Biology Master Thesis Defense by Karissa Collins
Advisor: Dr. Robert Drew
Committee Members: Dr. Robert Drew, Dr. Kenneth Oliveira and Dr. Whitney Hable
Abstract: The American eel (Anguilla rostrata) is a widely distributed catadromous species that undergoes a final metamorphosis from the yellow to silver phase prior to its spawning migration to the Sargasso Sea. This silver metamorphosis involves substantial morphological and physiological changes, yet the life history cues initiating this transition remain uncertain. In this study, age, total length, body composition, and energy reserves were examined in yellow and silver phase eels from four rivers in Southeastern Massachusetts (Paskamansett, Acushnet, Mill, and Jones rivers). Percent dry weight was strongly correlated with energy density across sexes and life stages, and composition of a standardized body section reliably predicted whole-fish values, indicating an efficient proxy for energetic assessment. Females migrated at older ages and larger sizes than males. Lipid content exceeded protein content at migration for both males and females, suggesting lipid reserves may be important at the onset of silver metamorphosis. Mean minimum lipid content was 16.09% for females and 15.03% for males, while energy density did not differ between sexes. These results suggest that energetic thresholds, particularly lipid reserves, may play a greater role in triggering silver metamorphosis than age, sex, or location in southeastern Massachusetts populations.
SENG Bldg., Rm. 305
Robert Drew
(508) 999-8905
mroberge1@umassd.edu