The use of data from a platform of opportunity (whale watching) to study coastal cetaceans on the south west coast of South Africa 

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Shore-based observations of five cetacean species in the Greater Dyer Island area, South Africa: Spatial distribution, seasonality, and group composition

Abstract

Shore-based observations of cetaceans were conducted from two stations near Gansbaai, South Africa (34°40’18” S, 19°28’16” E) to investigate behavioural and spatial and temporal patterns of habitat use. Hourly scans were conducted to provide information on species presence, location, group size, group composition, and surface behaviour. Focal groups were tracked with a surveyor’s theodolite to provide detailed information on movements. A total of 1558 hours and 26 minutes was spent on effort over 270 days between 24 August 2011 and 11 December 2014.
A total number of 1204 scans, where 1175 scans were conducted at sea state < 5. All sighting data were filtered to remove periods of poor weather conditions, only observations collected at sea state ≤ 2 for dolphin species, and ≤ 5 for baleen whales were analysed. The longest focal follow from each day was used for southern right whales and all focal follow tracks of dolphin species were included. Five cetacean species were regularly observed: southern right whales (Eubalaena australis), humpback whales (Megaptera novaeangliae), Bryde’s whales (Balaenoptera brydei), Indian Ocean humpback dolphins (Sousa plumbea), Indo-Pacific bottle- nose dolphins (Tursiops aduncus), while common dolphins (Delphinus delphis) were only seen on three occasions. The results of this study strongly support the temporal and spatial patterns of the five most regularly observed cetacean species described from data collected from a local whale watching vessel. Southern right whales were by far the predominant species in the area. There was a change group type from surface active groups (SAGs) in the beginning of the season to cow/calf pairs (cc-pairs) later in the season. Southern right whales predominantly used the area for socialising and/or nursing. The large bay area in Pearly Beach, in particular,was the preferred area of the cc-pairs. All southern right whales were found to be swimming at a speed less than 5.1 km/h. Swimming speed of cc-pairs (n = 121) ranged from 0.2 to 4.3 km/h (mean = 1.15 ± 1.13 km/h SE), SAGs (n = 83) ranged from 0.3 to 3.7 Km/h (mean = 1.00 64 Km/h SE), and unaccompanied (UA) were the fastest (n= 19), with speed ranging from 0.6 to 5.1 km/h (mean = 2.18 ± 1.39 km/h SE). The number of sightings on simultaneous days of southern right whales from the WWV and the theodolite scans were compared. The total number of sightings from the theodolite station was generally higher than the total number of sightings from the WWV during the months of September, October, and November. Sightings of other species were too few to provide any patterns. Humpback whales exhibited marked sea-sonality peaking in winter period (June – August) which was similar to the results of the WWV-study. The primarily observed behaviour of humpback whales was travelling and 80% of the tracked animals were travelling south-east towards Cape Agulhas. The temporal distribution of Bryde’s whales was similar to the results of the WWV-study but with a peak in February and March instead of in April. There were no clear patterns of the behavioural use of the area. The temporal peak of dolphin species in the summer period (December – February) was not as pro-nounced as in the WWV-study. The two inshore dolphin species were mainly observed in the bay areas where all four defined behaviours were observed and no clear trends in behavioural patterns was found. The dolphin species with the highest leg speed was the common dolphin (n = 8) with a top speed of 17.5 km/h down to 3 Km/h (mean = 11.96 ± 5.47 Km/h SE), followed by the Indo-Pacific bottlenose dolphin (n = 19) ranging from 1.5 to 9.3 Km/h (mean = 5.19 ± 2.20 Km/h SE), and the Indian Ocean humpback dolphin (n = 17) ranging from 0.9 to 6.3 Km/h (mean = 2.79 ± 1.66 Km/h SE). Three species are particularly using the inshore environment (southern right whale, Indo-Pacific bottlenose dolphin, and Indian Ocean humpback dolphin) and hence face potential human impacts from local vessels and construction sites disconnect-ing the along shore environment.

Key words

Distribution, Fine scale movements, Habitat utilization, Seasonality, Theodolite tracking, VADAR, Whale watching vessel.

