The environmental factors determining temporal distributions of cetaceans in Mossel Bay, South Africa
A variety of cetacean species make use of the bays along the South African coast for different purposes, including feeding, mating and calving. Sightings of five species of cetaceans were recorded from shore based locations between February 2010 and August 2014 in Mossel Bay, Western Cape. In this s...
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ftunivcapetownir:oai:localhost:11427/25346 2023-05-15T13:54:58+02:00 The environmental factors determining temporal distributions of cetaceans in Mossel Bay, South Africa Levy, David Blamey, Laura K Elwen, Simon James, Bridget 2017 application/pdf http://hdl.handle.net/11427/25346 https://open.uct.ac.za/bitstream/11427/25346/1/thesis_sci_2017_levy_david.pdf eng eng University of Cape Town Faculty of Science Marine Research (MA-RE) Institute http://hdl.handle.net/11427/25346 https://open.uct.ac.za/bitstream/11427/25346/1/thesis_sci_2017_levy_david.pdf Applied Marine Science Master Thesis Masters MSc 2017 ftunivcapetownir 2022-09-13T05:50:36Z A variety of cetacean species make use of the bays along the South African coast for different purposes, including feeding, mating and calving. Sightings of five species of cetaceans were recorded from shore based locations between February 2010 and August 2014 in Mossel Bay, Western Cape. In this study, we aimed to examine the underlying environmental variables: sea surface temperature (°C), chlorophyll a concentration (mg.m-3) and moon brightness (as % of full) that potentially affect presence patterns within the bay, and several temporal scales (diurnal, monthly, seasonal, annual). The study focused on three whale species: the southern right whale (Eubalaena australis), humpback whale (Megaptera novaeangliae) and Bryde's whale (Balaenoptera brydei); and two dolphin species: the Indo- Pacific bottlenose dolphin (Tursiops aduncus), and the Indian Ocean humpback dolphin (Sousa plumbea). Generalized additive models (GAM) were used to model the sighting rate of the common cetacean species in the area, by relating sighting rate to the environmental variables. Cow-calf groups and adults-only groups were modelled separately for humpback and southern right whales. Chlorophyll a concentration is commonly indicative of high trophic productivity, and sea surface temperature is indicative of biophysical processes that influence cetacean distribution, as well as cetacean migration preferences. Change in sea surface temperature (over the study period) was a significant contributing factor to the sighting rate of cow-calf paired groups and adults-only groups of both right whales and humpback whales, underlying their greater sighting rate during the winter and spring months annually; thus, conforming to the seasonal migration from Antarctica for breeding and calving. Chlorophyll a concentration was a significant factor contributing to Bryde's whale, bottlenose and humpback dolphin distribution. These species reside along the South African coast all year round, but are more frequently seen when trophic productivity is high. ... Master Thesis Antarc* Antarctica Humpback Whale Megaptera novaeangliae Southern Right Whale University of Cape Town: OpenUCT Gam ENVELOPE(-57.955,-57.955,-61.923,-61.923) Indian Pacific |
institution |
Open Polar |
collection |
University of Cape Town: OpenUCT |
op_collection_id |
ftunivcapetownir |
language |
English |
topic |
Applied Marine Science |
spellingShingle |
Applied Marine Science Levy, David The environmental factors determining temporal distributions of cetaceans in Mossel Bay, South Africa |
topic_facet |
Applied Marine Science |
description |
A variety of cetacean species make use of the bays along the South African coast for different purposes, including feeding, mating and calving. Sightings of five species of cetaceans were recorded from shore based locations between February 2010 and August 2014 in Mossel Bay, Western Cape. In this study, we aimed to examine the underlying environmental variables: sea surface temperature (°C), chlorophyll a concentration (mg.m-3) and moon brightness (as % of full) that potentially affect presence patterns within the bay, and several temporal scales (diurnal, monthly, seasonal, annual). The study focused on three whale species: the southern right whale (Eubalaena australis), humpback whale (Megaptera novaeangliae) and Bryde's whale (Balaenoptera brydei); and two dolphin species: the Indo- Pacific bottlenose dolphin (Tursiops aduncus), and the Indian Ocean humpback dolphin (Sousa plumbea). Generalized additive models (GAM) were used to model the sighting rate of the common cetacean species in the area, by relating sighting rate to the environmental variables. Cow-calf groups and adults-only groups were modelled separately for humpback and southern right whales. Chlorophyll a concentration is commonly indicative of high trophic productivity, and sea surface temperature is indicative of biophysical processes that influence cetacean distribution, as well as cetacean migration preferences. Change in sea surface temperature (over the study period) was a significant contributing factor to the sighting rate of cow-calf paired groups and adults-only groups of both right whales and humpback whales, underlying their greater sighting rate during the winter and spring months annually; thus, conforming to the seasonal migration from Antarctica for breeding and calving. Chlorophyll a concentration was a significant factor contributing to Bryde's whale, bottlenose and humpback dolphin distribution. These species reside along the South African coast all year round, but are more frequently seen when trophic productivity is high. ... |
author2 |
Blamey, Laura K Elwen, Simon James, Bridget |
format |
Master Thesis |
author |
Levy, David |
author_facet |
Levy, David |
author_sort |
Levy, David |
title |
The environmental factors determining temporal distributions of cetaceans in Mossel Bay, South Africa |
title_short |
The environmental factors determining temporal distributions of cetaceans in Mossel Bay, South Africa |
title_full |
The environmental factors determining temporal distributions of cetaceans in Mossel Bay, South Africa |
title_fullStr |
The environmental factors determining temporal distributions of cetaceans in Mossel Bay, South Africa |
title_full_unstemmed |
The environmental factors determining temporal distributions of cetaceans in Mossel Bay, South Africa |
title_sort |
environmental factors determining temporal distributions of cetaceans in mossel bay, south africa |
publisher |
University of Cape Town |
publishDate |
2017 |
url |
http://hdl.handle.net/11427/25346 https://open.uct.ac.za/bitstream/11427/25346/1/thesis_sci_2017_levy_david.pdf |
long_lat |
ENVELOPE(-57.955,-57.955,-61.923,-61.923) |
geographic |
Gam Indian Pacific |
geographic_facet |
Gam Indian Pacific |
genre |
Antarc* Antarctica Humpback Whale Megaptera novaeangliae Southern Right Whale |
genre_facet |
Antarc* Antarctica Humpback Whale Megaptera novaeangliae Southern Right Whale |
op_relation |
http://hdl.handle.net/11427/25346 https://open.uct.ac.za/bitstream/11427/25346/1/thesis_sci_2017_levy_david.pdf |
_version_ |
1766261174401236992 |