Dissertation

Age and growth of a subtropical marsh fish: The Gulf Killifish, Fundulus grandis

Vastano, Anthony R

2016

Overview

Fundulus grandis, the Gulf Killifish, is an abundant fish species with a widespread distribution throughout the marshes of the Gulf of Mexico. The wide distribution and high site fidelity of this species makes it an ideal indicator species for Gulf of Mexico brackish and salt marshes, which experience a diversity of anthropogenic disturbances. Despite the ecological, commercial, and scientific importance of F. grandis, little is known of its growth pattern, and age determination methods are currently lacking. Age and growth information is essential for understanding baseline growth patterns. By combining a tag-recapture study with a chemical marker to stain otoliths, I validated an ageing method for F. grandis using whole otoliths and determined growth rates of F. grandis in winter (n = 58) and summer (n = 36) in Louisiana. The recapture rates for tagged individuals during winter and summer were 10% and 12%, respectively. Mean somatic growth in length was significantly greater during the winter (0.085 mm per day) than the summer (0.054 mm per day). In contrast, mean otolith growth was significantly greater during the summer (1.37 µm per day) than the winter (0.826 µm per day). The observed uncoupling of somatic and otolith growth is attributed to warm summer temperatures which led to enhanced otolith growth while simultaneously reducing somatic growth. Fundulus grandis were aged to a maximum of 2.25 years. The parameters of the Von Bertalanffy growth model were estimated as: L ∞ = 87.27 mm, k = 2.43 year–1, and t 0 = –0.022. These findings reveal basic age and growth information for F. grandis, demonstrating faster growth and a shorter lifespan than its congener species, Fundulus heteroclitus.

• Publisher: ProQuest Dissertations & Theses
• Subject: Biological oceanography / Ecology
• ISBN: 1369607989, 9781369607987