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Bivalve Buddies

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By Emily Jankowski

 

Freshwater mussel in the stream.

For the rest of the ecosystem, salmon migration is something of a taxi service. Mostly this means bringing nutrients from the ocean upstream again, but some slower moving animals take it a bit more literally. The larval stage of freshwater mussels, known as glochidia, hitchhikes on fish in order to colonize new areas of streams and rivers. Don’t worry, the fish are not bothered by their passengers!

When ready, glochidia drop off of the fish and settle to the bottom to make a home among the sediment. Often mussels will use their foot to pull themselves into a position that offers them protection among the rocks while also giving them plenty of access to food in the current. Because mussels are filter feeders, they help to clean our waterways just by living in them! And for many animals, including otters, muskrats, and raccoons, mussels are a favorite meal. Piles of empty shells are a common site along mussel-bearing streams, hinting at the predators and prey you may not see. If they don’t get eaten first, mussels can live 60 or 70 years. Some individuals have even been known to reach 100 years old!

Emily excited to have found a western pearlshell!

Mussels can blend in easily with the rocks in the stream, but not too long ago we got lucky and noticed one in Friday Creek (pictured). It appears to be a western pearlshell mussel (Margaritifera falcata). Like most mussels in our region, it favors salmonids as a host for its glochidia stage. Perhaps this mussel was once attached to the gills of a chinook! And if we’re lucky, the salmon we help make good habitat for today will host the glochidia of future mussels-that will grow up to help clean the water for future salmon!

Freshwater mussels across the US are struggling to keep up in a world that once harvested their shells for buttons and continues to pollute and sediment load their waters. Many species are endangered. If you’re interested in freshwater mussels, check out @musselsPNW for more information, or this section of the Xerces Society website for additional resources.

 

When Going With the Flow Leaves You Stranded

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By Erin Matthews

Chum salmon begin their life in a nest (called a Redd) built by their parents in a gravel bottomed stream usually in the lower sections of the river.  At barely an inch long, these newly hatched masters of evasion and disguise are only visible by a vigilant human observer.   Unlike other species of salmon, chum begin the long, treacherous,  journey to the ocean immediately after hatching—before they are even strong enough to swim against the currant!  They drift to the ocean, occasionally resting in off-channel habitat such as sloughs or ponds to rest, take shelter from the awesome power of the Skagit river currents, and to feed on bugs or plankton.  Those tiny fry that are lucky and strong enough to dodge birds, bigger fish, and other predators, spend a few months growing larger and stronger at the mouth of the river and estuary before leaving for the wide open ocean. 

But if a little chum takes refuge in a pond or slough, what happens if the river drops and strands them?  That is a question that the Skagit Fisheries Enhancement Group field staff were pondering on a lovely sunny Monday afternoon in early May.  At a stewardship site near Concrete WA called the Lower Baker Flood Plain, a team of staff, and volunteers dropped a research net into a pond that (despite being only a few meters from the banks of the river) had been disconnected from the Skagit for several weeks.  In a perfect, simple world, by early May all Skagit chum fry would be fat and happy living in the estuary where the Skagit River merges with Skagit Bay. 

Much to our surprise, we netted 17 chum in the shallow end of the pond.  Staff carefully recorded size and species of each individual fish, noting that these fish were especially large and well fed for their age, before releasing them back into the pond.  These little fish were doing well for now, no doubt benefiting from the nurturing environment of the pond which offered an abundance of shelter, food, and a water temperature cool enough for high dissolved oxygen levels but warm enough for the fry to grow larger faster than their counterparts in colder Skagit River water. 

Chum rarely rear in fresh water, and when they do they still must reach the ocean by the end of summer in order to survive.  Luckily for these fish, a heat wave washed over the Skagit in mid-May, which rapidly kick started spring snow melt and raised the water level of the Skagit enough to reconnect the pond and river, creating an exit for the fry.  If all goes well, the next time SFEG drops the research net into the Lower Baker Flood Plain pond we will not find any salmon. 

Controlling an Invasive Thug

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By Bengt Miller SFEG Stewardship Coordinator

 

If you are familiar with the term Polygonum then you deserve a pat on the back and a gold star. Polygonum is the name for a group of plants known collectively as the buckwheats. Within this family there is also a genus called Polygonum. These plant species are known collectively as knotweeds. The various species: Japanese Knotweed, Giant Knotweed, Bohemian Knotweed (a hybrid between Japanese and Giant) and Himalayan Knotweed are all listed as noxious weeds in Skagit County. All are required for control, except Bohemian Knotweed.

 

The Washington State Department of Agriculture has recognized the negative impacts knotweed has on riparian areas and has set aside funds specifically for the control of this invasive species. Knotweed poses the biggest threat to riparian areas. These stream corridors provide the perfect habitat for knotweed: the constant moisture provides a great growing medium, regardless of the soil type. In addition, knotweed propagates by fragmentation, meaning parts that are broken off the parent plant readily sprout into new plants.  Streams provide an ideal mode of transport, and thus one plant that is fragmented by beaver or weedwhacking can form a whole new colony. Once established knotweed forms a dense monotypic stand, reaching up to 13 feet tall, that outcompetes native understory vegetation. This is exceptionally troublesome because studies have shown that streams with large knotweed infestations have up to 40% fewer macroinvertebrates, due to the lower nutrient levels of knotweed leaves versus native species. These macroinvertebrates are the primary food source for juvenile salmon. Hence there is an inverse relationship between knotweed density and the number of juvenile salmon in a stream.

 

SFEG has been working since 2010 to control knotweed in the Skagit Watershed. The Upper Skagit Knotweed Control Program has the mandate to control knotweed anywhere in the Skagit Watershed upstream of Rockport. We survey for and treat knotweed on public and private land. Because SFEG is not a state agency we do not have any regulatory authority and depend on the willingness of private landowners to participate in the program. We are able to treat knotweed at no cost to the landowner because of grants from the United States Fish and Wildlife Service, National Fish and Wildlife Foundation, Mount-Baker Snoqualmie National Forest and Washington Department of Agriculture. Their support of the program has been vital.

 

Since the project began, the effort has identified over 2,000 patches of knotweed and has achieved 81% control in the floodplain and 70% control of knotweed in the entire Upper Skagit Watershed. In 2017, SFEG and the Washington Conservation Corps (WCC) surveyed within the 100-year floodplain along 34.5 mainstem river miles of the Skagit and Sauk Rivers, plus 5.2 miles of various tributaries, traversing approximately 3,269 acres (5.1 mi²) in which 3,087 individual knotweed stems in 137 patches were treated. The average size of each patch treated was 215 square feet. The average of less than one stem per acres is unheard of in infested watersheds.

 

This program is recognized throughout the state as a success. You can paddle, hike or drive along the banks of the Skagit or Sauk Rivers upstream of Rockport and with the exception of a few spots you will not see knotweed without a map showing where it is located. This is a stark contrast to the lower portions of the Skagit River, where knotweed continues to proliferate, sometimes being the only established vegetation on riverside gravel bars, and is a tribute to the quick and continued action taken by organizations in the Skagit Coordinated Weed Management Area.

 

If you would like to learn more about knotweed or are a Skagit landowner with property upstream of Rockport and would like a free knotweed survey conducted on your property contact Bengt Miller with the Skagit Fisheries Enhancement Group at bmiller@skagitfisheries.org.

 

Foraging tip: young, tender knotweed shoots can be collected and cooked similar to asparagus. Apparently they taste similar to rhubarb.