Development of a quantitative PCR assay for detection of redside shiner (Richardsonius balteatus) from environmental DNA

Objective A quantitative PCR (qPCR) assay for the detection of redside shiner (Richardsonius balteatus) environmental DNA (eDNA) was designed as a side product of a larger project aimed at using eDNA to determine the presence and geographic extent of native and non-native fishes in the reservoirs and associated tributaries above the three mainstem dams (Ross, Diablo, Gorge) on the Skagit River, Washington, USA. The eDNA survey results can be used to help guide additional sampling efforts that include traditional sampling methods, such as electrofishing and netting. Results The redside shiner qPCR assay (RSSCOI_540-601) was validated by testing for sensitivity using redside shiner genomic DNA from three different populations and by testing for specificity against 30 potentially sympatric species. No non-target amplification was observed in our validation tests. We then evaluated the assay on field-collected water samples where there are known populations of redside shiner and a negative control site where the target species is known to be absent. The field-collected water samples tested positive at the redside shiner sites and tested negative at the negative control site. The assay could provide resource managers with an effective means for surveying and monitoring redside shiner populations.

Redside shiner (Richardsonius balteatus) shoals provide a behavioral competitive refuge for subordinate juvenile steelhead trout (Oncorhynchus mykiss)

We examined the relative effects of zero, three, and nine redside shiner (Richardsonius balteatus) on the aggression-related damage among three juvenile steelhead (Oncorhynchus mykiss) in aquaria at 15 and 20°C. No steelhead died when in the presence of nine redside shiner. When redside shiner were not present, mortality among the smallest steelhead was 80%. Thus, the survival of smaller juvenile steelhead was significantly enhanced by the presence of redside shiner. A second experiment was conducted in 6800-L stream channels at 15°C with natural substrate. In separate trials, 10 and 7 steelhead were held either alone or with 20 redside shiner. In the absence of redside shiner, fin damage was significantly greater among smaller steelhead. In both experiments, if a redside shiner group was present, the smallest steelhead frequently took refuge within the shiner group, thereby avoiding attack by dominant steelhead. We have termed this phenomenon a behavioural competitive refuge.

Reproductive isolating mechanisms between the peamouth, Mylocheilus caurinus, and the redside shiner, Richardsonius balteatus, at Stave Lake, British Columbia, Canada

Since at least 1952, the peamouth, Mylocheilus caurinus and the redside shiner, Richardsonius balteatus, have engaged in extensive hybridization (5.7–14.1% of the combined gene pools) in Stave Lake, British Columbia. A research project initiated in 1966 and continued to 1991 demonstrated that genetic swamping of the two species has not occurred. A study was conducted to determine the strength of premating and postmating isolating mechanisms between these two species. Temporal isolation is weak because both species had spawning periods in Devils Creek that overlapped by approximately 1.5 months. Also, both species spawned at night, and only on nights preceded by a sunny day. Both species were group spawners and both spawned on the first riffle of Devils Creek. Hybrid sterility is not well developed. While male F1 hybrids have low fertility, female F1 hybrids are as fertile as females of either species and would allow swamping if other postmating mechanisms were not operating. Hybrid inferiority was examined by laboratory experiments in which we measured survival of fingerling hybrids. While F1 hybrids displayed survival equal to that of M. caurinus, hybrid backcrosses to M. caurinus showed a 20% lower survival rate than M. caurinus. Also, hybrid backcrosses to M. caurinus included a significant proportion (8.4%) of deformed individuals.

A long-term study of hybridization between the peamouth, Mylocheilus caurinus, and the redside shiner, Richardsonius balteatus, at Stave Lake, British Columbia

Hybridizing populations of the peamouth, Mylocheilus caurinus, and the redside shiner, Richardsonius balteatus, from Stave Lake, British Columbia, were examined three times over a 26-year interval to determine (i) whether swamping or introgression was occurring, (ii) whether the hybrids were being continually produced, and (iii) whether the composition of the hybrid population was constant. The hybrids were present at all three sampling periods with a rate of hybridization of 5.7% in 1966–1967, 14.1% in 1982, and 6.7% in 1991. F1 hybrids comprised no less than 80% of the hybrids at each sampling period. The remaining hybrids were mostly hybrid backcrosses to M. caurinus. Analysis of mitochondrial DNA (mtDNA) revealed that F1 hybrids were produced by females of both species, although not in equal proportions each year. Hybrid backcrosses to M. caurinus were more abundant as fingerlings than as adults, suggesting that selection is operating against them. After a 26-year interval, no evidence of swamping was detected when diagnostic morphological characters were employed. An analysis of allozyme data suggests that introgression is not occurring. The continued production of the hybrids over the three sampling periods suggests continuity in the environmental factors responsible for hybridization. Likewise, the greater proportion of F1 hybrids than backcrosses over the three sampling periods suggests a continued selective disadvantage of the backcrosses.

