Methods

Methods:

Objective 1: oceanographic modelling of climate change trends

Global Climate Models (GCMs) are used extensively to project the response of earth system to rising greenhouse gases in the atmosphere. However, due to the complexity of these models, at present they are formulated at relatively low spatial resolution (e.g., typically between 1 and 2 degrees, or 100 to 200 km). This enables GCMs to project the climate evolution over time scales of centuries and longer for various future scenarios of greenhouse gas concentrations in the atmosphere. While global GCMs are valuable for providing global- and basin-scale trends in our future climate, they are not designed to resolve many of the important ocean features that will control the response of the marine system to future climate change. In particular, features like mesoscale eddies and boundary Currents are poorly resolved in the present suite of GCMs. These unresolved features will be important to the local impact of climate change on marine ecosystems (Poloczanska et al., 2007; Hartog et al.,2010). With limited computing resources, various downscaling techniques have been developed to provide climate change projections that resolve the important ocean boundary current and eddy features and to improve the regional climate change projections for marine impact studies (Katzfey et al., 2009).

Objective 2: effect of climate change on fish stocks

This objective will be achieved by:

a. understanding the key environmental trends occurring in the marine environment in WA

b. determining the effect environmental variability is having on fish stocks at the appropriate spatial and temporal scale using some case studies such as western rock lobsters, prawns, scallops, blue swimmer crabs, pearl oysters, whitebait, tailor and dhufish (The main focus of this assessment will be to examine the effect of environmental variables on the recruitment of fish stocks, although factors affecting other biological parameters such as size at maturity and growth will also be considered. Fisheries data collected from a number of sources are used to assess the effect of environmental conditions on fisheries which then may be useful in assessing effects of climate change on fisheries.)

c. examining the historical variability of these environmental variables (Once environment variables at appropriate spatial and temporal scale have been identified as affecting fish stocks when the historic trend of that variable can be examined for evidence of climate change. Frequently the information from fish stocks may only be available for relatively short periods of 10-20 years, which may not be suitable for assessing long-term trends. However the environmental time series may be available for a significantly longer period e.g. 30-40 years which can be used to assess climate change trends.)

d. assessing the likely future trends of these environmental variables from methods under Objective 1

e. hypotheses on the effect of these trends on the fisheries can then be developed and examined using stock assessment models (The western rock lobster fishery is probably one of best candidates to study climate change effects on a fishery in Australia as it has long-term time series (about 35-40 years) in a number of biological variables as well as juvenile abundance and the stock is spread over 10 degrees of latitude. Climate change effects such as increasing water temperatures over the last 30-35 years may have resulted in a decrease in size at maturity, decrease in the size of migrating lobsters from shallow to deep water, and hence an increase in abundance deep water relative to shallow water (Caputi et al. 2010). Some of these changes (such as the increasing frequency of El Niño events) may have negative implications on the western rock lobster fishery but others such as increasing water temperature may have some positive influence.)

Objective 3: development of management policies to deal with climate change effect on fish stocks

This objective will be achieved by:

a. developing policies on key issues such as management boundaries (For example, changes in the spatial distribution of fish stocks poses some interesting policy dilemmas to evaluate when there are fixed management boundaries. Does fisheries management maintain the current zone structure and recognize that there could be some long-term ‘winners’ and ‘losers’ in that situation or does it adjust the management to maintain some historical equity in the system?)

b. reviewing individual management of some case study fisheries (e.g. rock lobster, dhufish)

c. ensuring management decision-rule frameworks for fisheries are sufficiently robust to be able to take into account long-term changes in abundance and distribution of fish stocks that may be due to climate change effects

d. these policies will need to be developed in consultation with researchers, managers and key stakeholders (WAFIC, Recfishwest)

X
Enter your NCCARF - National Climate Change Adaptation Research Facility username.
Enter the password that accompanies your username.
Loading