The Ecology of Large Marine Predators in the Hauraki Gulf
type: CreativeWork
description: Knowledge of the distribution and abundance of wildlife populations is essential for the description of a species niche and the development of effective conservation and management strategies. Knowledge gaps exist for many large marine predators, who are often rare, difficult to study, and of high conservation concern. The Hauraki Gulf, New Zealand, is a trophic hotspot that supports a diverse range of large marine predators, yet most of the existing research pertains to single-species or species groups. This study aimed to perform a comprehensive study of the fine-scale distribution patterns of cetaceans, sharks and potential prey patches, and to estimate the local abundance of the common dolphin Delphinus delphis and the nationally endangered Bryde’s whale Balaenoptera eden brydei. Double-observer line transect aerial surveys were conducted in the Gulf from November 2013 to October 2014 to collect distribution data on cetaceans, sharks, and their prey patches, as well as to collect abundance data using mark-recapture distance sampling methods. Platform-of-opportunity and dedicated boat surveys were conducted during the same period to collect photo-identification data to estimate Bryde’s whale abundance with mark-recapture (MR) methods. Bryde’s whale abundance was estimated with a custom-made MR model to minimise bias associated with heterogeneity in capture probabilities resulting from the use of opportunistic data. Boosted regression tree models were applied using sightings data from aerial surveys to model the occurrences of three cetacean species and four shark species to identify biological and environmental drivers of habitat use and to produce monthly prediction maps of suitable habitat with spatially explicit maps of uncertainty. Aerial survey data and mark-recapture distance sampling (MRDS) techniques were used to estimate the abundance of common dolphin and Bryde’s whale populations with a novel, probabilistic approach to reduce biases associated with err…
abstract: Knowledge of the distribution and abundance of wildlife populations is essential for the description of a species niche and the development of effective conservation and management strategies. Knowledge gaps exist for many large marine predators, who are often rare, difficult to study, and of high conservation concern. The Hauraki Gulf, New Zealand, is a trophic hotspot that supports a diverse range of large marine predators, yet most of the existing research pertains to single-species or species groups. This study aimed to perform a comprehensive study of the fine-scale distribution patterns of cetaceans, sharks and potential prey patches, and to estimate the local abundance of the common dolphin Delphinus delphis and the nationally endangered Bryde’s whale Balaenoptera eden brydei. Double-observer line transect aerial surveys were conducted in the Gulf from November 2013 to October 2014 to collect distribution data on cetaceans, sharks, and their prey patches, as well as to collect abundance data using mark-recapture distance sampling methods. Platform-of-opportunity and dedicated boat surveys were conducted during the same period to collect photo-identification data to estimate Bryde’s whale abundance with mark-recapture (MR) methods. Bryde’s whale abundance was estimated with a custom-made MR model to minimise bias associated with heterogeneity in capture probabilities resulting from the use of opportunistic data. Boosted regression tree models were applied using sightings data from aerial surveys to model the occurrences of three cetacean species and four shark species to identify biological and environmental drivers of habitat use and to produce monthly prediction maps of suitable habitat with spatially explicit maps of uncertainty. Aerial survey data and mark-recapture distance sampling (MRDS) techniques were used to estimate the abundance of common dolphin and Bryde’s whale populations with a novel, probabilistic approach to reduce biases associated with err…
author: Hamilton, Olivia
license: https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm
date published: 2020
date modified: 2026-07-24T01:03:37Z
provider: University of Auckland
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: ResearchSpace@Auckland

PropertyValue
property ID: Handle
value: https://hdl.handle.net/2292/56694