The ecology of hybrids between the peamouth, Mylocheilus caurinus, and the redside shiner, Richardsonius balteatus, at Stave Lake, British Columbia, Canada

Extensive hybridization between the peamouth, Mylocheilus caurinus, and the redside shiner, Richardsonius balteatus, at Stave Lake, British Columbia, provided an opportunity to examine the ecology of hybrid fishes over a 26-year period. Spatial distribution and feeding ecology of the hybrids were compared with those of the parental species. At Stave Lake, M. caurinus was primarily oriented to the limnetic zone at all depths, while R. balteatus was oriented to surface waters in the littoral zone. The hybrids (F1 hybrids and hybrid backcrosses to M. caurinus combined) mimicked the M. caurinus pattern, being significantly more abundant in the limnetic zone. Adult M. caurinus consumed primarily zooplankton with occasional adult insects, while R. balteatus consumed primarily adult insects. The diet of hybrids was not significantly different from that of M. caurinus; they consumed large quantities of zooplankton and some insects.

Myxobolid parasites (Myxozoa: Myxobolidae) infecting fishes of western Montana, with notes on histopathology, seasonality, and intraspecific variation

Cypriniform and salmonid fishes of the Columbia River drainage of western Montana harbor five members of the myxozoan family Myxobolidae. Myxobolus muelleri inhabits Ptychocheilus oregonensis (northern squawfish), Mylocheilus caurinus (peamouth), Richardsonius balteatus (redside shiner), and Catostomus macrocheilus (largescale sucker). Cysts appeared in gills, musculature, subcutis, and visceral mesenteries. Unencysted spores infiltrated mesenteries and viscera. Spore size and shape in the various tissues and hosts were highly varied. Muscle and subcutaneous cysts were associated with connective tissue proliferation and muscle degeneration; cyst rupture was associated with diffuse inflammation and rodlet cell proliferation. Infection prevalence in muscles and kidneys was high in adult and juvenile hosts (78–100%) throughout the year. Seasonal prevalence of gill and subcutaneous infections fluctuated markedly. Cysts of Myxobolus dujardini occurred in gills of the northern squawfish, peamouth, and redside shiner. Unicauda sp. was found in the eye capsule, gall bladder, mesenteries, and kidney of northern squawfish. Henneguya zschokkei occurred in intermuscular connective tissue of Prosopium coulteri (pygmy whitefish) and Prosopium williamsoni (mountain whitefish). Myxobolus sp. occurred in the gills of Catostomus catostomus (longnose sucker).

Interactions Between the Redside Shiner (Richardsonius balteatus) and the Steelhead Trout (Salmo gairdneri) in Western Oregon: The Influence of Water Temperature

Water temperature influenced interactions between redside shiner (Richardsonius balteatus) and juvenile steelhead trout (Salmo gairdneri) (≥1 +) in the field and laboratory. Trout in cool water when shiner were absent and at intermediate water temperatures with shiner present occupied a similar range of habitats. Shiner alone in warm water occupied habitats similar to trout, but in the presence of trout occupied slower, deeper areas than when alone. In laboratory streams, production by trout was the same in the presence and absence of shiner in cool water (12–15 °C). In warm water (19–22 °C), production by trout decreased by 54% in the presence of shiner compared with when shiner were absent. Production of shiner in cool water decreased in the presence of trout, −0.3 g∙m−2∙d−1 together compared with 0.5 g∙m−2∙d−1 alone, but was not affected by the presence of trout in warm water. Trout distribution was not influenced by shiner in cool waters, but was influenced at warm temperatures. Shiner occupied all areas of the laboratory channels in the absence of trout in cool waters but were restricted to a few pools in the presence of trout. Distribution of shiner was not influenced by trout at warm temperatures.

Feeding Activity and Rates of Digestion of Northern Squawfish (Ptychocheilus oregonensis)

Trapnet catches of northern squawfish (Ptychocheilus oregonensis) at Griffen and Cultus lakes, British Columbia, indicated peak activity and feeding in the twilight and dark hours. At Griffen Lake, squawfish force-fed 2.0 g of redside shiner (Richardsonius balteatus), and held at 17–20 C, digested at a rate of roughly 14%/h. At Cultus Lake, squawfish trapped during the peak of feeding activity, and held at 10–12 C, were sacrificed at 6-h intervals, and showed a digestion rate of sockeye salmon (Oncorhynchus nerka) smolts of 14%/h. Larger fish ate larger volumes of food. Regression techniques are not completely adequate for describing the course of digestion, which apparently involves an initial period of retention of food, followed by a fairly rapid evacuation of most of the ingested material. Most fish cleared their stomach contents in 24 h, and one half had done so between 12 and 18 h. In the laboratory, squawfish force-fed rainbow trout (Salmo gairdneri) had rates of digestion which increased with temperature, from about 5%/h at 4–6 C, to 40–50%/h at 24 C. Larger weights of food were digested at slower rates, but there were no consistent differences in rate of digestion by different sizes of squawfish.The rates of digestion are higher than those reported for various predatory European fishes.