Geology topics

C.P. Paukert

Publications and source records attributed to C.P. Paukert.

22 records · Page 2Linked to original sources

USGS2002

Seasonal and diel habitat selection by bluegills in a shallow natural lake

Habitat use by bluegill Lepomis macrochirus may be dictated by the avoidance of predators and the availability of prey. Previous work suggests that bluegills large enough to avoid predators will select habitats based on foraging profitability. However, these studies focused on smaller fish (<150 mm standard length) in laboratory experiments or in natural systems with distinct vegetated and open-water habitats. Our objective was to use radio telemetry to determine monthly and diel vegetation selection by larger (>200 mm total length [TL]) bluegills in a shallow (mean depth = 1.2 m), 332-ha, natural lake (Pelican Lake, Nebraska) with both emergent and submergent vegetation distributed throughout. A total of 78 bluegills (200-273 mm TL) were implanted with radio transmitters and relocated daily for 6 d per month (April-September); up to 20 of the tagged fish were relocated every 2 h for a 24-h period once each month. Regardless of diel period, bluegills used open-water, emergent vegetation, submergent vegetation, and mixed emergent - submergent vegetation habitat types in similar proportions. During April, June, and July, male bluegills positively selected emergent vegetation, whereas female bluegills showed no vegetation selection preference during any month. Throughout the study period, bluegills never avoided open-water habitats, suggesting that larger individuals may continue to use open-water habitats in proportion to their availability. In addition, emergent vegetation appeared to be important, particularly for male bluegills. Although the mechanism for the positive selection of emergent vegetation by males was unclear, the protection or enhancement of such habitats may facilitate the preservation of quality bluegill populations in shallow lakes.

Transactions of the American Fisheries Society↗

USGS2002

Effect and acceptance of bluegill length limits in Nebraska natural lakes

Bluegill Lepomis macrochirus populations in 18 Nebraska Sandhill lakes were evaluated to determine if a 200-mm minimum length limit would increase population size structure. Bluegills were trap-netted in May and June 1998 and 1999, and a creel survey was conducted during winter 1998-2001 on one or two lakes where bluegills had been tagged to determine angler exploitation. Thirty-three percent of anglers on one creeled lake were trophy anglers (i.e., fishing for large [???250 mm] bluegills), whereas 67% were there to harvest fish to eat. Exploitation was always less than 10% and the total annual mortality averaged 40% across all 18 lakes. The time to reach 200 mm ranged from 4.3 to 8.3 years. The relative stock density of preferred-length fish increased an average of 2.2 units in all 18 lakes with a 10% exploitation rate. However, yield declined 39% and the number harvested declined 62%. Bluegills would need to reach 200 mm in 4.2 years to ensure no reduction in yield at 10% exploitation. Both yield and size structure were higher with a 200-mm minimum length limit (relative to having no length limit) only in populations with the lowest natural mortality and at exploitation of 30% or more. Although 100% (N = 39) of anglers surveyed said they would favor a 200-mm minimum length limit to improve bluegill size structure, anglers would have to sacrifice harvest to achieve this goal. While a 200-mm minimum length limit did minimally increase size structure at current levels of exploitation across all 18 bluegill populations, the populations with the lowest natural mortality and fastest growth provided the highest increase in size structure with the lowest reduction in yield and number harvested.

North American Journal of Fisheries Management↗

USGS2002

Sample size requirements for in situ vegetation and substrate classifications in shallow, natural Nebraska Lakes

We assessed the precision of visual estimates of vegetation and substrate along transects in 15 shallow, natural Nebraska lakes. Vegetation type (submergent or emergent), vegetation density (sparse, moderate, or dense), and substrate composition (percentage sand, muck, and clay; to the nearest 10%) were estimated at 25-70 sampling sites per lake by two independent observers. Observer agreement for vegetation type was 92%. Agreement ranged from 62.5% to 90.1% for substrate composition. Agreement was also high (72%) for vegetation density estimates. The relatively high agreement between estimates was likely attributable to the homogeneity of the lake habitats. Nearly 90% of the substrate sites were classified as 0% clay, and over 68% as either 0% or 100% sand. When habitats were homogeneous, less than 40 sampling sites per lake were required for 95% confidence that habitat composition was within 10% of the true mean, and over 100 sites were required when habitats were heterogeneous. Our results suggest that relatively high precision is attainable for vegetation and substrate mapping in shallow, natural lakes.

North American Journal of Fisheries Management↗

USGS2000

Abiotic factors affecting summer distribution and movement of male paddlefish, Polyodon spathula, in a prairie reservoir

Six male paddlefish, Polyodon spathula , were implanted with ultrasonic temperature-sensing transmitters and tracked during June through August 1997 to quantify effects of physicochemical conditions on their distribution and movement in Keystone Reservoir, Oklahoma. Paddlefish moved about twice as much during night than day. Movement rate of paddlefish was related to reservoir water level, inflow, and discharge from the reservoir at night; however, none of these variables was significant during the day. Location in the reservoir (distance from the dam) was negatively related to water level and positively related to inflow during day and night periods. Location in the reservoir was negatively related to discharge during the day. Paddlefish avoided the highest available water temperatures, but did not always avoid low dissolved oxygen concentrations. Paddlefish avoided the Cimarron River arm of the reservoir in summer, possibly because of high salinity. Our study demonstrates that distribution of paddlefish during summer and movement in Keystone Reservoir was influenced by physicochemical and hydrologic conditions in the system. However, biotic factors (e.g., food availability) not measured in this study may have been influenced by abiotic conditions in the reservoir.

Oklahoma↗