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Published: February 24, 2009
Pages: 65
Author(s): Peter McHugh, Mark Baltzell, and Laurie Peterson
Executive Summary
Background and Overview
The Washington Department of Fish and Wildlife (WDFW) implemented mark-selective Chinook fisheries (MSFs) in Marine Areas 11 (June 1-Sept. 30) and 13 (May 1-Sept. 30) for the second time during the summer of 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 these fisheries was to provide meaningful opportunity to the recreational angling public while minimally impacting ESA-listed Puget Sound Chinook salmon.
WDFW's Puget Sound Sampling Unit (PSSU) implemented an intensive monitoring program in Area 11 in order to collect the data needed to provide in-season catch estimates and to estimate key parameters characterizing the fishery and its impacts on unmarked salmon. Area 11 sampling activities included dockside creel sampling, test fishing, and on-the-water effort surveys. Among other parameters, Area 11 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. In contrast, a reduced sampling program was employed in Area 13 for logistical reasons. Area 13 monitoring activities included sampling for the estimation of: i) mark rates (based on voluntary trip reports provided by private anglers), ii) indices of Chinook salmon encounters and angling effort (i.e., sample-frame observations, not fishery totals), and iii) the age, length, and CWT composition of landed catch.
Area 11 Summary
Creel samplers staffed six different access sites (two on any given sampling day) on 85 of the 122 days that Area 11was open to Chinook retention under mark-selective regulations. Samplers interviewed an estimated 26% of all anglers fishing in the area (n = 17,131 anglers). Additionally, they sampled an estimated 28% (n = 2,063) of all marked Chinook harvested during the fishery. Other PSSU staff conducted 13 on-the-water effort surveys (6 on weekdays, 7 on weekends), and spent 82 days (609 hours) on the water pursuing Chinook using test-fishing methods, in support of Area 11 monitoring efforts.
Based on the combination of sampling activities, we estimated that nearly 66,000 trips were completed by Area 11 anglers between June 1st and September 30th. With a season-wide CPUE of 0.10 Chinook retained per angler trip, these anglers harvested a grand total of 7,377 marked Chinook during the fishery. Anglers additionally released an estimated 5,379 Chinook (3,056 marked, 2,322 unmarked). Overall, 2008 catch rates were similar to those observed in Area 11 during the summer of 2007; both catch and effort totals were substantially lower in 2008 compared to 2007.
During the four-month Area 11 fishery, harvested Chinook averaged 73 cm (range: 26 to 97 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, >99% of legal size). Further, more than four-fifths of all harvested individuals were 3-year olds (i.e., brood year 2005). In addition to taking length measurements and scale samples, ramp samplers recovered 155 CWTs from marked Chinook harvested in Area 11. The majority of these recoveries (58%) were from South Puget Sound facilities, primarily Lakewood complex, VoightÂes Creek, and Nisqually hatcheries.
Over the entire Area 11 season, test fishers encountered 112 Chinook salmon, 71% of which were marked (all sizes) and 85% of which were of legal size (both mark-status groups). With a "CPUE" (legal-marked Chinook encounters / angler trip) of 0.49, test fishers encountered legal-marked Chinook at a substantially higher rate than did the private recreational fleet. Test-fishery Chinook total lengths were similar for the two mark-status groups, averaging 70 cm (marked and unmarked mean; range: 21-93 cm). For the four-month season combined, we estimated the size/mark-status composition at 71% legal-marked (LM), 14% legal-unmarked (LU), 12% sublegal-marked (SM), and 2% sublegal-unmarked (SU).
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 Area 11. In total, 12,703 Chinook were encountered (retained and released) during the Area 11 fishery, with 8,365 of these being legal-marked, 2,017 legal-unmarked, 2,069 sublegal-marked, and 252 sublegal-unmarked individuals. Among released encounters, an estimated 163 legal-marked, 300 legal-unmarked, 394 sublegal-marked, and 50 sublegal-unmarked Chinook (906 overall) were estimated to have died due to handling and release effects of the Area 11 fishery. Thus, in total, 7,934 marked (93% due to direct harvest) and 371 unmarked Chinook mortalities occurred as a result of the Area 11 MSF. Overall, estimated impacts were similar to (legal-marked harvest) or considerably less than (sublegal encounters or mortalities) what was expected based on pre-season Fishery Regulation Assessment Model runs (model run 2108). Finally, regarding impacts of MSFs on the coded-wire tag (CWT) program, we estimated that 20 unmarked Chinook belonging to double-index tag (DIT) groups may have died due to the handling-and-release impacts of respective Area 11 MSF.
Area 13 Summary
Between May 1st and September 30th, 2008, samplers conducted Baseline sampling2 at 22 different sites used to access the Area 13 MSF. As a result, samplers acquired catch (kept and released) and effort information about nearly 3,100 completed angler trips. Over all interviews, ramp samplers observed anglers harvest a total of 180 Chinook (179 marked, 1 unmarked) and recorded 392 angler-reported Chinook releases (109 marked, 54 unmarked, and 229 of unknown mark status). Given these observations, we estimated the season-wide Area 13 CPUE at 0.06 Chinook retained per angler trip, a value that was low in general and less than half of what was observed during 2007.
During the five-month Area 13 fishery, harvested Chinook averaged 74 cm (range: 54 to 99 cm) in total length and were larger than the legal minimum size limit (>22 in or 56 cm TL) in most instances (>99% of 170 marked fish). Further, 85% of all harvested individuals were 3-year olds (i.e., brood year 2005). In addition to collecting length data and scales, ramp samplers recovered eight CWTs from marked Chinook harvested in Area 13, the majority of which were from South Puget Sound facilities (two North Puget Sound tags were also recovered).
Though we did not test fish in Area 13 during its mark-selective Chinook season, we estimated the overall and legal-sized mark rate based on angler-supplied voluntary trip reports (VTRs). In total, 20 separate VTRs were returned, providing size/mark-status details on 42 individual Area 13 Chinook encounters. Though VTR coverage was not seasonally extensive (i.e., most returns were for May and June), VTR-supplied data, in combination with dockside interview results, suggest that high (i.e., 60-80%) mark rates were present throughout the Area 13 MSF. However, Area 13 VTR results also illustrate the need for taking measures to obtain as broad of a cross section as possible when using this self-selected sampling medium.
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.
2 The Area 13 fishery was monitored using a reduced, Baseline sampling approach. While this approach does not provide a means for generating in- or immediately post-season estimates of fishery total catch and effort, these sampling observations (i.e., CPUE) will be combined with catch record card (CRC) data to obtain these values at a later time.