Table 1.

Number of surveys and observations of roach for each of the three periods for roach: beginning of acidification period, heavy acidification period, and recovery period

Sampling period	No. of surveys	Lakes with Single observation	Lakes with Two observations	Lakes with Three or more observations
Beginning of acidification period <1960	237	33	23	29
Heavy acidification period 1960–1990	219	32	22	31
Recovery period >1990	170	55	11	29