title: Unveiling the depths of the Motiti archipelago: Biodiversity and stressors of mesophotic sponge reefs

authors: Donald, Emma Paige

abstract: Compounding environmental stressors exacerbated by global warming are threatening marine ecosystems worldwide. In New Zealand, recent events such as Cyclone Gabrielle and unprecedented marine heatwaves have brought these concerns to light. Sponge communities dominate the mesophotic reefs of the Motiti archipelago in the Bay of Plenty, which are under ‘no-take’ protection and yet were largely unexplored prior to this research. This study utilised remotely operated vehicle footage and taxonomic identification to establish a baseline of the diversity and current state of Motiti’s mesophotic sponge communities, which are sentinels of the health of their environment. Comprehensive analysis revealed a rapid shift in assemblage composition taking place at the time of surveying, potentially towards species more resilient to sedimentation and elevated temperatures. Additionally, this study reports the discovery of new sponge species, extends geographical occurrence records, identifies large-scale necrosis in line with the 2022 Bay of Plenty marine heatwave, and presents the ‘rapid sponge death’ hypothesis. Conservative findings support previous studies that point towards temperate mesophotic sponges being climate change ‘losers’, highlighting the urgent requirement for regular, long-term monitoring of this sponge diversity hotspot to inform management plans. This study also provides a basis for future research endeavours which are now paramount to understand the complex interactions and the extent of change occurring in this functionally important ecosystem.

text: Unveiling the depths of the Motiti archipelago: Biodiversity and stressors of mesophotic sponge reefs Compounding environmental stressors exacerbated by global warming are threatening marine ecosystems worldwide. In New Zealand, recent events such as Cyclone Gabrielle and unprecedented marine heatwaves have brought these concerns to light. Sponge communities dominate the mesophotic reefs of the Motiti archipelago in the Bay of Plenty, which are under ‘no-take’ protection and yet were largely unexplored prior to this research. This study utilised remotely operated vehicle footage and taxonomic identification to establish a baseline of the diversity and current state of Motiti’s mesophotic sponge communities, which are sentinels of the health of their environment. Comprehensive analysis revealed a rapid shift in assemblage composition taking place at the time of surveying, potentially towards species more resilient to sedimentation and elevated temperatures. Additionally, this study reports the discovery of new sponge species, extends geographical occurrence records, identifies large-scale necrosis in line with the 2022 Bay of Plenty marine heatwave, and presents the ‘rapid sponge death’ hypothesis. Conservative findings support previous studies that point towards temperate mesophotic sponges being climate change ‘losers’, highlighting the urgent requirement for regular, long-term monitoring of this sponge diversity hotspot to inform management plans. This study also provides a basis for future research endeavours which are now paramount to understand the complex interactions and the extent of change occurring in this functionally important ecosystem.

year: 2023

title: Climate change vulnerability and adaptation assessment for Fiji: Supplementary Fiji coastal impacts study

authors: Feresi, Jone

subjects: Fiji

abstract: This document presents extended case studies of the impacts of climate change on the Fiji coast. In particular the study evaluates:
1.	Coastal erosion at 3 representative sites on the coast of Viti Levu. 
2.	 Inundation at 3 representative sites on the coast of Viti Levu.

text: Climate change vulnerability and adaptation assessment for Fiji: Supplementary Fiji coastal impacts study This document presents extended case studies of the impacts of climate change on the Fiji coast. In particular the study evaluates:
1.	Coastal erosion at 3 representative sites on the coast of Viti Levu. 
2.	 Inundation at 3 representative sites on the coast of Viti Levu.

year: 2000-06-30

title: Boat electrofishing salvage of fish in the Lower Mangamahoe Dam reservoir

authors: Hicks, Brendan J.

abstract: The aim of the survey was to salvage fish from the Lower Mangamahoe Dam reservoir before dewatering and dam removal. We used the University of Waikato’s 4.5 m-long, aluminium-hulled electrofishing boat to catch a total of 140 fish weighing an estimated 37.0 kg along 8 fishing tracks sites on 24 February 2022. These tracks comprised 2,807 lineal m and 11,228 m2 in area. Shortfin eels (Anguilla australis) and common bullies (Gobiomorphus cotidianus) were the only fish species present. Mean density of eels caught was 2.9 fish 100 m–2 and mean biomass was 7.84 g m–2. The eels and bullies were transferred to sites downstream in the Waiwhakaiho River by iwi members of the two hapū - Ngāti Te Whiti and Ngāti Tawhirikura. Water clarity, expressed as black disc distance (BDD, 1.05 m), was good for a shallow lake, and water temperature and water conductivity were close to optimum for electrofishing. Poor water clarity can reduce the efficiency of electrofishing, so we left time after fishing each track for the sediment suspended by the propellor wash to sink before refishing a track.

text: Boat electrofishing salvage of fish in the Lower Mangamahoe Dam reservoir The aim of the survey was to salvage fish from the Lower Mangamahoe Dam reservoir before dewatering and dam removal. We used the University of Waikato’s 4.5 m-long, aluminium-hulled electrofishing boat to catch a total of 140 fish weighing an estimated 37.0 kg along 8 fishing tracks sites on 24 February 2022. These tracks comprised 2,807 lineal m and 11,228 m2 in area. Shortfin eels (Anguilla australis) and common bullies (Gobiomorphus cotidianus) were the only fish species present. Mean density of eels caught was 2.9 fish 100 m–2 and mean biomass was 7.84 g m–2. The eels and bullies were transferred to sites downstream in the Waiwhakaiho River by iwi members of the two hapū - Ngāti Te Whiti and Ngāti Tawhirikura. Water clarity, expressed as black disc distance (BDD, 1.05 m), was good for a shallow lake, and water temperature and water conductivity were close to optimum for electrofishing. Poor water clarity can reduce the efficiency of electrofishing, so we left time after fishing each track for the sediment suspended by the propellor wash to sink before refishing a track.

year: 2022