Reproductive Development in the Sicklefin Chub in the Missouri and Lower Yellowstone Rivers

We describe aspects of sicklefin chub (Macrhybopsis meeki) reproductive development from three study areas encompassing greater than 2,700 km of the Missouri and Lower Yellowstone rivers. The sicklefin chub was collected between late July and early October in 1996 and 1997. A total of 193 sicklefin chub was collected and examined for reproductive characteristics. Twenty-nine sicklefin chub were found to be reproductively mature females. Some sicklefin chub matured at age 2, but most matured at age 3 and all matured by age 4. Females first became mature at 70 to 79 mm total length (TL) in the Upper Missouri River reach in central Montana, 80 to 89 mm TL in the Missouri and Lower Yellowstone rivers in eastern Montana-western North Dakota, and 90 to 99 mm TL in the lower Missouri River in Nebraska, Iowa, Kansas, and Missouri. Gonad mass of gravid females averaged 6.9% of total body mass and ranged from 1.7 to 13.5%. Total number of oocytes per female, ranged from 7 to 1,561. Reproductive development of the sicklefin chub appeared to be group synchronous or asynchronous indicating multiple spawnings during a spawning season. This variability in spawning mode required cautious interpretation of gonadosomatic index values and oocyte counts as estimates of total fecundity, because some females might have released a cohort of oocytes prior to their capture

The Influence of the Clean Water Act and Tributaries on the Fish Community of the Big Sioux River, South Dakota

This study was initiated to l) compare fish communities in the Big Sioux River, South Dakota, between 1967 and 1994 and 2) investigate fish use of five tributaries as spawning and nursery areas. Fish species richness was higher in 1994 than in 1967. The greatest fish community changes between years, as indicated by low community similarity indices, were below Brookings and Sioux Falls, and in the lower river. Distributions of reproductive and feeding guilds were not different between years, however, some individual fish species distributions were different between years. Dissolved oxygen levels have increased and ammonia levels have decreased across years (1974-1994) at sites immediately below Brookings and Sioux Falls. However, such improvement was not found at a site near the mouth that represented the entire watershed. Levels of nitrate and phosphorus were higher since 1974. Other water quality parameters (i.e., suspended solids and fecal coliform) have not changed across years. Species migrating up tributaries to spawn were white suckers Catostomus commersoni and creek chubs Semotilus atromaculatus. Juveniles of both species were also abundant in tributaries. Juveniles of other species including northern pike Esox lucius, shorthead red horses Moxostoma macrolepidotum, and yellow perch Perea flayescens were also collected in tributaries. The results suggest that improvements in municipal waste treatment since the passage of the Clean Water Act in 1972 have improved the water quality below Brookings and Sioux Falls. However, increased levels of nitrate and total phosphorus suggests that nonpoint source pollution continues to degrade the majority of the river. The fish community may have responded favorably to improvements in water quality but some changes in the fish community could be due to higher stream discharges in 1994. Tributaries provided spawning and nursery habitat for some species including important recreational fish species. Controlling nonpoint-source pollution and protecting tributaries is important for maintaining and improving the fishery resources of the Big Sioux River

Evaluation of Four Larval Fish Sampling Methods in a Large Midwestern River

Understanding limitations of larval fish capture gears is critical for developing appropriate sampling protocols and interpreting catch data. We evaluated genera richness, genera diversity, assemblage similarities, abundance indices (i.e., density or catch per unit effort [CPUE]), and sample size requirements between a surface slednet and glow-stick light traps used in 2014 and 2015 and a benthic slednet and light-emitting diode light (LED) traps used in 2015 in the Minnesota River. The surface slednet captured the greatest number of larval fish genera (15) while the LED light trap captured the fewest (1). Similarities of assemblages sampled was highest between surface and benthic slednets (58%) and lowest between the benthic slednet and LED light trap (0%). All evaluated gears had low and variable catch rates; the highest variability was observed for the LED light trap (CV = 800), and the lowest variability was observed for surface slednets (CV = 173). Slednets required less effort to detect a 25% change in total larval fish abundance compared to light traps. Low CPUEs or densities were possibly the result of suspended sediment loads (85.3 ± 8.5 Nephelometric Turbidity Units) that blocked light trap entrance slots and clogged net pores. Further, not targeting habitats critical to adult spawning and larval rearing (e.g., log jams or shallower or inside bends of meanders) may have influenced CPUEs and densities. We recommend modifications to evaluated sampling gears (e.g., nets with larger mesh sizes) or the evaluation of additional larval fish sampling methods (e.g., larval seines or pumps) coupled with a stratified random sampling protocol that incorporates complex habitats for sampling larval fish within the main channel of the Minnesota River or other river systems with similar high turbidity levels

Brook Trout Distribution, Genetics, and Population Characteristics in the Driftless Area of Minnesota

<div><p></p><p>The Driftless Area in southeastern Minnesota is on the southwestern edge of the native range of Brook Trout <i>Salvelinus fontinalis</i>. It was assumed that native Brook Trout were extirpated from this region in the early 1900s due to degraded stream conditions and stockings of eastern-origin Brook Trout and European Brown Trout <i>Salmo trutta</i>. Our objectives were to examine Brook Trout populations in the region to determine their spatial and genetic distribution and quantify population characteristics. Information on presence or absence of Brook Trout was gathered by electrofishing 174 streams in southeastern Minnesota. Brook Trout were present in 68% of coldwater streams compared with only in 3% in the early 1970s. The increase is likely due to increasing stream discharge throughout the Driftless Area, enabling recolonization or successful establishment of stocked populations. Streams with higher base flow discharge also had higher abundance, larger size at maturity, and larger Brook Trout present. Genetic data on 74 populations were analyzed to characterize genetic variation within populations, assess genetic structure among populations, and determine possible origins. Numerous populations were not associated with known hatchery sources but were primarily composed of geographic groupings that could represent remnant lineages. Although population characteristics were similar among genetic origins, potentially remnant populations should be given conservation priority because they have proven their ability to sustain themselves in this region. Management actions that emphasize maintaining or increasing stream base flows throughout the region will likely enhance remnant Brook Trout populations in the Driftless Area.</p><p>Received July 25, 2014; accepted March 17, 2015</p></div

Brown trout Salmo trutta growth and condition along a winter thermal gradient in temperate streams

Winter harshness and the degree to which it can impact stream dwelling salmonid populations has received considerable attention from fisheries biologists, although some debate exists regarding the importance of winter severity for local populations. Groundwater input may buffer stream water temperature and benefit fish in buffered vs. unbuffered streams. Overwinter growth and condition of individual brown trout were measured in 24 groundwater-dominated streams, and the relations between winter growth and condition to stream thermal regime (quantified by regressions of air and water temperature) and diet quality (amount and caloric density of prey) were examined in a subset of 16 streams. Brown trout growth rate (mg*g-1*day-1) was positive overwinter in 18 of 24 streams, and there was no significant change in condition between early and late winter. Juvenile fish grew faster than adults, but there was no significant difference in condition between adults and juveniles. Thermal regime positively influenced winter growth for both adults and juveniles, likely mediated through moderation of water temperature by groundwater, whereas diet had no significant effect on growth.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author