Not only does a loss of early timed wild winter steelhead limit our fishing opportunity it can also reduce the resilience of our steelhead populations. Spawning early is risky business as it takes ...More
Not only does a loss of early timed wild winter steelhead limit our fishing opportunity it can also reduce the resilience of our steelhead populations. Spawning early is risky business as it takes place during the window of peak Northwest winter runoff when redds could be scoured, but let’s not forget that coho make a living doing the same thing – largely by spawning in smaller streams, which is also what early-timed steelhead appear to do. So while it is risky, there are some advantages. First, early freshwater entry allows more time for returning adults to reach portions of the watershed that later timed fish are unable to reach when flows are lower, thereby increasing their spatial distribution within a watershed. Second, fry that emerge from the gravel at an earlier date have more time to grow and essentially have a head start on later emerging fish. More growing time leads to a greater body size and it has been shown that larger smolts survive at higher rates than smaller counterparts. Hence, not only does spawn timing spread steelhead out in space it spreads them out in time. This helps spread risk of negative influences, such as landslides and floods, which in turn, increases the resilience of the population. This is important because models predict warmer summer stream temperatures and an earlier onset of summer for the Northwest over the coming century, in many cases resulting in less hospitable conditions for late emerging fry. As temperature and flow regimes change over the next few decades early spawning fish are likely to become more important as their particular life history strategy is disproportionately favored. Managing our fisheries to protect the breadth of spawn timing and the overall diversity of steelhead should therefore improve the abundance and capacity of wild populations, in turn creating better fishing.
Something to be thankful for this weekend. WDFW has submitted their plan to NOAA for a Skagit River catch and release fishery.
Moving between fresh and saltwater environments would kill the vast majority of fish species on this planet, yet salmonids have developed a strategy known as smoltification to deal with this ...More
Moving between fresh and saltwater environments would kill the vast majority of fish species on this planet, yet salmonids have developed a strategy known as smoltification to deal with this physiological challenge. A buildup of the enzyme ATPase in gill tissues has been linked to migratory behavior and signals that juvenile salmonids are entering the smolt stage. This enzyme allows them to maintain osmotic balance when entering salty sea water, and if levels drop too low they will not survive the transition. ATPase levels are tightly linked to water temperature and research suggests the threshold for maintaining elevated levels is a surprisingly cool 13°C (55°F). Interestingly, fish that reared in cold water are able to maintain elevated ATPase levels longer than fish reared in warm water providing them with a longer window to complete their transition. Photoperiod also plays into this equation as migratory behavior significantly decreases by the summer solstice in mid-June. Smolts generally begin their migration in early spring and are aided by late winter rains and high flows. For coastal fish this is a relatively easy task as they may only have to swim a few miles. Inland summer steelhead face additional challenges on their many hundreds of miles long journey and any hindrance can mean they do not reach the ocean within their optimal physiological window, likely resulting in death. This has implications for climate change which is predicted to increase temperatures in headwater streams and in watersheds with large impoundments which increase surface water temps and slow juvenile migrations.