Development of a seafloor model of disturbance impacts on benthic structure in the Hawke’s Bay

Download

As part of the Hawke’s Bay regional study, we applied a seafloor model of disturbance and recovery dynamics to explore the implications of changes in the scale and intensity of different stressors for seafloor ecosystems. Exploratory scenarios, parameterised using local data on seafloor sediments and fisheries catch, were used to understand implications of individual stressors of land-based sediment inputs and of intensity of bottom impacts from trawl fisheries on benthic communities.

A final set of scenarios was then designed by the Hawke’s Bay Coastal and Marine Group to explore the outcome on seafloor communities when combinations of reductions in sediment and fishing stressors were applied.

These scenarios varied three different levers:

1. Reductions in sediment mud content on the seafloor
2. Reductions in fishing intensity
3. Implementation of spatial closures (fishery restrictions)

Key points

• The datasets used to parameterize the seafloor model helped to increase understanding of spatial variation in location of two major stressors (bottom fishing impact and sediments from land). 
• The seafloor model highlighted the magnitude of interventions required to enable recovery of the seafloor ecosystem, particularly benthic structure which was a focal element of the model. 
• The model outputs highlight the complexities of ecosystem-based management where multiple overlapping uses and stressors must be managed within a complex and dynamic system such as the Hawke’s Bay coastal environment.  

Related reports

• Enabling ecosystem-based management in the Hawke’s Bay: Overview of stages one and two of the case study process
• Applying analogue simulation - A qualitative process to explore the socio-ecological flow-on impacts in a system in response to modelled biophysical changes