Eucyclogobius newberryi, the Northern tidewater goby, is a species of goby native to lagoons of streams, marshes, and creeks along the coast of California, United States. The Northern tidewater goby is one of six native goby species to California. Etymology The genus name translates as "true cycloid goby", referring to the scales, while the species epithet is in honor of J. S. Newberry (1822-1892), an American geologist, physician and explorer, who collected fishes for the species describer, Charles Frédéric Girard, just not this species. Description A small fish, only rarely longer than 5 cm (2 in), the northern tidewater goby is elongate with a blunt tail. Color is a mottled gray, brown, or olive; living fish are translucent or mostly transparent. Tidewater gobies, like many fish, exhibit countershading and tend to be mottled slightly darker on the dorsal side. The upper part of the first dorsal fin is clear or cream-colored, while the second dorsal is longer than the first, and close in size to the anal fin. The large mouth extends back to or past the posterior edge of the eye, and is angled upwards. The eyes are spaced far apart. Unusually among gobies, the scales are cycloid instead of ctenoid; they are always absent from the head, and often from the underside too. Breeding individuals will demonstrate color changes, with the males becoming more black with white spots as females become tan or reddish-brown with golden or dark-brown sides. Females may also take on a darker color while fighting. Similar fish include the longjaw mudsucker, which can be distinguished from the northern tidewater goby by its more horizontal mouth and shorter rays in the anal fin compared to the 2nd dorsal fin. Distribution and habitat Their range extends from Tillas Slough at the mouth of the Smith River in Del Norte County, California, south to Agua Hedionda Lagoon in San Diego County. While once recorded in at least 87 coastal locations, they are now gone from many, including San Francisco Bay, although they can still be found nearby at Rodeo Lagoon in Marin County and in San Pedro Creek in Pacifica. Despite the common name, this goby inhabits lagoons formed by streams running into the sea, as well as semi-closed estuaries. The lagoons are blocked from the Pacific Ocean by sand bars, admitting salt water only during particular seasons, and so their water is brackish and cool. The