Period | Sampling locations | Total | |||||
---|---|---|---|---|---|---|---|
Ishikari | Hidaka | Daisetsu | Akan | Konsen | Shiretoko | ||
pre–1964 | [6] | 1 [1] | [3] | [3] 3* | [2] | 19 | |
1965–1980 | [1] | [2] | 3 | 3 | 1 [6] | 16 | |
1981–1988 | [1] | 2 | 3 [1] | 7 [1] | 4 [3] | 22 | |
1989–1996 | 1 | 17 | 12 | 21 [1] | 29 | 81 | |
1997–2004 | 25 | 21 | 36 | 44 | 126 | ||
2005–2012 | 17 | 29 | 20 | 39 | 70 | 175 | |
Total | 6 | 22 | 78 | 66 | 108 | 159 | 439 |