Puget Sound Salmon - Habitat Loss

Habitat Loss

Although salmon spend only a part of their life cycle in near-shore areas, these habitats are critical to the survival of salmon populations. Shoreline habitats of Puget Sound have suffered significant losses over the last 125 years. When marshes are lost, young salmon lose food and shelter. Studies show a 73 percent decline in salt marsh habitats bordering Puget Sound. Nearly all salt marsh habitats within major urban areas along Puget Sound have been destroyed. The Puyallup River Delta, for example, lost 100 percent of its nearshore habitat. Other factors that contribute to habitat loss are pollutants, bulkheads, loss of shoreline vegetation and the blockage from docks and piers. Polluted estuaries and nearshore areas have caused juvenile salmon to suffer adverse effects as they pass through the estuaries. Human-caused stresses can cause immune dysfunction, increased susceptibility to disease, and impaired growth. Bulkheads can disrupt shore drift and shoreline vegetation, thus eliminating cover and food sources for young salmon. Loss of shoreline vegetation along the shore is of particular importance to juvenile salmon because it stabilizes the shoreline, provides shade, acts as a protective cover, organic input and food source for young salmon moving in close to shore. Docks and piers can block light to underwater habitats such as eelgrass meadows, and sources of food and shelter for juvenile salmon and other marine life.

In conclusion, of all of the threats that salmon are faced with, including climate change, disease and animal predation, habitat loss is one of the greatest threats. Salmon face many obstacles throughout their cycle that add on the four mentioned before: loss of access to historic habitat, habitat destruction, pesticide use, aquaculture, urban development and encroachment onto riparian areas and increasing water temperatures in streams. It is critical to have open passages to natal or home streams for adults to spawn. If their energy is depleted before they spawn, they die without producing the net generation of fish. Warming water temperature and low water levels in streams also accelerate pre-spawn mortality.