Fishing / Shellfishing - Selective Fishing
Date Published: October 03, 2007
Number of Pages: 85
During July 2007, a pilot recreational mark-selective fishery for Chinook salmon (Oncorhynchus tshawytscha, "Chinook") was implemented in Marine Catch Areas 9 and 10. This fishery represents the first experience using mark-selective regulations for Chinook in Marine Areas 9 and 10. The mark-selective regulations allow retention of adipose fin-clipped ("marked") hatchery Chinook salmon, while all "unmarked" Chinook must be released unharmed. Area 9 includes the marine waters inside and south of the Partridge Point - Point Wilson line, extending south and west of a line from Possession Point to Shipwreck, and north of the Apple Cove Point - Edwards Point line (Figure 1). Area 10 encompasses the marine waters extending south from the Apple Cove Point - Edwards Point line to a line projected true east-west through the north tip of Vashon Island (Figure 2).
The Areas 9 and 10 selective Chinook fishery began on July 16, 2007 with tremendous popularity among the angling public. This was the first time that Areas 9 and 10 were open for Chinook fishing during the summer since 1993, providing anglers a unique opportunity to catch Chinook salmon in the middle of an urban area. The selective Chinook fishery in Areas 9 and 10 was scheduled to begin on July 16, 2007 and continue through August 15 (31 days), or until the combined quota of 7,000 retained hatchery Chinook was attained (of which, only 1,700 Chinook could be harvested in Area 10), whichever occurred first. In total, the Area 9 selective Chinook fishery was open for 16 days, from July 16 through July 31. The Area 10 selective Chinook fishery was open for 13 days, from July 16 through July 28.
The pilot Chinook selective fishery in Areas 9 and 10 was patterned after the summer pilot Chinook selective fishery in Areas 5 and 6 (WDFW 2007b), which we have successfully conducted each summer season since 2003 in order to collect the data necessary to enable evaluation and planning of future mark-selective fisheries. The Areas 9 and 10 selective Chinook fishery was also patterned after the pilot seven-month winter selective Chinook fishery in Areas 8-1 and 8-2, which we have successfully conducted for two seasons, from October through April in 2005-06 and 2006-07 (WDFW 2007a and 2007c). The objectives of the Areas 9 and 10 pilot Chinook selective fishery were similar to the objectives of the Areas 5 and 6 pilot Chinook selective fishery and the Areas 8-1 and 8-2 selective Chinook fishery: 1) increase recreational fishing opportunity while meeting conservation goals for Puget Sound Chinook salmon defined by the Puget Sound Chinook Harvest Management Plan; and 2) collect information necessary to enable evaluation and planning of future potential Chinook markselective fisheries.
We implemented an intensive sampling design during the Chinook selective fishery in Areas 9 and 10 from July 16 through July 31, 2007. The study design consisted of comprehensive data collection strategies, including dockside sampling, on-the-water surveys, test fishing, and voluntary trip reports from charter boats and private (non-charter) boats, to obtain the critical data parameters needed to evaluate the selective fishery. Resulting data were used to estimate total salmon encounters and total effort, adipose mark rate by species, species composition of encounters, unmarked Chinook retention error, legal-size (22 inches or larger total length) versus sublegal-size (less than 22 inches) Chinook encounters, mortalities of retained and released Chinook, as well as mortalities of marked and unmarked double index tag (DIT) groups. Test fishing boats fished the entire proposed length of the fishery, from July 16 through August 15, in order to collect information necessary to enable evaluation and planning of future potential Chinook mark-selective fisheries.
We contacted all known charter boat operators that fished in Areas 9 and 10 during the two-week fishery. During daily interviews, charter operators reported complete counts of salmon landed; further, based on private-fleet released:retained ratios, we estimated charter releases and combined these values with landings to quantify total charter encounters. Charter boats were ultimately treated separately and excluded from our creel survey estimates due to their high catch per unit of effort compared to private boats. We estimated total salmon encounters for private boats via the Murthy estimator method (Murthy 1957, Cochran 1977), incorporating dockside sampling and on-the-water surveys, while a complete census approach was used for charter boats.
