Oncorhynchus mykiss calisulat, Campbell & Habibi & Auringer & Stephens & Rodzen & Conway & Finger, 2023

Campbell, Matthew A., Habibi, Ensieh, Auringer, Grace, Stephens, Molly, Rodzen, Jeff, Conway, Kevin W. & Finger, Amanda J., 2023, Molecular Systematics of Redband Trout from Genome-Wide DNA Sequencing Substantiates the Description of a New Taxon (Salmonidae: Oncorhynchus mykiss calisulat) from the McCloud River, Zootaxa 5254 (1), pp. 1-29 : 21-24

Oncorhynchus mykiss calisulat ssp. nov., Campbell and Conway

urn:lsid:zoobank.org:act:60E62FE9-D41A-46E7-8A5F-ADF021D1CBFB

McCloud River Redband Trout, Cali Sulat ( Figure 8 and Table 3 )

Holotype. WFB 5020, formerly WFB 76-05- 23, 120 mm SL; USA, California, Shasta County, McCloud River, Sheepheaven Creek (no latitude or longitude provided), 8 October 1974. Sturgess, Hoopaugh and Staley, collectors.

Paratypes. USA: California: WFB 5021 , 1, 118 mm SL; same as holotype— WFB 5022 , 1, 118 mm SL; same as holotype— WFB 5023 , 1, 104 mm SL; same as holotype— WFB 5024 , 1, 75 mml SL; same as holotype — TCWC 2872.01 , 23 (2 c&s), 79–144 mm SL; McCloud River, Sheepheaven Creek , 41.32735, -121.8276, 1974 — LACM 38568-1 , 2, 96–101 mm SL; McCloud River, Sheepheaven Creek , 41.32278, -121.82389, 1 June 1974

Diagnosis. Oncorhynchus mykiss calisulat is distinguished from O. m. stonei, by a lower number of gill rakers on the first arch (14–18, mode 15 vs. 17–22, 20), a lower number of branchiostegal rays (8–11, 9 vs. 10–13, 12) and a greater number of scales in the lateral series (151–174, 162 vs. 139–160, 146). The numbers of gill rakers on first gill arch, branchiostegal rays and pectoral fin rays (13–14, 13) are distinctive in comparison to other Pacific Trouts, with the number of gill rakers on first gill arch (14–18, mode 15) the lowest of any Pacific Trouts. Oncorhynchus m. calisulat is further distinguished from O. mykiss and O. aguabonita by 44 SNPs with fixed allele differences described by Habibi et al. (2022).

Description. SeeFigure8forgeneralappearanceandTable3formorphometricandmeristiccharactersobtained from holotype and paratypes. Chromosomes 2N = 58, NF = 104. Characterized by small overall adult size (largest specimen examined 143 mm SL) with well-developed parr marks present on adults. Body laterally compressed, greatest depth midway between occiput and dorsal fin origin. Head short, 25–30% of SL, laterally compressed. Eye large, diameter greater than snout length. Snout rounded in lateral aspect. Mouth large, posteriormost tip of upper jaw (maxilla plus small supramaxilla) located posterior to imaginary vertical line through posterior margin of orbit. Scales in lateral line row, 113–123 (mean of 117 reported by Gold 1977; holotype 116). Scales in lateral series, 151–174 (mean of 162 reported by Gold 1977; holotype 151). Scales above lateral line 32–36 (mean of 33 reported by Gold 1977; holotype 32). Scales below lateral line 23–27 (mean of 25 reported by Gold 1977; holotype 26). Pyloric caeca 29–42 (mean of 36 reported by Gold 1977). Dorsal-fin rays 10–15 (holotype 15), comprising iv,9, v,10 (holotype) or v, 11 in x-rayed (n=3) and cleared and stained material (n =2). Anal-fin rays 10–13 (holotype 12), comprising iii,9 (holotype) or iiii, 9 in x-rayed and cleared and stained material. Pectoral-fin rays 13–14 (holotype 13). Pelvic-fin rays 9–10 (holotype 9). Caudal-fin rays 10+8 (holotype) or 10+9. Dorsal procurrent ray 10–13 (holotype 12). Ventral procurrent rays 10–12 (holotype 12). Branchiostegal rays 8–11 (holotype 9). Gill rakers on first arch 14–18. Basibranchial dentition vestigial, with 0–5 teeth on basibranchal 1 ( Schreck and Behnke 1971; Gold 1977; 0 or 1 tooth only on basibranchal 1 in cleared and stained material examined herein). Basihyal with two rows of large, slightly recurved teeth. Total vertebrae 60–63 (holotype 61).

