Fishing / Shellfishing - Selective Fishing
Date Published: June 15, 2010
Number of Pages: 51
Author(s): Mark Baltzell, Steve Caromile, Karen Kloempken, and Laurie Peterson
The Washington Department of Fish and Wildlife (WDFW) implemented a mark-selective Chinook fishery (MSF) in Marine Area 9 for the second season during the winter 2008-09 (November 1-30, 2008 and January 16.April 15, 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 pilot 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 Area 9 throughout the fishery 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 aerial 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 and 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 four different access sites on 80 of the 151 days that Area 9 was open in winter 2008-09 under mark-selective harvest regulations. Samplers interviewed an estimated 36% of all participating anglers (n = 2,523 angler trips) and sampled 34% of all marked Chinook harvested (n = 299). Additionally, other PSSU staff conducted 20 aerial effort surveys, and spent 65 days (. 288 hours) on the water pursuing Chinook using test fishing methods, in support of Area 9 monitoring efforts. Based on these activities, we estimated that 7,064 angler trips were completed by private fleet anglers during winter 2008-09 in Area 9. With a CPUE of 0.13 Chinook landed per angler trip, these anglers harvested a grand total of 885 marked Chinook; they released an estimated 6,646 Chinook (3,651 marked, and 2,995 unmarked). Harvested Chinook averaged 70 cm (range: 53 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, 296 legal /301 total or 98%). Nearly two-thirds (64%) of all harvested individuals were 4-year olds (brood year 2005), with age-3 fish making up the majority of the remainder. In addition, 22 CWTs were recovered from harvested fish, the majority of which were from Puget Sound (73%) and Hood Canal (18%) release sites, and two CWTs (9%) were recovered from a lower Columbia River release site.
Over the season in Area 9, test fishers encountered 312 Chinook salmon; of these, 18% were legal size, and the legal-size mark rate was 84%. With a \CPUE. of 0.37 (LM Chinook encounters / angler trip), test fishers experienced more than twice the legal-marked Chinook encounter rate as did private fleet anglers. Chinook encountered by test fishers (for marked and unmarked fish combined) averaged 42 cm (range: 23 to 91 cm) in total length and as a group were predominantly 2 years in age (45% of marked and 40% of unmarked totals). Unmarked Chinook encountered in the test fishery were predominantly one year old (45%). We estimated the overall mark rate at 64% and the size/mark-status composition at 15.4% legal-marked, 2.9% legal-unmarked, 48.4% sublegal-marked, and 33.3% sublegal-unmarked.
By combining dockside sampling results (i.e., legal-marked Chinook harvest estimates) and test fishery size/mark-status composition data, we generated size/mark-status group-specific estimates of encounters and mortalities. In total, 7,545 Chinook were encountered (retained and released) during the Area 9 fishery, with 1,001 of these being legal-marked, 172 legal-unmarked, 3,535 sublegal-marked, and 2,837 sublegal-unmarked individuals. Among released encounters, an estimated 20 legal-marked, 24 legal-unmarked, 704 sublegal-marked, and 567 sublegal-unmarked Chinook (1,315 overall) were estimated to have died due to handling and release effects. Thus, in total, 1,609 marked (55% due to direct harvest) and 604 unmarked Chinook mortalities occurred as a result of the winter 2008-09 Area 9 mark-selective fishery.
The number of fish estimated to have been impacted by the 2008-09 winter Area 9 fishery was considerably less than half of what was predicted based on Fishery Regulation Assessment Model runs (model run 2108). Whereas FRAM predicted that a total of 17,081 Chinook would have been encountered, actual encounters were estimated from creel surveys to be 44% of this value. Field data also suggested that actual legal-sized and sublegal-sized Chinook encounter rates were 18% and 60% lower, respectively, than those expected as a result of pre-season modeling.
Finally, regarding impacts of MSFs on the coded-wire tag (CWT) program, we estimated that 4 unmarked Chinook belonging to double-index tag (DIT) groups may have died due to the handling-and-release impacts of the pilot winter 2008-09 Area 9 mark-selective Chinook 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.