More than 330 fish species inhabit the seas surrounding the British Isles. For Charting Progress 2 we have assessed three aspects of this fish community, ranging from the species commonly found in coastal waters and estuaries to those in the deep sea.

We have provided assessments of the following. First, the demersal (bottom-living) fish community which includes both commercial and non-commercial species, using data from scientific demersal trawl surveys (trawls on the seabed), usually over a systematic grid of stations. Second, transitional and estuarine fish, which includes those marine fish that tend to be found in lower salinity water, particularly in their juvenile stage and ‘transitional’ or ‘diadromous’ fish that migrate between marine and freshwater, such as salmon, eels, sturgeonand lamprey. The data used for this category are more piecemeal and the analysis is based on community information (e.g. diversity of fish species in estuaries) as well as numbers of salmon and eels counted returning to rivers. Finally, for completeness, we have also included the assessment in Chapter 5 carried out by the Productive Seas Evidence Group which focuses on assessed commercial species and the proportion of these that are either not at full reproductive capacity and/or not being harvested sustainably. This assessment consists of an analysis of the number of stocks exploited sustainably within each region. The data for this come from commercial catch statistics, via complex fish stock assessment models.

Although these assessments include many of the 330 fish species found in the UK seas, there are notable gaps. For example, for fish associated with rocky habitats, deep sea fish and open water pelagic fish such as sharks or tuna.

The demersal fish assessment compares status within the community or population, to that of 10 to 25 years ago, when rigorous monitoring programmes were generally established. However, this chapter also refers to a wider discussion of status in relation to historic baselines covered in more detail in the Feeder Report prepared by the Healthy and Biologically Diverse Seas Evidence Group, and in particular how current populations compare to those that existed 100 years ago.

We have made a detailed quantitative assessment for each region, using fish surveys from institutes in England, Scotland, Wales and Northern Ireland as well as in France and the Netherlands. We have constructed time series for 15 community and ecosystem indicators, to assess changes over the past 20 years, and particularly since Charting Progress was published in 2005. This is the most comprehensive assessment ever performed for fish communities in the UK. We have also supplemented this assessment with existing data on the status of fish communities in estuaries and transitional waters.

Since Charting Progress many new sources of data have emerged. In particular, there are now regular monitoring programmes for deep-water fish assemblages off the west of Scotland and around Rockall; new initiatives to involve commercial and recreational fishermen in data collection; and programmes to collate information from members of the public, to capture incidences and occurrences of rare and unusual fish around the UK that are otherwise difficult for fisheries agencies to monitor. The diversity and overall abundance of soft-bottom demersal fish have improved appreciably in most regions over the past five years. This probably reflects reduced fishing, although life history traits such as average size and age-at-maturity typically show little or no change, and seem to respond more slowly to reductions in human pressures.

The Fisheries section in Chapter 5, suggests that this reduction in pressure has been largely associated with a combination of EU controls on total allowable catches and the large-scale decommissioning of fishing vessels in the UK. The UK whitefish (demersal trawl) fleet was reduced in size by around 15% by the two decommissioning schemes in 2001 and 2003. The condition of many estuaries has improved in recent years because of higher levels of urban waste water treatment and reductions in the input of hazardous substances. A gradual increase in fish diversity and overall numbers in estuaries has been linked to better conditions. As a result, the number of adult salmon and sea trout returning to rivers has increased on many rivers, although there have been declines in the River Thames where they were previously re-stocked, Rivers Awe and Morar in western Scotland and the Bush in Northern Ireland.

The number of European eel juveniles has fallen in many of the regions where this species occurs as has the abundance of yellow or silver eels, and this reflects an Atlantic-wide downturn in the numbers of elvers returning to rivers. Causes of this decline are unclear but suggestions include changes in oceanic conditions, overexploitation, freshwater habitat destruction, contaminants and introduction of the parasite Anguillicola crassus from Asia.

Although the general situation for most estuarine and marine fish communities seems to have improved in recent years, the prospects of certain vulnerable fishes have continued to deteriorate. This includes many deep-water fish species; sharks, rays and skates; and transitional/ diadromous species that move between fresh and salt water, such as the European eel and sturgeon. Many of these fish are listed as requiring protection under appropriate legislation. Recent improvements in the status of fish communities need to be considered within a longer historical context since the populations of many species remain severely depleted compared to those of 50 or 100 years ago. To place current values into a longer historic context, we have used the limited data that exist for earlier periods. This suggests that fish are smaller on average than before but that species diversity may have increased in some regions, compared to historic times.

Commercial fisheries continue to exert a significant pressure on target and nontarget fish populations, both directly through fishery removals, and indirectly by removing predators, prey, competitors or essential habitats. There are other pressures which may have an impact on fish, including the impact of new offshore infrastructure; the release of endocrine-disrupting substances from sewage works; pesticides and plastics manufacturing; the extraction of sand and gravel; the loss of coastal habitats; and the extraction of water or alteration of river flows in estuaries.

Climate change is beginning to have a detectable impact on fish populations, with marked changes in distribution, the timing of migration, overall reproductive output (recruitment) and growth rates.

The mix of species present in each region has changed appreciably over the past 50 to 100 years and predictions suggest that a very different assemblage of fishes might exist in UK waters in years to come.

Warm-water fishes such as red-mullet, seabass, anchovy and John Dory are spreading rapidly around the UK, whereas cold-water species such as cod have retreated northwards in recent years. Such distribution shifts will have profound consequences for commercial fisheries and for the achievement of stated conservation objectives.

In the UK we consume an average of 23.6 kg of fish products per person per year, and predictions based on consumer preferences and trade projections have suggested that this will continue to be the case for the foreseeable future. The UK human population is however, anticipated to rise from 61 million to 78 million by 2050. This equates to a total UK demand for fish products of 1.8 million tonnes compared to 1.4 million tonnes today and aquaculture in the UK is increasing to meet this demand. It is clear that indigenous and global fish resources will come under increasing pressure in the future.

After more than 100 years of intensive fisheries research in the UK, we know a lot about fish. However, much of the analysis has focussed on soft-bottom demersal species; trends with respect to estuarine, coastal, deepwater and migratory species are much more uncertain and we need to interpret these trends with care.

To improve our assessment there is a need for research into the state of open-water mesopelagic species, fishes that occupy rocky habitats and some diadromous species – notably lampreys, sturgeon and shads.

We also need to understand the causes of decline in salmon and eel recruitment in some catchments, as well as the population status of highly migratory fishes, for example oceanic sharks.

In the future, we will need to understand much more about the potential impact of climate change (including ocean acidification), the risks posed to fish populations by introduced and potentially invasive species such as the newly arrived comb-jelly (Mnemiopsis leidyi), but also incoming pathogens, toxic algae and jellyfish that are known to cause occasional ‘fish kills’, and the consequences of increasing pressures, such as from construction in the marine environment.