River Ryton - Fauna

Fauna

In order for wildlife, particularly fish, to thrive, the quality of the water needs to be good. The Environment Agency use a six stage rating scale, from 'A' to 'F', called the General Quality Assessment, to classify rivers. 'A' on the GQA is the best quality of water, while 'F' is the poorest. Factors which affect the quality are levels of ammonia, levels of dissolved oxygen and the Biochemical oxygen demand (BOD), which measures the amount of dissolved oxygen needed by organisms to break down organic matter in the water. These factors are generally worse when the water is discharged from sewage treatment processes, and tend to be worse in summer, when such discharges make up a greater proportion of the total flow in the river. Water quality has steadily improved as a result of investment in the treatment processes, funded by the water industry's Asset Management Plan. Good flows help the water to purify itself. The upper Ryton is rated at 'B' on the GQA scale, and Oldcotes Dyke is rated at 'C'.

The river Ryton supports various types of fish. Very few live in the upper reaches, including the Anston Brook, because the water is only of moderate quality. A number of small streams contribute to the improvement of water quality, so that wild brown trout thrive as far as Worksop. Some trout and various types of cyprinids inhabit the water below Worksop, although abstraction of water results in spawning grounds and the habitats where the young fry live drying out during most summers, which has resulted in a decline in their numbers. Nevertheless, the lower reaches are still used for organised angling, and are the only part of the River Idle system where this activity takes place.