Abstract Title

Differences in Maximum Cardiac Function and Specific Dynamic Action Between Selected and Non-Selected Rainbow Trout

Additional Funding Sources

This project was made possible by the NSF Idaho EPSCoR Program and by the National Science Foundation under Award No. OIA-1757324.

Abstract

Redband Trout (Oncorhynchus mykiss gairdnerii) are an aquatic species facing rising stream temperatures as a result of climate change. For the primary research project, redband trout were collected from streams in three ecotypes throughout Idaho: cold montane, cool montane, and desert. They are currently being reared in a common garden experiment at 15°C, 18°C, and 21°C, which represent the average temperatures of cold montane, cool montane, and desert streams, respectively. However, due to the limited availability of the redband trout, hatchery rainbow trout were used for this research. We compared two strains of rainbow trout: one that is selected for growth (CX), and one that is not actively selected for a specific trait (NS). The purpose of these experiments is to collect preliminary data for maximum cardiac function and respirometry studies on hatchery rainbow trout as surrogates to develop methodology for future redband trout studies. For the first experiment- maximum cardiac function- the temperature was increased from their rearing temperature (15°C) at a constant rate throughout the experiment until the fish’s heart experience arrhythmia. For the second experiment- respirometry- water temperature was maintained at 15°C while measuring oxygen consumption rate using the oxygen loggers. These data were then used to determine each individual’s specific dynamic action (SDA) and standard metabolic rate (SMB). In the findings for cardiac function, it is shown that 26°C is the upper thermal limits for cardiac function in both CX and NS strain. All the fish’s heartbeat reaches to its max before going into arrythmia. Fish that were in the selected group had a lower beat per minute (bpm) than the non-selected group. The fish that were on the FMFO feed overall had a higher bpm than the fish that were on the PMFO feed, but only by 10bpm. When working with respirometry, the SMB ranges from 80-110mg O2 kg-1 h-1. SDA occurred within 48h after feeding. CX and NS showed differences in both SMR and SDA, suggesting the selection for growth has result adjustment in respiratory function. The question remains on how redband trout can cope with these temperature changes in different thermal environments. This information will be useful in future studies for redband trout after recognizing that the strain of rainbow trout selected for growth had a lower cardiac output than the non-selected strain. It aligns with the hypothesis that high growth will result in lower cardiorespiratory performance at higher temperatures and could be costly to redband trout if temperatures keep rising.

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Differences in Maximum Cardiac Function and Specific Dynamic Action Between Selected and Non-Selected Rainbow Trout

Redband Trout (Oncorhynchus mykiss gairdnerii) are an aquatic species facing rising stream temperatures as a result of climate change. For the primary research project, redband trout were collected from streams in three ecotypes throughout Idaho: cold montane, cool montane, and desert. They are currently being reared in a common garden experiment at 15°C, 18°C, and 21°C, which represent the average temperatures of cold montane, cool montane, and desert streams, respectively. However, due to the limited availability of the redband trout, hatchery rainbow trout were used for this research. We compared two strains of rainbow trout: one that is selected for growth (CX), and one that is not actively selected for a specific trait (NS). The purpose of these experiments is to collect preliminary data for maximum cardiac function and respirometry studies on hatchery rainbow trout as surrogates to develop methodology for future redband trout studies. For the first experiment- maximum cardiac function- the temperature was increased from their rearing temperature (15°C) at a constant rate throughout the experiment until the fish’s heart experience arrhythmia. For the second experiment- respirometry- water temperature was maintained at 15°C while measuring oxygen consumption rate using the oxygen loggers. These data were then used to determine each individual’s specific dynamic action (SDA) and standard metabolic rate (SMB). In the findings for cardiac function, it is shown that 26°C is the upper thermal limits for cardiac function in both CX and NS strain. All the fish’s heartbeat reaches to its max before going into arrythmia. Fish that were in the selected group had a lower beat per minute (bpm) than the non-selected group. The fish that were on the FMFO feed overall had a higher bpm than the fish that were on the PMFO feed, but only by 10bpm. When working with respirometry, the SMB ranges from 80-110mg O2 kg-1 h-1. SDA occurred within 48h after feeding. CX and NS showed differences in both SMR and SDA, suggesting the selection for growth has result adjustment in respiratory function. The question remains on how redband trout can cope with these temperature changes in different thermal environments. This information will be useful in future studies for redband trout after recognizing that the strain of rainbow trout selected for growth had a lower cardiac output than the non-selected strain. It aligns with the hypothesis that high growth will result in lower cardiorespiratory performance at higher temperatures and could be costly to redband trout if temperatures keep rising.