Year

2021

Season

Fall

Paper Type

Master's Thesis

College

College of Arts and Sciences

Degree Name

Master of Science in Biology (MS)

Department

Biology

NACO controlled Corporate Body

University of North Florida. Department of Biology

First Advisor

Dr. Jim Gelsleichter

Second Advisor

Dr. Adam Rosenblatt

Third Advisor

Dr. William Driggers III

Department Chair

Dr. Cliff Ross

Abstract

The spinner shark, Carcharhinus brevipinna, is a large coastal shark species that is common on the U.S. southeast coast and caught in both commercial and recreational fisheries. Little research has been conducted on the life history of C. brevipinna in the Northwestern Atlantic, presenting challenges for fishery management. This is especially true for reproductive biology, warranting a need to determine how rapidly individuals are reproducing and contributing to the population. This study aimed to characterize reproduction in C. brevipinna by determining size-at-maturity, reproductive seasonality, periodicity, and fecundity. This was accomplished by analyzing changes in reproductive tract morphology and histology, and plasma concentrations of gonadal steroid hormones. This was accomplished through two study components, one using archived data and the other using newly collected data. Results from both components were consistent and examined collectively. Size-at-maturity was determined to be 130 and 140 cm FL for males and females, respectively. Marked increases in testis width, epididymis width, and presence of mature spermatozoa from April - July in mature males suggest a seasonal pattern with copulation occurring during this period. Marked increases in maximum follicle diameter (MFD), oviducal gland width, and presence of enlarged vitellogenic follicles in mature non-gravid females was observed during this same period, with newly pregnant females observed in August, suggesting concurrent reproductive cycles between sexes. Pregnant females with full-term embryos observed in June indicate parturition to occur June - July following a 12-month gestation. Individual MFD of non-gravid females collected spring - summer showed at least two cohorts, as well as no vitellogenesis not occurring in gravid females suggests a non-annual periodicity. Litter size was significantly correlated with maternal length and ranged from 4 – 8 pups. This study provides new up-to-date information on the reproductive potential and biology of C. brevipinna aiding in stock assessment and management.

Available for download on Saturday, January 07, 2023

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