Identifier

etd-0606102-124240

Degree

Master of Science (MS)

Department

Oceanography and Coastal Sciences

Document Type

Thesis

Abstract

Little is known regarding the feeding behavior of many shark species. Even less is known about shark feeding habits in Louisiana coastal waters. The stomach contents of gillnet-captured blacktip sharks (n=356), Carcharhinus limbatus, and Atlantic sharpnose sharks (n=55), Rhizoprionodon terraenovae, were examined in this study. Roughly half of the blacktip stomachs (52%) and sharpnose stomachs (45%) contained prey items. The primary prey item in terms of percent number, occurrence, and weight for blacktips and sharpnose was the gulf menhaden, Brevoortia patronus. Both blacktips and sharpnose appear to mainly be piscivores; however, no members of Sciaenidae, the most common family of teleosts in the sampling area in terms of number of species, were found in sharpnose stomachs. Based on temporal gillnet sampling, neonate blacktips undergo an increase in feeding activity in the late afternoon /early evening hours, whereas blacktips without an umbilical scar do not appear to follow this same pattern. Using a combination of the stomach content analysis and the derived Scale of Degradation for menhaden found in the stomachs of the blacktips, a digestion rate of approximately 24 hours was estimated for blacktips. Zero and one year old blacktips from this study grew at a rate of approximately 7.6 g/day and 0.47 mm/day. A comparison of the growth rate to the top 10% of stomach content weights yielded growth efficiencies between 13-25% depending on the frequency in which blacktips filled their stomachs with prey. I concluded that menhaden are an important food source for both blacktips and sharpnose in the area, providing the sharks with an abundant and nutritional food source, and directly contributing to the high growth rates for blacktips in the area.

Date

2002

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Richard Condrey

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