gear type, fuel consumption and other costs. The first simulation was set up to simulate todays fishing on Calanus and was presented at the ICES/PICES Zooplankton Production Symposium (Bergen, May 2016). Present harvest is relatively small and our simulations showed very little impact on the total population of Calanus or the Herring stock foraging on Calanus. The fishing boat module has also been used to simulate an up-scaled fishery and results from these simulations is used in the newly developed management plan for copepods. Continuing effort will be put on implementing an "optimal fishing boat", that has complete information about costs and distribution of the species to be fished. This will give us information about the maximum potential utilization of a resource. There will also be continued work on simulating a fishery on mesopelagic fish and the opportunities of such harvest (catch/cost/earnings).

Due to the growing need for raw material for fish feed production, there is an increasing pressure for extending harvest of zooplankton. At present there are fisheries for Calanus finmarchicus along the Norwegian coast and Antarctic krill (Euphausia super ba), but such fisheries are likely to be expanded in the near future. Zooplankton plays a key role in the ecosystem as both grazers and prey and thus acts as a link between the phytoplankton and planktivorous fish. Given the anticipated wish for an expans ion of zooplankton harvesting, it is important to start building up knowledge on how to assess the stocks and the effect such harvest may have on other parts of the ecosystem in general and on already harvested stocks in particular. The overall objectiv e of HALO is to quantify how harvest of lower trophic level organisms may affect ecosystem dynamics in the Norwegian Sea. The project will utilize an ecosystem model, NORWECOM.E2E, to assess the feasibility of harvesting species on lower trophic levels an d evaluate possible effects on higher trophic levels with special focus on already commercially exploited fish stocks. The NORWECOM model is spatial and allows for modelling both a spatially and temporal distributed fishery. It is therefore an ideal way o f studying possible geographical ecosystem effects of zooplankton harvest as well as evaluating periods where zooplankton harvest is particularly advantageous or disadvantageous. The model system will be extended with an mesopelagic fish module as well as a fishing vessel module.

Funding scheme:

MARINFORSK-Marine ressurser og miljø