Ming-Tsung Chung, Kris-Emil Mose Jørgensen, Clive N. Trueman, Halvor Knutsen, Per Erik Jorde and Peter Grønkjær.
The relationship between physiology and temperature has a large influence on population-level responses to climate change. In natural settings, direct thermal effects on metabolism may be exaggerated or offset by behavioural responses influencing individual energy balance. Drawing on a newly developed proxy, we provide the first estimates of the thermal performance curve of field metabolism in a wild fish. We investigate the thermal sensitivity of field metabolic rate in two sympatric, genetically distinct ecotypes of Atlantic cod from the Skagerrak coast of southern Norway. The combined ecotype median of field metabolic rate increased with increasing temperature until around 16°C, coincident with the thermal optimum for growth for juvenile Atlantic cod. Individual cod experienced temperatures in excess of the thermal optimum for field metabolic rate, indicating some degree of thermal limitation of field metabolism in a complex natural environment with the potential for thermal refugia. The two cod ecotypes showed different thermal performance curves for field metabolic rate, revealing that genetic components to temperature sensitivity persist beyond acclimation effects. The cold-adapted fjord ecotype maintained higher field metabolic rates at cooler temperatures than the warm-adapted North Sea ecotype, which showed clear preference for warmer waters around the thermal optimum. Field metabolic rates of the two ecotypes were strongly influenced by year and location of sampling, implying more complex behavioural responses to environmental conditions. We emphasise that the energy uses reflecting physiological conditions in the field should be considered in the evaluation of the effect of climatic variables on fish population dynamics and demonstrate that otolith isotopes provide an analytical framework to answer this question.
Our new method of otolith metabolic proxy is released today in the journal “Communications Biology” from Nature. We are excited to demonstrate how we use stable carbon isotope values recorded in otoliths to reconstruct fish field metabolic rate. Our study provides the first high-resolution metabolic rate estimates for fish in the field. Moreover, our approach now allows researchers to make use of the large archives of otoliths systematically collected for more than 100 years in order to investigate historical and contemporary changes to fish physiology.
Capelin (Mallotus villosus) feeding is strongly influenced by the zooplankton community in the fjord ecosystem. Our study examined the stomach content of capelin to conclude the importance of larger zooplankton and euphausiids in capelin’s ecology and the influence of Arctic and sub-Arctic fjord ecosystems. More details: https://link.springer.com/article/10.1007/s00300-018-2400-8
The Kapisillit River is the only salmon (Salmo salar) river in Greenland, in which the population size of Atlantic salmon is currently much lower than in the late 1950s and in aa loss of genetic diversity. Our study emphasise the importance of management and monitoring in fishing mortality. More details: https://onlinelibrary.wiley.com/doi/full/10.1111/fme.12306
Three‐spined stickleback (Gasterosteus aculeatus) in populations in Denmark and Greenland have been applying to test the evolutionary hypothesis of genomic parallelism. This study provides empirical evidence and support. More details: https://onlinelibrary.wiley.com/doi/full/10.1111/mec.14782
One more master student defence this past Tuesday. Kasper showed that stable nitrogen and carbon isotope values recorded in muscle tissues of larval fish can tell us their mother size.
On Monday (25/06), Kris-Email told us how we can analyse otolith microstructure, daily increments, to investigate different growth rates between two genetically distinct populations of Atlantic Cod (Gadus morhua) in the Norwegian fjords.
On the 23rdof April, I started my internship at NAFO. I am now halfway through it, and I don’t look forward to the ending of it. I have enjoyed it immensely, with both different projects and with wonderful people to welcome me. But a little background information on NAFO.
The new publication, which Peter and Kris-Emil are participated in, was released in April. Two ecotypes of Atlantic cod, “fjord” and “North Sea”, show different life history traits but stable coexistence within the same habitat. Click it and read more.
Fish Ecology Lab 