The rise and fall of the spiny lobster (Jasus edwardsii) in the Hauraki Gulf, northeastern New Zealand
type: CreativeWork
description: The spiny lobster (Jasus edwardsii) is a critical sea urchin predator on Australasian rocky reefs. In New Zealand, J. edwardsii also supports the country’s most valuable inshore commercial fishery, and subsequently is subjected to intense fishing pressure. While marine reserves have long been shown to be effective in rebuilding lobster populations, declines inside reserves and in fished areas in the Hauraki Gulf, northeastern New Zealand, over the last two decades raise concerns about the plight of this important species. While the recent fisheries assessment suggests improvements in the wider stocks, fisheries-independent assessments are needed to evaluate this. Furthermore, ocean warming has resulted in the expansion of long-spined sea urchins (Centrostephanus rodgersii) in northeastern New Zealand, and it is unknown if this has been facilitated by declines in J. edwardsii populations. The overall aim of this thesis was therefore to investigate the current state of lobster populations in the Hauraki Gulf, and better understand the cause and potential ecological consequences of large-scale declines. This was achieved by carrying out a region-wide dive survey of fished locations and fully protected marine reserves across the Hauraki Gulf, tracking lobster movement in the Cape Rodney-Okakari Point (CROP) marine reserve with a passive acoustic array, and carrying out feeding assays to determine the ability of J. edwardsii to consume C. rodgersii, and its preference for another barren-forming sea urchin, Evechinus chloroticus. Lobster densities in three marine reserves and their adjacent fished locations have not significantly increased following the 2018 catch reduction, and both vulnerable (legal-sized) and spawning stock biomass in the fished population of the Hauraki Gulf are estimated to be ≤5% of reserve biomass. These estimates are in stark contrast to fisheries estimates and suggest the recent stock assessment has grossly overestimated the state of the J. edwar…
abstract: The spiny lobster (Jasus edwardsii) is a critical sea urchin predator on Australasian rocky reefs. In New Zealand, J. edwardsii also supports the country’s most valuable inshore commercial fishery, and subsequently is subjected to intense fishing pressure. While marine reserves have long been shown to be effective in rebuilding lobster populations, declines inside reserves and in fished areas in the Hauraki Gulf, northeastern New Zealand, over the last two decades raise concerns about the plight of this important species. While the recent fisheries assessment suggests improvements in the wider stocks, fisheries-independent assessments are needed to evaluate this. Furthermore, ocean warming has resulted in the expansion of long-spined sea urchins (Centrostephanus rodgersii) in northeastern New Zealand, and it is unknown if this has been facilitated by declines in J. edwardsii populations. The overall aim of this thesis was therefore to investigate the current state of lobster populations in the Hauraki Gulf, and better understand the cause and potential ecological consequences of large-scale declines. This was achieved by carrying out a region-wide dive survey of fished locations and fully protected marine reserves across the Hauraki Gulf, tracking lobster movement in the Cape Rodney-Okakari Point (CROP) marine reserve with a passive acoustic array, and carrying out feeding assays to determine the ability of J. edwardsii to consume C. rodgersii, and its preference for another barren-forming sea urchin, Evechinus chloroticus. Lobster densities in three marine reserves and their adjacent fished locations have not significantly increased following the 2018 catch reduction, and both vulnerable (legal-sized) and spawning stock biomass in the fished population of the Hauraki Gulf are estimated to be ≤5% of reserve biomass. These estimates are in stark contrast to fisheries estimates and suggest the recent stock assessment has grossly overestimated the state of the J. edwar…
author: Nessia, Hayley Rose
keywords: Jasus edwardsii, fisheries-independent, urchin barrens, lobster diet, lobster movement, lobster fishery
license: https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm
date published: 2023
date modified: 2026-07-24T01:03:56Z
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/2292/71085