In recent decades, the European or common barbel (Barbus barbus) has become one of the most sought-after fish species in the angling world (Figure 1), giving it significant socio-economic value (Britton and Pegg, 2011). It is also one of England’s native fish species, believed to have been present in at least some English rivers for more than 10,000 years. In this article, I’ll provide a brief overview of this iconic fish species’ ecology and highlight some of the issues that are affecting it in its natural range.
‘Old whiskers’, ‘Torpedo’, ‘Bronze bosses’: the barbel has a few nicknames, mostly related to its physical appearance, or at least the distinctive features of it. Within the UK, barbel are found in many lowland rivers throughout England but are almost entirely absent from Scotland and are generally only found in eastern Welsh rivers but not throughout Wales. They are believed to be native to eastern English rivers between Yorkshire and the Thames (Wheeler and Jordan, 1990) but have been widely stocked in many other rivers, with those such as the Severn and Wye (Figure 2) now renowned amongst anglers for their populations of barbel.
Barbel are cyprinids and there are several species from the genus Barbus that all share similar anatomical features (Figure 3). These include adaptations to living in faster flowing water, such as a streamlined body with large, almost mini-wing like, pectoral fins and powerful tails. Barbel species also have downward-facing mouths and two pairs (four in total) of barbules (sometimes referred to as barbels or whiskers) on their upper lips, which hint at their preferred benthic feeding habits (Figure 4).
The common barbel, like most of its relatives, is predominantly found in relatively shallow parts of rivers with gravel and cobble, or sometimes sand, substrate (Figure 5). The predominant flow types would be fast glide and run, although riffles may be present, especially in areas where barbel spawn (Figure 6 – article main image), and deeper pools or glide areas may be used for shelter during higher flows or very hot or very cold weather. Barbel also like to seek refuge and forage amongst aquatic plants (especially Ranunculus sp.) or underneath overhanging trees or submerged tree roots and branches.
Common barbel reproduce in the UK between May and July, with precise timing seemingly linked to river flow conditions and ambient water temperatures (e.g., Britton and Pegg, 2011). In my local stretch of the River Wye in Herefordshire, barbel were spawning in mid-June this year (2022) following a spell of high temperatures and prolonged sunny spells. Spawning typically takes place in relatively shallow water of between 12 and 88 cm (Gutmann Roberts et al., 2019 and references therein), but depths around 40 cm are more common (e.g., Melcher & Schmutz, 2010). Water velocities close to the riverbed at spawning sites are generally between 16 and 96 cm/s and flowing over a gravel/pebble substrate with particle size ranges of between 2 and 60 mm (Gutmann Roberts et al., 2019 and references therein).
Eggs produced by barbel are generally no more than 3 mm in diameter (Pinder, 2001) and take up to between 10 and 20 days (depending on water temperatures) to develop and hatch (Bašić et al., 2018). The eggs are deposited and fertilised in redds, which comprise a shallow excavation or crater with excavated substrate in a small mound downstream of the excavation. These can sometimes be seen as lighter patches of gravel where the algae- and silt-covered top layer of gravel has been excavated by spawning barbel, leaving cleaner gravel beneath (Figure 7). Following hatching, larval barbel remain in the gravel for several days until their yolk sacks have been used up.
Juvenile barbel often spend the early parts of their lives in shallow, marginal slack water areas close to faster water (Adrian Pinder pers. comm.). This probably facilitates faster growth (by occupying the areas of water that will have the highest temperatures in the summer) while also giving access to regular replenishment of oxygen from mixing with nearby faster water and is likely to be a location that accumulates an abundance of small invertebrate prey items. Barbel can live up to at least 20 years (Britton et al., 2012) and reach weights of up to 21lbs 2oz (current British record).
As adult fish, barbel have been shown to move up and down rivers frequently, sometimes covering large distances. During higher flows in the winter, there is a net drift of barbel downstream, presumably because lower energy levels at that time of year mean they are less able to maintain their resident positions against the higher velocity water (Baras and Cherry, 1990). Barbel are also considerably less active during the colder winter months, presumably to save energy when food availability is low.
Increasing daylength and ambient temperatures in the spring see an increase in barbel activity and movements (especially in upstream directions), some of which may be associated with migrations towards spawning grounds ready for spawning in the late spring/early summer (Twine, 2013 and references therein).
Researchers have shown that during the summer, many barbel remain within given areas, presumably selected as they contain a range of suitable habitats to meet their needs in terms of refuge areas, foraging opportunities and water quality (Figure 8). Peak activity during the summer is generally around the times when light intensity changes most noticeably, typically around dawn and dusk. Intense periods of feeding occur at these times, generally in relatively shallow water, including close to or over riffles where prey abundance can be high. Outside of this period, feeding activity is much reduced, with the majority of barbel tending to remain in or close to refuges. Similarly, at high water temperatures (>20oC), barbel will remain in refuge areas or deeper water, where the temperature may be cooler.
