During the night of March 22nd, Mount Redoubt erupted five times, sending plumes of ash and steam up to 15,000 feet in the air and giving Anchorage a dusting of fine gray ash.
Cook Inlet Area (from Anchorage Daily News)
Redoubt is one of several volcanoes, along with Mounts Spurr, Iliamna, and Augustine, located on the western edge of the Cook Inlet. The eruption should be of particular importance to anyone looking to schedule an Alaska fishing trip because of its close proximity to several popular fishing spots. Redoubt is about 50 miles west of Kenai and 100 miles southwest of Anchorage.
Many geologists expect this eruption to be similar to the 1989 eruption. During that eruption, Redoubt spewed ash and lava intermittently for four months and scientists expect something similar this time around. Hopefully, this will allow us to make an educated guess about the effects the current eruption may have on sport fishing in the area.
Luckily for us, Joseph M. Dorva of the Alaska Volcano Observatory and Alexander M. Milner of the Institute of Arctic Biology did a study on aquatic life in the aftermath of that eruption entitled Effects of Recent Volcanic Eruptions on Aquatic Habitat in the Drift River, Alaska. The Drift River was chosen for this study because it drains Mount Redoubt and suffered the brunt of the damage during the 1989-1990 eruption.
According to the study, the Drift River was affected in several ways during the last eruption, all of which cut down on both the salmon population and the insects young salmon eat. Debris flows added as much as ten meters of sediment to the channels of the river. Boiling hot lahars (a mixture of mud and water) were the biggest threat to the river however. They reshaped the entire river valley, cutting new river channels, destroying nearly all the riverbank vegetation, and wiping out aquatic life by either boiling it to death or washing it out to sea.
These changes affected the salmon population in the Drift River in several ways, both in the short term and in the long term. First, the debris flows coated the course gravel salmon generally prefer to lay their eggs on in sediment, destroying many of the spawning sites. Shifting currents and new river channels also changed fish access to these areas, making it almost impossible for some salmon to even find their way back to their spawning grounds. The lahars also wiped out nearly all the insects juvenile salmon depend on for food. Stocks of these bugs remained low for several years and were just beginning to rebound five years after the eruption. This disproportionately affects King Salmon who spend up to a year in their spawning grounds before migrating to saltwater.
Dorya and Milner found that these stream changes affected salmon stocks for years to come. The most drastic of these was that nearly an entire year’s worth of salmon were completely lost due to the eruption by starvation, boiling, or being swept prematurely out to sea. The changes in the stream also significantly hampered the ability of salmon to spawn in future years. The most significant change was the loss of stream bank vegetation, particularly the mature Spruce trees. Salmon, particularly King Salmon, prefer cool, clear, slow moving water while they are young. The spruce trees along the banks of the Drift River ensured that the water stayed both clear of debris by holding the bank together and keeping shaded and cool. These trees take many years to germinate and grow back.
Mount Redoubt 1989 Eruption
So what does this all mean for fishing in the Kenai Peninsula and Cook Inlet? Dorva and Milner themselves admit that they can’t draw any statistically significant correlations between the plight of the Drift River and fish stocks in the Cook Inlet. However, even if only a few rivers are affected by the eruptions, it still means less overall fish are in the inlet and surrounding areas. If the eruptions are bad enough, a worse case scenario could be decreased bag limits in the Kenai Peninsula area to allow fish stocks in the Cook Inlet to replenish. Depending on wind direction at the time of the eruption, the Kenai Peninsula could also end up covered in ash from Mount Redoubt. this has the potential to cause flooding and disrupt spawning until river currents scour out the ash.
Another effect that should not be overlooked is the eruption’s effect on air travel. The ash clogs airplane engines and will ground flights. This happened during the 1989 eruption, when ash blew 150 miles away into the path of a KLM jet. All four engines of the plane clogged and flared out and the plane dropped two miles before the crew restarted them and landed the plane safely.
It’s still too early to tell if the eruption that took place last night will be like the one in 1989. Volcanology is still an inexact science when it comes to predicting exactly when and how eruptions happen. But, if you’re planning an Alaska fishing trip for this summer, make sure you keep abreast of new developments with Mount Redoubt. If you want to keep really up to date, or are just interested, the Alaska Volcano Observatory has a webcams setup streaming real time video on several volcanoes, including Mount Redoubt.
Related posts:
- What Everyone Ought to Know About the Mount Redoubt Eruption and Cook Inlet Fishing
- Where to Go on your Alaskan Fishing Trip