Tule Perch

The tule perch Hysterocarpus traskii is a surfperch (Embiotocidae) native to the rivers and estuaries of central California, United States of America. It is the sole member of its genus, and the only freshwater surfperch.

The tule perch is small, at most 15 cm in length, and deep-bodied, with a definite hump shape between the head and the dorsal fin. Color is variable, with a dark back that may have a bluish or purplish cast, and a whitish or yellowish belly. The sides may have a pattern of narrow or wide bars; the frequency of barred patterns varies according to subspecies. The dorsal fin has a noticeable ridge of scales running along its base, and consists of 15-19 spines followed by 9-15 soft rays. The anal fin has 3 spines and 20-16 soft rays, while the pectoral fins have 17-19 rays.

They are fish of the lowlands, inhabiting lakes, sloughs, streams, and rivers, generally in areas with beds of vegetation or overhangs. They generally gather in groups, sometimes in large numbers. Their diet is primarily small invertebrates sucked up from the bottom or picked from the midwater column.

The tule perch occurs in three separate areas in California, which have become differentiated into subspecies:

• Hysterocarpus traskii traskii originally occurred throughout the Sacramento River-San Joaquin River and out into the estuaries around San Francisco Bay, and is still common as far north as the Pit River, although it has mostly disappeared from the San Joaquin basin. The only unbarred fish occur in this subspecies, about 43% existing in this color pattern.

• Hysterocarpus traskii lagunae, the Clear Lake tule perch, is native to Clear Lake and the two Blue Lakes. Although threatened by alien fish introductions and loss of habitat, it remains common in the lake. A broad-barred color pattern is common only in this subspecies, at 27% of individuals.

• Hysterocarpus traskii pomo, the Russian River tule perch, occurs only in the Russian River and the lower parts of its tributaries.

The formal description of the tule perch was first read by W. P. Gibbons at a meeting of the California Academy of Natural Sciences on May 15, 1854, and then published in the San Francisco newspaper The Daily Placer Times and Transcript on May 18, making it a rare case of a new species being published in a newspaper rather than book or scientific journal. Gibbons chose the genus name Hysterocarpus "womb-fruit" referring to the livebearing common to all surfperches, and traskii (sometimes seen as traski) in honor of J. B. Trask who sent Gibbons the first specimens of this fish.