The use of internal heart rate loggers in determining cardiac breakpoints of fish

Michael R Skeeles; Alexander C Winkler; Murray I Duncan; Nicola C James; Kerry-Ann van der Walt; Warren M Potts

doi:10.1016/j.jtherbio.2020.102524

The use of internal heart rate loggers in determining cardiac breakpoints of fish

J Therm Biol. 2020 Apr:89:102524. doi: 10.1016/j.jtherbio.2020.102524. Epub 2020 Jan 22.

Authors

Michael R Skeeles¹, Alexander C Winkler², Murray I Duncan³, Nicola C James⁴, Kerry-Ann van der Walt³, Warren M Potts²

Affiliations

¹ Department of Ichthyology and Fisheries Science, Rhodes University, Grahamstown, 6140, South Africa. Electronic address: michaelskeeles@gmail.com.
² Department of Ichthyology and Fisheries Science, Rhodes University, Grahamstown, 6140, South Africa.
³ Department of Ichthyology and Fisheries Science, Rhodes University, Grahamstown, 6140, South Africa; South African Institute for Aquatic Biodiversity, Grahamstown, South Africa.
⁴ South African Institute for Aquatic Biodiversity, Grahamstown, South Africa.

PMID: 32364965
DOI: 10.1016/j.jtherbio.2020.102524

Abstract

As marine environments are influenced by global warming there is a need to thoroughly understand the relationship between physiological limits and temperature in fish. One quick screening method of a physiological thermal tipping point is the temperature at which maximum heart rate (ƒ_Hmax) can no longer scale predictably with warming and is referred to as the Arrhenius break temperature (T_AB). The use of this method has been successful for freshwater fish by using external electrodes to detect an electrocardiogram (ECG), however, the properties of this equipment pose challenges in salt water when evaluating marine fish. To overcome these challenges, this study aimed to explore the potential use of implantable heart rate loggers to quantify the T_AB of Chrysoblephus laticeps, a marine Sparid, following the ECG method protocols where ƒ_Hmax is monitored over an acute warming event and the T_AB is subsequently identified using a piece-wise linear regression model. Of the nine experimental fish, only five (56%) returned accurate ƒ_Hmax data. The T_AB of successful trials was identified each time and ranged from 18.09 to 20.10 °C. This study therefore provides evidence that implantable heart rate loggers can estimate T_AB of fish which can be applied to many marine species.

Keywords: Chrysoblephus laticeps; Climate change; Conservation physiology; Marine.

MeSH terms

Animals
Electrodes, Implanted
Heart Rate Determination / instrumentation
Heart Rate Determination / methods*
Heart Rate*
Perciformes / physiology*
Thermotolerance*