Japanese Eelgrass Management on Commercial Clam Beds in Willapa Bay David Beugli Eelgrass in Willapa Bay We have two common species of eelgrass in Willapa Bay • The non-native Japanese or dwarf eelgrass; Zostera japonica • The native Pacific eelgrass; Zostera marina What is Japanese Eelgrass? • Zostera japonica is a marine flowering plant that is native to the Northwestern Pacific. • Introduced to the West Coast of North America • Perennial plant that can spread by seed or rhizomes Zostera japonica typically occupies tidelands with an elevation of 0’ to -5’ MLLW Zostera marina can be found both intertidal and subtidal with an elevation preference of -1’ to -15’ MLLW Eelgrass Distribution in Willapa Bay Why do we want to control Zostera japonica? The Good • Facilitates native eelgrass l • Stabilized sediments • Creates habitat for some fish and invertebrates • Forage source for some species of waterfowl • May aid in carbon sequestration Why do we want to control Zostera japonica? The Bad • Modifies habitat for benthic invertebrates which can result l in changes to prey availability for shorebirds/fish/crabs • Facilitates invasive species such as Polychaeta's, snails. • Ecosystem engineer- sediment accretion prevents tidal drainage, increase water temperatures • Destroys commercial shellfish beds Management of Zostera japonica? California: Listed as a both an invasive and noxious weed – small population is controlledl by hand Oregon: Not listed and is ignored by land managers Washington: Listed it a Class C noxious weed. This has led to the creation of a NPDES permit NPDES Permit • 2014 NPDES Permit Issued by Ecology • General Permit any licensed clam farmer can apply • Specifically for the use of Imazamox on commercial clam beds in Willapa Bay only What is Imazamox? • Herbicide registered by the EPA for aquatic uses • Categorized as a reduced risk herbicide, meaning its not considered a human health risk • Only toxic to plants, rapidly absorbed, degrades quickly, little risk of off site movement • Little risk to non-target plants • Example of clam grounds treated for japonica • 3 months after treatment you can see the bare tidelands • Control requires direct contact on drained tidelands Treatments are highly precise Research Site • Permit allows for treatments to occur within Willapa Bay on sites that have permit coverage • Treatments may only occur between April 15 – June 30 • Buffers of 30’ are required for the native Zostera marina Willapa Bay • ~ 77,000 surface acres • ~ 45,000 intertidal acres Privately owned tidelands • ~9000 acres actively farmed • ~6000 acres considered for clam cultivation Currently ~1,200 acres of commercial clam beds are covered under NPDES permits This is: 1.6% of the total area of Willapa Bay (77,000 acres) 4.6% of the tidelands that could contain eelgrass (26,000 acres) 20% of the 6,000 acres designated for clam culture in Willapa Bay Total Acres of Japonica Treatment 315 294 311 102 86 2014 2015 2016 2017 2018 Take Away • Everyone needs to be informed and understand what is actually going on • Scale and scope are important, small number of acres, in Willapa Bay, and only on commercial clam grounds • Safeguards are in place for the native Zostera marina Call to Action! • The NPDES permits are up for another 5 year renewal • Ecology has opened a new public comment period (Sep 18 – Nov 4) • Now is the time to help inform your friends, educate them about the facts, and get the message out! David Beugli Ph. (360) 642-3755 [email protected] www.WGHOGA.net.