Barbel are reportedly most active during the autumn months (Baras, 1995), especially early autumn, which may be a strategy to maximise energy stores ahead of the colder winter, when food is less abundant and greater energy is required to find it.
As mentioned earlier, barbel can live for a relatively long time and mature relatively slowly, with males taking 3–4 years and females up to 8 years to become sexually mature. This leaves them susceptible to a range of pressures over a prolonged period, which can affect their ability to successfully reproduce and thrive in rivers. Some of the issues facing barbel include:
- Habitat fragmentation (e.g., by man-made structures such as weirs or potentially by low river flows caused by over abstraction and/or prolonged dry weather, creating overly shallow areas that larger barbel cannot pass;
- Entrainment and impingement at water abstractions, resulting in mortalities, especially at larval and juvenile life stages;
- Destruction and modification of habitats, which can create bottlenecks for different life stages – barbel require different habitats throughout their life cycles and the juxtaposition of these is important for maintaining viable populations;
- Poor water quality due to pollution from a range of sources, including, for example, waste water discharges, run-off from agricultural land, poor livestock and land management and run-off from road networks;
- Climate change that results in more extreme weather patterns (e.g., prolonged dry weather causing low flows or periodic intense downpours resulting in flood flows); and
- Predation of all life stages from a range of predators, including human poaching, piscivorous birds (e.g., herons, goosanders and cormorants, piscivorous fishes (e.g., pike and perch) and piscivorous mammals such as mink and otters.
Although barbel populations within the UK are generally not considered at imminent risk of extinction, there are anecdotal reports from anglers than numbers have declined in some rivers. The dominant reasons for decline are, in the majority of cases, likely to be linked to habitat quality, including the physical habitat, water quality and prey availability, or habitat accessibility. Whilst predation has been sensationalised in the angling press, the overall impact on barbel populations is likely to be considerably less significant compared with habitat and water quality issues and an over-focus on predators, while making attractive headlines and boosting publication sales, distracts from the more important issues facing barbel and other aquatic life in rivers.
Barbel is of course only one species that needs our rivers to survive. Many other species, including ourselves, also rely upon rivers for a host of different things. The protection and enhancement of our rivers is therefore important for a variety of reasons. These include the preservation of drinking water and crop irrigation resources, the protection of our wildlife and biodiversity and the protection of a resource that has significant socio-economic value – a report by the Environment Agency estimated expenditure on coarse fishing in 2005 was close to £1 billion, with 36% of coarse anglers stating that they fished in rivers (Environment Agency, 2007; referenced in Twine, 2013).
Since the desperate times of the industrial revolution, our rivers have improved considerably, at least in terms of water quality. In recent decades, there has also been an increase in interventions to improve the situation for fish and other wildlife in rivers by opening up barriers (e.g., weirs) to improve longitudinal connectivity between habitats, improving the screening at water abstraction intakes to reduce mortalities of fish and enhancing/restoring habitat to create more diverse habitats and improve opportunities for spawning, foraging and other key life stages. Sadly, many of these activities are not having the effects desired, due to overriding issues relating to water quality. Increased intensification of agriculture, poor land management practices leading to increased run-off and continued population growth coupled with a lack of investment in water treatment facilities has seen water quality in many rivers deteriorate noticeably. This was highlighted in a recent documentary presented by George Monbiot (https://www.youtube.com/watch?v=5ID0VAUNANA). Urgent action is therefore needed to address pollution issues and reverse this new decline in the quality of our rivers for barbel, for other wildlife and for ourselves.
Dr Peter Walker is a Technical Director and Aquatic Consultant working for RSK Biocensus Ltd. He has published multiple articles on aquatic ecology related topics and is a recognised specialist in aquatic ecological consultancy. Peter can be contacted via email at peter.walker@rskbiocensus.com.
Figure legends
Figure 1. Angler Stewart Walker with a large River Wye barbel.
Figure 2. Photograph of a section of the middle River Wye between Hay on Wye and Hereford.
Figure 3. A Prespa barbel (Barbus prespensis) caught by the author during electrofishing surveys in Albania.
Figure 4. The head of a large barbel showing the four prominent barbules or ‘whiskers’ used to help it detect food items amongst gravel and pebbles on the riverbed.
Figure 5. Gravel, pebble and cobble substrate on a riverbed – the preferred substrate over which barbel like to feed and spawn.
Figure 6. Typical barbel habitat on the River Wye.
Figure 7. A barbel redd (indicated by the red circle) amongst gravel, pebble and cobble substrate close to a riffle on the River Wye.
Figure 8. Adult barbel in its preferred habitat of shallow fast flowing water and gravel and pebble substrate.
References
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