On warm summer evenings at twilight hundreds of bats swarm over the surface catching insects. During the day it is the swallows’ turn to feed on the abundant mosquitoes and mayflies emerging from the pond, while fish and amphibian larvae feed on tiny creatures below the surface. In late winter, waterfowl raft on the quiet waters to rest and feed until time to migrate farther north to nest. Raptors use the standing dead trees near the shore to watch for a meal, while woodpeckers and cavity-nesting birds use them for nesting or as a food source. Beaver, river otter, and other mammals can be observed on occasion. If we can sit still long enough, we could be rewarded with a bear or bobcat sighting.

water storage

Also important is the water storage service that wetlands and beaver ponds provide for a wide variety of living things that require stored, open, or flowing water for their existence. The Puget Lowlands are soaked by between 30 and 80 inches of rainfall each year, mostly from October through April. This rain recharges the porous glacial soil “sponge” that slowly releases a supply of water that becomes streamflow throughout the rain-free months of summer.

Wetland ponding keeps the water table closer to the surface through the summer and allows a quicker return of surface flows critical to salmonids (a family of cold-water fishes, including salmon, trout, chars, freshwater whitefishes, and graylings) once the rains return in October. The more water retained (less runoff), the better. If the water table is three feet below the surface by August, it will take several weeks of rainfall to bring it back to the surface where intermittent streams can begin to flow. If it is at or near the surface, flow can begin with the first heavy rains of fall. These could be critical weeks for salmonids and other species that use the wetlands and intermittent streams to reproduce and rear young. 

More than salmon use our wetlands for survival. This pair of Western Brook Lamprey were filmed underwater mating in an un-named tributary to Wildcat Creek. They will lay between 10 and 15 thousand eggs and then die. The young will drift downstream and hopefully end up where they will thrive. Photo by Frank Stricklin.

wetland nurseries

All salmonids require stream flow at some life stage. Chum salmon generally use the larger rocks found lower in our watersheds to lay eggs. The fish hatch and head to near-shore salt water habitats (estuaries) right away. This strategy works well when heavy fall rains arrive on schedule. However, coho salmon and sea-run cutthroat trout utilize the intermittent streams found in upper reaches of our watersheds to lay eggs. Once hatched, the fry must reach wetlands where they will spend about fifteen months maturing before fall rains flush them out to sea. They must find sanctuary before their natal stream dries up for the summer. Their odds of survival are greatly increased if they reach the safety of a wetland where they have deeper water, cover, and abundant food. The large and small woody debris found in wetlands provide cooling shade and a place to hide from predators.

Glass and metal sculpture near the mouth of Clear Creek in Silverdale, WA.

The author, seated, and Arno Bergstrom standing at the fish passage bridge installed in Newberry Hill Heritage Park in fall 2019. Now we need rain! Photo courtesy Karl Erickson. Read the article by Arno in Issue 2 of Salish Magazine.

Table of Contents, Issue #9, Autumn 2020