Yellow spheres – RATS (Relegate All Top Species)
Orange spheres – MICE (Models of Intermediate Complexity for Ecosystem assessments)
Purple spheres – CATS (Complex Assess Tools)
WHY MICE?
Substantial advances have been made in the last two decades in implementing an ecosystem approach to fisheries, but there remain gaps in the toolbox of approaches needed to address the complex science and management issues (Fig. 1).
These include methods for simultaneously assessing the status of both fisheries and other non-targeted species, including those of high conservation concern, and evaluating the trade-offs among management plans aimed at addressing conflicting objectives. There is a need for models of intermediate complexity that draw on the rigorous quantitative and statistical methodology of stock assessment approaches and extend this to representation of multiple co-existing species and stressors in an ecosystem.
Stakeholders increasingly expect ecosystem assessments as part of advice on fisheries management. Quantitative models to support fisheries decision-making may be either strategic (‘big-picture’, direction-setting, contextual) or tactical (focused on management actions on short time scales), with some strategic models informing the development of tactical models.
Fig. 2. Overview of a Models of Intermediate Complexity for Ecosystem assessments (MICE) examples illustrating the direct and indirect impacts of variable size-specific catches for tuna, sharks and billfish by commercial long-liners in the Coral Sea. Inter-connected components are (A) Ecological information, including multispecies trophic or competitive network and spatial habitat processes; (B) Environmental information, including physical and habitat drivers of ecological processes; (C) Human components of the system, including different fishing sectors and their behaviours, other stake-holders and economic drivers; (D) Anthropogenic effects, including fishing mortality; and (E) Management, including input and output controls as well as other environmental policies (from Plagányi et al. 2014).
WHAT ARE MICE?
“Models of Intermediate Complexity for Ecosystem assessments” (MICE) have a tactical focus, including use as ecosystem assessment tools. MICE are context- and question-driven and limit complexity by restricting the focus to those components of the ecosystem needed to address the main effects of the management question under consideration (Fig. 2).
Stakeholder participation and dialogue is an integral part of this process. MICE estimate parameters through fitting to data, use statistical diagnostic tools to evaluate model performance and account for a broad range of uncertainties. These models therefore address many of the impediments to greater use of ecosystem models in strategic and particularly tactical decision-making for marine resource management and conservation.
Mice are small, fast and smart and hence we use the term to represent “Models of Intermediate Complexity for Ecosystem assessments” (MICE), with these models having a tactical focus, including use as ecosystem assessment tools. MICE are context- and question-driven and limit complexity by restricting the focus to those components of the ecosystem needed to address the main effects of the management question under consideration.
They therefore have an intermediate level of complexity in representation of biological, physical and human components, compared with the CATS (Complex Assessment Tools) such as Atlantis who are good at strategic planning and RATS (Relegate All Top Species) (that stay down and avoid the top predators) that focus on lower trophic levels only. MICE focus on the sweet spot in the variance –complexity trade-off (Collie et al. 2014). There are a growing number of examples being developed both within Australia and for other systems.
MICE on the Great Barrier Reef
MICE are being used to model the complex dynamics of Crown of Thorns Starfish (COTS) and coral interactions on the Great Barrier Reef, as a basis for supporting management strategies given COTS are a leading cause of coral decline, along with cyclones and bleaching (Plagányi et al. 2020; Rogers and Plagányi 2022). The Coral-COTS MICE has also been embedded in a network model (CoCoNet) to explore how connectivity between neighbouring reefs supports coral and COTS recruitment (Condie et al. 2018). Recent work as part of the COTS Control Innovation Program has expanded on the original Coral-COTS MICE to include more reefs and sites and assess the effectiveness of the current management control program. The MICE has also been used to test and refine management targets (Rogers et al. 2024) and highlighted the potential for creation of “Effort Sinks” – where management resource use is not optimised (Rogers et al. 2023).
Catchment-to-coast management with MICE
MICE can also integrate across ecosystems to inform management. Recent applications across tropical northern Australia have linked river-to-sea ecosystems (Plagányi et al. 2024 and Blamey et al. 2023). These MICE have then been used to quantify the impacts of upstream river development on downstream estuarine and coastal fisheries and species of conservation concern. This research helps inform on the likely water resource development alternatives and consequences across tropical Australian catchments (see summary here).
MICE and climate change
MICE are also being used to inform on the impacts of climate change on key fisheries and marine ecosystems across northern Australia.
The Gulf of Carpentaria is home to Australia’s largest wild-caught prawn fisheries. Prawns are fast-growing, short-lived crustaceans whose populations fluctuate widely depending on prevailing environmental conditions. MICE are currently being used in an FRDC-funded project to better understand how changes in the environment are impacting these fisheries. See further info here and here.
Torres Strait marine ecosystems are rich in biodiversity, support important fisheries and hold immense cultural significance for Torres Strait Islanders. These ecosystems are under threat from climate change and there is a need to better understand and quantify these impacts to inform decision-making. CSIRO has a long history of working in the Torres Strait, including key fisheries like the Tropical Rock Lobster. We’re using our decades of research and partnering with the TSRA and Torres Strait Islanders to develop a spatial MICE for the Torres Strait that will inform on short, medium and long-term changes to key fisheries and habitats.
Whales and MICE
During the 1900s, many whales were commercially harvest almost to extinction. We used MICE to look at whale numbers from 1890 to now, and then coupled this with food availability and ocean physics, to understand how future changes to the ocean will influence their numbers (Tulloch et al. 2018; Tulloch et al. 2019).
Making MICE social – SOPI
Consistent with the MICE philosophy of focusing on key interactions, we can extend these models into the human domain. To illustrate the concept, we developed an approach drawing on the social science Sense of Place concept (van Putten et al. 2018), which describes the emotions associated with a place. It is a combination of characteristics that makes a place special and unique. Our conceptual framework investigates how socio-psychological processes may influence ecosystem dynamics using a Sense of Place Index (SoPI) to capture feedback in a marine SES model. The psychological characteristics captured by the sense of place concept have important, practical implications for predicting the long-term dynamics of managed resources.
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