Marine Fish May Not Live at Optimum Temperatures

In many areas of the world’s oceans, fish and invertebrate communities in shallow waters are not living at their optimum temperature. That’s according to a study by researchers from Australia, Sweden and the US, who believe they can now assess whether species loss, species gain or a mixture of the two will be the main form of change in any particular location

"We can’t do anything about species loss/range contractions – other than reduce warming rates through global cooperation in reducing fossil fuel consumption," said Rick Stuart-Smith of the University of Tasmania, Australia. "But we can do things to reduce species gain. This includes well-managed MPAs [marine protected areas] and conservative fisheries management in temperate areas, where the study shows species loss will be minimal e.g. south eastern Australia, and species range extension the main form of change."

Stuart-Smith and colleagues looked at the geographic and thermal distributions of 2695 reef fish and 1225 mobile macroinvertebrate species, using data from the Global Biodiversity Information Facility and Reef Life Survey along with remotely-sensed mean sea surface temperatures.

"Marine species have broad thermal distributions, and it is only at the very warmest locations they occur at which they are likely to be lost from the local community," he said. "Many species share the locations at which they are living at their warmest edges, making these locations most vulnerable to loss of a greater proportion of species."

The team compiled the first global data set of abundance-weighted community temperature index (CTI) values from systematic quantitative sampling. The community temperature index is the average thermal preference temperature of the species in the sample. "Thermal bias is how much this deviates from the local sea temperature," said Stuart-Smith. "For example, if the CTI was 20°, but the local sea temperature was 18° on average, then the thermal bias would be +2°. This means that the average species present at that location would actually do even better – be most abundant – if the water was 2° warmer."

Source: Environmental Research

Taxonomy

• Environment
• Marine
• Climate Change