NEW STUDY: Climate affects long-term growth patterns in black bream
Otoliths ‒ fish ear bones ‒ are incredibly useful in fish research because they can be used to estimate age and growth rate. Otoliths accumulate layers of calcium carbonate throughout the fish's life, and these layers can be counted in a similar manner to tree rings.
In this new study, Zoe Doubleday from University of Adelaide and colleagues used otoliths for precisely this purpose.
"Using otolith growth chronologies, we reconstructed long-term growth histories of black bream from two climatically divergent regions in southeast Australia," Dr Doubleday told ASFB.
The researchers collected black bream, Acanthopagrus butcheri, from a single estuary in South Australia (a warm and dry climate) and multiple estuaries in Tasmania (a relatively cool and wet climate).
They examined the fish otoliths to collect years of continuous growth data for individual fish. These growth histories were then related to key climate variables, such as temperature, rainfall, freshwater inflow, and El Niño–Southern Oscillation events.
"We found marked differences in growth trends between the two regions, as well as climate-growth relationships," says Dr Doubleday.
The growth rates of Tasmanian black bream decreased over time and were negatively correlated with temperature. In South Australia, fish growth rates were positively correlated with both temperature and rainfall.
The authors suggest that Tasmanian black bream populations are more responsive to regional environmental variation, and may therefore be more vulnerable to global warming.
"This study stresses the importance of examining species response to climate change at an intra-specific level," says Dr Doubleday, "and further supports the emerging use of calcified tissues as tools for generating long-term ecological data in aquatic systems."
Citation: Doubleday Z, Izzo C, Haddy J, Lyle J, Ye Q and Gillanders B (2015). Long-term patterns in estuarine fish growth across two climatically divergent regions. Oecologia, 1-12. doi: 10.1007/s00442-015-3411-6
The image shows measurements across an otolith