Abstract
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 success and the Gulf Stream Index co‐varied until the late 1990s, indicating a gradual progression between periods of warm‐and‐dry and cold‐and‐wet summers. Since the late 1990s, there has been an increased prevalence of warm‐and‐wet summers, and recruitment success has oscillated between extremes on an almost annual basis. The north wall (northern boundary) of the Gulf Stream has been undergoing a displacement south since the late 1990s, and the speed and amplitude of the change appears to support the hypothesis that there was a regime shift in the climate of the North Atlantic Ocean. It is possible that a continued displacement south of the north wall of the Gulf Stream will lead to further increases in river discharge, reductions in water temperature and reduced fish growth and recruitment success in the long term.