Future thermal regimes for epaulette sharks (Hemiscyllium ocellatum): growth and metabolic performance cease to be optimal

Abstract

Climate change is affecting thermal regimes globally, and organisms relying on their environment to regulate biological processes face unknown consequences. In ectotherms, temperature affects development rates, body condition, and performance. Embryonic stages may be the most vulnerable life history stages, especially for oviparous species already living at the warm edge of their distribution, as embryos cannot relocate during this developmental window. We reared 27 epaulette shark (Hemiscyllium ocellatum) embryos under average summer conditions (27 °C) or temperatures predicted for the middle and end of the twenty-first century with climate change (i.e., 29 and 31 °C) and tracked growth, development, and metabolic costs both in ovo and upon hatch. Rearing sharks at 31 °C impacted embryonic growth, yolk consumption, and metabolic rates. Upon hatch, 31 °C-reared sharks weighed significantly less than their 27 °C-reared counterparts and exhibited reduced metabolic performance. Many important growth and development traits in this species may peak after 27 °C and start to become negatively impacted nearing 31 °C. We hypothesize that 31 °C approximates the pejus temperature (i.e., temperatures at which performance of a trait begin to decline) for this species, which is alarming, given that this temperature range is well within ocean warming scenarios predicted for this species’ distribution over the next century.

Elasmobranch Responses to Experimental Warming, Acidification, and Oxygen Loss—A Meta-Analysis

“…For example, the logistic constraints associated with controlled exposure in a laboratory context enfold an inherent bias toward the use of species and life stages amenable to captivity rearing. On the flip side, observations obtained from particularly robust species are likely to represent an underestimation of the general effects, representing conservative indicators (Heinrich et al, 2014;Wheeler et al, 2021). Moreover, the effects of anthropogenic CO 2 emissions extend far beyond decreasing pH, rising temperatures, and oxygen loss.…”

Evaluation of Shifts in the Potential Future Distributions of Carcharhinid Sharks Under Different Climate Change Scenarios

“…This makes them susceptible to negative impacts as a result of climate change (Rosa et al, 2014;Schlaff et al, 2014). Unlike bony fish, the k-selected life strategy of the Chondrichthyans, characterized by long generation times and low fecundity, impedes their adaptation to rapid environmental change imposed upon them as a result of human activities (Wheeler et al, 2021). In addition, the projected negative future change (loss of suitable area) in our modeled species could be related to some theoretical expectations, in which the physiology and behavior of ectothermic and tropical species are strongly affected by temperature gradients (Chin et al, 2010;Feary et al, 2013;Rosa et al, 2014;Schlaff et al, 2014).…”

Swimming performance of sharks and rays under climate change

“…This behavior is already observed in several benthic sharks and rays and may become even more widespread with ocean warming. Ocean acidification is likely to increase the energy costs during swimming, and to prolong recovery times after bursts, but is also likely to increase body size and favor underwater walking by increasing mineralization of pelvic fins which is observed in several benthic rays and sharks already (Bilecenoglu and Ekstrom 2013;Jung et al 2018;Di Santo 2019;Wheeler et al 2020Wheeler et al , 2021.…”