This study investigated whether a putative shift in climate regime in the North Atlantic in the 1990s coincided with changes in the growth and recruitment of roach Rutilus rutilus in the north‐east of England. The relationships between R. rutilus growth and recruitment and the environment were significantly different before and after the putative shift in climate regime. Water temperature, river discharge, growth, recruitment...

The influence of parasitism on first‐year growth and recruitment success of two cyprinid species in the Yorkshire Ouse catchment, England, was investigated using a 14‐year dataset. This study demonstrated a significant role of parasitism in growth and recruitment success of roach, Rutilus rutilus (L.), and European chub, Squalius cephalus (L.) populations. Muscle infections by Bucephalus polymorphus Baer (Digenea), Myxobolus p...

Approximately 5000 young of the year (0+) cyprinids comprising roach, chub, dace, minnow, bleak, bream, barbel and gudgeon were examined histologically for the presence of myxozoan infections. Thirteen myxozoans were identified to species, the majority being Myxobolus spp. In addition, two species of Myxidium and of Sphaerospora were recorded. All organs were examined, with the majority of infections being found in the gills,...

A method for determining relative year class strength (YCS) in unexploited freshwater fish populations from individual surveys, based on reconstruction of the mortality schedule of the target population, is described. The method was tested against traditional approaches of assessment of YCS and the limitations and applicability discussed. The method is useful for analysing the factors regulating YCS in freshwater fisheries.

Fixed location hydroacoustic fish monitoring was carried out at a series of sites in the tidal River Hull, north‐east England, in July 1996 during periods of moderate freshwater flows and spring tides. This was followed by a corresponding series during a period of lower freshwater flows and spring tides in autumn 1996. The surveys indicated substantial numbers of fish living upstream and downstream of a depleted oxygen zone wh...

Validation of hydroacoustic in‐situ target strength is problematic in large, deep lowland rivers, which cannot be sampled easily by conventional methods such as netting or electric fishing. A sampling programme involving three different techniques (split beam sonar, angling census and post‐angling competition data collection) was conducted to examine methodologies suitable for target strength validation. This combination of te...

Barbel Barbus barbus exhibited substantial movements in the River Nidd between March and July 1994, with some individuals moving nearly 20 km upstream, although there was considerable individual variation. Most upstream movement occurred during May. Fifteen of the 23 fish tracked attempted to pass the weir, and of these six were successful. Barbel tended to approach the weir around dusk and dawn, reflecting observed patterns o...