Salmon Conservation Areas Must be Widened
According to a new study, areas of salmon conservation should be expanded to streams that don't actually contain salmon, but whose waters run into salmon habitat. In other words, the entire watershed should be protected and not just the rivers where there are large salmon runs. This is because the various feeder streams have different characteristics which is necessary to keep options open for the salmon. For example, steeper, faster streams contribute colder water, and slower meandering streams contribute warmer water. Some salmon have adapted to reproduce better in one condition than another. A healthy mix of river inputs not only helps the salmon populations grow, but also helps their predators: gulls, bears, and other animals.
This finding was put forth in a report by researchers from the University of Washington (UW) led by professor Daniel Schindler and doctoral student Peter Lisi. They suggest that the great importance of having diverse stream inputs is that it creates multiple spawning times for salmon throughout the year. This allow predators more time to catch their meals.
They focused their research on the Wood River watershed in southwest Alaska. "In any one stream, salmon might spawn for two to four weeks," said Lisi. "Animals like coastal brown bears and Glaucus-winged gulls gorge themselves at one stream for a few weeks and then just move to another stream that might have water temperatures a few degrees warmer and therefore support salmon populations that spawn at a later time. It's easy for animals to move when such streams are as little as a mile or two apart."
The researchers call this attribute of a network of streams, "hydrological diversity". Such an attribute more than triples the time predators have access to salmon during summer from just a few weeks to more than three months.
The implications of this finding have the potential of completely altering current conservation plans. Normally, conservation officials try to focus on which individual streams and rivers to protect to keep a healthy salmon population. According to the study, the entire watershed would need to be protected in order to maintain hydrological diversity.
The research study will be presented at the Ecological Society of America's annual meeting in Portland, Oregon on August 8th. It will be part of a session on linkages between aquatic and terrestrial systems.
For example, a healthy salmon population not only helps its predators but is also linked to the pollination of plants on the watershed such as the kneeling angelica. This 3-6 foot plant is pollinated by the bowfly which rely on the carcasses of salmon to lay their eggs. Having more salmon carcasses throughout a longer portion of the year gives the bowfly a population boom. After emerging from the carcass, they pollinate the kneeling angelica before breeding again.
For more information: http://www.esa.org/portland/
Salmon Run image via Shutterstock