ASPECTS OF SMALLTOOTH SAWFISH LIFE HISTORY IN SOUTH FLORIDA INFERRED FROM ANALYSES OF VERTEBRAE
Rachel Marie Scharer
University of West Florida
Master of Science (MS), University of West Florida
2012
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Abstract
Smalltooth sawfish, Pristis pectinata, is the first elasmobranch listed as endangered under the US Endangered Species Act, yet basic life history data critical for its conservation and recovery are lacking. To address this lack of information, I examined aspects of smalltooth sawfish life history via analysis of vertebrae collected from deceased fish (n = 15). First, I estimated fish age by counting opaque bands in vertebrae sections. Age estimates ranged from 0.4 to 14.1 years for fish that ranged in size between 0.60 and 4.35 m total length. A von Bertalanffy growth function fit to size at age data resulted in parameter estimates of 4.65 m for L, and 0.206 for K, and - 0.80 y for t0. Rostral teeth were also examined for aging but no opaque zones were present. Analysis of vertebrae sections with laser ablation-inductively coupled plasma-mass spectrometry also was conducted to infer fish salinity history based on Sr:Ca and Ba:Ca ratios across vertebrae transects. The Ba:Ca ratios showed no patterns or peaks consistent with salinity. However, a consistent pattern existed within Sr:Ca among vertebra samples for the first two years of life, with peaks of high and low Sr:Ca either indicating migrations or seasonally variable estuarine salinity.