CORE Metadata, citation and similar papers at core.ac.uk Provided by NERC Open Research Archive Hydrobiologia DOI 10.1007/s10750-011-0925-8 LOCH LEVEN RESEARCH Changes in the fish community of Loch Leven: untangling anthropogenic pressures I. J. Winfield • C. E. Adams • J. D. Armstrong • R. Gardiner • A. Kirika • J. Montgomery • B. M. Spears • D. C. Stewart • J. E. Thorpe • W. Wilson Ó Springer Science+Business Media B.V. 2011 Abstract Loch Leven, U.K., contains brown trout over a century, although a decline in fishery perfor- (Salmo trutta), eel (Anguilla anguilla), minnow (Phox- mance led to extensive stocking between 1983 and inus phoxinus), perch (Perca fluviatilis), pike (Esox 2006, including with non-native rainbow trout (On- lucius) and three-spined stickleback (Gasterosteus corhynchus mykiss). This review combines historical aculeatus), with brook lamprey (Lampetra planeri) information with contemporary gill-net and hydroa- and stone loach (Barbatula barbatula) also present in coustic surveys. In 2008, brown trout, perch and three- its tributaries. Arctic charr (Salvelinus alpinus), Atlan- spined sticklebacks were abundant, but pike and stone tic salmon (Salmo salar) and flounder (Platichthys loach were rare. The obstruction of migratory routes flesus) are now extinct. The brown trout population has was probably responsible for the loss of Atlantic supported a world-renowned recreational fishery for salmon and flounder, while a lowering of water level likely caused the extinction of Arctic charr and contributed to a reduction in pike abundance. Perch Guest editors: L. May & B. M. Spears / Loch Leven: 40 years abundance has fluctuated markedly, being influenced of scientific research by disease and eutrophication, although a reduction in I. J. Winfield (&) nutrients and associated recovery of macrophytes are Centre for Ecology & Hydrology, Lancaster Environment likely to have benefitted this species. Although the Centre, Library Avenue, Bailrigg, Lancaster LA1 4AP, brown trout population has undoubtedly shown a long- UK e-mail: [email protected] term decline, individuals are currently in excellent condition. C. E. Adams Scottish Centre for Ecology and the Natural Environment, Keywords Population Á Eutrophication Á Lake level Á University of Glasgow, Glasgow G12 8QQ, UK Fishery Á Brown trout (Salmo trutta) Á Rainbow trout J. D. Armstrong Á R. Gardiner Á D. C. Stewart Á (Oncorhynchus mykiss) Á Perch (Perca fluviatilis) Á J. E. Thorpe Cormorant (Phalacrocorax carbo) Freshwater Laboratory, Marine Scotland, Faskally, Pitlochry PH16 5LB, UK A. Kirika Á B. M. Spears Centre for Ecology & Hydrology, Bush Estate, Penicuik, Introduction Midlothian EH26 0QB, UK J. Montgomery Á W. Wilson Along with phytoplankton, which may periodically Kinross Estate Office, Kinross KY13 8AS, UK appear to colour an entire lake vivid green, and birds, 123 Hydrobiologia which at certain times of year teem on its water angling community (e.g. Montgomery, 1994) and surface, terrestrial margins and in the skies above it, a predation by cormorants (Phalacrocorax carbo) lake’s fish populations commonly enjoy the highest (e.g. Stewart et al., 2005) all potentially involved. public profiles of all of its flora and fauna. However, in Many of these influential factors have a long local contrast to phytoplankton, which are easy to sample, history (May & Spears, 2011) and so an under- and birds, which are easy to count, the assessment and standing of the contemporary fish community monitoring of lake fish communities is technically requires a correspondingly long-term perspective. difficult and presents a number of continuing meth- This article reviews historical published and odological challenges (Kubecˇka et al., 2009). When unpublished information in combination with contem- the complexities and uncertainties of fisheries socio- porary gill net and hydroacoustic surveys to describe economics within a multi-use landscape (e.g. Arling- long-term changes in the fish community of Loch haus et al., 2002) are added to this situation, objective Leven. Observed alterations in the fish community are and confident understanding and management of lake then interpreted in the context of historical and current fish communities become extremely difficult to anthropogenic pressures. achieve. The history and contemporary state of the fish community of Loch Leven in east-central Scotland, Materials and methods U.K., is a good example of this complexity, even though a total of only 12 resident and migratory fish Study site species has been recorded in this large, shallow and eutrophic lake (see below). Amongst these species, Loch Leven is a large (surface area approximately the local population of brown trout (Salmo trutta) 13.3 km2) but relatively shallow (mean depth 3.9 m, has received by far the greatest attention in terms of maximum depth 25.5 m) lake located in east-central research effort and fisheries exploitation, with com- Scotland, U.K. (56° 120N, 3° 220W; altitude 107 m). mercial netting having been practised here from This culturally eutrophicated water body