Abstract
Due to the important role of Calanus finmarchicus as key prey for the abundant pelagic fish stocks (Northeast Atlantic mackerel, Norwegian spring spawning herring, blue whiting) in the Norwegian Sea, an increase in the quota of C. finmarchicus has raised public concern. Here, 2 vessel types were implemented in an individual-based model within the NORWECOM.E2E ecosystem model, one ordinary vessel similar to the vessels used in the real fishery, the other with perfect knowledge of the C. finmarchicus distribution to account for possible future development of the fishery. The perfect vessels were free to move among all grid cells, whereas the other vessel type was restricted. Differences between the vessel types were large in terms of catch per unit effort and hotspots for catches. Operating with 10 perfect vessels, the catches were on average 54000 t yr-1, almost 3 times higher than for the ordinary vessels. Increasing to 60 perfect vessels, catches increased to 349000 t yr-1. The vessels with full knowledge of distribution and concentration located new hotspots distant from the traditional fishing grounds. Due to area restrictions in the current quota, allowing only 3000 t caught within the 1000 m depth contour, the perfect vessels shifted their activity offshore. In the simulated ecosystem, no ecosystem effects were found, neither on the C. finmarchicus biomass nor on the Norwegian spring spawning herring biomass. This finding indicates that the proposed quota of C. finmarchicus supports a sustainable fishery.
Highlights
The demand for marine oils from the aquaculture and human health industries is rising (FAO 2020)
We investigate the effects of the harvest patterns, number of vessels, fishery efficiency and potential ecosystem impact under different ecological conditions for a selected period (1995−1999), with the aim of exploring the sustainability of a C. finmarchicus fishery in the Norwegian Sea
When applying the Morris screening method on the model including 11 parameters, among them concentration of Calanus finmarchicus and distance from fishing grounds, catch price turned out to have the largest impact, whereas the concentration of C. finmarchicus resulted in the highest variability (Fig. 4, green dots)
Summary
The demand for marine oils from the aquaculture and human health industries is rising (FAO 2020). A sufficient annual increase in fisheries catches to produce fishmeal and fish oil is challenging within a conventional harvesting regime, as the majority of the world’s fish stocks are fished at or above sustainable levels (FAO 2020). This situation has led to a growing interest in increased harvest of zooplankton. The krill stock in the Southern Ocean has been harvested for decades, managed by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). The division of the quota, with a more restricted fishery close to shore, aims to limit unwanted bycatch of fish eggs and larvae
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