Fig. 3
Long-term (1974–2015) data series on annual survival rates (in % of initial nm−2, assessed in late winter) of adult (at least 1.8 years old) Limecola balthica on Balgzand. a Means with 1 SE of 5–13 estimates at the separate sampling sites with sufficient data (squares: n = 12 or 13; circles: n = 5–9; years with n ≤ 3 omitted); b Mean percentages shown separately for (open circles) a group of 3 sites in the NE part of Balgzand (numbered 9, 10, and 11 in Fig. 1) where reduced survival started in 1997, and (solid squares) a group of 6 sites in the SW half of Balgzand (numbered 2, 3, 4, 5, A, and B in Fig. 1) where reduced survival started in 1999 (compare Fig. 4). The horizontal lines indicate the long-term mean values for the first half (1974–1995) of the period of observation, full line for the 6 SW sites, dashed line for the 3 NE sites