Conservation News
Conservation Crises
By Dougald Scott
Conservation Crises
By Dougald Scott
Since I'm writing this piece two weeks before the newsletter deadline, there may be a conservation crisis that is missing in this column. For that I apologize; but it's spring and time to hit the road.
A conservation crisis that's not going away for a long time is the warming of our planet. Global warming is here, and probably has been for some time; the land and seas are gradually warming. Whether this trend is solely caused by human activities is debatable. What is certain is that human activities have produced a tremendous increase in gasses that trap solar energy from the sun. It is also certain that the earth is heating up. Scientific studies indicate that we can't stop global warming for quite a long while, but if we take corrective action now, we can slow the warming process.
What does global warming mean to those of us who enjoy fly fishing for trout and salmon? The following is part of an article from the Osprey, the newsletter published by the Steelhead Committee of the Federation of Fly Fishers. It is authored by Nathan Mantua and William Pearcy, experts in climatology and global climate change.
Spawning and Incubation Periods
Warmer temperatures with no change in precipitation rates would lead to an increased runoff in fall and winter during storms, and a reduction in late spring and summer snow melt. This suggests a potential for dewatering redds of late spring spawners, but a more rapid development time for incubating eggs. Such changes would likely favor an advance in the median timing for spawning in streams that have historically had a significant snow melt runoff pulse in late spring and early summer.
Instream Rearing
Warmer water temperatures during all but the warm season will accelerate metabolic and growth rates during the instream rearing period. In contrast, lower flows and higher water temperatures in summer and early fall will reduce the availability and quality of warm season rearing habitat. In basins like those on the west slopes of the Cascades and Olympics that historically developed a significant winter snow pack, fall and winter high flow events will likely become more frequent as snowlines rise. Warmer water temperatures may lead to enough growth rate increases that many juveniles smolt at earlier ages. Warmer stream temperatures, for both winter and summer run fish, may push favorable rearing areas farther upstream to cooler headwaters and tributaries and thus reduce a basin's capacity to produce smolts.
Smolt Migration
In snow melt basins the timing of the spring freshet will come earlier in the year, and the volume of spring runoff will likely decrease. Will such changes in runoff be matched, or missed, by changes in the development of smolts in a warmer future?
Marine Survival and Growth
Will the marine environment become more or less favorable for maturing steelhead? The answer to this question will depend on ocean currents, stratification, and how those changes influence steelhead prey and predators. It is clear that steelhead habitat at sea consists of the cool upwelled waters of the California Current and subarctic waters of the North Pacific. It is less clear how changes in those regions lead to changes in the marine food web, steelhead survival, growth, migration and population productivity. Some scientists postulate that the predicted ocean temperature increases with C02 doubling will shift the thermal limits of salmonids in the North Pacific Ocean far to the north or even into the Bering Sea in this century, thus limiting the area and carrying capacity of the marine environment for anadromous fishes in general. El Nino events are another example of how important marine conditions can be: during El Nino periods of 1982-83 and in the mid- 1990s, warm, unproductive coastal waters diminished many runs of steelhead and salmon along the Northwest coast. The future behavior of El Nino and other natural swings in Pacific climate will be very important for the subarctic ecosystems of the North Pacific, yet there is now great uncertainty about the impacts of globĀ al warming on the future behavior of El Nino.
The Spawning Migration
Flow changes may have major impacts on timing and success for summer and winter run spawners. For instance, if snowmelt timing continues to advance, and spawning migration times for summer runs have evolved to take advantage of spring flows, will they be able to evolve with a rapid advance in snowmelt runoff timing? Will winter run fish evolve their migration and spawn timing to find optimal flows and temperatures for winter/spring spawning? This will be a question of rapid adaptation and evolution.