Winter distribution and habitat use by fish in a regulated lowland river system of south‐east England

Abstract

The macrohabitat preferences of 1+ fish (10 cm FL) and the microhabitat use of 0+ juvenile fishes in the River Lee catchment (UK) were examined from data collected over a 3‐year period between late autumn and early spring using depletion sampling and point abundance sampling, respectively. Canonical correspondence analysis and habitat profiles revealed preferences in the more rheophilous fish species (e.g. brown trout, Salmo trutta L., barbel, Barbus barbus (L.)) for features characteristic of upstream natural channels and meander sections of the by‐passed old river, with the more ubiquitous (e.g. perch, Perca fluviatilis L.) and limnophilous fishes [e.g. pike, Esox lucius L., tench, Tinca tinca (L.)] preferring habitats mainly in downstream channelised stretches. The microhabitat of 0+ juvenile fishes in the River Lee was similar to that reported elsewhere for the same species, influenced mainly by channel width, depth, and distance from the bank, though microhabitat overlap in 0+ roach, Rutilus rutilus (L.), and gudgeon, Gobio gobio (L.), was greater in the Lee than observed in larger, more open river systems.

Age and growth of European barbelBarbus barbus(Cyprinidae) in the small, mesotrophic River Lee and relative to other populations in England

“…Combined with surface run-off from agricultural land, the water quality of the river is typically mesotrophic. Generally consistent with the barbel zone (Huet, 1949), other fish species present (in relatively high abundance) were chub Leuciscus cephalus, European minnow Phoxinus phoxinus, gudgeon Gobio gobio, stone loach Barbatula barbatula, European bullhead Cottus gobio and dace Leuciscus leuciscus, with occasional occurrences of roach Rutilus rutilus, perch Perca fluviatilis, threespine stickleback Gasterosteus aculeatus and (stocked) brown trout Salmo trutta (Copp and Bennetts, 1996;Pilcher and Copp, 1997;Copp et al, 2005). In this part of the river, benthic invertebrates have been found to be dominated by Baetis rhodani, Ephemerella ignita and Chironomidae larvae (Copp et al, 2005), and drifting invertebrates by Caenis robusta, B. rhodani, E. ignita, Asellus aquaticus and Chironomidae (Edmonds-Brown et al, 2004).…”

“…These studies suggest that likely exceptions to confined movement include the downstream displacement of small B. barbus (over the water retention structures) during virtually all discharge rates, and the upstream movement by some larger B. barbus during extreme high discharge events (evinced by angler captures of tagged barbel; Vilizzi et al, 2006). As such, the present study demonstrates that recruitment problems in the R. Lee may not be due to a shortage of juvenile habitat, as originally perceived (Pilcher and Copp, 1997;Watkins et al, 1997;Copp et al, 2002), but rather to some other factors that affect the intermediatesized fish, the most likely being the impediment to free movement imposed by water retention structures. Similar to C. nasus in the Upper Rhône (Persat and Chessel, 1989), the recruitment gap in B. barbus of the R. Lee could be due to larger fish occupying the entire 'suitable' habitat, leaving none for up-coming recruits, which are forced to move elsewhere in the system.…”

“…Increasingly threatened within its native range (Peňáz et al, 2003), the IUCN status of B. barbus therefore carries the caveat of being "locally threatened by water pollution and river regulation". In the UK, where B. barbus is native to eastern rivers between Yorkshire and the Thames (Wheeler and Jordan, 1990), declining population densities have been reported for some of the more urbanised rivers, including the River Lee, Hertfordshire (Pilcher and Copp, 1997;Watkins et al, 1997). River regulation has been identified as a major threat to barbel populations (Pilcher et al, 2004), with compounding adverse effects of elevated nutrient levels on the species' morphology (Tyler and Everett, 1993), physiology (Peňáz et al, 2005) and migratory behaviour (Lucas and Frear, 1997;Vilizzi et al, 2006).…”

“…Thus, information on population size structure and growth is needed for rivers where B. barbus stocks are thought to be in decline so as to inform environmental managers in the formulation of habitat enhancement/rehabilitation and re-stocking strategies that aim to conserve the populations and increase the related angling amenity Pegg and Britton, 2011). To investigate a perceived decline in the B. barbus population of the River Lee, a small mesotrophic water course in South East England, collaborative research focused on the possible casual factors (Copp and Bennetts, 1996;Pilcher and Copp, 1997) through studies of the species' environmental biology (e.g. Watkins et al, 1997;Copp, 2001, 2013a,b;Copp et al, 2002Copp et al, , 2005Vilizzi et al, 2006).…”

Bias, precision and validation of ageing 0+ European barbel Barbus barbus (L.) from their otoliths

“…Increasingly threatened in parts of its native range in Central Europe [4], B. barbus populations are endangered locally by water pollution and river regulation, including in the U.K., where the species is native to eastern rivers between Yorkshire and the Thames [5]. Apparent declines in population densities, such as in the River Lee, Hertfordshire [6,7], have emphasised the need for accuracy (hence, validation) and precision in the ageing of 0+ (young-ofyear) B. barbus so as to improve understanding of growth rates during early life for appropriate management and conservation of B. barbus stocks [3,8].…”