Macroinvertebrate Abundance and Habitat Associations in the Big Bend Region of the Rio Grande with Comments on the Life History of Corydalus cornutus




Fordham, Rebecca K. Marfurt

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Arid aquatic environments represent unique and ecologically distinct systems, ranging from highly stable to highly fluctuating water bodies/streams along expansive discharge, water temperature, and salinity gradients. These environments typically support a diverse macroinvertebrate assemblage with a number of endemic taxa. The primary objective of this study included quantifying monthly occurrence and abundance, longitudinal distribution, and habitat associations of the macroinvertebrate community in the Rio Grande, located in northern Chihuahuan Desert. Leptophlebiidae (Order: Ephemeroptera) comprised the most abundant family (21 % in relative abundance), followed by Cheumatopsyche (Order: Trichoptera; 14%) and Simulidae (Order: Diptera; 7%). Macroinvertebrate assemblage changed along a downstream gradient, suggesting that upstream pollution inputs favor dipteran taxa at sites 1 and 2, although generalist species occurred at all sites. As water quality improved longitudinally, downstream assemblages shifted to favor ephemeropteran and trichopteran taxa. As a secondary objective, I studied feeding habits and life history information for a top invertebrate predator, Corydalus cornutus, in the Rio Grande and its tributaries to compare feeding and fecundity in the Rio Grande and Devils River. I found no difference in egg number and number of hatched eggs between sites, although lower numbers occurred at the site farthest downstream (San Ygnacio; 68 ± 26%) than at both Dolan (91 ± 9%) and Kickapoo (84 ± 17%). Food selection consisted primarily of detritus, followed by Cheumatopsyche and Simulidae. This study will aid biomonitoring efforts by establishing an index of change in assemblage structure.



Corydalidae, invertebrate communities, water quality


Fordham, R. K. M. (2008). Macroinvertebrate abundance and habitat associations in the Big Bend Region of the Rio Grande with comments on the life history of Corydalus cornutus (Unpublished thesis). Texas State University-San Marcos, San Marcos, Texas.


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