In Area 9, for the period extending from July 16-31, we estimated via creel surveys that privateboat anglers retained a total of 4,938 Chinook (4,905 marked 33 unmarked or of undetermined mark status) in 18,160 angler trips, with an overall catch per unit of effort (CPUE) of 0.27 Chinook per angler trip. We also estimated that anglers released a total of 9,949 Chinook (2,070 marked, 3,465 unmarked, 3,353 unknown mark status, and 1,061 apportioned unidentified salmon). Thus, the total number of Chinook encountered (retained plus released) by private boats in Area 9 was estimated at 14,888. In addition, thirteen charter boats fished in Area 9 during the month life of its fishery, and reported a total retained Chinook catch of 334 (all legal/marked). Additionally, we estimated that charters encountered and released 363 Chinook during their Area-9 fishing activities. Adding charter and private-boat encounters together suggests that a total of 15,584 Chinook salmon were encountered by anglers in the Area-9 selective fishery.
In Area 10, for the the period extending from July 16-28, we estimated via creel surveys that private-boat anglers retained a total of 1,507 Chinook (1,469 marked and 38 unmarked) in 8,374 angler trips, with an overall CPUE of 0.18 Chinook per angler trip. We also estimated that anglers released a total of 6,777 Chinook (1,066 marked, 1,225 unmarked, 2,561 unknown mark status, and 1,924 apportioned unidentified salmon). Thus, the total number of Chinook encountered (retained plus released) by private boats in Area 10 was estimated at 8,284. In addition, thirteen charter boat operators fished in Area 10 and reported landing a total of 70 legal-marked Chinook during their Area-10 activities. Charter releases were estimated at 107 (55 marked, 52 unmarked) for Area 10. Combining Chinook encounters due to charter activity (177) to the estimated Chinook encounters for private boats (8,284) resulted in a total estimate of 8,461 Chinook encounters (1,577 retained and 6,884 released) in Area 10 during its 13-day season.
Thus, for Areas 9 and 10 combined, we estimated a total of 24,045 Chinook encounters (6,850 retained and 17,195 released) during the fishery. More than 95% of this total estimate encounters was due to private-boat fishing activities.
The test boats in each area fished with downriggers over 94% of the time, reflecting the primary gear type used by the recreational fleet. The Area 9 test boat fished for a total of 137 hours during the fishery, while the Area 10 test boat fished for a total of 125 hours. Over the course of the fishery, the test boat in Area 9 encountered a total of 183 Chinook (141 legal and 42 sublegal), while the test boat in Area 10 encountered a total of 138 Chinook (39 legal and 99 sublegal). Based on the combined test fishing data from July 16 through August 15, 77% of the Chinook encountered in Area 9 were legal-size, compared to 28% in Area 10. The adipose mark rate in Area 9 was 78% for legal-size Chinook and 83% for sublegal-size Chinook. In Area 10, the adipose mark rate was 72% for legal-size Chinook and 85% for sublegal-size Chinook.
A number of anglers who fished from private boats in Areas 9 and 10 submitted Voluntary Trip Reports (VTR’s) containing information on each fish they encountered during the selective Chinook fishery. Participating anglers recorded a total of 163 Chinook encounters on VTR’s for Areas 9 and 10 combined, of which 134 of the encounters (82%) were from Area 9. Of these 134 Chinook, 80 (60%) were legal-size, and 75% of these fish were marked. The 54 sublegalsize Chinook consisted of 31 marked and 23 unmarked (57% mark rate). A total of 29 Chinook encounters were recorded on VTR’s in Area 10. Of these, 11 (38%) were legal-size, and 73% were marked. The 18 sublegal-size Chinook reported in Area 10 consisted of 16 marked and 2 unmarked (89% mark rate).
