Assessing the Risk of an Aquaculture Development on Shorebirds Using a Bayesian Belief Model

ABSTRACT

One of the largest Ramsar-designated wetlands in New Zealand is located at Miranda, in the Hauraki Gulf, at the head of a large sheltered embayment (the Firth of Thames). The habitat is particularly significant in that it supports large populations of nationally important, and Arctic migratory, shorebirds. At present regulatory authorities are processing applications for a new marine farming region in the Firth and both regulators and stakeholders have expressed a desire to investigate possible interactions between the possible marine farms and the Ramsar wetland. The specific objective of this study was therefore to use existing information to investigate the risks of the possible aquaculture activities on the ability of the southern Firth habitats to support shorebirds. The study involved the development of a hazard assessment, and then investigating risk pathways through the use of a Bayesian network model, and a complex systems model. The hazard assessment identified multiple pathways through which the farms may interact with the wetland habitat; including through changes to primary productivity, detrital pathways and sediment dynamics. Furthermore, both the Bayesian network model and complex systems model suggested that the ability of the habitat to support shorebirds is nonlinearly dependent on both the habitat size, and quality; both of which could potentially be influenced by the establishment of the farms.

Keywords:

• Bayesian
• ecological risk assessment
• New Zealand
• Ramsar
• shorebirds
• probability network
• mussel farming

ACKNOWLEDGMENTS

Phil Battley is thanked for his helpful review of this manuscript, and contribution to the bird parameters used in the models. Bill Brownell, David Melville, Ibrahim Elmetri, Barry Robertson, Nigel Keeley, and Tim Dodgshun are thanked for providing invaluable assistance and advice on local conditions at the Firth of Thames and the birds used in this study.