South Coast Salmon Bulletin August 30, 2018 Assessment Update Barkley/Alberni (Area 23) Terminal Chinook

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1 1 South Coast Salmon Bulletin August 30, 2018 Assessment Update Barkley/Alberni (Area 23) Terminal Chinook Pre-season Expectations Somass/Robertson Creek Hatchery chinook: The forecast terminal return of adult Stamp/RCH chinook to Barkley Sound and Alberni Inlet in 2018 is approximately 83,000 (range 60,000 to 105,000). The predicted adult age composition is 34%, 52% and 14% of 3, 4 and 5-year old fish, respectively. With this expected age composition and a target of 39M eggs, the escapement target is approximately 23,000. Directed chinook fisheries are expected in the terminal Alberni Inlet area for all sectors. However, in-season information from escapement monitoring and fishery assessment programs may be used to modify run size expectations and adjust fishing plans (see below). Other stocks: Terminal returns of other WCVI stocks are also forecast to be moderately abundant in Pre-season forecasts: Conuma Hatchery Terminal Return: 40,000 (range 25,000 to 55,000); Nitinat Hatchery Terminal Return: 21,000 (range 15,000 to 27,000); Terminal return of other WCVI index stocks: 28,000 total (range 19,000 to 37,000). This forecast return results largely from index stocks that are enhanced. Some modest increase in the escapement of wild populations has been observed over the last 4 years and this improvement is expected to be maintained in However, spawner levels in the SWVI Conservation Unit remain below upper biological benchmarks. Therefore, wild WCVI chinook remains a stock of concern.

2 2 In-season Assessment A) Observed Catch Table 1. Estimated catch of chinook in Area 23 through August 29. Fishery Total Maa-nulth Treaty 8 terminal chinook to August 22 Other FSC (Hupacasath, Tseshaht FN) Alberni Inlet Recreational August Barkley Sound Recreational August* Tsu-ma-uss Economic Opportunity Commercial Gillnet (Area D) Commercial Seine Net (Area B) Total: : Aug 24 (effort: 23, CPUE: 14) 64: Aug (effort: 20 boats, CPUE: 3.2) Catch of 1716 with effort of 2746 boat trips (avg. CPUE of 0.63) Preliminary to Aug 29. Catch of 4916 with effort of 5374 boat trips (avg. CPUE of 0.92) Preliminary to Aug 29. Total: 13,973 12,535: Aug (effort: 105, CPUE: 119) 1438: Aug (effort: 47 boats, CPUE: 31). Avg weight of 14 lb/fish. Total: : Aug (effort: 23 boats, CPUE: 47) 1621: Aug (effort: 12 boats, CPUE: 135). Avg. weight:14-15 lb/fish. Total 23,684 * A portion of the recreational fish landed is not associated with Area 23 stocks. n/a B) Escapement and Biological Sampling Results WCVI chinook fisheries and escapement indicators are being sampled for stock and age composition through the WCVI Chinook Run Reconstruction Project. Age composition results are available for the August 19/20 Tsu-ma-uss EO fishery: Pre-season Forecast Aug 19/20 Tsu-mauss EO Age 3 34% 47% Age 4 52% 47% Age 5 14% 6%

3 3 The following graphs plot the daily escapement of adult chinook through the Stamp Falls fishway since August 1, 2018, and observed versus expected adult escapement to date. The total escapement of Stamp/RCH chinook observed to August 28 is 815 adults and 54 jacks. Figure 1: Daily escapement counts of adult Chinook at the Stamp Falls fishway. Figure 2: Observed (red line) and expected (black line) cumulative adult escapement for Stamp Falls Chinook with an expected total escapement of 23,000, assuming average escapement timing from the past 5 years.

4 4 C) In-season Run size Assessment Terminal Recreational CPUE Index Terminal area fisheries provide an indication of the actual run size. For terminal areas and time periods where effort is directed towards a dominant stock, an in-season CPUE index of terminal abundance is developed from recreational fishery catch statistics. The index relates catch per unit effort for the year in the terminal area sport fisheries to total terminal return (catch plus escapement) of Somass/RCH chinook using simple linear regressions. Relationships were calculated for standardized weeks starting mid- August from historical catch, effort and abundance data for return years 2000 to For catch per unit effort to be related to abundance, the following conditions are assumed. First, that run timing is similar from year to year. Secondly, that catchability is similar from year to year and linear over the forecasting range. Thirdly, that the contribution of Somass/Robertson Creek Hatchery fish to the terminal catch during the period of interest is relatively constant. Notwithstanding these and other assumptions, the Barkley recreational CPUE abundance index appears to provide an index of the terminal Somass/Robertson Creek Hatchery chinook run starting in about mid-august. However, the CPUE index is most informative during the last week of August and first week of September (week 84 and 91). Figure 1 shows the relationship for standardized Weeks 83 through 91. Based on the average CPUE for Week 83 of 0.97, this relationship predicts a terminal Somass chinook return of 72,000 chinook (95% prediction intervals 17,000 to 126,000). Summary of Terminal Estimates from Pre-season and In-season Recreational CPUE Estimates: Week CPUE Terminal Estimate 95% Prediction Interval Pre-season 83,000 60,000 to 105,000 Week ,000 17,000 to 126,000 Distant Fishery Indicator SEAK AABM: South-east Alaskan (SEAK) AABM fisheries have been used as a distant fishery index for Somass/Robertson Creek Hatchery chinook terminal run size. This relationship, which uses age-specific coded wire tag (CWT) recovery and terminal return data, was applied in On average, about 18 to 20% of WCVI production is removed by SEAK AABM fisheries. Much of the SEAK AABM fishery occurs prior to mid-july and therefore maturing WCVI fish are vulnerable to the fishery. The Alaskan Department of Fish and Game (ADFG) samples the SEAK AABM fisheries for CWTs and publishes the sample results inseason (i.e. within a week or two of the fishery). Robertson Creek Hatchery is a CWT indicator stock; therefore it is possible to retrieve the estimated number of RCH fish intercepted in the SEAK fishery in-season and prior to the terminal area fisheries. Using these data and estimates of Somas/Robertson Creek Hatchery terminal return, agespecific linear regressions were generated for each of the three main adult age classes

