Cottus gulosus (Girard 1854), Inland Riffle Sculpin (Fig. 1) Originally described by Charles Girard as Cottopsis gulosus from the San Joaquin River, as follows: “Largest specimens a little over three inches {76 cm} in total length; of which the head forms the third, the caudal fin excepted. Preopercle provided with two small spines, such as may be observed in several species of Cottus proper, the head otherwise is smooth; mouth proportionately large; posterior extremity of upper maxillary reaching a vertical line, which would pass behind the pupil. A space of five twentieths of an inch exists between the origin of the first dorsal and the occiput. Second dorsal connected with the first by a low membrane proceeding from the last spiny ray. Tips of posterior soft rays not quite reaching the base of caudal. Anal, about as high as second dorsal, but shorter. Caudal, well developed and posteriorly rounded. Origin of ventrals midway between the tip of lower jaw and the anus. Pectorals broad and large, its longest rays extending posteriorly as far as the fifth ray of second dorsal. D IX. 18. A 13. C 3. 1. 5. 4. 1. 2. V I. 4. P 15. Lateral line uninterrupted from thoracic region to base of caudal. Abdomen beset with minute prickles; skin elsewhere smooth. Ground color reddish brown; head and dorsal region spotted with black. Dorsal, caudal and pectorals barred with black; first dorsal provided posteriorly with an elongated black spot. Anal and ventrals unicolor. (Girard 1854; p.130). This description still fits the species complex today, although larger samples show more variation in fin ray counts and characters (Table 1). Characteristics of Riffle Sculpins used in this study (n = 23) are as follows: anal-fin rays (12–15), dorsal spines (6–10), dorsal rays (14–19), dorsal fins usually joined, black spot on dorsal (yes), palatine teeth present (variable), mouth vs eye (variable but maxilla mostly reaches mid-eye), chin pores (0–2), pelvic fins spines + rays (1+2–3), pelvics touch vent when depressed (variable but mostly not), pectoral fin rays (13–16), preopercular spines (1–2), lateral line completeness variable, and lateral line pores (26–38). Holotype. USNM 291, Cottopsis gulosus from San Joaquin River, California (two specimens), Collected by A. L. Heermann and described by Charles Girard (1854). Diagnosis. It is distinguished from other members of the C. gulosus complex as a distinct lineage determined by genomic studies and its limited geographic distribution (Figs. 1, 3). In streams, it can co-occur with C. asper from which it can be most easily separated by its short anal fin (12–15 rays vs. 16–19 for C. asper) and short pelvic fins, which do not touch the vent when depressed. Distribution. C. gulosus is the name historically assigned to all populations in the species complex as described in this paper, including C. pitensis. Our study shows that the name should be restricted to (a) populations found in streams in the western Sierra Nevada, on the east side of the southern Central Valley, from the American River watershed in the north to the Kern River watershed in the south (Fig. 2), including the San Joaquin River and its tributaries and (b) populations in the Sacramento River and streams tributary to it, except the Pit River. Baumsteiger et al. (2014) used mitochondrial and nuclear DNA to examine a large sample (n = 872) of sculpins assigned to the C. gulosus species complex. They found a distinct, genetically-based separation of C. gulosus from streams flowing into the southern Central Valley, from similar sculpins in streams flowing into the northern Central Valley (Sacramento Valley). These populations here are treated here as new subspecies. The two river systems join in the tidal Sacramento-San Joaquin Delta. A similar break was found in the distribution of the Sacramento Riffle Sculpin lineage at the mouth of the Pit River (now under Shasta Reservoir); sculpins above this break are genetically Pit Sculpins while those below the break are a subspecies that shows evidence of ancient hybridization with C. pitensis (Baumsteiger et al. 2014). Etymology. Cottus was the Roman name for European sculpin, while gulosus roughly translates as ‘big mouth’ or ‘gluttonous’ (Moyle 2002).

Published as part of Moyle, Peter B. & Campbell, Matthew A., 2022, Cryptic Species of Freshwater Sculpin (Cottidae: Cottus) in California, USA, pp. 501-527 in Zootaxa 5154 (5) on page 516, DOI: 10.11646/zootaxa.5154.5.1, http://zenodo.org/record/6655473