The efficacy of salmonid population environmental remediation efforts in the Archery Pond system


Hanna Jackson

Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada

*This report is a class project NOT peer-reviewed science


Questions

Has the species composition of fishes changed over the last 6 years at the Archery Pond System? Have the average sizes of the species present changed over this period?

Results

We trapped fish with minnow traps in Archery Pond off-channel habitat to assess the relative abundances and lengths of fish over the past 6 years. Coho salmon appear to be in the similar numbers, measured as catch per trap set, currently as they were in 2014 (Figure1A). Rainbow trout populations have decreased significantly from 2014 and 2018 and then did not change in 2020 (Figure 1B). Three-spined sticklebacks and sculpins that were not present in 2014 are now present at low density in the lake at only 0.2 three-spined sticklebacks per trap set and 0.3 sculpins per trap set (Figure 1C, 1D). The lengths of coho salmon and rainbow trout didn’t change significantly year-to-year (Figure 2).

Figure 1. We trapped fish in minnow traps in the Archery Pond system three times over six years and tracked their change in abundance over time.




Figure 2. We measured the lengths of salmonids captured in minnow traps in the Archery Pond system.


Discussion

Because off-channel habitat provides critical conditions for salmonids (Morley et al. 2005), efforts have been made to provide artificially constructed versions to increase salmon yields. Off-channel habitat produces higher densities of salmonids than the main stem of streams (Martens and Connolly 2014). Further, it has been found that constructed off-channel habitat, when compared to natural off-channel habitat, produce higher densities of juvenile coho (Morley et al. 2005). In our experiment, we found no evidence that supported these previous findings. Over the course of six years, coho salmonid abundance in two artificial off-channel habitats were variable, but on the long term neither increasing nor decreasing (Figure1A), while rainbow trout abundances decreased from 2014 to 2018 and stayed low to 2020 (Figure 1B). Species of less economic interest, the sculpin and three-spined sticklebacks however, increased in abundance during this same time (Figure 1C,1D).


It has also been found that with increased density, comes increased density dependence, leading to a decrease in the size of juveniles (Rosenfeld et al. 2008). We found that there was no change in length of either of the species that had consistent data through the six years, coho salmon and rainbow trout, over the years sampled. Growth is highly dependent on temperature and prey availability (Lusardi et al. 2020), which we have no available data on, but may have contributed to these results.

Our results may indicate that coho salmon and trout experienced factors such as harsh climate, upstream disturbance or decreased food availability that negated the positive effect of the off channel habitat for the coho salmon and rainbow trout. The absence of these species may have released three-spined stickleback and sculpin of competition, allowing them to increase in abundance over the course of the six years. It is also possible that our results show that this off-channel habitat is not helpful to the coho salmon and rainbow trout stocks, however this can’t be know with the limited data collected and requires further analysis of factors that influenced the productivity of these fish stocks over this period of time.

Literature Cited

Lusardi, R. A., B. G. Hammock, C. A. Jeffres, R. A. Dahlgren, and J. D. Kiernan. 2020. Oversummer growth and survival of juvenile coho salmon (Oncorhynchus kisutch) across a natural gradient of stream water temperature and prey availability: An in situ enclosure experiment. Canadian Journal of Fisheries and Aquatic Sciences 77:413–424.


Martens, K. D., and P. J. Connolly. 2014. Juvenile Anadromous Salmonid Production in Upper Columbia River Side Channels with Different Levels of Hydrological Connection. Transactions of the American Fisheries Society 143:757–767.


Morley, S. A., P. S. Garcia, T. R. Bennett, and P. Roni. 2005. Juvenile salmonid (Oncorhynchus spp.) use of constructed and natural side channels in Pacific Northwest rivers. Canadian Journal of Fisheries and Aquatic Sciences 62:2811–2821.


Rosenfeld, J. S., E. Raeburn, P. C. Carrier, and R. Johnson. 2008. Effects of Side Channel Structure on Productivity of Floodplain Habitats for Juvenile Coho Salmon. North American Journal of Fisheries Management 28:1108–1119.