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Summary: The paddlefish (Polyodon spathula Walbaum, 1792) is a springtime migrant that requires discrete abiotic conditions such as water temperature, discharge, and substrate composition for successful spawning and recruitment. Although population declines have prevailed throughout much of the species range, Oklahoma paddlefish are abundant and support popular recreational snag fisheries – most notably in Grand Lake. This stock utilizes the Grand Lake's two primary headwaters, the Neosho and Spring rivers, with only episodic recruitment success. However, relationships between suitable spawning habitat and water level have not been evaluated in this system. Using consumer‐grade sonar equipment, this study identified and quantified hard river substrates (such as cobble and bedrock) and investigated proportional habitat availability at a variety of simulated river conditions. Sonar data were used to construct 49‐m2 grids of depth and bottom hardness (H) ranging from 0.0 (soft) ‐ 0.5 (hard). Ground‐truthing samples of bottom composition were collected with a grab sampler and by visual identification. Substrate types were pooled into two categories: soft substrates (H < 0.386) and spawning substrates (H ≥ 0.386) allowing for estimation of available spawning habitat in each river. Spawning habitat comprised 69% of total available habitat for the Neosho River (6.5 ha/km) and 58% for the Spring River (7.9 ha/km). Estimated spawning habitat was simulated over a range of river stages and predictive models were developed to estimate proportional spawning habitat availability (PHA). Although the Spring River contains more concentrated spawning habitat in closer proximity to Grand Lake, the Neosho River contains a greater quantity over nearly twice the distance to the first migration barrier, has a larger watershed, and demonstrates greater PHA at lower river stages. Model results were validated in context of known high and low recruitment years, where a greater frequency and duration of days with ≥90% PHA were observed in good recruitment years, particularly in the Neosho River. In total, results suggest the Neosho River has greater value for paddlefish reproduction than the Spring River. Research‐informed harvest management will remain critical to the conservation of wild‐recruiting stocks for continued recreational use in Oklahoma. [ABSTRACT FROM AUTHOR]

Habitat selection has been quantified for age-0 and adult pallid sturgeon Scaphirhynchus albus Bull. Illinois State Lab. Nat. Hist., 7, 1905, 37, but little is known regarding habitat use of the juvenile fish. The objective of this study was to quantify habitat use and selection of juvenile pallid sturgeon in the Missouri River, Nebraska, USA. Thirty-seven age-4 pallid sturgeon with transmitters were released in July of 2014, plus an additional 21 in September, with habitat monitored using biotelemetry. Age-1 and age-4 hatchery reared pallid sturgeon were found to avoid areas associated with the outside bend and thalweg habitats that were characterized by rapid water velocity (>1 ms−1), which accounted for 50% of the area in the channelized Missouri River. Age-1 pallid sturgeon selected an off-channel habitat and inside bend habitat while age-4 pallid sturgeon selected an off-channel and inside bend channel border habitat. Juvenile pallid sturgeon in unaltered rivers have been shown to associate with island tips and sand bars, habitat that is largely absent in the channelized Missouri River. This study indicates that juvenile pallid sturgeon in the Missouri River, Nebraska are selecting habitats with shallow water and slow water velocity, similar to those associated with island tips and sand bars in unaltered reaches. [ABSTRACT FROM AUTHOR]

Saugeye, a hatchery-produced hybrid of walleye, Sander vitreus (Mitchill), × sauger, Sander canadense (Griffith & Smith), is commonly stocked by several state fishery management agencies in the United States. Saugeye is a top-level predator that can restructure fish communities and provide supplemental angling opportunities. However, there are few published studies explaining distributions and habitat selection of saugeye. This study determined seasonal home range estimates and habitat selection of saugeye in a small warmwater impoundment using ultrasonic telemetry. Seasons for this study were defined as winter, spawn, spring, summer and autumn. Mean home range estimates were greatest during spawn when water temperature increased from 7.5 to 15 °C and lowest in winter when water temperature decreased below 7.5 °C. Saugeye selected open water and mid-water ledge habitat during each season, but rock/gravel shoreline was increasingly selected during winter and spawn. These results corroborate previous studies that suggest saugeye exhibit seasonal variation in distribution and habitat use patterns. Managers should consider distribution and habitat selection trends of saugeye when assessing stocks or determining whether to introduce the species in a small warmwater impoundment. [ABSTRACT FROM AUTHOR]

Telemetry data were used to quantify seasonal resource selection and rank-preferred habitat types for blue suckers Cycleptus elongatus in the middle Missouri River and its tributaries, Iowa, Nebraska, South Dakota, U.S.A. Habitat diversity required by C. elongatus to complete its annual life-history cycle was evident by interseasonal variation in habitat selection. Tributaries and unchannelized portions of the middle Missouri River system were selected during the inferred spawning season (spring), habitats along shorelines in the channelized middle Missouri River were selected for postspawning (summer) and areas of reduced current were generally selected for the period preceding spawning (autumn). This study provides insight into mature C. elongatus behaviour throughout its annual life cycle. Furthermore, these results document the interseasonal variability in habitat selection of C. elongatus and highlight the need for development of habitat selection models for other imperilled fish species in aquatic systems affected by anthropogenic developments. [ABSTRACT FROM AUTHOR]

Mitomycin C-treated ascites cells of Ia antigen-positive GRSL14 tumor cells and spleen cells from GRSL14 tumor-bearing mice stimulated lymphocyte proliferative responses in normal syngeneic GR spleen cells. Furthermore, mitomycin C-treated T cells purified from spleen cells of tumor-bearing mice also stimulated normal GR spleen cells. Anti-Ia sera inhibited the stimulating ability of tumor cells and of spleen cells of tumor-bearing mice. These data suggest a role for I region gene products in immune surveillance for syngeneic tumors.

Rabbit anti-Ia sera was produced by immunization with detergent-solubilized extracts from splenic, lymph-node and thymus cells. The antisera contained activity against H-2 as well as Ia molecules. By a sequential immunoprecipitation assay it was shown that the rabbit anti-mouse H-2s serum precipitated a second Ia molecule in the H-2s haplotype. Previous studies with alloantisera have shown only one Ia molecule associated with this haplotype. Sequential precipitations with alloantiserum against the whole I region were used to show that this second Ia molecule is coded by genes within the I region. Since only I-A- and I-E-region coded molecules are immunoprecipitable in most haplotypes, we presume that the rabbit antiserum could be identifying the I-E-subregion coded molecule in the H-2s haplotype. The rabbit antiserum reacts with an isotypic specificity on the molecule. The studies suggest that the I-E subregion does exist in the H-2s haplotype even though alloantiserum cannot be produced to identify allotypic variants associated with this subregion.