Fishing / Shellfishing - Selective Fishing
Date Published: February 17, 2009
Number of Pages: 65
Author(s): Peter McHugh, Mark Baltzell, Karen Kloempken, and Laurie Peterson
Background and Overview
The Washington Department of Fish and Wildlife (WDFW) implemented mark-selective Chinook fisheries (MSFs) in Marine Areas 5 and 6 for the sixth time during the summer of 2008 (July 1-August 9). 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.
WDFWes Puget Sound Sampling Unit (PSSU) conducted comprehensive fishery monitoring activities during the Areas 5 and 6 mark-selective Chinook fisheries. The study designs used in the two areas during 2008, however, differed markedly from those previously employed (2003-2007). First, a scaled-back version (i.e., with fewer sites and days sampled) of the former dockside sample design (i.e., Intensive or \Murthy. [probability-based] sampling) was used to provide coarse in-season estimates of catch and effort for Area 5; to ensure that long-term fishery sampling targets were not compromised, this effort was accompanied by a high level of opportunistic Baseline Sampling. The Area 6 design consisted of Baseline angler/catch sampling only and therefore did not have an on-the-water (i.e., boat surveys, test fishing) sampling component1. Finally, a pilot study was conducted in both areas to evaluate the feasibility of using angler-supplied voluntary trip reports (VTRs) as a means for collecting reliable information about the size/mark-status composition of Chinook encountered in MSFs.
Area 5 sampling activities included dockside creel sampling (Intensive and Baseline), test fishing, and on-the-water effort surveys. Among other parameters, Area 5 efforts emphasized data collection needs for the estimation of: i) the mark rate of the targeted Chinook population (test fishing and VTRs), 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 mortalities2, and v) the total mortality of marked and unmarked double index tag (DIT) CWT stocks. The Area 6 design provided data for the estimation of: i) mark rates (based on VTRs), 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.
For the VTR feasibility study portion of our 2008 monitoring plan, we used an extensive on-site form distribution/collection effort in both areas and assessed program efficacy using two criteria. First, we evaluated whether this \enhanced. VTR program could yield a sizeable and representative response from anglers fishing in the Areas 5 and 6 MSFs. Secondarily, we considered whether the Chinook encounters data acquired from VTRs were comparable to those collected by test fishers (Area 5 only).
Area 5 Summary
For in-season catch and effort estimation, creel samplers staffed one of three different access sites on 12 of the 40 days that Area 5 was open to Chinook retention under mark-selective regulations. Additionally, Baseline sampling occurred at three different access sites on a grand total of 73 site-days. In combination, samplers interviewed 4,809 anglers (933 Intensive; 3,876 Baseline) who fished in Area 5 and sampled 1,000 (157 Intensive; 843 Baseline) of the marked Chinook landed during the fishery. Other PSSU staff conducted 3 on-the-water effort surveys (2 weekday, 1 weekend), and spent 25 days (140 hours) on the water pursuing Chinook using test-fishing methods, in support of Area 5 monitoring efforts. Based on the combination of sampling activities, we estimated that 13,004 trips were completed in Area 5 between July 1st and August 9th. Landing an estimated total of 2,819 marked Chinook during the fishery, these anglers experienced a season-wide CPUE of 0.22 Chinook retained per angler trip. Additionally, anglers released an estimated 2,678 Chinook (479 marked, 2,199 unmarked). Overall, total effort was substantially lower and catch rates were moderately higher than documented during past Chinook MSF seasons in Area 5 (i.e., 2003-07). As a result, the 2008 catch total was similar to the average value for the past five seasons (2003-07 mean catch = 2,757). However, due to the uncertainty associated with estimates produced by the reduced 2008 sampling design, these comparisons should be regarded as preliminary; draft 2008 creel estimates will be supplanted by final Catch Record Card (CRC) values when they become available. During the forty-day Area 5 fishery, harvested Chinook averaged 72 cm (range: 52 to 99 cm) in total length and were larger than the legal minimum size limit (>22 in or 56 cm TL) in nearly all instances (dockside marked Chinook observations, >98% of legal size). Further, nearly four-fifths (78%) 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 86 CWTs from marked Chinook harvested in Area 5. The majority of these recoveries (72%) were from Puget Sound or Hood Canal production facilities (24, 17, and 17% from North, Central, and South Puget Sound, 11% from Hood Canal); Columbia River-origin CWTs groups comprised nearly all of the 28% CWT remainder. Over the entire Area 5 season, test fishers encountered 50 Chinook salmon, 60% of which were marked (all sizes) and 92% of which were of legal size (both mark-status groups). With a \CPUE. (legal-marked Chinook encounters / angler trip) of 0.58, 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 76 cm (marked and unmarked mean; range: 46-96 cm). For the forty-day season, we estimated the size/mark-status composition at 58% legal-marked (LM), 34% legal-unmarked (LU), 2% sublegal-marked (SM), and 6% sublegal-unmarked (SU).
