Jyrki Torniainen

Oxygen and carbon isoscapes for the Baltic Sea: Testing their applicability in fish migration studies

Abstract Conventional tags applied to individuals have been used to investigate animal movement, but these methods require tagged individuals be recaptured. Maps of regional isotopic variability known as “isoscapes” offer potential for various applications in migration research without tagging wherein isotope values of tissues are compared to environmental isotope values. In this study, we present the spatial variability in oxygen (δ18OH2O) and dissolved inorganic carbon (δ13 CDIC) isotope values of Baltic Sea water. We also provide an example of how these isoscapes can reveal locations of individual animal via spatial probability surface maps, using the high‐resolution salmon otolith isotope data from salmon during their sea‐feeding phase in the Baltic Sea. A clear latitudinal and vertical gradient was found for both δ18OH2O and δ13 CDIC values. The difference between summer and winter in the Baltic Sea δ18OH2O values was only slight, whereas δ13 CDIC values exhibited substantial seasonal variability related to algal productivity. Salmon otolith δ18Ooto and δ13Coto values showed clear differences between feeding areas and seasons. Our example demonstrates that dual isotope approach offers great potential for estimating probable fish habitats once issues in model parameterization have been resolved.

Short sea migration and precocious maturation in reared Atlantic salmon post-smolts in the northern Baltic Sea

Short sea migration and precocious maturation in reared Atlantic salmon post-smolts in the northern Baltic Sea Panu Orell*, Jaakko Erkinaro, Mikko Kiljunen, Jyrki Torniainen, Tapio Sutela, Mikko Jaukkuri, and Aki Mäki-Petäys Natural Resources Institute Finland, University of Oulu, PO Box 413, Oulu FI 90014, Finland Department of Biological and Environmental Science, University of Jyvaskyla, PO Box 35, Jyvaskyla FI 40014, Finland Natural History Museum, University of Jyvaskyla, PO Box 35, Jyvaskyla FI 40014, Finland *Corresponding author: tel: þ358 405305830; e-mail: panu.orell@luke.fi

Influence of the marine feeding area on the muscle and egg fatty‐acid composition of Atlantic salmon Salmo salar spawners estimated from the scale stable isotopes

Fatty acids in muscle tissue and eggs of female Atlantic salmon Salmo salar spawners were analysed to evaluate the dietary quality of their final feeding areas in the Baltic Sea. The final likely feeding area was identified by comparing stable carbon and nitrogen isotope composition of the outermost growth region (final annulus) of scales of returned S. salar with that of reference S. salar caught from different feeding areas. Some overlap of stable-isotope reference values among the three areas, in addition to prespawning fasting, decreased the ability of muscle tri-acylglycerols to discriminate the final likely feeding area and the areas dietary quality. Among three long-chained polyunsaturated fatty acids, docosahexaenoic acid (DHA; 22:6n-3), eicosapentaenoic acid (EPA; 20:5n-3) and arachidonic acid (ARA; 20:4n-6), the proportions of ARA in total lipids of spawning S. salar muscle and eggs showed a significant negative correlation with increasing probability of S. salar having returned from the Baltic Sea main basin (i.e. the Baltic Sea proper). The results suggest that ARA in muscle and eggs is the best dietary indicator for dietary characteristics of final marine feeding area dietary characteristics among S. salar in the Baltic Sea.

The origins of northern European Autographa gamma individuals evaluated using hydrogen stable isotopes: Autographa gamma migration

1. Many insect species are migratory. As the spring progresses, adults gradually depart from their over‐wintering habitats and arrive in northern zones where they reproduce during the summer. Understanding this transgenerational and highly adaptive migratory behaviour is crucial when interpreting life cycle dynamics of many insect pests.