Guest essay by Eric Worrall
James Cook University researchers have discovered if you heat fish above their natural tolerance range while mistreating them (simulating catch and release), a lot of them drop dead.
Rising temperatures may drive fishing-induced selection of low-performance phenotypes
Climate warming is likely to interact with other stressors to challenge the physiological capacities and survival of phenotypes within populations. This may be especially true for the billions of fishes per year that undergo vigorous exercise prior to escaping or being intentionally released from fishing gear. Using adult coral grouper (Plectropomus leopardus), an important fisheries species throughout the Indo-Pacific, we show that population-level survival following vigorous exercise is increasingly compromised as temperatures increase from current-day levels (100–67% survival at 24–30 °C) to those projected for the end of the century (42% survival at 33 °C). Intriguingly, we demonstrate that high-performance individuals take longer to recover to a resting metabolic state and subsequently have lower survival in warm water compared with conspecifics that exercise less vigorously. Moreover, we show that post-exercise mortality of high-performance phenotypes manifests after 3–13 d at the current summer maximum (30 °C), while mortality at 33 °C occurs within 1.8–14.9 h. We propose that wild populations in a warming climate may become skewed towards low-performance phenotypes with ramifications for predator-prey interactions and community dynamics. Our findings highlight the susceptibility of phenotypic diversity to fishing activities and demonstrate a mechanism that may contribute to fishing-induced evolution in the face of ongoing climate change.
Read more: http://www.nature.com/articles/srep40571
I have no doubt overheating already stressed fish causes higher mortality, and fish which “fight” harder (exhibit more stress) are more likely to die. But the inference that this will skew species towards low-performance phenotypes seems absurd.
Even assuming the world does warm as predicted, if tropical waters become too warm for some species, and for whatever reason those species have trouble adapting, they affected species will simply migrate to feeding grounds which are a few hundred miles further away from the equator, until they find their optimum temperature range.