the estuary. Another type of estuary habitat is formed by native Olympia oysters (Ostrea lurida). These are historically abundant in Yaquina Bay, and in addition to creating hard surfaces in the estuary, oysters also filter the bay water and provide food for local people. In fact, settlement on the mouth of Yaquina Bay is attributed in part to the oyster fishery. In subtidal areas, marine mammals such as harbor seals and California sea lions are sometimes present in Yaquina Bay. Sea lions in the estuary are mostly male. They move through the estuary, but spend a lot of time near the Bayfront or hauled out on docks, perhaps due to the additional food or safety. Some fish species present in Yaquina Bay include English sole and sculpin, in addition to river lamprey, lingcod, anchovies, Pacific herring, sturgeon, flounder, and salmon. Clams and Dungeness crabs are also present within the bay and make up a resource for recreational fishers. The estuary as a nursery Yaquina Bay has been shown to be a site for spawning and development of many species. Pacific Herring and bay goby larvae are abundant, but other larval fishes such as sculpin, anchovy, smelt, clingfishes, cod, stickleback, pipefish, prickleback, gunnels, sandlance, rockfish, greenlings, lumpfish, and flounder are present in the estuary. Although there are larval fish present in the estuary, the Pacific herring was found to be the only commercial species that relies on the estuary for spawning and development. Yaquina Bay also provides a nursery environment for English sole. Multiple species of juvenile salmon, including chum, coho, and chinook, also pass through Yaquina Bay during their life cycle, often transitioning from shallower to deeper waters as they grow. Chemistry of Yaquina Bay The Yaquina Bay estuarine chemistry is influenced by daily tides, river sediment input, summer upwelling along the coast, and biological processes. Tides Yaquina Bay experiences mixed semidiurnal tides, ranging from 1.9-2.5 m (6.2-8.2 ft) daily. The influx of water from the ocean changes the salinity of the estuary, creating a salt intrusion that has been estimated to reach as far as 21.8 km (13.5 mi) upriver. Daily tidal changes affect estuary mixing and stratification. Flood tides coming from the ocean bring coastal nutrients like nitrogen and phosphorus into the estuary. During mixing events, the Yaquina Bay estuary experiences changes in gradients for salinity, concentration of chemical species, and suspended sediment, which in turn influences biological