Date of Award

5-2012

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Entomology

Advisor

Morse, John C.

Committee Member

Adler, Peter H.

Committee Member

Slack, William T.

Abstract

Although North American sturgeon have been the focus of extensive research in the last several decades, more research is essential to ensure their conservation. The free-flowing Lower Mississippi River (LMR) is occupied by two sympatric sturgeon, pallid [ Scaphirhynchus albus (Forbes & Richardson)] and shovelnose sturgeon [Scaphirhynchus platorynchus (Rafinesque)]. These species are considered 'endangered' and 'threatened,' respectively. Recent studies have documented the life history of adult sturgeon in the Mississippi River, but studies focusing on young-of-year and juveniles are limited because young fish are difficult to collect and identifications are problematic. Spawning sites in the LMR are unknown and though extensive effort has been put forth to capture young sturgeon for scientific study, specimens are seldom collected and rarely in large numbers. This gap in knowledge is substantial because recruitment success is important for the recovery and survival of both species. This study takes an ecosystem approach in exploring microhabitat associations of larval and juvenile pallid and shovelnose sturgeon based on their diets. During systematic sampling (2001-2010) of the LMR (river kilometer 131.32-1361.18), 75 total specimens (pallid and shovelnose) were obtained using a 3.05 m modified Missouri trawl. Gut contents were analyzed and prey items were identified to the most refined taxonomic level possible. By examining microhabitats and behaviors of sturgeon prey items (mostly benthic macroinvertebrates), the microhabitat-feeding associations of sturgeon were predicted. These findings suggest that both species are specific in the type of microhabitat in which they feed. The majority of prey items (71.8%) of both sturgeon species belong to a single subgroup of Chironomidae (Harnischia complex) that are predominantly burrow in sand substrates, typically in shifting sediments of large river systems. Several other sturgeon prey items also occupy this microhabitat. These data can be paired with collection data to assess habitat use, availability, and threats, and to make recommendations for conservation. Also studied was general early life history information related to feeding of young-of-year sturgeon. Based on this study, I conclude that larval and juvenile pallid and shovelnose sturgeon have different feeding habits than adults. This study also provides an updated checklist of invertebrates known to occur in the Mississippi River.

Included in

Entomology Commons

Share

COinS