Carefully shaking wet beach sand through a series of mesh screens can be a lot of fun. On a drippy gray weekend morning near the start of winter, our small group of naturalists and citizen scientists is looking for signs of forage fish. We had gathered to do this wet and cold work at the Heron Meadow at the center of Vashon Island. Snuggled next to a historic barn, this is also where the Vashon Nature Center (VNC) has set up their field station in a shipping container out of which they have been leading volunteers in the art of forage fish sample processing for years.

Forage fish is a catch-all category for all of the various species of smaller fish that are consumed by larger animals like salmon and sea birds. Because science still largely hierarchizes nature using the framework of consumerism, the great schools of herring, surf smelt, and sand lance are seen as ‘sea snacks’ rather than the center of a system supporting multitudes of species. In the VNC study, we were looking specifically for the eggs of sand lance and surf smelt deposited on the beach during spawning events.

This home of ours, Vashon Island, is really just a pile of heterogenous debris dropped by the most recent glacier to come and scour out the Salish Sea. Locally, this last glacial period is called the Vashon Glaciation or Stade, and it lasted for about 3000 years. It consisted of just one relatively small lobe of the Cordilleran ice sheet that covered Western Canada. This smaller lobe traveled down the Frasier River valley near modern day Vancouver B.C. and grew as far south as Tenino, which is just south of Olympia. Read Our Icy Past for more details about the movement of this “powerful ice blanket” across the region. It was an incredibly cold time, and there were musk ox, saber-toothed tigers, bison, and camels as well as mastodons and mammoths roaming around.

However, this was the furthest south the ice sheet could reach, and it had a tendency to melt from the bottom, eroding channels and creating ice cold rivers that molded the earth even faster. The ice lobe repeatedly advanced and retreated, usually melting faster than it could form, being here only because it was pushed slowly from behind by the bigger ice sheet to the north. Glaciers pick up loads of rocks and substrate, and the last one left these piles of unsorted stuff, or till, as it melted away, bringing to us an erratic array of granite boulders and the deposit that is Vashon Island, for which it is named. Read The Language of Glaciers for more details about types of glacial deposits and their other earthly molding powers.

Looking for eggs under a microscope. photo by John F. Williams

Sand lance eggs stuck to sand grains under a microscope.  photo by Holly Weinstein

When the Salish Sea was covered in ice, the great age of global glaciers was already in decline, and they were shrinking worldwide. The Vashon Glaciation reached as far as it could approximately 17,000 years ago when it began to melt for good. It melted very fast by glacial standards. Sometimes the edge retreated as fast as 1,000 feet per year, and as it did so, it left behind a great body of meltwater. Some of this water drained to the ocean through southern channels, but much of it remained in the Puget Sound trough as a series of freshwater glacial lakes. As the edge of the ice receded northward, channels between the lakes were opened and they joined to form the large Glacial Lake Russel, which took up most of the South Sound and lasted the longest — for approximately 1,000 years. This freshwater lake eventually grew to include the waters in present-day Hood Canal.

As the western edge of the glacier melted even faster, it left a very large Glacial Lake Bretz covering almost all of what is now Puget Sound. Eventually the ice retreated enough to allow the water to combine with the ocean at what we now call the Strait of Juan de Fuca which had been formed earlier, also carved by ice from the same sheet. The ecological chaos that ensued must have been incredible. That was approximately 15,000 years ago, and to this day Puget Sound has been filled with seawater.

These kinds of ecological events are implicated in the evolution of anadromous fish such as salmon, that habitually spend part of their life in fresh water and part of it in salt water. Now that salmon are generally considered a culturally and commercially important species, we have dedicated quite a lot of attention and money to restoring the stocks and understanding how they best thrive — including understanding the fish they eat.

The first forage fish survey VNC ever conducted was in 2016 when they visited a shoreline site on the southeastern tip of the island. It was a long walk down a slippery cobble beach on one of those pitch-dark winter nights, complete with a sleeting, freezing rain. Picking their way with headlamps, they spotted a few items washed ashore by recent high tides including, notably, a red wooden table resting in the rocks. The three surveyors walked to three locations that first night of the study: a control site, an experimental site, and a reference site. The experimental site will undergo restoration of the beach: from bulkhead armoring to a more natural habitat. The reference site will remain a more natural habitat, while the control site will foreseeably remain a bulkheaded, or armored, area of shoreline. This work is also adding to our understanding of shoreline restoration: to detect when and if restored sites are used as habitat by forage fish and to compare it to yet undisturbed or still armored stretches of shore in the same area.

Here, a shoreline with natural habitat allows for movement of beach substrate. Substrate, in this case, is the sediments and materials covering the beach such as sand, mud, cobble, and all the broken up bits of shells. Vashon Island has been eroding into the water ever since its creation. And the organisms that use the nearshore environment have come to rely upon the natural processes that move these materials along the beach. When the shoreline gets bulkheaded or armored, it is ostensibly to stop that movement, and habitat quality is measurably altered. Bulkheads change the way the water moves along the shore, causing the waves to scour away the sand and smaller particles in different places than it otherwise would. Only the larger cobbles and less-desirable areas for forage fish spawning are left. This is just part of what happens when natural shoreline is armored, and when this kind of change occurs repeatedly along the shoreline, the loss is immeasurable.

On that night of freezing rain, with the lights of Tacoma in sight just beyond the dark waters of the Sound, the surveyors use a 100 foot tape to measure two transects, or lines, parallel to the tideline and discuss the best places to collect samples. It seems that certain species prefer to spawn at different ‘heights’ on the beach. For example, the sand lance prefers to use the lower parts of the beach where sand is present and only uncovered when the tide is at its lowest. When a likely area of sand is identified at the lower beach levels, they shovel a few shallow scoops using a hand trowel at the appropriate places, and deposit them into plastic bags with handwritten, waterproof labels. It takes a while because this is the first time doing it, and they want to be sure to get it right. They also collect photographs of the beach according to the protocol. Then everything is repeated twice at each site, so they have six bags of heavy wet sand to haul back up the beach. At a later time it will be processed through the sieves and sent to the Department of Natural Resources to be examined under a light microscope.

Eventually we will all learn that some of the samples they collected on that first night contained thousands of sand lance eggs and was the first time spawning was recorded for this beach. When they stop at the washed-up table for a brief break, they decide right then and there to bring it back to be the new desk for the Nature Center’s budding office. Laughing and moving slowly back to their starting point, helping each other, they transport the table along with the bags of sand and eventually manage to squeeze it into the back of the car, barely leaving room for one of the passengers. That was six years ago and to this day the table still serves as a desk for the Vashon Nature Center.

Here’s a short movie (from 2010) about collecting forage fish eggs in Kitsap County and viewing them under a microscope.

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