 Introduction

The research field of marine mammology has expanded rapidly both concerning new applied technologies for example D-tags (Johnson and Tyack 2003, Madsen et al. 2006, Boye et al. 2010), satellite tags (Mate et al. 1997, Wade et al. 2006, Baird et al. 2010, Mate et al. 2011, Elwen et al. 2012, Garrigue et al. 2015), Unmanned Aircraft Systems (Koski et al. 2009, Durban et al. 2015), and passive acoustic monitoring (Bailey et al. 2009, Parks et al. 2011, Marques et al. 2013). Yet, there are 45 cetacean species listed as “data deficient” out of 87 evaluated species by the IUCN cetacean specialist group (IUCN 2015) and remote locations, still need to be investigated (Elwen et al. 2011). Knowledge on fine scale temporal and spatial patterns of cetacean species is of paramount importance in order to define and apply a conservation plan. Particularly, inshore cetacean species are exposed to human impacts in the form of underwater noise from e.g. ship-ping (McKenna et al. 2013), ship collisions (Kemper et al. 2008), entanglement in fishing gear (Atkinson and Sink 2008, Leandro et al. 2010, Meÿer et al. 2011), construction (Thompson et al. 2010), pollution (Cockcroft et al. 1989, Atkinson and Sink 2008) and ocean based tourism (Elwen and Leeney 2010).
The study area is situated approximately 55 km from the southernmost point in South Africa, Cape Agulhas, and is part of the inshore Agulhas Bank temperate shallow shelf system which forms the southern boundary of the Benguela upwelling system and hence is affected by both current systems (Hutchings et al. 2009b). The cetacean fauna of the study area has been poorly studied to date (Chapter 2, Vinding et al. 2015). Results from the analysis of 10 years of cetacean observation data obtained from the local whale watching vessel analysed as part of this PhD (Chapter 2) showed that five main species of cetaceans known to frequent the study area regu-larly: southern right whales (Eubalaena australis), humpback whales (Megaptera novaeangliae), Bryde’s whales (Balaenoptera brydei spp.), Indian Ocean humpback dolphins (Sousa plumbea) and Indo-Pacific bottlenose dolphins (Tursiops aduncus), and two occasionally observed spe-cies: killer whales (Orcinus orca), and common dolphins (Delphinus spp) (Chapter 2, Vinding et al. 2015). These species occur within a few kilometres from the coast where human impacts are highest (Halpern et al 2008). Along the South African coast there are multiple human threats to marine life including physical changes to the coastline (Sink et al. 2012), effects of fisheries including depletion of prey (Atkinson and Sink 2008), entanglement in fishing gear (Atkinson and Sink 2008, Meÿer et al. 2011), potential establishment of nuclear power stations (Griffiths and Robinson 2011), pollution (Cockcroft et al. 1989, De Kock et al. 1994, Atkinson and Sink 2008), and boat traffic including recreational, eco-tourism, and fishing vessels (Turpie et al. 2005, Waerebeek et al. 2006, Elwen and Leeney 2010, Meÿer et al. 2011). The human activities potentially impact cetaceans in the study area include two whale watching operators, eight shark cage diving operators, abalone fishing (legal and illegal), seasonal small vessel activity (particularly holiday periods), modification of river estuaries with potential implication for access for dolphins and their prey, potential fin-fish farming, and the possible construction of a nuclear power station.
Cetacean surveys along the approximately 3000 km long South African shores has been con-ducted (Findlay et al. 1992, Elwen et al. 2011), but consistent and long term data sets are not available for some of the inshore species and some of the more remote areas, which still needs to be investigated in details with regards to spatial and temporal distribution and habitat use of inshore cetacean species (Elwen et al. 2011). Particularly the Indian Ocean humpback dolphin is of high conservation priority, due to low numbers and strictly inshore distribution (Elwen et al. 2011). A species in South Africa for which a long term ID-cataloug exist is the southern right whale, which has been studied in South Africa since the 1969 by Peter B. Best (Best 2000). From these aerial studies it is known that southern right whales exhibit site fidelity, where most female calves (>93.4%) born at the South African coast return to give birth to their first calf, with 52.9% found in the same area or adjacent area. From other studies by Peter Best it is known that the yearly right whale season extend from June until December/early January with a peak in September (Best and Scott 1993).
This study investigated the detailed behaviour patterns, spatial, and temporal distribution of the cetacean species in the area before further human impacts are implemented in the region. An additional aim was to investigate how reliable the results from the WWV are in comparison to a more strictly structured scientific survey. If the results from the WWV study show the same or very similar temporal and spatial distribution patterns for the five species as the present theod-olite study, there is evidence that WWV data can be used as a reliable source to obtain baseline data in otherwise data-deficient areas.

