Summary
- Portage Creek can be used as an index stream' to gauge the health of Black Bay steelhead populations. In the past, strong year classes showed up in most north shore tributaries. The 2008 and 2009 year classes appear to be strong everywhere but Black Bay tributaries. This may be due to poor survival of immature steelhead in Black Bay, rather than low production in the stream environment.
- The attractive steelhead fishery witnessed between 2002 and 2006 was the result of three excellent years of juvenile production (1998, 2000 and 2001). These year classes have almost disappeared from the fishery through a combination of natural mortality and a small amount of lake harvest (exploitation). We are now left with one good production year (2004) and several poor years to sustain the spawning population. The 2013 steelhead spawning population showed poor juvenile survival for all the years from 2005 to 2010.
- When steelhead adults enter the rivers and streams they become increasingly vulnerable to angling. The research in Portage Creek shows that two to three anglers over four weeks can catch 25 to 40% of the spawning population. Forty percent of the steelhead captured initially were caught more than once, some as many as six times within the same spring. In rivers open to the public, a high percent of the annual steelhead migration will potentially be caught several or more times. The vulnerability of steelhead to being angled many times during the spawning migration gives anglers the perception of a much larger run than actually exists.
- Lake Superior tributaries are relatively unproductive. Adult steelhead stocks may have difficulty maintaining their population size if harvest is high. Anglers are often concerned about mortality of released steelhead. The Portage Creek research relies on angling to capture steelhead. Not only are these fish caught by normal angling practices, but they are also biologically sampled and tagged. Angling and handling mortality appears to be extremely low (< 2%). If handled carefully, a high percent of released steelhead will survive. Healthy steelhead stocks can therefore be maintained in catch and release fisheries, in spite of their vulnerability to being angled.
- The research on Portage Creek also allows us to monitor the natural fluctuations of a wild steelhead population in Black Bay, Lake Superior. We were able to document the recovery of an over-harvested population in the 1990's. Now we are witnessing a declining adult population that appears to be naturally caused (occurring throughout Black Bay tributaries). Adult steelhead populations in Black Bay are presently weighted towards older, multiple repeat spawners. This indicates that lack of recruitment, not angler harvest, is responsible for the decline in population size. If conditions improve for young steelhead survival, Portage Creek again could produce a strong year class similar to 2004 (the strongest year class since the study began [Figure 3]). In order to allow maximum juvenile contribution of these strong years, maintaining suitable habitat and minimizing harvest should be critical management priorities.
- One of the most important aspects of this research is the partnership between government, industry and anglers working together to collect valid scientific data that contributes to fisheries management.