A limitation on Catch and Release.
The main purpose of the salmon when swimming up the river is to save energy for building the reproductive glands and avoid oxygen dept, so strong fertilized eggs of diversity are produced in the spawning process. We therefor suggest that Catch and Release (CR) is limited to water temperatures under the temperature where the salmon gets oxygen dept when fighting in CR. For the Sockeye Salmon this water temperature is 15 °C and for the Atlantic Salmon the literature suggests 16 °C. Without this upper limit of water temeperature for CR, the salmon will produce lesser eggs and ultimately lose its biological diversity and go against extinction.
Figure from: The swimming energetics of salmon, J R Brett.
J. R. Brett, ”Temperature tolerance in young Pacific Salmon (with some ref. to Atlantic Salmon) Journal of the Fisheries Research Board of Canada, Volume IX, no 6 265-323.
J. R. Brett, ”Some principles in the thermal requirements of fishes”, The Quart. Rev. of Biol. Vol 31, no 2, 75-87.