Fraser River Sockeye Fisheries and Fisheries Management - Cohen ...

Table I-2 Mean values for purse seine expansion lines by period. The expansionlines in use in 2009 are in red.J.S. Area 20 Area 20 Area 12 Area 12 Area 13 Area 13Year Div Summer Late Summer Late Summer Late1995 50% 612 2451997 77% 148 101 124 801998 78% 736 824 294 330 223 2041999 50% 524 412 210 165 141 1132000 36% 473 952 188 381 72 602001 20% 565 727 226 291 244 4692002 SB 51% 602 647 241 259 203 2162003 SB 65% 596 563 223 223 176 1502004 SB 59% 754 318 262 161 262 161Used '04 59% 587 587 219 252 179 1842005 SB 70% 575 1367 245 560 162 261Used '05 70% 596 563 223 223 176 1502006 SB 61% 460 313 182 128 140 60Used '06 61% 540 541 225 244 179 1712007 SB 45% 396 498 149 194 166 170Used '07 540 541 225 244 176 1712008 SB 10% 442 527 138 210 363 87Used '08 540 541 225 244 179 171Mean 561 650 209 250 194 169Subset of years: 477 496 182 198 188 180Use '09 486 190 184As with gillnet information, the restructuring of the in-season run-size estimation towardsBayesian methods resulted in a reexamination of the historical assessment of purse seinecatchability in the context of uncertainty, incorporating both retrospective and Bayesianhierarchical analyses (Michielsens 2010). To circumvent the circularity in the previousmethod, we considered using an approach that incorporated the geography of the testfishing locations:N Tot N 12 N 20NTot CPUEd , 12q12 CPUEd, 20q20Dataq 20 = x q 122 Estimated parametersSimplify the problem by relating thecatchability of the two fisheriesThe test fishing sites are in narrower locations in Area 12 (3.6 km or 9 inside seine netlengths Figure I-4), resulting in fish being more concentrated in those areas than in Area20 (11.1 km or 20 west coast seine net lengths, Figure I-5). As such we used a ratio (20net lengths/9 net lengths or 2.2) as an informed scalar to relate catchability to the areaswept:I-7