Lake fertilization : state of the art after 7 years of application / by J.G. Stockner and K.D. Hyatt.: Fs97-6/1324E-PDF

"A review of what has been learned after seven years of fertilizing coastal lakes in British Columbia to increase sockeye salmon production is presented. Though all the evidence is not yet in and some assumptions need validation, information gathered over the past seven years strongly supports the view that lake fertilization is working and is clearly one of the most cost-effective techniques for sockeye enhancement. Increased production at primary and secondary trophic (food) levels has been seen in all fertilized lakes. Smolts leaving most fertilized lakes are larger than in the pretreatment condition, and observed marine survival of returning adults surpasses anticipated levels. Provision of new "optimal" escapement targets provided to regional managers by scientific staff working on some sockeye stocks in fertilized lakes has led and will lead in future to much greater adult production. Before the technology can confidently be transferred to management, information is required in three basic areas: (1) the fertilizer application strategy for a variety of nursery lakes must be "fine tuned" to assure optimal trophic efficiency without creating wasteful energy "sinks", (2) we must validate in-lake survival estimates of juvenile sockeye in "untreated" lakes or in "treated" lakes where background data are available and, (3) we must determine whether empirical models relating fertilizer loads to trophic response developed for British Columbia coastal, fast-flushing lakes can be validly extrapolated to large, slow-flushing, dimictic interior lake systems. A bibliography of program publications from 1977-1984 is provided as an Appendix"--Abstract, page iii.

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