Identifier

etd-04092015-171013

Degree

Master of Science (MS)

Department

Renewable Natural Resources

Document Type

Thesis

Abstract

The greatest diversity of crayfishes, especially of rare Orconectes species, is found in the central Louisiana watersheds (Red River, Mermentau, Calcasieu, and Vermillion-Teche), and most species are widely distributed among the drainages. The purpose of this research was to lay groundwork for species distribution and metacommunity modelling for crayfishes in this region. To address this goal, two field studies were performed in the summers of 2013 and 2014, as well as an indoor laboratory study. Analyses of broadly distributed species indicated no significant correlations between species abundances and habitat variables nor any significant environmental gradients for those species. Within-drainage variability of habitat was substantial in this study and a large range of site conditions were sampled within any particular drainage, despite significant drainage differences. Subsequent analysis of drainage-restricted species indicated that drainage-scale modelling is suitable for endemic species such as Procambarus pentastylus and P. natchitochae. However, more restricted Orconectes maletae, O. blacki, and O. hathawayi could not be effectively modelled at the drainage scale, in part because they were not detected in the majority of samples. Examination of gear types and times of day indicated that catch per unit effort (CPUE) and average total length of crayfish was greater with electrofishers than with dipnets; however, no differences between time of day were detected for either CPUE or crayfish total length. Differences in estimates of sample diversity using different combinations of gears and times of day were detected when calculated on a per individual basis, but not on a per site basis. In intraspecific competition trials, body size and chelae width were found to be significant biological factors in determining the odds of dominance in O. blacki and P. pentastylus. Presence of predator cue (water conditioned by Micropterus salmoides) generally reduced frequencies of dominance interactions in both species and generally increased median shelter occupancy times for both species. This research provides much needed information on the distributions and ecology of central Louisiana crayfishes, and future studies will be needed to quantify genetic units, dispersal corridors, and interspecific interactions between other co-occurring species and to characterize the central Louisiana crayfish metacommunity.

Date

2015

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Kaller, Michael D.

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