First Report of Freshwater Jellyfish in Montana

The first known sample of freshwater jellyfish [(Craspedacusta sowerbyi ) Lankester, 1880 (Cnidaria: Limnomedusae: Olindiidae)] in Montana came from an artificial pond on an abandoned golf course in Cascade County near the town of Great Falls in 2009. The pond is located ~600 m from the Missouri River and is part of a four pond network connected by a dry artificial stream.The initial collection occurred on 25 August 2009. Hydromedusa were observed swimming near the surface, collected with a dip net. Mean diameter of the jellyfish measured 29 mm. A second visit occurred on 3 September 2009 to make museum collections and record habitat conditions. Surface water temperature was 18.1 degrees C. The substrate of the pond was primarily coarse sand with a few piles of rock 12-25 cm in diameter. No vegetation was present in the water or along the shoreline. Two plankton tows were made from a small raft with a 30-cm diameter 80-micron Wisconsin net at the deepest part of the pond. Plankton collected were Bosmina spp., Cyclops spp., Nauplii of Cyclops and trace amounts of rotifers Kellicotia spp., Conochilius spp., and Asplanchna spp. The location of this population raises concern about possible expansion into the Missouri River. Given the ability of this organism to select for specific plankton and affect their reduction, the ecological impacts of this species could be far reaching if it becomes established in the Missouri River reservoirs

Rainbow Trout Spawning Characteristics and Relation to the Parasite Myxobolus cerebralis in the Missouri River, Montana

The myxosporean parasite Myxobolus cerebralis is responsible for significant declines of rainbow trout (Oncorhynchus mykiss) populations in several western states, including Montana. Despite a high prevalence of the parasite in Montana’s Missouri River, there have been no apparent impacts to the rainbow trout population. This study examined long-term M. cerebralis monitoring data from the Missouri River system below Holter Dam and evaluated rainbow trout spawning characteristics such as migration distance, spawning location, site fidelity and amount of spawning in the Missouri River and tributaries over three years in an attempt to explain why the population has not declined in the presence of M. cerebralis. Over 13 years of monitoring, a mean 5.3 percent of rainbow trout handled during population estimates had clinical signs of M. cerebralis infection. In experiments using sentinel fish 53 percent of the spawning habitat had high severity of M. cerebralis, 38 percent had low to moderate severity, and 9 percent had no infection. Radio telemetry showed spawning locations varied among years and tagged fish lacked spawning site fidelity. The distance that radio-tagged rainbow trout migrated to spawning locations was significantly different among river sections of the study area. Twenty-eight percent of the spawning redds were found in the Missouri River and 72 percent in the tributaries. Relative to previous studies, we found less tributary spawning and an increase in Missouri River spawning, where M. cerebralis infection severity is lower. Our findings suggest that diverse spawning behaviors may contribute to rainbow trout population stability by spreading the risk of M. cerebralis impact over spawning locations that have a broad range of infection severity

Effects of Rotenone on Columbia Spotted Frogs Rana luteiventris during Field Applications in Lentic Habitats of Southwestern Montana

Fisheries managers are restoring native populations by removing nonnative fishes worldwide. Increasingly, the piscicide rotenone is used to accomplish this. Fish introductions and removals change the aquatic environment, and it is important to consider the impacts of these actions on nontarget species, including amphibians. Laboratory experiments have shown that rotenone can negatively affect tadpoles. We therefore assessed the effects of rotenone used on two wild amphibian populations. The commercial piscicide formulation CFT Legumine (5% rotenone) was applied at 1 mg/L (50 μg/L rotenone) to a lake containing nonnative trout in Yellowstone National Park (YNP) in 2006 and two fishless wetlands on private lands in southwestern Montana in 2008. Amphibian surveys were conducted immediately prior to and after the rotenone treatments to obtain tadpole population estimates. Follow-up surveys were conducted 1 year posttreatment to estimate tadpole recovery. In YNP, additional surveys were conducted 2 and 3 years postapplication to observe longer-term effects of fish removal and the subsequent introduction of native fish. Within 24 h following application of rotenone, there was 100% mortality in gill-breathing tadpoles, but nongillbreathingmetamorphs, juveniles, and adults were apparently unaffected. In the years following, tadpoles repopulated all waters and population levels were similar to, or, in the case of YNP because of concurrent fish removal, higher than pretreatment levels. In YNP, tadpole abundance and distribution decreased after westslope cutthroat trout Oncorhynchus clarkii lewisi were stocked in the treated lake