Do docks impede passing salmon?

Our shoreline neighbor Dr. Don Flora offers his comments regarding the impact of residential docks on passing salmon. We offer a brief introduction and a link below…

There are studies showing that docks’ shadows affect the welfare of juvenile salmon headed toward the sea. Wide docks (ships’ piers and ferry terminals) create sharp breaks between sunlight and deep shade. One effect, shading-out of eelgrass, is observed but the impacts on salmon have not been measured and aren’t discussed here.

It has been supposed that predator fish, lurking in the darkness, will dash out to consume the passing salmon. Shade-based predation has been discounted, as discussed later.

Abrupt light-to-dark transitions, on sunny days under large docks, cause some salmon to detour around the discontinuity. Shade-driven diversion has been reported. But not under narrow residential docks.

If residential docks are making a difference to emigrating juvenile salmon, how large might that impact be? Small, according to calculations shown here. An average of 93 feet are added to the 55-mile swim from Kitsap County’s Sinclair Inlet to Puget Sound’s exit.

Here’s a link to Dr. Flora’s commentary on residential docks and passing salmon, or read the document below. Why is this relevant? Because state and local planners want to outlaw residential docks to save salmon.

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