Abstract
The Tasman and Golden Bays (TBGB) are a semi-enclosed embayment system in New Zealand that supports numerous commercial and recreational activities. We present three ecosystem models of the TBGB ecosystem with varying levels of complexity, aimed at contributing as tools to aid in understanding this ecosystem and its responses to anthropogenic and natural pressures. We describe the process of data compilation through to model validation and analyse the importance of knowledge gaps with respect to model dynamics and results. We compare responses in all three models to historical fishing, and analyse similarities and differences in the dynamics of the three models. We assessed the most complex of the models against initialisation uncertainty and sensitivity to oceanographic variability and found it most sensitive to the latter. We recommend that scenarios relating to ecosystem dynamics of the TBGB ecosystem include sensitivities, especially oceanographic uncertainty, and compare responses across all three models where it is possible to do so.
Highlights
End-to-end ecosystem models which can deal with bottom-up and top-down system controls have become popular for exploring scenarios involving human induced impacts including fishing and climate change (Rose, 2012)
The analyses presented in this paper describe the development and assessment of three ecosystem models of the Tasman and Golden Bays
The most complex of these models is an end-to-end ecosystem model using the Atlantis framework, that is spatially and temporally resolved, and has the most complete representation of the system, including oceanographic dynamics, light, nutrients, primary production, the foodweb consisting of 51 species groups, fisheries, and feedback loops within these components
Summary
End-to-end ecosystem models which can deal with bottom-up and top-down system controls have become popular for exploring scenarios involving human induced impacts including fishing and climate change (Rose, 2012) These models can be included as useful tools in providing a holistic approach to understanding system-wide repercussions of how we manage our marine resources (McGregor et al, 2019; Smith et al, 2017; Stecken & Failler, 2016). As a full end-to-end ecosystem model, it is capable of including bio-physical components of an ecosystem, species functional groups, fishing fleet dynamics, social and economic dynamics (Audzijonyte et al, 2017, 2019) With sufficient data, this modelling approach can be extremely useful for management strategy evaluation (Plagányi, 2007). An Atlantis model is developed using components relating to the bio-physical, ecological, and human use aspects of an ecosystem This component structure allows for additional dynamics to be added incrementally. Calibration: the base historical TBGB_AM was calibrated without fishing such that this model had stable biomass trajectories over the 1900–2014 model period, realistic diets, growth rates, natural mortalities, with these compared to the alternative models where appropriate
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