COQMON-7 | Lower Coquitlam River Fish Productivity Index
Total Page:16
File Type:pdf, Size:1020Kb
Coquitlam-Buntzen Project Water Use Plan Lower Coquitlam River Fish Productivity Index Implementation Year 12 Reference: COQMON-7 Study Period: 2000-2017 Results Prepared by: Jody Schick Jason Macnair 529 Gower Point Road, 2919 Ontario St., Vancouver B.C. Gibsons, BC., V5T 2Y5 V0N 1V0, [email protected] [email protected] March 31, 2019 Coquitlam River Fish Monitoring Program: 2000-2017 Results Final Report Prepared for: BC Hydro Prepared by: Jody Schick1* and Jason Macnair2 _____________________________________________________________________ 1 529 Gower Point Road, Gibsons, BC., V0N 1V0, [email protected] 2 2919 Ontario St., Vancouver B.C. V5T 2Y5, [email protected] * Author to whom correspondence should be addressed ii Executive Summary As part of the Coquitlam River Water Use Plan (LB1 WUP), a long-term adaptive management study is being conducted in the Coquitlam River to compare anadromous fish production under two experimental flow regimes. Fish population monitoring under the first flow regime (Treatment 1, dam release flows from 0.8-1.4 cms) occurred from 2000 until the completion of the Coquitlam Dam seismic upgrade in October 2008, with the exception of 2001(8 years). Fish production under Treatment 2 (release flows from 1.1-6.1 cms) will be monitored for up to 9 years. The Lower Coquitlam River Fish Productivity Index Monitoring Program (COQMON-07) focuses on four anadromous species: Steelhead Trout (Oncorhynchus mykiss) and Coho Salmon (Oncorhynchus kisutch), Chum Salmon (Oncorhynchus keta) and Pink Salmon (Oncorhynchus gorbuscha), and includes adult escapement and smolt outmigration monitoring for each species. Higher returns during 2007-2014 allowed Chinook Salmon (Oncorhynchus tshawytscha) escapements to be estimated as well. Since 2006, night snorkeling surveys have also been included in the monitoring program to provide estimates of late summer standing stocks of juvenile Coho and Steelhead. This report summarizes monitoring results of 8 years during Treatment 1 (2000-2008) and the 9 years of Treatment 2 (2009-2017) for the four major components of the COQMON-07: adult salmon escapement surveys, Steelhead redd counts, juvenile standing stock surveys, and smolt trapping. The primary emphasis of this report is on 2016 fall salmon escapement estimates and outmigration, fall standing stock and Steelhead escapement in 2017. Summaries of all data years for each species and life stage are presented and discussed as well. Estimates of adult escapement, late summer juvenile standing stocks and egg-to-smolt survival estimates should be considered preliminary and will change as additional observer efficiency data are accumulated in future years. Coho escapement to the Coquitlam River in 2002-2016 (880-13,290 adults) likely exceeded that necessary to seed available juvenile habitat based on preliminary stock-recruitment analysis. The 2015 escapement estimate of 6,867 was based on 14 surveys under relatively favourable survey conditions that spanned the entire spawning period. High water events were minimal and short in duration. As with the Pink, Chum and Chinook, there was insufficient survey life and observer efficiency information to calculate the uncertainty of Coho escapement estimates. The 2017 late summer standing stock fry estimate was 59,166 (95%CI ±29%) based on night snorkel surveys, which was above average compared with previous years (18,405-91,367 fish). During 2017, 9,810 (95%CI ± 1,080) Coho smolts originating from mainstem habitats outmigrated past the lowermost trapping site and an additional 4,340 smolts outmigrated from the four off-channel habitats above RST2. Using smolt yield as the primary measure of freshwater carrying capacity, there was no difference in mean smolt abundance between Treatment 1 and Treatment 2 when including off-channel smolts (mean: 12,949 and 12,507 smolts, respectively; 2-tailed t-test p=0.97) but is significantly different for mainstem origin smolts (mean: 5,479and 7,848, respectively; 2-tailed t-test p=0.05), when excluding the 2009 transition year. This reflects a 43% increase in mean abundance from Treatment 1 to Treatment 2. However, the 95% confidence intervals of the percent change in smolt yield from Treatment 1 to Treatment 2 are broad, ranging from no-increase to a nearly two-fold increase in abundance (95% CL: -0.5% to 87%). While this may represent a meaningful change in abundance, we are uncertain whether the iii change was due to Treatment 2 flows or a regional increase in freshwater productivity that occurred over a similar time period. If smolt yield from the Alouette River– an adjacent watershed with similar hydrology – is a reliable control for changes in productivity in the Coquitlam River that would have occurred if there was no change in flow treatment, Treatment 2 may have had no effect or even a negative effect on productivity. This is because there was a greater