Aspects of population biology and behaviour of mobulid rays
type: CreativeWork
description: Manta and devil rays (Mobula spp.) are charismatic yet threatened species that remain poorly understood. The Inhambane Province in Mozambique is known to be home to the largest populations of manta rays in Africa, including the reef manta ray (M. alfredi) and the oceanic manta ray (M. birostris). However, research on other mobulid species, and in the region south of Tofo, including Závora in Mozambique and South Africa, has been limited. This thesis identifies critical sites and describes their characteristics, including habitat use, population abundance, and behaviour, for three species of mobulids: M. alfredi, M. birostris, and the shortfin devil ray, M. kuhlii. Chapter 1 comprises a literature review on the status and knowledge on mobulids in a global context, and within the southern African region, with focus on M. alfredi and M. birostris, due to the increased amount of information available on these species. Chapter 2 provides detailed information on the methodologies used throughout the thesis, some of which overlap. Chapter 3 utilises an 11-year photographic mark-recapture dataset spanning from 2010-2021 to investigate the size and structure of the M. alfredi population that aggregate at 'Red Sands' (RS), a reef cleaning station located at Závora, Mozambique. A total of 583 individual M. alfredi were identified using photographic mark recapture (photo-ID) of the unique ventral spot patterning. Pollock's Robust Design models were used to estimate annual abundances, emigration, annual apparent survival, and capture probability at RS during peak season, July-November, between 2016-2021. The resulting abundance estimates varied each year, with a range of 35 individuals (95% CI 30-45) up to 233 individuals (95% CI 224-249). Lagged Identification Rates were additionally used to describe the residency patterns of M. alfredi at Red Sands, revealing that despite site affinity to RS, individuals were overall transient within a given season, with an average residency o…
abstract: Manta and devil rays (Mobula spp.) are charismatic yet threatened species that remain poorly understood. The Inhambane Province in Mozambique is known to be home to the largest populations of manta rays in Africa, including the reef manta ray (M. alfredi) and the oceanic manta ray (M. birostris). However, research on other mobulid species, and in the region south of Tofo, including Závora in Mozambique and South Africa, has been limited. This thesis identifies critical sites and describes their characteristics, including habitat use, population abundance, and behaviour, for three species of mobulids: M. alfredi, M. birostris, and the shortfin devil ray, M. kuhlii. Chapter 1 comprises a literature review on the status and knowledge on mobulids in a global context, and within the southern African region, with focus on M. alfredi and M. birostris, due to the increased amount of information available on these species. Chapter 2 provides detailed information on the methodologies used throughout the thesis, some of which overlap. Chapter 3 utilises an 11-year photographic mark-recapture dataset spanning from 2010-2021 to investigate the size and structure of the M. alfredi population that aggregate at 'Red Sands' (RS), a reef cleaning station located at Závora, Mozambique. A total of 583 individual M. alfredi were identified using photographic mark recapture (photo-ID) of the unique ventral spot patterning. Pollock's Robust Design models were used to estimate annual abundances, emigration, annual apparent survival, and capture probability at RS during peak season, July-November, between 2016-2021. The resulting abundance estimates varied each year, with a range of 35 individuals (95% CI 30-45) up to 233 individuals (95% CI 224-249). Lagged Identification Rates were additionally used to describe the residency patterns of M. alfredi at Red Sands, revealing that despite site affinity to RS, individuals were overall transient within a given season, with an average residency o…
author: Carpenter, Michelle
keywords: Biological Sciences
date published: 2023
date modified: 2026-07-22T22:23:06Z
provider: University of Cape Town
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Department of Biological Sciences

PropertyValue
property ID: Handle
value: http://hdl.handle.net/11427/39291