Categories:
Published: February 20, 2009
Pages: 63
Author(s): Peter McHugh, Mark Baltzell, and Laurie Peterson
Executive Summary
The Washington Department of Fish and Wildlife (WDFW) implemented a winter mark-selective Chinook fishery (MSF) in Marine Areas 8-1 and 8-2 for the third time between November 1, 2007 and April 30, 2008. Consistent with the 2004 Puget Sound Chinook Harvest Management Plan (Puget Sound Indian Tribes and WDFW 2004) and the intent of previous Puget Sound/Strait of Juan de Fuca mark-selective Chinook fisheries, the primary goal for this fishery was to provide meaningful opportunity to the recreational angling public while minimally impacting ESA-listed Puget Sound Chinook salmon. WDFWÂes Puget Sound Sampling Unit (PSSU) implemented an intensive monitoring program in Areas 8-1 and 8-2 during the November-April season in order to collect the data needed to estimate key parameters characterizing the fishery and its impacts on unmarked salmon. Sampling activities included dockside creel sampling, test fishing, and on-the-water effort surveys. Among other parameters, efforts emphasized data collection needs for the estimation of: i) the mark rate of the targeted Chinook population, ii) the total number of Chinook salmon harvested (by size [legal or sublegal] and mark-status [marked or unmarked] group), iii) the total number of Chinook salmon released (by size/mark-status group), iv) the coded-wire tag- (CWT) and/or DNA-based stock composition of marked and unmarked Chinook mortalities1, and v) the total mortality of marked and unmarked double index tag (DIT) CWT stocks.
Creel samplers staffed 15 different access sites (9 in 8-1, 6 in 8-2; 2 total on any given sampling day) on 125 of the 182 days that Areas 8-1 and 8-2 were open to Chinook retention under mark-selective regulations. Samplers interviewed an estimated 28% and 49% of all anglers fishing in Areas 8-1 (n = 907 private, 6 charter) and 8-2 (n = 2,718 private, 61 charter), respectively. Additionally, they sampled 36% and 54% of all marked Chinook harvested in the two respective areas (n = 244 in 8-1, 469 in 8-2). Other PSSU staff conducted 42 on-the-water effort surveys (22 in 8-2, 20 in 8-2), and spent 245 days (1,279 hours) on the water pursuing Chinook using test fishing methods, in support of Areas 8-1 and 8-2 monitoring efforts.
Based on the combination of sampling activities, we estimated that nearly 9,000 angler trips (3,288 in 8-1, 5,678 in 8-2) were completed by private and charter anglers in the two combined areas between November and April. With a season-wide CPUE of 0.21 Chinook retained per angler trip in Area 8-1 and 0.16 in Area 8-2, these anglers harvested a grand total of 674 and 869 marked Chinook in the respective areas (1,543 total); they released an estimated 2,321 Chinook (1,441 marked, 881 unmarked) in Area 8-1 and 1,540 Chinook (1,056 marked, 484 unmarked) in Area 8-2 (i.e., 3,860 releases overall). Over the two areas, harvested Chinook averaged 64 cm (range: 45 to 91 cm) in total length and were larger than the legal minimum size limit (>22 in or 56 cm TL) in most instances (dockside marked Chinook observations, 95 and 91% of legal size). Nearly two-thirds of all harvested individuals were 3-year olds (i.e., brood year 2004 for age-3 fish caught before [10%] and 2005 for fish caught on or after January 1, 2008 [56%]). In addition to taking length measurements and scale samples, ramp samplers recovered 56 CWTs from marked Chinook harvested in the Areas 8-1 and 8-2 fishery. The majority of these tags (87.5%) were from Puget Sound (48.2% from north, 21.4% from central, and 17.9% from south Puget Sound facilities) and Hood Canal (10.7%) release sites.
During their six months of sampling in Areas 8-1 and 8-2 while it was open under mark-selective regulations, test fishers encountered 562 Chinook salmon, 73% (70% in 8-1, 79% in 8-2) of which were marked and 50% (54% in 8-1, 45% in 8-2) of which were of legal size. With a Â\CPUE. of 0.50 (legal-marked Chinook encounters / angler trip; 0.69 for 8-1, 0.35 for 8-2), test fishers encountered legal-marked Chinook at a higher rate than private fleet anglers but at a rate similar to that of charter anglers. With mean lengths of 56 cm (8-1 marked and unmarked mean) and 55 cm (8-2 marked and unmarked mean), the distribution of encountered Chinook lengths was centered about the legal size limit (56 cm) in both areas. Further, based the results of scale-reading efforts, brood year 2005 fish made up an overwhelming majority (80+%) of test fishery encounters. Throughout the six-month season, test fishery samples indicated that high mark rates and moderate legal-size fractions persisted during each month, with one in three Chinook encounters being legally harvestable (i.e., >22 in [56 cm] and marked) on average. In total, we estimated the season-wide size/mark-status composition at 37.8% legal-marked (LM), 16.2% legal-unmarked (LU), 31.8% sublegal-marked (SM), and 14.1% sublegal-unmarked (SU) in Area 8-1 and 36.2% LM, 8.3% LU, 42.8% SM, and 12.7% SU in Area 8-2. Finally, in addition to fishing in Areas 8-1 and 8-2 during its MSF season, test fishers sampled Chinook in both areas during the October 2008 closure in order to maintain a consistent time series of monitoring (i.e., it was open under MSF regulations during October 2005 and 2006). Results demonstrate that high mark rates existed in both areas before seasons opened and that the majority of Chinook present were sublegal in size (76% in 8-1, 91% in 8-2).
By combining dockside-sampling results (i.e., legal-marked Chinook harvest estimates), test fishery encounters data, and charter census results, we generated size/mark-status group-specific estimates of encounters and mortalities for the two combined areas. In total, 5,428 Chinook were encountered (retained and released) during the combined Areas 8-1 and 8-2 fishery, with 1,642 of these being legal-marked, 505 legal-unmarked, 2,398 sublegal-marked, and 3,281 sublegal-unmarked individuals. Among released encounters, an estimated 31 legal-marked, 73 legal-unmarked, 457 sublegal-marked, and 176 sublegal-unmarked Chinook (737 overall, 60% in 8-1, 40% in 8-2) were estimated to have died due to handling and release effects. Thus, in total, 2,033 marked (77% due to direct harvest) and 271 unmarked Chinook mortalities occurred as a result of the Areas 8-1 and 8-2 fishery. Although estimated unmarked (legal and sublegal) and sublegal-marked Chinook impacts were considerably less than what was expected based on pre-season Fishery Regulation Assessment Model runs (model run 3907), the impact of the Areas 8-1 and 8-2 fishery on legal-sized, marked Chinook (i.e., modeled harvest) was similar to what was anticipated. Finally, regarding impacts of MSFs on the coded-wire tag (CWT) program, we estimated that 7 unmarked Chinook belonging to double-index tag (DIT) groups may have died due to the handling-and-release impacts of 2007-2008 Areas 8-1 and 8-2 fishery.
1 Though the necessary tissue samples have been collected, DNA-based estimates of stock composition are presently unavailable for Puget Sound/Strait of Juan de Fuca mark-selective fisheries. In the present report, CWT-based (unexpanded) estimates of the stock composition of marked Chinook harvest are provided.