Metabolic Responses and Resilience to Environmental Challenges in the Sedentary Batrachoid Halobatrachus didactylus

JUAN MANUEL MOLINA; ANDREAS KUNZMANN; JOÃO PENA REIS; PEDRO GUERREIRO

Congreso; The IX Iberian Congress of Ichthyology; 2022

In a context of climate change, warming of the seas and expansion of hypoxic zones are challenges that most species of fish are, or will be subjected to. Understanding how different species cope with these changes in their environments at individual level can shed light on the how populations and ecosystems will be affected. We provide first-time estimates on metabolic rates, thermal and oxygen-related limits for Halobatrachus didactylus, a coastal sedentary fish that lives in intertidal environments of north-east Atlantic. Using respirometry in different experimental designs we found that this species is highly resistant to acute thermal stress ( CTmax: 34.82 +/- 0.66 ºC) and acute hypoxia (Pcrit: 0.404 +/- 0.034 mg O2L-1). We found size-specific differences in this stress response, with smaller individuals being more sensitive. We also quantified its routine aerobic scope and daily activity patterns, finding this fish to be extremely sedentary, with one of the lowest standard metabolic rates found in temperate fish (SMR: 16.93 mg O2 kg–1h–1). H. didactylus activity increases at night, when its metabolic rate increases twofold (RMR: 33.93 mg O2 kg–1h–1). The resilience of this species combined with its changing environment could force it to move northward and also eastward into the Mediterranean. Anecdotal evidence exists of some individuals found as far as Greece. Further, studies combining respirometry with biomarkers such as oxidative stress enzymes, damaged DNA and haematological parameters would also provide a more mechanistically complete panorama of how H. didactylus and other batrachoids cope with the unpredictable and variable world they thrive in.