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Environment And Ecology
USGS beach study in Kitsap to correlate forage fish spawn habitat in local bays

Members of the United States Geological Survey research crew pull in a seine through eelgrass. (Photo by Dave Ayers)United States Geological Survey (USGS) scientists began their shoreline forage fish study in Kitsap County the weekend of June 9 with what might be a local resident’s all too common problem — boat trouble.

These scientists access beaches by boat and work along the shoreline during both day and night periods wearing visually identifiable USGS clothing, and the boat clearly marked as a USGS research vessel.

The USGS research boat, shown here, had its first Kitsap visit to a boat mechanic. But the crew made up for lost time picking up the pace and working at all hours, tides allowing, and work could continue through July 8.

A sand lance is shown on a measuring device. (Photo by Dave Ayers)The crew — Theresa (Marty) Liedtke, the team’s fish biologist, with Colin Smith, Lisa Gee, Ryan Tomka and Dave Ayers — come from the USGS Western Fisheries Research Center of the Columbia River Research Laboratory in Cook.

The researchers are using “purse seine” nets to collect fish and plankton samples along shorelines — called beach seining — from Sinclair Inlet to Liberty Bay, Agate Pass to Madison Bay, beaches in Bainbridge Island, Manchester, Port Orchard and South Kitsap.

Forage fish, also known as prey fish or bait fish, such as surf smelt and Pacific sand lance, lay their eggs on fine, sandy beaches found throughout Puget Sound. This study will evaluate the use of these nearshore habitats by forage fish in their early life stages, and their possible links to economically and ecologically important species such as orcas, salmon and sea birds.

I first met the USGS crews back in 2007; including Liedtke, Gee, and Smith (see this article) when they were sampling randomly selected beaches around Liberty Bay. Then they were collecting data on each beach’s presence/absence of shoreline armoring, shade, material (sand, mud, cobble, gravel), presence of large woody debris, condition of uplands (roadway, landscaped yard, forested), and sources of freshwater, examining beach material samples to look for forage fish eggs.

Scientists from all four USGS disciplines — biology, geography, geology and water — contributed to that work that included monitoring wave action and water clarity (turbidity) in eelgrass beds, examining light levels, and measuring groundwater discharge to Liberty Bay and nearby waters to determine if (1) sand lance and surf smelt spawning is associated with groundwater discharge rates to intertidal beaches; (2) eelgrass growth is associated with groundwater discharge rates to subtidal areas; and (3) it’s affected by the overall contribution of groundwater to Liberty Bay.

They then developed models to look at various beach conditions in order to understand what variables were most linked with beach spawning, and help land planners to protect those aspects.

Now, five years later, they continue to sample other locations to make the model more robust. On June 18 they counted over 2,000 sand lance near Agate Pass and Keyport.

“And that was actually less than in May,” said Liedtke, “which indicates that they’ve either moved offshore as they’ve matured or been victim to predators — like shore birds that investigators have proved consume one-third of all forage fish.”

While young, they’re not very strong swimmers and measure just 30 mm in length when they leave the “nearshore nursery” to move off into deeper waters. The question posed by these scientists is, where do they go? So, Liedtke said the team is using deeper seines to capture more mature sand lance in order to determine where their habitat is.

Then, to test their theories, they will also compare habitats with eelgrass to those that have none to determine preference and challenges to survival. Because, if young forage fish can hide in eelgrass beds or shaded areas, they may be less likely to be picked off by predators.

Liedtke said that they will also test fish tissues using carbon isotopes because those that have been raised up in eelgrass have a unique carbon signature compared with species found in areas without. “With that kind of information, we can put our restoration dollars to work on the right habitat improvements … and try to preserve what we’ve got left,” Liedtke added.

The whole USGS crew said they are finding landowners extremely positive and supportive, adding that lessons are going both ways as old-timers share rich histories and chronicles of the past while these scientists teach landowners the value of forage fish in the food chain.

More project information is located at http://puget.usgs.gov. Questions or concerns can be directed to Theresa Liedtke at tliedtke [at] usgs [dot] gov or 509-538-2299, ext. 270. Visit USGS.gov or follow them on Twitter @USGS and our other social media channels, or subscribe to their news releases via e-mail, RSS or Twitter.

Kathleen Byrne-Barrantes's picture
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