Coloration. In preservative ( Fig. 8A, C ), background color olive brown dorsally, fading to lighter cream brown ventrally. Circular to dorsoventrally elongate dark brown parr marks on body side; 7-10 (holotype 9). Small dark brown spots, each covering surface of 3–5 scales, scattered over dorsolateral and lateral surface of body; densest above lateral line below and posterior to dorsal fin and on caudal peduncle; few above lateral line anterior to dorsal fin or below lateral line anterior to anal fin. Dorsal surface of head with few small dark brown spots, similar in size to small spots on body. Lateral surface of head dusted with tiny dark brown melanophores, most prominent on cheek and operculum. Dorsal and caudal fin with small dark brown spots similar in size to small dark brown spots on side of body. Pectoral, pelvic and anal fin light creamy brown; with weak (holotype) or dense scattered dark brown melanophores. Adipose fin whitish; without (holotype) or with few small dark brown spots; posterior margin outlined dark brown. In life ( Fig. 8D ), body background color light olive brown dorsally, fading to pale yellow ventrally. Brick red lateral stripe extends along body side, deepest below dorsal fin. Parr marks dark blue-grey. Small spots on body, dorsal fin, and caudal fins black. Dorsal, adipose and caudal fins yellow. Pectoral, pelvic and anal fin orange. Tip of dorsal, pelvic and anal fins white. Posterior margin of adipose fin outlined black. Side of operculum orange red. A weak yellow cutthroat mark on ventrolateral surface of head.

Etymology. From the Winnemem Wintu name for the subspecies cali sulat, beautiful trout.

Distribution. Known from the McCloud River drainage basin upstream of McCloud Falls. Human mediated movements of other Rainbow Trout into the range of this subspecies has resulted in admixture of some McCloud River Redband Trout populations with other Rainbow Trout. Given that McCloud River Redband Trout appeared to occupy the McCloud River, and, likely the Upper Sacramento River Basin prior to Coastal Rainbow Trout (O. m. irideus ) and Great Basin Redband Trout (O. m. newberrii ) moving into the Upper Sacramento River Basin, there is a slight possibility that other populations closely related to McCloud River Redband Trout may have persisted above natural barriers to fish movement outside the core distribution of McCloud River Redband Trout known today. Rutter (1908) provides a detailed description of trout from a tributary of the Upper Sacramento River, South Fork Battle Creek, and comments on their similarity to McCloud River Redband Trout. The description of 11 South Fork Battle Creek specimens collected upstream of Battle Creek Falls, a barrier to fish movement, indicates similarity to key anatomical features of McCloud River Redband Trout. An average is only provided for the number of scales in the lateral series (163 vs. 162). Other characteristics are presented as a range (gill rakers 15–19 vs. 14–18; branchiostegal rays 10–12 vs. 8–11), with no pectoral-fin ray counts provided. Combined with additional evidence presented by Rutter (1908), it could be interpreted that Redband Trout historically were present as far south as the Feather River ( Behnke 1992). Future investigations of isolated populations can provide insight into the number of Redband Trout lineages that historically occupied the Upper Sacramento River Basin and their natural contribution to Coastal Rainbow Trout populations.

Associated Species. The McCloud River Redband Trout is the only known native fish from the McCloud River upstream of McCloud Falls.

Figures

FIGURE 8. McCloud River Redband Trout, Onchorhynchus mykiss calisulat, ssp. nov., Sheepheaven Creek. A. WFB 5020, holotype, 120 mm SL. B. same specimen as in A, radiograph. C. TCWC 28772.01, paratype, 144 mm SL. D. Illustration of O. m. calisulat, ssp. nov., showing life colors, © J. Tomelleri, used with permission.