Non-lethal methods for assessing the health and status of fish species of conservation concern.

Development of nonlethal sampling methods has increased in response to the need for studying the impacts of global change and anthropogenic perturbations on threatened and endangered species. This dissertation focuses on how a commonly occurring relative of a species of conservation concern can be used as a surrogate species for developing and validating nonlethal methods for studying the ecology and ecotoxicology of endangered species. The two model-organisms used in this dissertation are the Alligator Gar Atractosteus spatula, a long-lived apex predator threatened by habitat loss and harvest oriented fishing, and the Longnose Gar Lepisosteus osseus a commonly occurring ubiquitous relative of Alligator Gar. This dissertation examines commonly used endpoints in ecology and ecotoxicology studies from non-lethally collected fin, muscle biopsy, and pectoral fin rays, and compares these benchmark values to those from lethally collected fillets and otoliths. Specifically, the endpoints measured were stable isotopes of nitrogen (δ15 N) and carbon (δ13 C), mercury (Hg), and age estimates. Following method development and validation, this dissertation then demonstrates how these non-lethal methods can be applied in real world ecology and ecotoxicology studies. The first study tests the Hg aerial deposition hypothesis that apex predators (represented by Alligator Gar) in areas of high Hg deposition will exhibit higher Hg levels than those in areas with less aerial Hg deposition. The second case study explores δ15 N and δ13 C isotope signals in large river food webs and if these signals are impacted by enriched municipal and industrial wastewater discharge. The resulting information discovered from this dissertation suggests non-lethal tissues adequately reflect endpoint values from lethally collected tissues and that future studies should consider using commonly occurring surrogate species for method development and validation. Additionally, evidence from the first case study suggests that aerial deposition of Hg is not the primary modulator in apex predators, rather biomagnification through diet is likely the main driver of Hg concentrations. Results from the second case study demonstrate that enrichment from wastewater can impact stable isotope signals causing a decoupling between predator and prey relationships that may lead to erroneous conclusions about large river food web ecology.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Doctoral

Grantor

Baylor University.

Year dc:date.issued

2024

Author dc:creator

• Moran, Zach S. (Zachary S.), 1992-

Advisor dc:contributor.advisor

• Matson, Cole W.

• Ecology.
• Alligator gar.
• Longnose gar.
• Stable isotopes.
• Mercury.
• Ecotoxicology.
• Endangered species.

Statement dc:rights

• Baylor University works are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. Contact libraryquestions@baylor.edu for inquiries about permission.

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/2104/13134

OAI identifier oai:identifier

oai:baylor-ir.tdl.org:2104/13134