Fishing / Shellfishing - Selective Fishing
Date Published: June 11, 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 7 for the second winter season from February 1 through 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. WDFW’s Puget Sound Sampling Unit (PSSU) implemented an intensive monitoring program in Area 7 throughout the 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 aerial effort surveys, and we collected voluntary trip reports from charter boat operators and the angling public. 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 52 of the 74 days that Area 7 was open under mark-selective harvest regulations. Samplers interviewed an estimated 37% of all participating anglers (n = 2,991 angler trips) and sampled 50% of all marked Chinook harvested (n = 713 ad-marked Chinook sampled). Additionally, other PSSU staff conducted twelve aerial effort surveys, and spent 42 days (246.5 hours) on the water pursuing Chinook using test fishing methods, in support of Area 7 monitoring efforts. Based on these activities, we estimated that 8,167 angler trips were completed by a combination of private fleet, charter, and derby anglers during the fishery. With a CPUE of 0.17 Chinook landed per angler trip, we estimate that these anglers harvested a grand total of 1,420 marked Chinook, while they released an estimated 1,073 Chinook (349 marked and 724 unmarked). Harvested Chinook averaged 74 cm (range: 48 to 115 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, 706 legal-marked/713 total marked, or 99%). The majority (88%) of all harvested individuals were 4-year olds (brood year 2005), with age-3 fish primarily making up the catch remainder. In addition, 81 CWTs were recovered from harvested fish, the majority of which were from Puget Sound (82.7%, predominantly from north Puget Sound facilities) and Hood Canal (9.9%) release sites.
During their sampling in Area 7, test fishers encountered 40 Chinook salmon, of which 93% were legal size, and 65% of the legal-size fish were ad-marked. The overall mark rate (legal and sublegal Chinook combined) in the test fishery was also 65%. With a “CPUE” of 0.28 (LM Chinook encounters / angler trip), test fishers experienced a legal-marked Chinook encounter rate that was nearly two times that of charter, derby, and at-large private fleet anglers combined. Chinook encountered by test fishers averaged 73 cm (range: 49 to 87 cm) in total length and were predominantly 4 years in age (73% of marked and 79% of unmarked totals). Given the limited number of test fishery encounters, we chose to pool data across sources (test fishery, charter angler, and private fleet VTRs) in order to estimate the mark rate and size/mark-status composition of the pool of Chinook encountered in the Area 7 fishery. As a result, we estimated the overall mark rate at 71% and size/mark-status composition at 64.6% legal-marked, 28.6% legal-unmarked, 6.1% sublegal-marked, and 0.7% sublegal-unmarked.
By combining dockside sampling results (i.e., legal-marked Chinook harvest estimates) with the size/mark-status composition data from the test fishery as well as private fleet and charter boat VTRs, we generated size/mark-status group-specific estimates of encounters and mortalities. We estimated that a total of 2,501 Chinook were encountered (retained and released) during the Area 7 winter 2009 mark-selective Chinook fishery, with 1,615 of these being legal-marked, 716 legal-unmarked, 153 sublegal-marked, and 17 sublegal-unmarked individuals. Among released encounters, an estimated 31 legal-marked, 106 legal-unmarked, 28 sublegal-marked, and 3 sublegal-unmarked Chinook (169 overall) were estimated to have died due to handling and release effects. Thus, in total, 1,597 Chinook (1,479 marked and 118 unmarked) mortalities occurred (89% due to direct harvest) as a result of the Area 7 fishery.
The number of fish estimated to have been impacted by the Area 7 winter 2009 fishery was considerably less than was predicted based on pre-season modeling results with the Fishery Regulation Assessment Model (FRAM). Whereas FRAM predicted that a total of 5,107 Chinook would have been encountered during the fishery, field data indicated that actual encounters were 49% of this value.
Finally, regarding impacts of MSFs on the coded-wire tag (CWT) program, we estimated that 8 unmarked Chinook belonging to double-index tag (DIT) groups may have died due to the handling-and-release impacts of the pilot winter 2009 Area 7 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.