Climate-Induced Changes to Fisheries Habitat in Lake Michigan: An Integrated Assessment

While it is becoming clear that the Great Lakes will likely experience significant warming due to
climate change, the potential effects of this warming and other climatic features on fisheries
resources in Lake Michigan are not well understood. Given that Great Lakes fish stocks support
numerous economically important sport and commercial fisheries, elucidating and adapting to
future climate‐driven changes in Great Lakes fish habitat is vitally important. Presently,
management of Great Lakes fisheries can be characterized as primarily reactionary and focused
on short‐term processes. However, a different paradigm may be necessary if fisheries managers
and resource users are to proactively prepare for the consequences of climate change. Effective
management within such a long‐term perspective may necessitate not only evaluation of
human dimensions of fisheries management, but also the development and application of
innovative, forward‐looking investigative methods which can be effectively communicated to a
diverse management audience.

Interestingly, most analyses of likely future climatic impacts on adult fishes in the upper Great
Lakes suggest that many ichthyofauna will benefit from warmer conditions. The upper Great
Lakes, including Lake Michigan, are deep, cool water bodies with limited suitable thermal
habitat, and thus these analyses have suggested that warmer climates will increase the net
volume of suitable thermal habitat and thereby positively impact adult life stages of most fish
species. We suggest that such analyses are insufficient because impacts of future climate may
differ among life stages and will undoubtedly differentially impact spatio‐temporally distinct
fish populations. For example, climate change impacts on nearshore physical and chemical
processes and resulting spatio‐temporal overlap between young and adult fish and suitable
habitat can have huge impacts on population production.

We will use an Integrated Assessment (IA) framework to accomplish our three overarching
objectives: 1) evaluate cross‐institutional knowledge gaps and structures that facilitate or
impede proactive management of Lake Michigan fisheries in the face of climate change, 2)
project how future climates are likely to affect nearshore Lake Michigan fisheries habitat and
3) effectively communicate potential climate‐induced impacts on fisheries habitat to relevant
stakeholders. In order to properly manage fisheries in the face of climate change, it is vital to
understand what drives management of Lake Michigan. First, we will conduct iterative
web-based surveys of managers and resource users throughout the region to better understand
knowledge gaps and factors that might inhibit adaptive change. Second, we will quantify
thermal habitat using existing circulation models and down‐scaled climate models, and we will
use output from these models to quantify spatio‐temporal bioenergetics‐based growth rate
potential (an index of habitat quality) for ecologically and economically important fish species.
Finally, we will disseminate findings from this research to a broad audience using pre‐assessed
communication tools. Thereby, we will provide managers and users with information and
decision support to adapt fisheries management and fishing expectations in response to a
changing climate.