Adaptation Actions for a Changing Arctic: Perspectives from the Barents Area

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Adaptation Actions for a Changing Arctic: Perspectives from the Barents Area

4500 Catch, thousand tonnes

Saithe Herring Shrimp Greenland halibut Haddock Redfish Polar cod Atlantic cod Capelin

3750

3000

2250

1500

750

0

1965

1970

1975

1980

1985

1990

1995

2000

2005

2010

Figure 2.8 Total catches of the most important fish stocks in the Barents Sea since the mid-1960s. The data include catches in all ICES areas: I, IIb and IIa (i.e. along the Norwegian seas and the Norwegian coast south to 62°N). Redfish refers to Sebastes mentella (ICES, 2014a).

productivity and infaunal abundances are significantly lower than in open-water areas south of the Polar Front, while the numbers of taxa present are similar (Cochrane et al., 2009). Epifauna biomass (mostly brittle stars, sponges, shrimps) is over five times greater in the north-eastern Barents Sea influenced by ArcticWater than at stations in Atlantic-Water influenced regions, with the exception of areas in the south- western Barents Sea where sponge fields dominated by a large biomass of Geodia-sponges prevail (Jørgensen et al., 2015) . Areas in the southwest, the central Barents Sea and north of 80°N have a high biomass of species easily taken by bottom trawls (Jørgensen et al., 2016), including large-bodied Arctic species such as seapens and cephalopods, sponges and ophiuriods (Jørgensen et al., 2015). In the Pechora Sea, despite its southerly location,Arctic species are common in its northern parts, which are influenced by cold-water currents. Boreal species predominate in areas of the Pechora Sea that are affected by warmer coastal waters, showing that this area functions as a transitional zone between the boreal and Arctic biogeographic regions (Denisenko et al., 2003). Temperature (Lüning, 1990) and substrate characteristics (Saher et al., 2012) are important in the distribution of benthic algae, and areas exposed to the mechanical effects of sea ice or icebergs are generally devoid of macroalgae (Gutt, 2001; Wulff et al., 2011). Marked changes in surface salinity due to melting of sea ice and freshwater input from rivers have affected algae distribution, and an abrupt increase in macroalgal presence has been recorded in Arctic fjords together with changes in the abundance of benthos that are thought to be indicative of a climate-driven ecological regime shift (Kortsch et al., 2012).

appears to be determined bymore old and large cod in the stock and the northward shift in the distribution of capelin following its recovery to high abundance (2008–2013). Such trends have been seen in the past; both the cod and herring stocks increased significantly between 1920 and 1940 when water temperatures increased (Toresen andØstvedt,2000;Hylen,2002).This increase in stock size was probably an effect of enhanced recruitment, because catches also increased over this period. The northern expansion of cod is a prime example of the‘borealization’ of the Barents Sea ecosystem. Haddock has also recently reached a historic high in abundance and has increased its distribution range over the past few decades (1950–2013; Mehl et al., 2013; McBride et al., 2014). This is related to large stocks, an increasing proportion of large individuals in the stocks and higher water temperatures, similar to the situation for Atlantic cod. 2.2.2.3 Benthos More than 90% of the invertebrates in the Arctic belong to the benthic community (Sirenko, 2001; Gradinger et al., 2010). Animals that live on (epifauna) or in (infauna) the sediments are collectively referred to as benthos.Most species of benthos are largely stationary.The composition of the bottom fauna of a region reflects prevailing environmental conditions including large-scale oceanography (Carroll et al., 2008; Cochrane et al., 2009, Jørgensen et al., 2015). For example, infauna (mostly worms and bivalves) density and species richness in the Barents Sea area are 86% and 44% greater at stations near the Polar Front than at stations in either Atlantic- or Arctic- dominated water masses (Carroll et al., 2008). InArcticWater north of the Polar Front, sea ice suppresses water column