WFW conducts surveys to monitor the distribution of oyster drills and inspects facilities to ensure risk of transfer from one area to another is minimized. Restricted Areas: WDFW designates areas infested by oyster drills as Restricted Areas, and movement of shellfish and equipment from these areas to areas considered Unrestricted (free of oyster drills) or Undesignated is prohibited or restricted with conditions intended to minimize risk. Permits: Transfer permits from the Washington Department of Fish and Wildlife are required for the transfer of shellfish, shellfish aquaculture products (including oyster seed, cultch and shell), aquaculture equipment (including aquaculture vehicles and vessels) or any marine organisms adversely affecting shellfish. The movement of shellfish, equipment, vessels, debris, and other items that spend time on marine shorelines occupied by oyster drills can lead to their introduction to areas previously free of them. Japanese oyster drills are non-native pests and WDFW has measures in place to limit their spread from established areas. Its distribution in Washington is still patchy (localized) as the species has limited natural dispersal ability, and WDFW is working to keep it from being introduced to new areas of our shoreline. It is found in high densities in some locations in Puget Sound, Hood Canal, the Strait of Juan de Fuca, and Willapa Bay. The species is native to the NW Pacific (Japan, northern China, South Korea) and ahs since been introduced to the Pacific coast of North America from British Columbia to Oregon and parts of California, as well as to several European countries. Because of this strategy, human-aided dispersal (such as moving shellfish, equipment, or debris with hitchhiking drills) is the chief pathway for further spread in Washington. Hatching juveniles are miniature versions of adults and emerge as "crawl away" juveniles with no pelagic (waterborne drifting/swimming) larval stage-which limits their dispersal ability. They can be discerned from native whelk egg capsules by their pronounced twisted "vase-like" shape. Egg capsules are laid in clusters and can be orange, yellow, and pink in color. Larger shellfish, with thicker shells, are less vulnerable to drill predation.ĭrills gather and lay benthic rice-grain-sized egg capsules on hard structures in Spring. They are especially fond of small juvenile or "spat" oysters. Drills feed on a range of shellfish, such as Pacific oysters ( Magallana gigas), Manila clams ( Venerupis phillipinarum), Olympia oysters ( Ostrea lurida), mussels ( Mytilus spp.), and barnacles. They use secretion of an acid and a raspy tongue-like structure called a radula to puncture or "drill" holes through their prey's shell, then using secretion of a digestive enzyme into the body of their prey to enable them to feed. They can also be found (often in lower densities) in soft substrates. They prefer hard substrate, especially structure provided by Pacific oyster shells, clusters, and beds/reefs (where they feed, shelter, and lay their eggs)-but can also be found on or around manmade structures like cinderblocks, aquaculture gear, and debris. Ecology and life historyĭrills are found in the intertidal zone in various locations in Puget Sound, Hood Canal, the Strait of Juan de Fuca, and Willapa Bay. A good description of native Nucella Lamellosa can be found here, courtesy of the Oregon Institute of Marine Biology. Their egg casings lack the twist and vase-shape of non-native drills, instead resembling a smooth, torpedo-like shape. They come in smooth-shelled, smooth-banded, and frilly shelled variations. Native whelks have a heavier, chunkier shell and are generally larger (commonly up to 54mm or 2.1 inches but reportedly reaching 100mm, or almost 4 inches). This species can be confused with native species of drilling predatory snails, such as the native dogwhelk ( Nucella lamellosa) to which it (and its egg casings) bear some resemblance. Native dogwhelks primarily eat barnacles and are not considered pests of aquaculture or native ecosystems, contrasting with the preferred diet and status of the non-native Japanese oyster drill. The shell can be brown, green, orange, beige, or striped and can reach about 50mm in length (1.9 inches) it is generally closer to 40mm (1.5 inches) in length. The Japanese oyster drill is a marine snail with a heavy shell featuring an ornate design. A comparison of Japanese oyster drill vs.
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