| Table 2. Estimated stock numbers. | ||||||
| Year\Age | 1 | 2 | 3 | 4 | 5 | 6+ |
| 1997 | 23742 | 7912 | 10705 | 1593 | 418 | 183 |
| 1998 | 23202 | 12914 | 2721 | 2778 | 407 | 111 |
| 1999 | 18492 | 11116 | 6198 | 671 | 593 | 112 |
| 2000 | 15642 | 10120 | 3794 | 1430 | 172 | 143 |
| 2001 | 13845 | 5107 | 3017 | 938 | 254 | 61 |
| 2002 | 21562 | 4960 | 1670 | 600 | 130 | 60 |
| 2003 | 6244 | 7987 | 1487 | 434 | 156 | 38 |
| 2004 | 28001 | 2492 | 2446 | 382 | 121 | 72 |
| 2005 | 15495 | 12702 | 606 | 774 | 98 | 55 |
| 2006 | 21816 | 6879 | 3492 | 182 | 167 | 45 |
| 2007 | 8517 | 6500 | 1344 | 670 | 54 | 86 |
| 2008 | 5642 | 1816 | 838 | 217 | 165 | 35 |
| 2009 | 18704 | 1213 | 229 | 130 | 50 | 23 |
| 2010 | 14985 | 4210 | 201 | 42 | 20 | 10 |
| 2011 | 16067 | 3882 | 623 | 42 | 13 | 7 |
| 2012 | 34822 | 3793 | 463 | 158 | 23 | 9 |
| 2013 | 39066 | 8465 | 897 | 209 | 53 | 17 |
| 2014 | 17885 | 13840 | 1820 | 456 | 136 | 46 |
| 2015 | 10759 | 3063 | 4055 | 1208 | 329 | 130 |
| 2016 | 2351 | 2341 | 1026 | 2453 | 709 | 272 |