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Spawning

The spawning migration of Portage Creek steelhead begins in early to mid-April, peaks during early May, and is usually completed by mid-June. Timing of the migration and upstream movement is influenced by flow regimes and water temperature. Redd (steelhead nest) construction occurs in the lower river from early April to late May, and in the upper river (above the falls) from early-May to June.

In the spring of 2013 the spawning migration began May 18 the latest observed since the study began in 1991.

Steelhead that migrate into Portage Creek during the fall rains (October and November) appear to over-winter back in Black Bay on Lake Superior rather than in the river. In the fall of 2007, eighteen steelhead adults were tagged within the study area of Portage Creek. Half of these were recaptured during the spring 2008 spawning migration. All recaptures occurred two to three weeks after the spring spawning migration began. If they had over-wintered in the river, they would have been darkly coloured (an indication of over-wintering behaviour), and more vulnerable to capture at ice-out the following spring.

Repeat Spawning

The number of adult steelhead spawning in consecutive years has increased from less than 100 individuals in the early 1990's to over 1000 from 2004 to 2008 (Figure 7). There is generally a higher natural mortality in male fish, resulting in lower repeat spawning numbers for that gender. Following the end of harvest in 1994, survival to multiple repeat spawning for both sexes has increased (Figures 8 and 9). In Portage Creek, repeat spawning steelhead over nine consecutive years has been documented using tag recaptures. In 2013, 71% of the spawning population were repeat spawners. Of this total, 30% had spawned at least four times. This spring, an estimate of 90 adult steelhead were spawning for the fifth to seventh time (validated by tag returns). The repeat spawning rate is abnormally high due to the strong 2004 year class (all repeats in 2013) and the lack of new fish recruiting into the spawning population from subsequent years.

Stray Rate and Movement patterns

Portage Creek steelhead move throughout Lake Superior, but generally return to spawn in their home stream. Tag returns from the south shore of Lake Superior, Nipigon Bay and the Sault Ste. Marie area illustrate the nomadic nature of this species. Approximately 2% of the Portage Creek tag returns are captured in foreign streams. Some of these returns are native to Portage Creek, but were feeding in a foreign stream. Many of these steelhead will return to Portage Creek for spawning.