increase in smolt abundance in the Alouette River (117%) over a similar time period than in the Coquitlam (mean increase: 43%). However, the reliability of the Alouette Rivers as a control is uncertain because of its low precision of the estimated change in abundance between treatments (95% CI: 25%-250%), including only the first five of nine Treatment 2 years, and the possibility that pre-2008 estimates were biased low. Redd counts suggested that Steelhead escapements during 2005-2015 (230-870 adults, 24 to 80 adults/km, 39,000-149,000 eggs/km,) were well above that necessary to seed available juvenile habitat based on stock and recruitment data for the Keogh River, a well-studied coastal stream, and based on preliminary stock-recruitment analysis from the Coquitlam River. The 2017 estimate of 398 adults was minimally influenced by modeling redd loss since the period between surveys was sufficiently short that virtually all redds constructed after one survey remained visible during the subsequent survey. The late summer standing stocks and 95%CI of Steelhead fry, age 1+ and 2+ parr for 2015 was 54,358 ±44%, 9,064 ±28% and 3,207 ±50%, respectively. Smolt yield for the mainstem upstream of the lowermost trap (RST 2) was 3,696 ±16% in 2017. Mean smolt yield for the Coquitlam River mainstem increased 24% from Treatment 1 to Treatment 2 (mean: 3,716 and 4,684 smolts, respectively). Although this result isn’t statistically significant, we expected that it will with additional monitoring if current trends continue (2-tailed t-test, p=0.07). The 95% confidence intervals of the percent change in smolt abundance from Treatment 1 to 2 ranged from -5% to 53%. This increase was almost entirely the result of increased smolt yield in reach 4. Mean abundance in reach 4 increased significantly from Treatment 1 to Treatment 2 (926 and 2,253 smolts, respectively; 2-tailed t-test, p< 0.01). As well, reach 4 abundance has been at least two-fold higher than during Treatment 1 in all but one year since 2009. This continues the trend of generally increasing abundance in reach 4 from less than 400 smolts in 1996 (prior to the start of Treatment 1) to over 2,800 smolts in recent years. Similar to Coho, increased Steelhead production may be the product of regional increases in freshwater productivity rather than Treatment 2 flows. If smolt yield from the Alouette River is a reliable control for changes in productivity in the Steelhead in the Coquitlam River that would have occurred if there was no change in flow treatment, Treatment 2 may have had no effect or even a negative effect on productivity. There has been a greater increase in mean smolt abundance in the Alouette River (78%) than for the Coquitlam River (24%) between Treatment 1 and 2. We are uncertain about the reliability of the Alouette River as a control for the same reasons as for Coho: low precision of the estimated change in abundance between treatments (95% CI: 10%-132%), small Treatment 2 sample size (3 years) and the possibility that pre-2008 estimates were biased low. Distinguishing between flow treatment and non-treatment effects will require further assessment of the reliability of the Alouette River as a control and or including considering other nearby rivers as controls. iv Chum escapement for 2016 was the highest since monitoring began in 2002 (78,120 adults). This was based on 11 evenly spaced surveys with moderate to good survey conditions. Considering this, the 2016 escapement estimate is likely a reliable index for evaluating freshwater production even though we still lack adequate information about survey life and observer efficiency. In 2017, 12.7 million (95% CI ± 17%) Chum fry outmigrated past the lowermost trap. This is likely a product of the exceptionally high escapement in 2016. Egg-to- fry survival ranged from 3.7%-26.8%, and averaged 10.0% during Treatment 1. Egg-to-fry survival during Treatment 2 averaged 24.7% and ranged from 12%-40%. Some or all our survival estimates could be biased high as they exceed the published values for Pacific Northwest streams. Survival estimates may be better interpreted as an index, only comparable within the Coquitlam River Monitoring Program. Mean survival was significantly higher during Treatment 2 then during Treatment 1 (2-tailed t-test p=0.01). Preliminary stock-recruitment analysis also suggests that Treatment 2 likely increased fry production compared with Treatment 1. These findings could change as we further refine the Chum escapement model as well as with further comparisons with other rivers. Chum salmon returns to Coquitlam River were greatly improved in 2002-2017 compared to escapements in years prior to the implementation of the Treatment 1 flow regime in 1997. No Pink escapement estimates were generated for 2016 or outmigration estimates for 2017 as spawning occurs during odd years for the Coquitlam River. Escapement during the most recent run year, 2015 was comparable to the 2009 and 2011 runs and less than 1/3 of 2013 returns.