Browsing by Author "D. Derek Aday, Committee Co-Chair"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • No Thumbnail Available
    Habitat Ecology of the Carolina Madtom, Noturus furiosus, an Imperiled Endemic Stream Fish
    (2008-12-09) Midway, Stephen Russell; D. Derek Aday, Committee Co-Chair; Thomas J. Kwak, Committee Co-Chair; Nick M. Haddad, Committee Member; Kevin Gross, Committee Member
    The Carolina madtom Noturus furiosus is an imperiled stream catfish (Ictaluridae) endemic to the Tar and Neuse river basins in North Carolina. The species is listed as State Threatened, and whereas the Tar Basin population resembles its historical distribution, the Neuse Basin population has shown recent significant decline. Quantifying habitat use and availability is critical for effective management and subsequent survival of the species. This study combined field and laboratory research to investigate habitat use and suitability, as well as efficacy of an artificial cover unit. To assess habitat suitability, we investigated six reaches (three in each river basin) to (1) quantify Carolina madtom microhabitat use, availability, and suitability, (2) compare suitable microhabitat availability between the two basins, and (3) examine the effectiveness of an instream artificial cover unit. We also conducted laboratory experiments to examine madtoms’ use of the same artificial cover unit relative to three natural cover types. Carolina madtom were located and their habitat use was quantified at four of six survey reaches; the species appeared to be absent at two reaches in the impacted Neuse Basin. Carolina madtom most frequently occupied shallow to moderate depths (0.5 m) of swift moving water over a sand substrate using cobble for cover. Univariate and principal components analyses both showed Carolina madtom use of instream habitat to be selective, or nonrandom. Interbasin comparisons suggested that most suitable microhabitats (particularly water depth and velocities) were more prevalent in the Neuse than in the Tar Basin, which is interesting considering that the Neuse population appears to be the more impacted of the two. Consequently, we suggest that other physical or biotic factors must be responsible for the decline in the Neuse Basin population. Our instream artificial cover units were occupied mainly by Carolina madtom (25% of the time), and rarely by a suite of other stream animals. Comparing areas with the artificial cover units (‘treated areas’) to those without them (‘control areas’), Carolina madtom abundance among all treated areas was statistically higher than the controls, demonstrating that madtoms will use suitable artificial cover when available. Microhabitat characteristics of occupied artificial cover units closely resembled those of natural microhabitat use. Results from the field component of the study provide habitat suitability criteria that can inform management and conservation of the Carolina madtom, and the artificial cover units present a cost-effective conservation and restoration option if increased management is deemed necessary. In the laboratory component of the study, Carolina madtom were placed in an experimental stream tank (44 cm x 88 cm in area and about 45 cm deep) and given 24 hours to make a selection among four cover options, three natural (one each of rock, leaf pack, and mussel shell) and the artificial cover unit. Among 30 experimental trials, Carolina madtom preferred the artificial cover unit, selecting it 63% of the time. Rock was selected 23% and leaf pack 13% of the time. Contrary to previous anecdotal observations, mussel shells were not selected during any trials. Results from the laboratory experiments, coupled with similar findings from instream work, indicate that artificial cover may be a viable option for species conservation and restoration. Given the State Threatened status and limited distribution, our results have implications for conservation and restoration of this native and endemic southeastern catfish. Successful management and conservation of declining Carolina madtom populations is dependent upon preserving Tar Basin habitat, identifying Neuse Basin impacts, and restoring Neuse Basin populations.
  • No Thumbnail Available
    Investigating Interactions between Largemouth and Spotted Bass, Lake Norman, North Carolina.
    (2009-06-14) Godbout, Jason; D. Derek Aday, Committee Co-Chair; Kevin Gross, Committee Member; James A. Rice, Committee Co-Chair
    Spotted bass Micropterus punctulatus were recently introduced into Lake Norman, which already supported a healthy largemouth bass M. salmoides population. After only ten years, spotted bass now make up about half of the black bass fishery. Because the two species are ecologically similar, and numbers and biomass of largemouth bass have been declining, biologists were concerned that spotted bass were negatively affecting largemouth bass. Additionally, morphological observations suggested the two species were hybridizing. To better understand these issues, hybridization, diet overlap, and habitat use by black bass in Lake Norman were quantified. Genetic analyses confirmed largemouth and spotted bass were hybridizing. Genetic information on individuals was paired with morphological characteristics at juvenile (50 – 100 mm total length, TL; n = 60) and adult (300 – 500 mm TL; n = 78) life stages, and reliable patterns for field identification of spotted bass, largemouth bass, and hybrids were developed (78-88% correct). To understand potential competition between the taxa, juvenile (n = 132) and adult (n = 120) black bass were collected for diet and habitat comparisons. Diet information was collected from juveniles from 31 July – 08 Aug 2007, 29 April 2008, and 10 June 2008 at different spatial scales. Zooplankton and benthic invertebrates were collected to estimate availability. Diet information was collected from adult fish from 29 April – 01 May 2008 and from 12 May – 16 May 2008. Habitat information on substrate and cover use was collected from locations of immobilized fish, and habitat availability of substrate and cover was estimated from 300-m transects (n = 12) throughout the reservoir. Proportion similarity index and Morisita’s index were used to quantify diet overlap by percent by number and percent by occurrence, and 10,000 bootstrap values were generated so that 95% confidence intervals could be estimated. Estimates of habitat selection were calculated with Ivlev’s index of electivity and the Strauss index of selectivity. Diet overlap values were high, and 95 % confidence intervals were typically in the upper half of the range of the indices. Based on prey availability samples, selection of invertebrate prey was largely opportunistic and similar between species. Habitat selection of both substrate and cover was similar with few exceptions. Because largemouth and spotted bass are hybridizing in Lake Norman, and overall, they show high overlap in use of prey items and habitat at both juvenile and adult life stages, they are likely competitors in Lake Norman. Our findings should guide future research and educate managers and anglers about the potential effects of introducing spotted bass or largemouth bass into lakes already containing a healthy black bass fishery.