drains a 1314 to 1873 and recreational fly fishing from 1844 catchment of 145 km2 and discharges into the Forth onwards (Thorpe, 1974a; Munro, 1994). The latter, Estuary via the River Leven. Further details of its at its height, supported 52 hire boats (W. W., bathymetry (Kirby, 1971), water quality history unpublished data). Management activities in support (Carvalho et al., 2011; May et al., 2011; Spears of angling activity have been documented by et al., 2011), phytoplankton (Bailey-Watts, 1982; Montgomery (1994), including an early example of Bailey-Watts et al., 1990), zooplankton (Gunn et al., the use of hatchery and rearing ponds in 1882 when 2011), macrophytes (Dudley et al., 2011), macroin- 60,000 fry and 4,000 2-year-old brown trout of vertrbrates (Gunn et al., 2011) and birds (Carss et al., unrecorded origin were placed in inflowing streams, 2011) are reported elsewhere. a practice that was expanded from the 1920s to 1936 resulting in up to 300,000 fry being hatched each Historical published and unpublished information year. Subsequently, the hatchery was closed during the Second World War and only reopened in the Published and unpublished information relevant to an early 1980s using ‘home-bred’ stock of exclusively understanding of the fish community of Loch Leven local origin (Montgomery, 1994). The Loch Leven was collated by searches of the published and grey trout fishery persists to the present with 13 boats literature, combined with unpublished data held by the available for hire (W. W., unpublished data) and a authors who collectively have been directly responsi- national and international reputation such that it was ble for, or involved with, almost all fish research and included as a venue for the 29th FIPS-Mouche all fisheries operations on the loch. This resulted in the World Fly Fishing Championships in June 2009. In identification of over 30 publications and reports recent years, however, it has experienced turbulent including, or supplemented with, data on fish popula- fortunes with various anthropogenic pressures (e.g. tions from the 1960s, 1970s, 1980s, 1990s and 2000s Duncan, 1994), the socio-economic vagaries of the and fisheries data from 1900 to the 2000s. 123 Hydrobiologia Contemporary hydroacoustic and gill net surveys from a total of seven other lochs sampled using the same gill-netting methodology in 2007 and 2008 by Before this study, the most recent sampling of the fish Winfield et al. (2008a, b, 2009b), and from Loch populations of Loch Leven had been undertaken using Leven perch sampled in March 2001 (D. C. S., survey gill nets during March and December 2001 unpublished data from gill netting) and August 1968 (Stewart et al., 2005). Consequently, a community (J. E. T., unpublished data from trawling). sampling programme using a combination of hydro- acoustics and survey gill nets as used on a series of other lochs by Winfield et al. (2009a) was begun in late 2007. Results On 10 October 2007, day- and night-time hydroa- coustic surveys were performed where water depth Historical fish community exceeded approximately 5 m in the southern area of the loch using a BioSonics DT6000 echo sounder A total of 11 native fish species has been recorded in (BioSonics Inc., Seattle, U.S.A.) with a 200 kHz split- Loch Leven, i.e. Arctic charr (Salvelinus alpinus), beam vertical transducer following the approach Atlantic salmon (Salmo salar), brook lamprey (Lam- described by Winfield et al. (2009a). The transducer petra planeri), brown trout, eel (Anguilla anguilla), was positioned approximately 0.5 m below the surface flounder (Platichthys flesus), minnow (Phoxinus of the water and data were recorded starting from a phoxinus), perch (Perca fluviatilis), pike (Esox lucius), range of 2 m. Following a standard hydroacoustic stone loach (Barbatula barbatula) and three-spined analysis employed extensively elsewhere in the U.K. stickleback (Gasterosteus aculeatus). However, brook by Winfield et al. (in press), the resulting data were lamprey and stone loach have always been largely used to produce densities of ‘small’ (i.e. -52 to restricted to tributary streams and flounder was -45 dB, length 40–99 mm), ‘medium’ (-44 to probably only an occasional visitor (Day, 1887). -37 dB, length 100–249 mm) and ‘large’ (greater Three of the above species became locally extinct than -37 dB, length greater than 250 mm) fish along during historical times. The Atlantic salmon and each of 18 transects. flounder, which both used to migrate along the Gill netting was undertaken using benthic and outflowing River Leven to and from the Forth Estuary, pelagic versions of the Norden survey gill net as were lost during the eighteenth century (Day, 1887), described by Appelberg (2000). The benthic version is while Arctic charr have not been recorded since 1837 bottom-set and is approximately 1.5 m deep and 30 m (Burns-Begg, 1874). long, with 12 panels of equal length having bar-mesh Only one fish species has subsequently been added sizes 5, 6.25, 8, 10, 12.5, 15.5, 19.5, 24, 29, 35, 43 and to the Loch Leven fish community, i.e.