Siphatales bicolor pectinifer

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General Information
Common Name: 
Lahontan lake tui chub

Conservation Status in California: Class 3, Near threatened (Moyle et al. 2011).
The only verified population in California is in Lake Tahoe which is undergoing change because of the intense human use of the Tahoe basin.

Life History: 

Life History: Lahontan Lake tui chub feed mostly on zooplankton, especially cladocerans and copepods, but also consume benthic insects such as chironomid larvae, annelid worms, and winged insects such as ants and beetles (Miller 1951, Marrin and Erman 1982). They are primarily mid-water feeders with gill-raker structure adapted to feeding on plankton. In contrast, the co-occurring obesus form is primarily a benthic feeder (Miller 1951). A comparison of stomach contents of both subspecies captured together in bottom-set gillnets indicated obesa had fed on benthic insects such as chironomids and trichopterans, while pectinifer had fed on planktonic microcrustacea (Miller 1951). There is no significant ontogenetic niche shift in diet for pectinifer; it feeds on plankton throughout its life (Miller 1951). In Pyramid Lake, both types of tui chubs feed primarily on zooplankton (mostly microcrustaceans) when less than 25 mm FL, but the obesa subspecies feed increasingly on benthic and terrestrial macroinvertebrates as they become larger (Galat and Vucinich 1983). There is an ontogenetic change in gill-raker numbers in the two forms that accompanies the differentiation of diets. When less than 25 mm FL, the two morphs are indistinguishable, even based on gill-raker counts, but the gill-raker number increases in pectinifer with size until the two forms are readily distinguishable at =50 mm FL.
Tui chubs fall prey to large trout and, to a lesser extent, to birds and snakes. Examination of stomachs of rainbow trout and lake trout in Lake Tahoe revealed that 10% and 7%, respectively, of their stomach contents consisted of lake tui chubs (Miller 1951).
In Lake Tahoe, spawning apparently occurs at night during May and June, and possibly later (Miller 1951). By early August, females do not have mature ova. Lahontan Lake tui chubs spawn by 11 cm SL (Miller 1951). They are probably serial spawners, capable of reproducing several times during a season (Moyle 2002). Snyder (1917) documented that reproductive adults spawned in near-shore shallow areas over beds of aquatic vegetation and found eggs adhering to the aquatic vegetation. He noted that young remained in the near-shore environment until winter when they were 1-2 cm in length and then migrated into deeper water offshore.
Growth (length increments) of tui chubs is linear until about age 4, when weight increases more rapidly and length increments decrease. The largest Lahontan Lake tui chub caught in Lake Tahoe was 13.7 cm SL (Miller 1951). These fish are considerably smaller than the tui chubs in Walker Lake, Nevada, where they grow to 21 cm SL (Miller 1951). It is likely that the largest Lahontan lake tui chubs are in excess of 30 years old (Scoppetone 1988, Crain and Corcoran 2000).

Habitat Requirements: 

Habitat Requirements: Lahontan Lake tui chub are schooling fish and inhabit large, deep lakes (Moyle 2002). They seem to be able to tolerate a wide range of physicochemical water conditions based on the fact that they are found in oligotrophic Lake Tahoe as well as in Pyramid Lake, a mesotrophic and highly alkaline lake. In Lake Tahoe, the larger fish (>16 cm TL) exhibit a diel horizontal migration by moving into deeper water (>50 m) during the day and back into shallower habitat at night (Miller 1951). However, they always remain high in the water column. The smaller individuals occupy shallower water. Additionally, there is also a seasonal vertical migration, with fishes located deeper in the water column during winter and moving back into the upper water column during summer (Snyder 1917, Miller 1951). Algal beds in shallow, inshore areas seem necessary for successful spawning, embryo hatching, and larval survival.


Distribution: Lahontan lake tui chubs are found in Lake Tahoe and Pyramid Lake, Nevada, which are connected to each other by the Truckee River (Fig. 22), and in nearby Walker Lake, Nevada. Plankton-feeding populations of chubs in Stampede, Boca, and Prosser reservoirs on the Truckee and Little Truckee rivers may also be Lahontan lake tui chubs because they have a superior oblique mouth and fine gill rakers and are never found in tributary streams (Marrin and Erman 1982, D. Erman, pers. comm.). Other tui chub populations in the Lahontan basin of uncertain taxonomic affinity also occur in Topaz Lake on the California-Nevada border and in Honey Lake, Lassen County.

Abundance Trends: 

Trends in Abundance: Actual abundance is not known, but is likely quite small compared to historic numbers. The Lake Tahoe population is the only confirmed population in California, but the chubs in Stampede, Boca, and Prosser reservoirs may also belong to this subspecies, although no sampling or analysis has been carried out to verify this assertion. Only small numbers have been collected from Lake Tahoe in recent years (P. Budry, UCD, unpubl. data) and the Lahontan lake tui chub has not been studied in Lake Tahoe since the late 1940’s (Miller 1951). In the intervening years the zooplankton community in the lake has changed. Daphnia, which are an important prey of adult chubs, have been nearly eliminated (Richards et al. 1975) by introduced kokanee salmon (Oncorhynchus nerka) and opossum shrimp (Mysis relicta), both of which feed on zooplankton.
Putative S. b. pectinifer populations in the three California reservoirs mentioned above and verified S. b. pectinifer populations in Pyramid and Walker lakes in Nevada are large but abundance estimates are lacking.


Description: Lahontan lake tui chubs can reach lengths of 35 to 41 cm FL. Their mouths are small, terminal, and oblique. Their pharyngeal teeth occur in a single row (5-5, 5-4, or 4-4) and are hooked, with narrow grinding surfaces. This subspecies is characterized by numerous (29-40), long, slender gill rakers, the primary characteristic that serves to differentiate it from sympatric S. b. obesa (Miller 1951, Vigg 1985, Moyle2002,). The inter-gill raker distances are usually less than the width of the gill rakers themselves. Other morphological characteristics that differentiate pectinifer from obesa are the more oblique mouth, the slightly concave profile of the head, and a uniform blackish or silvery body coloration (Miller 1951). Dorsal and anal fin rays usually number 8, but may range from 7-9; fins are short and rounded. Scales are large and there are 44-60 along the lateral line. Spawning males have reddish fins and develop small, white breeding tubercles on their body surfaces; females have reddish fins, slightly enlarged anal regions, protruding genital papilla, and deeper bodies.