Semester of Graduation

Spring 2023

Degree

Master of Science (MS)

Department

Renewable Natural Resources

Document Type

Thesis

Abstract

After spring migrations to natal rivers Gulf Sturgeon Acipenser oxyrinchus desotoi reside in freshwater holding areas prior to fall emigrations to nearby estuaries. Limited published information on the physical habitat characteristics of these holding areas is available, especially for juvenile fish in the western portion of the Gulf Sturgeon’s distribution. To further investigate freshwater occupancy and movement patterns, 32 acoustic receivers were deployed from late April to October of 2021 and 2022 in 1600-m reaches distributed throughout the lower Pearl River, Louisiana-Mississippi, the westernmost river within their distribution. Generalized linear mixed models and multi-state models were used to determine what physical habitat characteristics influenced Gulf Sturgeon mesohabitat occupancy and movement patterns by pairing daily detections of acoustically tagged juvenile and subadult Gulf Sturgeon with physical habitat characteristics (e.g. depth, woody debris accumulation, sinuosity, river stage, and specific conductance). Depth and woody debris accumulation were found to positively influence Gulf Sturgeon occupancy. Model results for occupancy yielded high occupancy probabilities across Middle and East Pearl River reaches with large areas of depth greater than 10 m (z = -10.164, p < 0.01). In the absence of large areas deeper than 10 m, large woody debris accumulations positively influenced occupancy. Movement to and from occupied reaches increased with increasing specific conductance (LRT = 24.371, p < 0.001), which probably reflects responses to other water quality variables in the river, such as salinity or erosional inputs. These data will be used to inform future models regarding summer riverine occupancy by identifying usage patterns in relation to mesoscale habitat availability and estimating holding area availability within the river. Additionally, local resource users were interviewed at access sites to the Pearl River drainage to gather baseline information on knowledge of Gulf Sturgeon, encounter histories, and attitudes towards conservation. Respondents lacked knowledge on Gulf Sturgeon ecology and anthropogenic threats to the species. Support for conservation was high, but results suggested the need for increased education and outreach regarding this threatened species and the Pearl River ecosystem as a whole, which can guide future outreach efforts by resource agencies in the western Gulf of Mexico.

Date

4-4-2023

Committee Chair

Kelso, William E.

DOI

10.31390/gradschool_theses.5762

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