Physiological adaptations in high-latitude fish

A fascinating adaptation of salmonid species (Atlantic salmon, brown trout and Arctic charr) is their anadromous life strategy, which implies that they spend parts of their life in the sea to gain access to the rich feeding grounds in the marine environment. Our research focuses on neuroendocrine mechanisms involved in the preparatory changes preceding seaward migration and in the regulation of their strong seasonal changes in appetite and growth.

Fish living in high-latitude environments have developed mechanisms that enable them to cope with the strong seasonality of these environments. For example, many species synchronize their annual feeding activity with the seasonal changes in food availability; summer is the time for intense feeding and energy deposition, whereas the winter is characterized by low feeding activity and energy saving. Moreover, some species have developed a migratory life-strategy to cope with spatial differences in food availability. The anadromous (sea-migrating) Arctic charr reside in freshwater throughout winter and perform annual migrations to the sea in summer. This species, which is the northernmost distributed freshwater fish and well adapted to the harsh and changing environment in the Arctic, has become our most important model species for studying adaptations to the high north in fish. By studies in the field and under controlled conditions in the laboratory we seek to obtain knowledge on how seasonal processes such as smolting (preparation for downstream migration and seawater residency) and appetite/growth is timed and regulated on the neuroendocrine level. In addition to a general improvement of our basic knowledge about how high-latitude fish work, our research is also motivated by applied aspects such as their vulnerability toward environmental changes and the need for knowledge within the growing aquaculture industry. It is also likely that extreme adaptations constitute mechanisms which may be of universal interest and a possible source of exploitation. The research encompasses the following main, integrated topics:

 

1) Temporal control; how do high-latitude fish keep track of time in order to anticipate and prepare for forthcoming seasons? (see section on chronobiology)

 

2) Smolting; neuroendocrine regulation of the preparatory changes preceding seaward migration.

 

3) Appetite regulation; how can the anadromous Arctic charr undergo months of fast and emaciation without being hungry?

 

Contact person: Even H. Jørgensen

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