Towards an objective and quantitative approach for coastal dolphin habitat: application to management and conservation

Author: Nardi Cribb

Cribb, Nardi, 2017 Towards an objective and quantitative approach for coastal dolphin habitat: application to management and conservation, Flinders University, School of Biological Sciences

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The definition of cetacean habitat has been established as a key priority in the development of management and conservation initiatives as well as threat abatement. Our understanding of the ecological underlying drivers of how cetaceans interact with their three dimensional habitat is however, very limited for many species. This lack of understanding in many cases is a result of the variety of multiple variables and factors, which previous studies have measured to consider habitat for these animals.

The main objective of this thesis was to reach a more objective and quantitative foundation to cetacean habitat studies through the development of a rationale and standardised approach. This approach specifically, considers investigating the underlying driving factors of cetacean habitat, rather than only describing cetacean distribution patterns or just relating their presence to the supposed distribution of prey or a limited number, if any, environmental features. Furthermore, it was key to develop a pre-study focus of either of these applications so that future studies may progress with a more standardised and quantitative approach which would ultimately produce more applicable results in which to develop effective management and mitigation techniques for these animals.

As habitat varies between species, locations, studies, and management priorities, habitat definitions should be broad, measure multiple variables and be tailored to the species and region under investigation. In particular, the assessment of the underlying abiotic and biotic patterns and processes that define cetacean habitat requires the use of objective and quantitative measurements and analyses that may help the scientific community to reach a consensus on how to study cetacean habitats, and ultimately define a research framework to unambiguously define habitats across species, genera and biogeographic regions. The information collected can be assessed to see whether it is applicable to a management context or not. Ultimately, habitat studies should be conducted with the primary aim to make them more targeted and effective in defining and describing habitat so the information obtained can also become more applicable to management.

The developed rationale and approach was primarily applied to two case studies, more specifically, two delphinid species from contrasting environments with differing life histories (i.e. Tursiops sp. in South Australian coastal waters and Stenella longirostris in a Fijian reef complex) and distinct management and threat criteria. Various field based studies examining key abiotic or biotic environmental features, and dolphin behaviour, were then applied to each location utilising a similar approach in which to identify key ecological drivers of habitat in each location. Additionally, two further non-invasive approaches (e.g. photo-identification techniques and fractal analyses) were applied to demonstrate their usefulness when first considering a habitat study as well as a way of considering the identification and quantification of local threats. These 2 techniques can be applied as an additional support to our primary habitat rationale and approach.

The implications of this work demonstrate that there are some unique and relevant considerations that should be addressed when undertaking a cetacean habitat study. Even though the ability to measure key factors of cetacean habitat is frequently constrained by available resources and practicality of field work, an immediate starting point is to apply a prior analyses of the species and study location and then a standardised, broad and quantitative approach which measures the primary range and optimal abiotic and biotic conditions of where the animals are sighted.

The overall findings of this thesis provide novel habitat information on two small delphinid species, but also demonstrate a useful approach to investigate cetacean habitat. Both the habitat rationale and approach and the two additional supporting habitat techniques presented here can be applicable to other species and locations where the identification of dolphin habitat or cetacean habitat in general is crucial. Additionally, this approach can be applied on a broader context at both local and regional scales.

Ultimately, the application of this approach aims to enhance our greater understanding of what habitat means for cetaceans with the intent to provide greater and more effective levels of protection and threat mitigation.

Keywords: dolphin, cetacean, habitat, conservation, management

Subject: Biological Sciences thesis

Thesis type: Doctor of Philosophy
Completed: 2017
School: School of Biological Sciences
Supervisor: Laurent Seuront