| Table 2. Estimated stock numbers. | ||||||
| Year\Age | 1 | 2 | 3 | 4 | 5 | 6+ |
| 1997 | 14491 | 6250 | 9963 | 1507 | 363 | 166 |
| 1998 | 12140 | 10681 | 2661 | 2573 | 350 | 105 |
| 1999 | 12331 | 8020 | 5254 | 621 | 530 | 95 |
| 2000 | 7156 | 7385 | 3433 | 1307 | 150 | 132 |
| 2001 | 3880 | 3907 | 2657 | 763 | 242 | 57 |
| 2002 | 7837 | 2481 | 1188 | 554 | 122 | 54 |
| 2003 | 2857 | 4427 | 894 | 267 | 115 | 29 |
| 2004 | 8647 | 1715 | 1656 | 240 | 83 | 51 |
| 2005 | 3917 | 3809 | 345 | 317 | 43 | 24 |
| 2006 | 5502 | 1962 | 1290 | 85 | 80 | 20 |
| 2007 | 2166 | 1883 | 445 | 321 | 29 | 41 |
| 2008 | 1027 | 667 | 401 | 110 | 78 | 20 |
| 2009 | 3958 | 446 | 135 | 91 | 33 | 19 |
| 2010 | 3132 | 2292 | 130 | 40 | 22 | 12 |
| 2011 | 4272 | 1788 | 564 | 43 | 13 | 8 |
| 2012 | 8732 | 1837 | 314 | 152 | 20 | 8 |
| 2013 | 14567 | 4137 | 710 | 127 | 40 | 12 |
| 2014 | 4000 | 9792 | 1464 | 375 | 80 | 12 |
| 2015 | 2985 | 1665 | 3505 | 731 | 191 | 70 |
| 2016 | 344 | 1276 | 539 | 1557 | 359 | 136 |