To understand how global warming will affect tropical aquaculture, we will study how a temperature rise from the current value of 27-32 °C to 32-37 °C will affect physiological performance, food conversion efficiency and growth in air-breathing fish. Particular emphasis will be placed on the role of the cardio-respiratory and digestive systems to address the prevailing hypothesis that compromised oxygen transport capacity determines temperature tolerance of aquatic ectothermic vertebrates.
4 air-breathing fish of importance in tropical aquaculture (pangasius, snakehead, climbing perch and rice eel) with marked differences in structure and function of their gills, air-breathing organs and cardiovascular systems have been selected. By correlating temperature sensitivities, physiological functions and anatomical structures, we will identify physiological bottlenecks and key-adaptations that allow some species to thrive, while others perish, in face of environmental change. Thus providing an essential basis for future decision making in light of climate change.
The capacity to continue this research beyond the time frame of the project (PhD's and Facilities) will be established in Can Tho. Further, an International annual PhD course on the physiology of air-breathing fish will be established at Can Tho University employing modern teaching techniques. This course will place emphasis on training young researches from universities in Southeast Asia (Indonesia, Bangladesh etc.).
Midterm report 2016:
The primary goal of iAQUA was to examine the effects of how temperature increases might impact commercially important air-breathing fish. To our surprise, we found temperature elevations from 27°C representing median Mekong river temperature to 33°C give a modest to large increase in growth, rather than the expected decrease. In Pangasionodon hypophthalmus, this increase is a stagering 400-800%, which after repeating the result in numerous growth trials can be claimed with great confidence.
We have found that aquaculture ponds in Vietnam have high concentrations of carbon dioxide, causing disturbances of acid base status on the short term and on the long term, alterations in blood ion content. Surprisingly, we found that all species are very accomplished at blood pH regulation, which goes against conventional wisdom for airbreathing fish. We are currently investigating the long-term effects on growth, and data so far indicate that there is a detrimental growth impact.