Climate change impacts on fish

Rising sea surface temperatures, ocean acidification and rising sea level will affect the 1600 species of fish that live on the Great Barrier Reef. These fish are an essential part of the ecosystem which supports commercial and recreational fisheries and tourism.

Sea surface temperature

Fish body temperature is moderated by water temperature. Increasing sea temperatures can affect important biological processes of fish including growth, reproduction, swimming ability and behaviour.

Reproduction is only possible in a narrow temperature range, and therefore could be affected by the forecast temperature rises associated with climate change. Temperature also influences the sex of fish, which may have an effect on population dynamics.

Some fish respond well to high sea temperatures, as these temperatures can shorten incubation time, increase growth rates and improve swimming ability in juvenile fish. Slight increases in temperature may be beneficial to some fish species as this can shorten incubation time, increase growth rates and improve swimming ability in juveniles. However these benefits are limited to relatively minor temperature increase.

Ocean acidification

Ocean acidification which is a change in ocean chemistry is  also likely to impact fish reproductive processes. Fish eggs are more sensitive to pH changes than fish adults, and thus the population numbers may dwindle if this impact is significant.

Ocean Acidification has also been shown to reduce the ability of fish larvae to find suitable habitat and find their way home.

Lots of species of fish live in and around coral reefs, and most feed on the microbes in the water, which provide fish with their carbon requirements. In general, the overarching affects of ocean acidification on coral formation and the abundance of carbon in the food chain will impact fish species through habitat and food availability.

Sea level rise

The projections for sea level rise in and around the Great Barrier Reef suggest much of the coast line will be inundated with water, resulting in major changes to mangrove and seagrass beds in these areas. These habitats provide protection and food resources for juvenile fish.

There are also species of fish on the Great Barrier Reef that live in both freshwater and saltwater habitats and changes to the pathways between these two habitats will make moving between them difficult for those species, including barramundi.