Recent research indicates that larger fish are more affected by climate change-induced droughts and fish kills than smaller fish. A study published in Environmental Biology of Fishes compared evidence from drought-induced fish kills, fisheries management literature, and physiological studies. The researchers discovered that when water becomes warmer and deoxygenated, larger and older fish within a species tend to die in greater numbers compared to their smaller and younger counterparts.
The study’s co-author, Dr. Daniel Pauly, emphasized the need to understand how different fish sizes tolerate droughts and extreme heat due to the increasing impact of climate change. The researchers attribute the increased vulnerability of larger fish to their gill surface area to body mass ratio. Larger fish have a smaller ratio, making it challenging for their gills, which are two-dimensional surfaces, to keep up with the growth of their three-dimensional bodies.
Under normal conditions, this affects only the growth rate of larger fish. However, when temperatures rise and oxygen decreases in the water, larger fish face double challenges, often resulting in their death. Smaller fish, on the other hand, have a more favorable gill surface area-to-body mass ratio, allowing them to survive and handle the higher oxygen demand caused by rising temperatures.
Several studies and field manuals reviewed in the research consistently reported that larger fish have less tolerance for oxygen-depleted and warm waters compared to smaller fish. In the Netherlands, fish kills demonstrated that lack of oxygen and heat stress significantly affected larger fish such as pike, perch, and tench more severely than juveniles.
In colder environments that are warming up, larger fish that have already reached their capacity to supply oxygen to their bodies struggle to deal with rapid temperature increases and critical oxygen levels. This explains why some fish in these places no longer reach their maximum sizes. Understanding the vulnerability of different fish sizes to climate change is crucial for effective conservation strategies.
For more information, you can read the full research article, “On being the wrong size, or the role of body mass in fish kills and hypoxia exposure,” published in Environmental Biology of Fishes.
More information:
Johannes Muller et al, On being the wrong size, or the role of body mass in fish kills and hypoxia exposure, Environmental Biology of Fishes (2023). DOI: 10.1007/s10641-023-01442-w
Citation:
Large fish more vulnerable to climate change-induced fish kills, study finds (2023, July 18)
retrieved 19 July 2023
from https://phys.org/news/2023-07-large-fish-vulnerable-climate-change-induced.html
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