Fishing / Shellfishing - Selective Fishing
Date Published: June 14, 2010
Number of Pages: 63
Author(s): Mark Baltzell, Laurie Peterson, Steve Caromile, and Karen Kloempken
The Washington Department of Fish and Wildlife (WDFW) implemented a pilot winter mark-selective Chinook fishery (MSF) in Marine Areas 8-1 and 8-2 for the fourth time from January 1 through April 30, 2009. 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. WDFWes Puget Sound Sampling Unit (PSSU) implemented an intensive monitoring program in Areas 8-1 and 8-2 during the January-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, sampling activities 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 10 different access sites (5 in 8-1 and 5 in 8-2; two total on any given sampling day) on 67 of the 120 days that Areas 8-1 and 8-2 were open to Chinook retention under mark-selective regulations. Samplers interviewed an estimated 25% and 34% of all anglers fishing in Areas 8-1 (n = 617 anglers) and 8-2 (n = 2,014 anglers), respectively. Additionally, they sampled 44% and 41% of all marked Chinook harvested in the two respective areas (n = 182 in 8-1, 214 in 8-2). Other PSSU staff conducted 10 on-the-water effort surveys (3 in 8-1 and 7 in 8-2), and spent 33 days (142 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 a total of 8,464 angler trips (2,518 in 8-1; 5,946 in 8-2) were completed by private and charter anglers in the two combined areas from January 1 through April 30, 2009. With a season-wide CPUE of 0.16 Chinook retained per angler trip in Area 8-1 and 0.09 in Area 8-2, these anglers harvested a grand total of 402 and 509 marked Chinook in the respective areas (911 total); they released an estimated 2,456 Chinook (1,502 marked, 954 unmarked) in Area 8-1 and 2,119 Chinook (1,632 marked, 487 unmarked) in Area 8-2 (i.e., 4,575 releases overall). Over the two areas, harvested Chinook averaged 70 cm (range: 54 to 92 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, 98 and 97% of legal size). Nearly three-quarters of all harvested individuals were 4-year olds (i.e., brood year 2005). In addition to taking length measurements and scale samples, ramp samplers recovered 23 CWTs from marked Chinook harvested in the Areas 8-1 and 8-2 fishery. The majority of these tags (70%) were from Puget Sound release sites, while the remaining tags (30%) were from Hood Canal release sites.
During their four months of sampling in Areas 8-1 and 8-2 while it was open under mark-selective regulations, test fishers encountered 180 Chinook salmon, 73% (66% in 8-1, 81% in 8-2) of which were marked and 20% (18% in 8-1, 23% in 8-2) of which were of legal size. With a \CPUE. of 0.24 (legal-marked Chinook encounters / angler trip; 0.24 for 8-1, 0.22 for 8-2), test fishers encountered legal-marked Chinook at a higher rate than private fleet anglers. With mean lengths of 44 cm (8-1 marked and unmarked mean) and 45 cm (8-2 marked and unmarked mean), the distribution of encountered Chinook lengths was centered below the legal size limit (56 cm) in both areas. Further, based on scale-reading results, brood year 2007 fish made up the majority (50%) of the test fishery encounters. Throughout the four-month season, test fishery samples indicated that high mark rates and low legal-size fractions persisted during each month, with one in five 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 15.8% legal-marked (LM), 2.0% legal-unmarked (LU), 50.5% sublegal-marked (SM), and 31.7% sublegal-unmarked (SU) in Area 8-1 and 21.5% LM, 1.3% LU, 59.5% SM, and 17.7% SU in Area 8-2.
By combining dockside-sampling results (i.e., legal-marked Chinook harvest estimates) and test fishery encounters data, we generated size/mark-status group-specific estimates of encounters and mortalities for the two combined areas. In total, 5,511 Chinook were encountered (retained and released) during the combined Areas 8-1 and 8-2 fishery, with 1,023 of these being legal-marked, 90 legal-unmarked, 3,021 sublegal-marked, and 1,377 sublegal-unmarked individuals. Among released encounters, an estimated 20 legal-marked, 10 legal-unmarked, 600 sublegal-marked, and 276 sublegal-unmarked Chinook (905 overall, 54% in 8-1 and 44% in 8-2) were estimated to have died due to handling and release effects. Thus, in total, 1,531 marked (60% due to direct harvest) and 312 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 2108), 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 two unmarked Chinook belonging to double-index tag (DIT) groups may have died due to the handling-and-release impacts of 2008-09 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.