Date of Award

2018

Degree Type

Thesis

Degree Name

Master of Science in Biological and Environmental Sciences (MSBES)

Specialization

Ecology and Ecosystem Sciences (EES)

Department

Fisheries, Animal and Veterinary Science

First Advisor

Austin Humphries

Abstract

The blue shark, Prionace glauca, is a pelagic elasmobranch that is found globally in tropic, sub-tropic, and warm temperate seas including the Mediterranean. Blue shark populations are not considered to be threatened, but a rapidly changing climate and uncertainties in fishing mortality are causing concern for changes in life history characteristics. Yet, no studies have examined such parameters for this species in over 35 years. We used 858 blue shark specimens, ranging from 1971 to 2016, to determine fork length, age, and weight at maturity, as well as measurements of reproductive organs (e.g., teste length, egg diameter) for both sexes. Males ranged from 62 to 300 cm and females ranged from 63 to 273 cm in fork length (FL). Ogives showed that males currently reach length at maturity (L50) at 211.2 cm and weight (W50) at 62.3 kg. Female blue sharks were smaller and lighter at maturity, with an L50 of 190.9 cm and W50 of 50.1 kg. Statistical models confirmed that L50, W50, and age at maturity all increased through time for males, while females showed only a significant increase in age at maturity and some organ measurements. Differences between individual reproductive organs for males and females were also present through time. These findings provide a current estimate of blue shark life-history parameters and demonstrate that there can be differential changes in life-history parameters between males and females through time.

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