By combining dockside-sampling results (i.e., legal-marked Chinook harvest estimates) and test fishery encounters data, we generated preliminary estimates of size/mark-status group-specific encounters and mortalities for Area 5. In total, an estimated 5,496 Chinook were encountered (retained and released) during the Area 5 fishery, with 3,188 of these being legal-marked, 1,869 legal-unmarked, 110 sublegal-marked, and 330 sublegal-unmarked individuals. Among released encounters, an estimated 62 legal-marked, 280 legal-unmarked, 13 sublegal-marked, and 66 sublegal-unmarked Chinook (421 overall) were estimated to have died due to handling and release effects of the Area 5 fishery. Thus, in total, 2,894 marked (87% due to direct harvest) and 346 unmarked Chinook mortalities occurred as a result of the fishery. Overall, these preliminary estimates of impacts were similar to pre-season expectations (i.e., Fishery Regulation Assessment Model results [FRAM, model run 2108]) for legal-marked Chinook salmon; substantial differences, however, were documented for other size/mark-status groups. Specifically, sublegal and/or unmarked Chinook impact estimates were considerably less than expected based on pre-season FRAM runs. Finally, regarding impacts of the Area 5 fishery on the coded-wire tag (CWT) program, we estimated that 11 unmarked Chinook belonging to double-index tag (DIT) groups may have died due to this MSF.
Area 6 Summary
Between July 1st and August 9th, 2008, samplers conducted Baseline sampling at three different sites used to access the Area 6 MSF. As a result, samplers acquired catch (kept and released) and effort information about nearly 1,574 completed angler trips. Over all interviews, ramp samplers observed anglers harvest a total of 350 Chinook (345 marked, 5 unmarked) and recorded 258 angler-reported Chinook releases (0 marked, 5 unmarked, and 253 of unknown mark status). Given these observations, we estimated the season-wide Area 6 CPUE at 0.22 Chinook retained per angler trip, a value that was above average relative to values documented for this fishery during its previous five seasons (2003-7 mean = 0.16). During the forty-day Area 6 fishery, harvested Chinook averaged 77 cm (range: 58 to 93 cm) in total length and were larger than the legal minimum size limit (>22 in or 56 cm TL) in all instances. Sixty-four percent of all harvested individuals were 3-year olds (i.e., brood year 2005); all but one of the remaining aged individuals were four years in age. In addition to collecting length data and scales, ramp samplers recovered 14 CWTs from marked Chinook harvested in Area 6, over half of which were from Central Puget Sound facilities. Outside of Puget Sound/Hood Canal tag groups, a single tag from each the Columbia River and Vancouver Island release regions was recovered. Though we did not test fish in Area 6 in 2008, we estimated the size/mark-status composition of encountered Chinook using results from our VTR study (described below). In total, we received a total of 59 VTRs from participating anglers which provided data on 133 Chinook encounters. From the VTR response, we estimated that 61% of Area 6 Chinook encounters were marked and that very few (<2%) were sublegal in size.
VTR Feasibility Study Summary
In both Areas 5 and 6, participation in our enhanced VTR program was substantially higher than observed in previous seasons (2003-07) and/or other Puget Sound marine areas (i.e., Marine Catch Areas 7-13). The only fishery for which a similar response was received was Area 5 in 2003; a concerted on-the-ground VTR distribution/collection effort also occurred during this season. Beyond exceeding past benchmarks in 2008, VTRs (n = 156) provided information on three times as many Area 5 encounters as did the test fishery (n = 50). Though we did not test fish in Area 6 during 2008, the VTR encounters total (n = 133) was approximately double the mean test fishery sample size (n = 59) for past Chinook MSF seasons in this area. Further, multiple metrics suggest that our enhanced VTR effort was successful at acquiring participation from a diverse and representative subset of Areas 5 and 6 anglers. In sum, VTR sampling activities were successful at achieving sample-size goals for this pilot study. For Area 5, we conducted additional analyses comparing size/mark-status composition estimates between VTR and test fishery encounters datasets. In brief, there was strong qualitative correspondence between the two samples and no statistically detectable differences for both legal/sublegal fraction (VTR vs. test fishery: 88% vs. 92%) and mark-rate comparisons (VTR vs. test fishery: 53% vs. 60%). Considering these similarities in conjunction with sample size potential, we conclude that VTRs can provide a cost-effective and reliable alternative to test fishing when distributed/collected in a strategic manner.
1 The Area 6 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 will be combined with catch record card data to obtain these values at a later time.
2 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.
Marine Areas 5 and 6 Mark-Selective Recreational Chinook Fishery, July 1-August 9, 2008 Post-season Report. Revised Draft: February 17, 2009. 64 pp. Washington Department of Fish and Wildlife. Olympia, Washington.