Methods

Study site

This study was conducted in the Greater Dyer Island area in Pearly Beach Bay (34°40’18” S, 19°28’16” E) (Figure 1). Pearly Beach Bay is characterised as a sandy bottomed gently sloping bay with adjacent rocky coastal reefs and kelp forest. A nearby island complex is a fully protected 390 ha nature reserve which consists of Dyer Island and Geyser Rock. Dyer Island is the largest of the two islands (20 ha), and hosts 12 different seabirds and five terrestrial bird species breed-ing on the island, including the endangered African penguin (Spheniscus demersus) (BirdLife South Africa 2015) and the adjacent Geyser Rock with a healthy and increasing colony of Cape fur seals (Arctocephalus pusillus pusillus) (Kirkman et al. 2013). The area is mainly known for the year round presence of great white sharks (Carcharodon carcharias), which supports a large shark-viewing industry operating eight vessels (MLRA 2008).
The study area is situated inshore of the Agulhas Bank which forms the southern boundary of the Benguela upwelling system and displays characteristics of both an upwelling system and a temperate shallow shelf system (Hutchings et al. 2009a). The prevailing wind changes throughout the year: in summer (December – February) winds are predominantly southerly or south-east-erly, Autumn (March – May) similar to summer months but more frequent north-westerly winds, in winter (June – August) is characterised by strong winds from north-west, south-east, or south-west, and in spring (September – November) predominantly southerly, south-easterly, or south-westerly (Law 1999).
Sea temperature was measured with a Starmon mini, underwater temperature recorder (Star Oddi 2016) every half-hour by the Department of Environmental Affairs, Ocean & Coasts (Ocean&Coast 2015) from 25 July 2012 at 12:00 until 2 September 2013 at 12:30 close to Quoin Point (34°45’48.50”S, 19°35’12.28”E) at 35 m depth of water and approximately 10 km from the study site. Average temperature over the entire period was 13.3°C, over the summer period (December – February) was 11.7°C, and over the winter period (June – August) was 14°C.

Summary 
Foreword and acknowledgements 
List of funding sources 
Abbreviations 
1 G eneral introduction 
1.1 Cetaceans
1.2 A im and motivation of the study
1.3 R esearch area
1.3.1 Greater Dyer Island Area
1.3.2 Potential human impacts
1.3.3 Protection status
1.4 R esearch design and methods
1.4.1 Platforms of opportunity (Whale watching)
1.4.2 Land-based observations (Theodolite tracking)
1.4.3 Passive Acoustic Monitoring
1.5 C oastal cetacean species
1.5.1 Right whales
1.5.2 Humpback whales
1.5.3 Bryde’s whales
1.5.4 Indian Ocean humpback dolphins
1.5.5 Indo-Pacific bottlenose dolphins
1.6 O rganisation of the report
1.7 Literature
2 The use of data from a platform of opportunity (whale watching) to study coastal cetaceans on the south west coast of South Africa 
2.1 Abstract
2.2 K ey words
2.3 Introduction
2.4 T he study
2.4.1 Study area
2.4.2 Data collection and validation
2.4.3 Data analysis
2.5 Results
2.5.1 Search effort
2.5.2 Cetacean occurrence and seasonal distribution
2.5.3 Temporal patterns
2.5.4 Spatial patterns
2.5.5 Observed on rare occasions
2.6 Discussion
2.6.1 Seasonality and distribution of cetacean species
2.6.2 Caveats and recommendations
2.7 Conclusion
2.8 Acknowledgements
2.9 Literature
3 C etacean data collection from commercial whale watching vess els: Consistency, validity, and value in local habitat monitoring 
3.1 Abstract
3.2 K ey words
3.3 Introduction
3.4 M aterials and methods
3.5 Results
3.6 Discussion
3.7 Conclusion
3.8 Literature
4 Shore-based observations of five cetacean species in the Greater Dyer Island area, South Africa: Spatial distribution, seasonality, and group composition 
4.1 Abstract
4.2 K ey words
4.3 Introduction
4.4 Methods
4.5 D ata collection
4.6 Analysis
4.7 Results
4.8 Discussion
4.9 Conclusions
4.10 Acknowledgement
4.11 Literature
5 P ass ive acoustic monitoring of southern right whales 
5.1 Abstract
5.2 K ey words
5.3 Introduction
5.4 Methods
5.5 D ata analysis
5.6 Results
5.7 Discussion
5.8 Conclusion
5.9 Acknowledgement
5.10 Literature
6 C oncluding remarks 
6.1 D istribution, habitat use, and behaviour
6.2 PAM
6.3 P latforms of opportunity
6.4 C onservation and management
6.5 Literature
7 A ppendix 1 
7.1 T he use of data from a platform of opportunity (whale watching) to study coastal cetaceans on
the south west coast of South Africa
8 A ppendix 2 
8.1 D ata collection from commercial whale watching vessel: the need for international
guidelines and systematic quality control
9 A ppendix 3 
9.1 O ccurrence of vagrant leopard seals, Hydrurga leptonyx, along the South African coast
10 A ppendix 4 
10.1 P ossible non-offspring nursing in the southern right whale, Eubalaena australis
11 A ppendix 
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