Water Intelligence Online © IWA Publishing 2002

Modelling the Relationships between Habitat and Population Dynamics of Brown Trout in a Lowland Chalk-Stream

Andrew Burrows
[Flood Hazard Research Centre, Middlesex University, UK]

The restoration of degraded streams to address the causes of declining wild brown trout populations can be improved with a better understanding of the relationships between stream biology and habitats. Studies that match physical and hydraulic characteristics of streams with population dynamics are increasingly important to the improvement of river habitat design. Habitat mapping of 2.5 km of the River Piddle, Dorset, UK led to the selection of a representative reach for application of the Physical Habitat Simulation Model (PHABSIM). The micro-habitat variables total depth, mean column velocity, substrate and cover type were measured three times over an annual cycle (1999-2000) for use in conjunction with annual electro-fishing data (1993-2000). PHABSIM was used to quantify the area of stream providing these conditions as a function of discharge and to predict stream carrying capacity for existing and modified conditions. For young trout age-0+ WUA and density were positively correlated in all years (1994-99). A highly significant correlation was found between WUA in February- March in numbers of trout age 0+ in September. Analyses of the suitability of spawning relative to fry rearing habitat suggested that spawning habitat was likely to be limiting fry numbers.

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UNIQUE ID: 200207039