Rhinichthys klamathensis

Rhinichthys klamathensis (Evermann and Meek 1898), Western Speckled Dace

Fig. 6.

Agosia klamathensis Evermann and Meek 1898:74; Snyder 1908:98

Apocope klamathensis Evermann and Clark 1931:55

Rhinichthys osculus klamathensis Shapovalov and Dill 1950:386; Hubbs et al. 1979:12; Shapovalov et al. 1981:25; Moyle 2002:161; Markle 2016:50

Holotype: USNM 48225 (64 mm SL) as Agosia klamathensis Evermann and Meek 1898. November 3, 1896, mouth of small creek flowing into Pelican Bay, Upper Klamath Lake, Oregon, USA, Seth Meek and A. R. Alexander.

Paratypes. USNM 48231 (39 specimens) and 125012 (38 specimens). Same date and place as holotype.

Diagnosis. A cryptic species readily recognized as Speckled Dace by small adult size (6–11 cm SL) and distinctive body shape. Dark blotches on sides merge into a line of dark pigmentation below eye, to snout. Meristics are in Table 3. The best way to characterize this abundant fish is as a distinct Speckled Dace lineage found throughout the Klamath, Sacramento, and Warner watersheds with three sub-lineages that cannot be readily distinguished from one another.

Description. According to Evermann and Meek (1898:74-75, Fig. 6) “ the fish from [Upper Klamath Lake]… possess certain characters which serve to distinguish it from A. nubila. While the differences are slight, they are plainly evident and must be recognized, and we therefore describe it as a new species (p. 74). Head 4 [times into standard length]; depth 4.5; eye 4.5 in head; D[orsal rays]i.8; A [anal rays] i,7; [lateral line] scales about 14–78–10 (average, 73 in 49 specimens).”

Body robust, subcylindrical, back somewhat elevated; snout rather long, mouth inferior, little oblique, the lower jaw included; maxillary not reaching front of orbit; upper lip without frenum; barbels present but small. Lateral line incomplete, interrupted in many places, about 30 pores developed. Origin of dorsal fin midway between front of pupil and base of caudal fin; pectorals rather short, reaching about three-fourth the distance to ventrals; ventrals reaching vent; anal[fin] large, its longest ray 1.5 in head.

Color in alcohol, olivaceous, mottled and blotched with darker on back and sides; under parts pale; an obscure pale streak from eye to base of caudal fin, below which is a broad dark band; dorsals, pectorals, caudal dusky; other fins plain; a black blotch at base of caudal. This form is distinguished from Agosia nubila chiefly by the smaller size of the scales. A. nubila has 49–66 lateral line scales (mean 57, n=73), while A. klamathensis has 68–78 (mean 73, n =49).

Overall, there are only minor (statistical) differences among the three subspecies from this basic description. However, Markle (2016) used lateral line scale number as the principal character to separate Western Speckled Dace from other dace taxa in Oregon. In contrast, Smith et al. (2017) could not readily distinguish lineages despite multivariate analyses of combined meristic, morphological, mtDNA, and fossil data from the entire region in which Speckled Dace sensu lato occur.

Distribution. The Western Speckled Dace is found throughout the Klamath and Sacramento watersheds, including streams as far south as the Santa Maria River in southern California. Its distribution in the Warner basin is mostly in springs and small cool-water streams. Only the headwaters of Twelvemile Creek are in California (Modoc County). Before the introduction of non-native game fishes, it probably had a wider distribution within the basin. See the subspecies accounts for more detailed distributional information.

Note: Geology. The Klamath River has not been connected to the ancestral Sacramento River system since the end of the Pliocene (ca. three mya); however, extensive deformation (e.g. down-faulting of the Klamath Graben) and vulcanism (both from the Cascade-arc and Medicine Lake volcanic fields) occurred almost continuously in the northern Sacramento and southern Klamath Basins (Colman et al. 2004). It is probable that this activity led to repeated drainage captures of between the two basins and allowed for intermittent gene flow among dace populations. Inter-basin connectivity presumably was less frequent between Klamath/Sacramento streams and those in the Warner Basin. The development of the Great Basin faulting and extension belt of down-faulting resulted in creation of the Warner Range (ca. 3 mya) which resulted in a permanent topographic separation of the basins sometime in the late-Pleistocene (1.0–0.1 mya) (Egger et al. 2011).

