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The fish of inland waters are diverse, long-lived, large-growing, and an important source of food for humans and other vertebrates, features which have combined to attract the attention of humans for millennia. Such historical interest, stemming principally from fisheries, has acted as a major global driver for studies of fish populations in terms of changes in population abundance and individual growth rates. Despite a long history of inland fisheries, the scientific quantitative sampling of fish from such habitats using passive, active, and remote techniques remains a significant challenge. The population dynamics of inland fish are reviewed with the approach that their future abundance is a function of present abundance plus immigration, minus emigration, plus reproduction, and minus mortality. The considerable locomotory powers of fish mean that migratory movements into and out of the local habitat are frequent and can have significant implications for local population dynamics, while reproduction is characterized by high fecundities and complex behaviors. Mortality is correspondingly high and is particularly severe in early life stages, leading to complex and highly dynamic age distributions for the population as a whole. As a result, fish populations of inland waters typically show great variations in abundance on both short- and long-term timescales and these are discussed.

Estimated pike Esox lucius recruitment varied by a factor of 16 for females from 1944 to 1991 and by a factor of 27 for males from 1943 to 1990 in Windermere, a temperate, mesotrophic U.K. lake. No significant stock–recruitment relationships were found, but analysis with general additive models (GAMs) revealed that early autumnal water temperature, strength and direction of the North Atlantic Oscillation displacement (corresponding to different climatic conditions in winter) and zooplankton abundance but above all, late summer water temperature were important explanatory variables over the entire time series. Female recruitment was also influenced by young-of-the-year winter temperature. There was no evidence that perch Perca fluviatilis year-class strength, lake level or the summer position of the Gulf Stream influenced recruitment. The fitted models explained up to c. 65% of the overall observed variation between years.

1. The motivation for this report was the documented recent deterioration in the water quality in the two basins of Windermere since around 2000. The aim was to analyse the long-term records to assess the likely causes of this deterioration. 2. Records were analysed between 1950 and 2007, where available, including data on lake physics (annual mean water temperature at the surface, water temperature at depth, duration of stratification), nutrient availability (mean winter concentration of total phosphorus, soluble reactive phosphorus and nitrate); responding chemical variables (minimum concentration of nitrate, minimum concentration of silica, maximum pH and minimum oxygen concentration at depth); phytoplankton chlorophyll a (annual mean, spring maximum and summer maximum); zooplankton grazing (spring mean and summer mean abundance); and the fish predation on zooplankton (hydroacoustic data, perch recruitment and Arctic charr abundance, the latter only available in the North Basin). 3. Changes in the period upto around 1991 are largely the result of increasing nutrient load to the lake. This led to increasing winter concentrations of soluble reactive phosphorus, nitrate and total phosphorus (latter significant in South Basin only). This caused increased concentrations of phytoplankton chlorophyll a as an annual mean and as spring and summer maxima in both basins. This in turn caused a greater depletion of silica in the late spring, increased pH in the summer (significant in North Basin only) and reduction in the minimum oxygen concentration at depth. 4. Since around 2000 there has been a significant reduction in water quality in both basins: summer phytoplankton chlorophyll a has increased, as has maximum pH and the minimum concentration of oxygen (only significant in the North Basin). Summer Secchi depth has declined in both basins. 5. Annual phosphorus load from the two wastewater treatment works (WwTWs) that discharge directly to the lake has fallen by about 50%

Understanding and predicting the likely consequences of anthropogenic disturbance on species and ecosystems is a major prerequisite of achieving the sustainable use of natural resources. It is also a key element in the management of sites with statutory designation. During planning and decision-making processes involving potential disturbance issues, land managers and responsible authorities are often required to take account of the needs and views of a diversity of site user groups. The effects and impacts of disturbance can occur over a range of spatial and temporal scales, and research into these consequences must address this problem. This paper provides (1) an overview of the field and analytical methodologies contributing to the development of an integrated method for collecting multi-scale bird, resource and disturbance data in freshwater systems, and (2) an overview of the drivers and need for such data in sustainable resource management. Whilst the results of the bird–habitat–disturbance modelling arising from these data will be published elsewhere, the types of information that will be generated are illustrated and their potential use within planning and decision-making processes discussed.

The Arctic charr occurs in lakes across Britain and Ireland and was previously described here as 15 separate species. Most authorities now agree that all these stocks belong to a single polymorphic species complex Salvelinus alpinus (L.). This fish is given little protection in British and Irish law and there has been a steady loss of natural populations in recent years in all the countries concerned. A few new stocks have been created either intentionally or accidentally. In Scotland, only a small proportion of the 258 recorded natural populations has been studied and at least 12 of these are now extinct. There are at least four introduced populations originating from native Scottish stocks, but the fate of stocks introduced from Canada for aquaculture is uncertain. In England, there are eight extant populations in Cumbria and four others extinct. The status of introduced stocks in England is uncertain but there is probably one population surviving in Yorkshire. In Wales, eight lakes with resident Arctic charr populations have been recorded, three of these populations are natural, one is extinct and four have been introduced. In Ireland, of the 74 known populations, approximately 30% are extinct. There is no evidence to indicate that introduced stocks (some of them from Iceland) in a small number of lakes have survived there. A range of factors is involved in the extinction of populations and these include pollution, eutrophication, acidification, afforestation, engineering, exploitation, aquaculture, introductions and climate change. Much research remains to be done and unique stocks of this valuable species will continue to be lost unless positive action is taken through local conservation management backed by appropriate national legislation.