Samplers recovered 255 coded-wire tags from Chinook harvested during the Chinook selective fishery in Areas 9 and 10. Of these, 253 were Puget Sound stocks and two were Canadian stocks. Fifty-four of these CWT recoveries were double index tags. Chinook from George Adams, Grovers Creek and Nisqually hatcheries contributed the highest number of double index tags. We estimated that anglers caught and released 290 legal-size, unmarked double index tagged Chinook, and that the mortality of unmarked legal-size double index tagged Chinook due to this selective fishery was 29 fish.
We compared two methods for estimating total legal-size and sublegal-size Chinook encountered during the fishery. The first method used the total number of Chinook encounters estimated from creel surveys and apportioned the encounters into the four categories of legal-size marked, legal-size unmarked, sublegal-size marked, and sublegal-size unmarked based on the proportions of these groups encountered during test fishing. Chinook encounters due to charter activities were added to private-boat counts to yield the total number of legal and sublegal Chinook encounters (24,045 total encounters: 15,584 in Area 9 and 8,461 in Area 10). Results of the "Method 1" estimation approach indicated that anglers released an estimated 5,571 legal-size and marked Chinook, or 32% of the fish they could have kept.
The second method for estimating the number of Chinook encounters was based on the assumption that anglers kept all Chinook that were legal-size and marked. For this method, total encounters were estimated by dividing the number of legal-size marked fish that anglers retained by the weighted proportion of legal-size marked fish from the test boats. The number of encounters in the remaining three categories was then obtained by multiplying the total encounters by the proportions for each corresponding category. Using this method, we estimated the total encounters at 13,770 Chinook. The true number of encounters thus likely lies between Method-1 and Method-2 estimates; i.e., between 13,770 and 24,405 Chinook encounters.
Using the "Method 1" approach of estimating encounters from the creel surveys and a release mortality rate of 15% for legal-size fish and 20% for sublegal-size fish, we estimated the total mortalities of Chinook in the selective fishery at 9,870, of which 9% were unmarked. Using the encounters estimated by assuming anglers kept all legal fish ("Method 2") and a release mortality rate of 15% for legal-size fish and 20% for sublegal-size size fish, we estimated total mortalities at 8,155 Chinook, of which 520 (6%) were unmarked fish.
Although we believe the true number of mortalities lies between our two estimates, we used the higher number to compare estimated mortalities against pre-season predictions of mortalities. This approach resulted in total and class-specific estimates (i.e., by size/mark-status groups) that were similar to and generally below the predicted mortalities of 680 unmarked legal-size and 543 unmarked sublegal-size Chinook produced in the final pre-season run of the Fishery Regulation Assessment Model (FRAM; Model 3907), suggesting the Areas 9 and 10 selective Chinook fishery neither hindered nor jeopardized the 2007 conservation and management goals for Puget Sound Chinook.
Due to the new Chinook selective fishery in Areas 9 and 10 that included the regulation requiring anglers to release salmon without bringing the fish on board their vessel, we worked throughout the season to educate anglers about the proper methods of releasing fish and fish identification. Dockside samplers offered anglers a "dehooker" and a pamphlet describing selective fisheries, how to identify salmon species and their mark status, and how to use the dehooker. Compliance with existing regulations, and the regulation prohibiting bringing unmarked salmon on board a vessel, was considered an integral part of a successful fishery. We estimated unmarked retention error (number of unmarked Chinook retained divided by total unmarked Chinook encounters) at <1% in Area 9 and 2.5% in Area 10.
In summary, the fishery was successful with respect to the objective of implementing monitoring and sampling programs to obtain management information for evaluation and planning of potential future selective Chinook fisheries. Estimated encounters were less than pre-season predictions. Compliance with fishing regulations was good during the fishery. The estimated number of mortalities of unmarked double index coded wire tagged fish was negligible.
Marine Areas 9 and 10 Selective Chinook Fishery July 16 – July 31, 2007 Post-season Report. Draft. October 3, 2007. Washington Department of Fish and Wildlife. Olympia, Washington.
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