As the result of these active geologic processes, each of the three major subspecies of R. klamathensis, as discussed here, is endemic to a single large watershed, plus some coastal watersheds in the case of Sacramento Speckled Dace. They share these waters with other endemic fishes. Dace ultimately colonized these three watersheds from the ancient Columbia River Basin during a series of volcanic and other geologic events that caused the predecessor of the upper Snake River to flow into the Pacific Ocean via the Klamath-Sacramento region, apparently during the Pliocene period. Fish fossils from ancient deposits in the Idaho region, that predate the rise of the Sierra Nevada and coastal mountain ranges, indicate a source of the predecessors of the highly distinctive endemic fish fauna of the lower Sacramento-San Joaquin Watershed (Minckley et al. 1986). It is likely that the Speckled Dace was not part of those early colonization events but arrived later, during a period when volcanic activity caused the upper Pit River to switch from flowing into the Sacramento River to flowing into the Klamath instead, which had its own endemic fish fauna. Some Klamath fishes (e.g. Cottus spp., Siphatales bicolor) were able to colonize the upper Pit watershed as a result. The ancestral Pit River then broke through the volcanic dike barrier and rejoined the Sacramento River system, bringing in its water members of the Klamath fish fauna. Alternately, Smith et al. (2017) suggest colonization of the Sacramento system could have come from a pass through the southern Sierra Nevada that apparently was open 3.2 million years ago or earlier. However, the genomic similarities between Sacramento and Klamath daces and between them and Warner Speckled Dace are presumably the result of their ancestors colonizing the region during a long geologically active period in the Klamath-Pit region. The genomic study of Su et al. (2022) supports this view (Figure 2) and that the Western Speckled Dace merits full species status.

Note: History. The three lineages that make up this species have different taxonomic histories (Evermann and Clark 1931, Moyle 2002). The Klamath Speckled Dace was recognized in 1898 as a species, and it retained its identity even when subsumed as a subspecies under R. osculus. The Sacramento Speckled Dace was largely ignored as a taxon despite its abundance and wide distribution. Presumably early workers such as Cloudsley Rutter, Charles Gilbert, and John Otterbein Snyder saw that it could not be readily distinguished from other Speckled Dace and accepted by default the use of an improper name (some variant of Agosia carringtoni) or else treated it as Lahontan Speckled Dace. The Warner Speckled Dace came to our attention because of controversy over the status of the population in remote Foskett Spring, which modern genetic analysis showed to be part of the Warner Speckled Dace lineage described in this paper. Su et al. (2022) show that, based on genomics, the three lineages are similar enough so that together they can be treated as a single species, Rhinichthys klamathensis.

Nevertheless, all three populations are isolated from one another, with long independent histories. The early history of each basin includes one or more periods of ancient interconnectedness which allowed Speckled Dace to colonize all three basins. The three lineages co-occur with other endemic fishes in their respective basins. The endemic fishes in each basin have close relatives in the other basins (e.g. Siphatales bicolor subspp.), as well as species unique to each basin.

Etymology. The name ‘Western Speckled Dace’ (Markle 2016, Smith et al. 2017) covers three lineages: Klamath Speckled Dace (R. k. klamathensis), Sacramento Speckled Dace (R. k. achomawi) and Warner Speckled Dace (R. k. goyatoka). Only the Klamath Speckled Dace has been previously named, so R. klamathensis becomes the species epithet for three subspecies. Klamath is an anglicized version of a name for the native peoples inhabiting the upper Klamath Lake region in Oregon (Gudde and Bright 1998). See subspecies accounts for further explanations.

Conservation Status. Sacramento and Klamath Speckled Dace are wide-spread and abundant in the large basins they inhabit. Warner Speckled Dace, including the population in Foskett Spring, are limited by the low availability of water in the desert Warner Basin. Their populations for now seem reasonably secure, although the basin has been invaded by non-native species. The Foskett Spring population was listed in 1985 as a Threatened species under the federal Endangered Species Act but it was delisted in 2019, following implementation of the recovery plan.