NM21 Occurrence of warm water species in fish stocks exploited by Scottish fisherman

Fishing is a commercially important activity within the UK employing more than 12,000 people and with a first-sale value in excess of £800 million in 2011 alone (Pinnegar et al, 2013). The industry is particularly important in Scotland and although it only contributes 0.39% to the GDP of the country, in some regions fishing is the mainstay of employment (Pinnegar et al, 2013) and about 60% of the UKs commercial marine fish is landed in Scotland (MCCIP, 2012).

In the past 30 years the average sea surface temperature (SST) has risen in the North Atlantic, with 2000 - 2009 being the warmest on record (IPCC, 2013). The most recent warming can be seen at more local scales in Scottish records for offshore temperature monitoring stations. Pinnegar et al (2013) identified key warm water species appearing in UK waters. The proposed indicator will monitor the appearance and increase in abundance of these potentially exploitable warm water fish species in Scottish waters. It will use data records arising from research surveys rather than commercial landings data, which can be biased by quotas and industry market forces. Significant shifts in the distribution and an associated increase in abundance of these warm water species could lead to Scottish fisherman adapting their practice and exploiting these new resources.

Related indicators:

NM1 Changes in average sea surface temperature (SST)

Squid (Loligo forbesi) is thought to respond to climate change (Hastie et al, 2009a) and is showing an increase in abundance in Scottish waters with an increasing number of fisherman targeting this species (Hastie et al, 2009b) (Figure 1). The European anchovy (Engraulis encrasicolus) has also increased in abundance in Scottish waters and it is thought this is in response to climate change (Beare et al, 2004). Research surveys have shown the anchovy numbers to be variable in recent years (Figure 1). The anchovy is starting to be targeted by some UK vessels (Pinnegar et al 2013).

Figure 1 Average catch per unit effort (CPUE, per hour of trawl) for the European anchovy (Engraulis encrasicolus) and squid (Loligo forbesi) in the Northern North Sea Area (east coast of Scotland) (data taken from the ICES NS-IBTS areas 1,2 and 3).

Other examples of new and expanding fish species with the potential for exploitation are the red mullet (Mullus surmuletus), John Dory (Zeus faber) and sea bass (Dicentrarchus labrax). These species have shown an increase in occurrence in southern UK waters with occasional records of sea bass in Scottish waters (Figure 2). Commercial fishermen in the UK are already beginning to respond to opportunities as new exploitable fish species appear in their regions stocks. We are already seeing warm water fish species appearing in Scottish waters with other species that are present in southern UK waters likely to appear and increase in abundance in the near future.

Figure 2 Average catch per unit effort (CPUE, per hour of trawl) for the red mullet (Mullus surmuletus), John Dory (Zeus faber) and sea bass (Dicentrarchus labrax) in the Northern North Sea Area (east coast of Scotland) (data taken from the ICES NS-IBTS areas 1,2 and 3).

Changes in fish distribution exhibit a strong link to long-term changes in temperature (Pinnegar et al, 2013). Simpson et al (2011) showed that 70% of the most abundant fish species in the UK and Ireland changed their distribution in response to climate and oceanic warming. In general, the currently exploited cold water, large bodied fish species have decreased in abundance in UK waters while some smaller bodied warm water species (such as those discussed in this indicator) have increased (Pinnegar et al, 2013). Analyses of long term datasets have shown exploited species such as cod, haddock, plaice and sole as well as non-exploited species have all shifted their North Sea distributions noticeably over the last 25 years (Perry et al, 2005; Dulvy et al, 2008).

Further temperature rises in UK waters are likely to have significant effects on fish distributions and impact commercial fisheries (Perry et al, 2005; Dulvy et al, 2008). Considerable progress has been made in recent years to make future projections for fisheries which make use of very complex ecosystem and fish distribution models. These models incorporate many elements, including not only climate models but fish physiology and food availability. However, there remains little consensus on the most appropriate methodology to use in different circumstances and the precise nature of the changes in the distribution of particular fish species is unclear (Pinnegar et al, 2013). In general, the models suggest that some of the currently exploited cold water fish species are expected to decrease in abundance in UK waters while some warm water species, like those listed above, are expected to increase. It is predicted that the fishing grounds for cod will become increasingly more remote, red mullet and plaice will become more readily available and there will be a continued increase in the anchovy and sea bass populations (MCCIP, 2012).

As the research on modelling future projections for fisheries has shown, the patterns of change are complex and species specific (Pinnegar et al, 2013).

MCCIP Report Cards and Scientific Reports - http://www.mccip.org.uk/annual-report-card/2013.aspx