5 5 associated with the Somass/RCH terminal run (Figure 2). When the recovery and return data are examined separately for each age class, the recoveries of RCH CWTs in SEAK AABM fisheries provide a reasonable index of the Somass/RCH terminal return. This approach also provides an in-season indicator for the terminal age composition which informs the escapement target and, potentially, terminal fishery management measures. There were 447, 1986 and 309 Age 3, Age 4 and Age 5 RCH CWT associated recoveries, respectively, observed in 2018 SEAK fisheries prior to August. The resulting terminal run size prediction by age is tabulated below, including the associated prediction intervals. Age 3 Age 4 Age 5 Total Upper 40,709 32,118 12,633 85,460 Mid 16,818 13,040 3,811 33,669 Lower Age Comp 50% 39% 11% Mid-point estimates using the age specific regressions predict terminal Somass/RCH returns which are lower than the pre-season forecast for all age classes. It is uncertain whether this relationship will be applicable in 2018 because the SEAK fisheries have applied a 10% reduction to all-gear allowable catch due to conservation needs of SEAK, Transboundary, and Northern BC chinook. It is unknown what impact these SEAK fishery modifications may have on CWT recoveries of RCH chinook. Earlier returning WCVI stocks Although there is some variation observed in production and survival across WCVI chinook stocks, over the longer term the terminal abundance of WCVI chinook is correlated among stocks. Chinook stocks originating from the NWVI area return about one month earlier than those originating from SWVI area. Therefore observed terminal returns of chinook in areas such as Nootka Sound also provide information in-season regarding expectations of the terminal return to the Somass/RCH system. The 2018 recreational CPUE index utilized for Conuma Hatchery chinook, suggests the terminal return is less than the pre-season forecast of terminal abundance. The pre-season forecast for Conuma chinook was 40,000 and the mid-point of the in-season CPUE index predicts a 25,000 terminal return. In-season run size adjustment At this time, no change to the pre-season forecast run size of 83,000 is recommended. Available information from early-season indicators (i.e., SEAK CWT index, Conuma Hatchery chinook in-season CPUE index, and week 83 Barkley recreational CPUE abundance index) suggest the terminal return of Somass/RCH chinook may be lower than the pre-season expectations. However, it is uncertain whether the SEAK CWT index will be applicable this year, and the week 83 Barkley recreational CPUE index does not have a strong relationship with terminal Somass/RCH chinook returns. As such, these early-season indicators provide some early information but will be further informed as more information becomes available from the terminal fisheries CPUE index next week.

6 6 D) Terminal Fishery Allocation Table 2 shows allocations associated with the pre-season expected run size for Somass/Robertson Creek Hatchery chinook. Table 2. Allocation of Somass/Robertson Creek Hatchery chinook associated with the preseason forecast of 83,000. These allocations may be adjusted when additional CPUE data and biological samples become available over the next few weeks. Forecast Terminal run ESC* TAC Level Maanulth** Exp. Sport Catch Total Comm TAC Tsumass FSC Tsumass EO Comm Net Pre-season 83,000 23,000 60,000 Abundant 1,820 27,390 30,790 1,500 14,645 14,645 *Stamp River/RCH escapement target is based on a target of 39M eggs and the predicted age composition of terminal adult returns to Barkley Sound and Alberni inlet from the pre-season forecast **Maa-nulth catch assumed to be 70% Somass. Total allocation of Area 23 chinook is 2,600 in the abundant run category. E) Run timing expectations Peak run timing of Somass/RCH chinook to the terminal area is expected to occur about August 31. Fishery plans are made given the expected abundance, available TAC, and assumption that about half the migration occurs prior to August 31 and half after. Table 3 updates the expected timing in relation to a 83,000 terminal run size.

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8 8 Figure 1. Barkley Sound recreational CPUE Somass/RCH terminal run indices for Standardized Weeks 83 through 91. Regressions are shown with 95% prediction intervals. The red horizontal line shows the 2018 predicted value based on the average CPUE in week 83. 8

9 9 Figure 2. The relationship between SEAK CWT recoveries of Age 3, 4 and 5 Somass/RCH chinook and Somass/RCH terminal run size for each age class. Regressions are shown with forecast prediction intervals. The red points are the number CWTs observed in 2018 SEAK fisheries prior to August (447, 1986 and 309 Age 3, Age 4 and Age 5 recoveries, respectively). 9

10 10 Table 3. Expectation of return to the terminal area based on average run timing of an August 31 peak migration. The abundance is adjusted for the escapement target of 23,000. Week 83,000 Starts Ends Pre-Season 25-Jul Jul 1-Aug Aug 8-Aug Aug 15-Aug Aug 22-Aug Aug 29-Aug Aug 5-Sep Sep 12-Sep Sep 19-Sep Sep 26-Sep 750 Total 59,920 For more information contact: Erin Porszt WCVI Salmon Stock Assessment Telephone (250)