International Management of Pelagic Fisheries in the Northeast Atlantic

Ekerhovd og Kvamsdal(2014) er vidareføring av Ekerhovd og Kvamsdal (2013) der ein estimerte parametra til ein modifisert logistisk økosystemmodell for dei pelagiske fiskebestandane i Norskehavet (Norsk vårgytande sild, makrell og kolmule) med Ensemble Kalman Filter. Sjølv om modellen inneheld relative få parametre gjer vi i Ekerhovd og Kvamsdal (2014) ytterlegare metodologiske grep for å handsame multidimenesjonaliteten i modellen. Den beste tilnærminga ser ut til å fange opp mykje av den observerte dynamikken i systemet samstundes som omfanget av estimerte modellfeil er moderate. Målsetjing til Ekerhovd og Steinshamn (2014) har vore å maksimere den diskonterte netto profitten frå dei pelagiske fiskeria om tala i Ekerhovd og Kvamsdal (2014) ved hjelp av ein aggregert tre-bestands bioøkonomisk modell. Eit viktigresultat er at profitten kunne vore opptil 30 % høgare om fiskebestandane hadde vorte optimalt forvalta i eit fleir-bestandsperspektiv.

The purpose of this project is to investigate what kind of sharing agreement could be robust to the kind of changes in stock migrations as we have seen in the past. We intend to model this as a multispecies fishery including herring, mackerel and blue whi ting in the Northeast Atlantic. There are three reasons for this. First, there are indications that the abundances of these stocks are related, where an increasing abundance of one stock can have negative effects on the other stock due to interspecific co mpetition for food. Second, there is reason to believe that a more robust agreement could be attained if it encompasses all the three species involved, as one nation that at a certain time might be disadvantaged in terms of one species could be better end owed with respect to another. Agreements that might seem unfair and disadvantageous with respect to one species only could be more favourable when several species or stocks are considered jointly. Third, there are economic or fleet interactions, as each f leet harvests all species to some degree. We will develop a model which takes the migratory dimension into account. Further, we will do this by applying a seasonal approach, where a share of each stock is located in a given EEZ or the high seas in each s eason. These shares will be modelled as variable over time, to take into account the variability in migratory behaviour. To some extent this variability in migratory behaviour is likely to be stochastic, but we will also investigate whether it depends on abundance or whether there are long term decadal trends in migratory behaviour related to environmental variables such as ocean temperature and salinity. We will employ game theory to find feasible solutions to the sharing problem and investigate the sta bility of possible coalitions between the individual nations (the EU, the Faroe Islands, Iceland, Russia and Norway). We will model all three species involved and also take into account possible changes over time.