| Table 2. Estimated stock numbers. | ||||||
| Year\Age | 1 | 2 | 3 | 4 | 5 | 6+ | 
| 1971 | 23110 | 32696 | 15098 | 4249 | 2001 | 565 | 
| 1972 | 10342 | 17211 | 17824 | 6337 | 1776 | 1112 | 
| 1973 | 18253 | 7824 | 9063 | 7719 | 2777 | 1390 | 
| 1974 | 24760 | 15611 | 9753 | 5304 | 2494 | 1027 | 
| 1975 | 23933 | 20361 | 7934 | 5129 | 1436 | 999 | 
| 1976 | 12269 | 20435 | 14769 | 3157 | 1767 | 849 | 
| 1977 | 23506 | 9507 | 13178 | 6595 | 876 | 880 | 
| 1978 | 18892 | 22359 | 5379 | 4788 | 1678 | 472 | 
| 1979 | 9539 | 15747 | 14078 | 1962 | 1728 | 599 | 
| 1980 | 15990 | 7109 | 11171 | 6134 | 624 | 831 | 
| 1981 | 15475 | 12819 | 4938 | 4971 | 2123 | 472 | 
| 1982 | 19378 | 12542 | 6429 | 2163 | 1174 | 775 | 
| 1983 | 16326 | 16607 | 7613 | 1956 | 419 | 462 | 
| 1984 | 10179 | 14149 | 8672 | 2494 | 468 | 238 | 
| 1985 | 7117 | 8774 | 8391 | 2754 | 592 | 160 | 
| 1986 | 18568 | 5914 | 4503 | 2064 | 560 | 183 | 
| 1987 | 4743 | 16215 | 3585 | 1264 | 441 | 161 | 
| 1988 | 7754 | 3869 | 6172 | 1037 | 281 | 111 | 
| 1989 | 3467 | 6362 | 2384 | 1951 | 263 | 115 | 
| 1990 | 14005 | 2758 | 2550 | 700 | 469 | 80 | 
| 1991 | 5487 | 12325 | 1341 | 589 | 147 | 113 | 
| 1992 | 9798 | 4976 | 5952 | 295 | 101 | 43 | 
| 1993 | 5788 | 8575 | 2675 | 2031 | 63 | 32 | 
| 1994 | 7864 | 5026 | 5610 | 1154 | 598 | 24 | 
| 1995 | 14612 | 6202 | 3492 | 2042 | 402 | 205 | 
| 1996 | 4131 | 12088 | 3958 | 1297 | 503 | 157 | 
| 1997 | 10334 | 3415 | 9307 | 1441 | 351 | 173 | 
| 1998 | 8759 | 9552 | 2349 | 2802 | 368 | 120 | 
| 1999 | 9144 | 6829 | 5561 | 655 | 586 | 107 | 
| 2000 | 3715 | 6319 | 3618 | 1431 | 161 | 151 | 
| 2001 | 2141 | 2708 | 2968 | 869 | 278 | 68 | 
| 2002 | 5230 | 1909 | 1322 | 748 | 163 | 72 | 
| 2003 | 1261 | 4414 | 1294 | 445 | 208 | 53 | 
| 2004 | 6094 | 1053 | 2441 | 476 | 154 | 98 | 
| 2005 | 2180 | 5403 | 655 | 883 | 135 | 70 | 
| 2006 | 2492 | 1823 | 3109 | 243 | 263 | 68 | 
| 2007 | 968 | 1438 | 892 | 878 | 79 | 116 | 
| 2008 | 670 | 568 | 590 | 263 | 178 | 46 | 
| 2009 | 2783 | 452 | 255 | 200 | 69 | 43 | 
| 2010 | 1433 | 2479 | 283 | 92 | 56 | 30 | 
| 2011 | 1551 | 1189 | 1410 | 123 | 24 | 22 | 
| 2012 | 2866 | 1165 | 579 | 546 | 50 | 10 | 
| 2013 | 3222 | 2254 | 673 | 190 | 161 | 19 |