Many fish are during feeding dependent on both an olfactory and gustatory sense. Olfaction that acts as the distance sense induces arousal, food search behaviour and attraction to the source, followed by examination of food items by the gustatory sense. During buccal handling the fish decide if the feed will be rejected or swallowed. Amino acids are often stimulatory to the gustatory sense and can act as feeding stimulants. There are, however, inter-species differences concerning what kinds of amino acids act as feeding stimulants or deterrents. The species differences are probably dependent on the natural food choice. As feeding stimulating molecules increase feeding and growth, but deterrents have the reverse effect, it is important to know what kind of molecules have either effect. In the present study we record mouth handling time in the omnivorous crucian carp, Carassius carassius, of agar pellets containing water extracts of meal consisting of ordinary food pellets, blue mussels or a commercial carp attractant. These tests were followed by testing with agar pellets with synthetic amino acids, based on the content of the water extracts of the food pellets that was the only feeding stimulant. Neither extracts of mussel meal or of commercial carp attractants had a stimulating effect, i.e. no significant difference in handling time compared to agar pellets with only water. A mixture of five of the major amino acids in the food pellet extract (40 mM alanine, 20 mM glycine, 20 mM arginine, 8 mM serine, 8 mM leucin) gave a significant longer handling time compared to agar pellets with only water. The handling time was also longer for the three amino acids that had the highest concentrations (40 mM Ala, 20 mM Gly, 20 mM Arg) and finally with only alanine (128 mM). Agar pellets with only Ala gave, however, a significant shorter handling time compared to agar pellets with food pellet extract. The mussel meal extract had the same content of free amino acids and their ranking order was the same as in extracts of food pellets, but at much higher concentrations. Based on the free amino acid content, the mussel extract should have stimulated feeding. This indicates that the mussel extract contained compounds that acted as feeding deterrents in omnivorous crucian carp that do not feed on blue mussels in their natural environment. Previous studies have shown that blue mussel extracts act as feeding stimulants in several bottom feeding carnivorous fish. We finally tested betaine (100 mM) but the molecule had no significant stimulating effect that has been observed in some other fish species. © 2016 The Authors

How were fishponds introduced, farmed and spread in Scandinavia and the Baltic Region in early modern times? What was their economic, social and religious importance? Which fish species were significant and why?

This book uncovers a long, now broken, tradition that barely left traces in the written record or physical environment. Its broad and multidisciplinary scope highlights the situation from medieval times until the late nineteenth century. Besides Scandinavia and the Baltic States, insights from England are also introduced.

Several socio-cultural domains have been identified: late medieval monastic fishponds; late medieval aristocratic fishponds associated with castles and manors; seventeenth and eighteenth century ponds rectory ponds as well as urban ponds from the seventeenth century to the nineteenth century.

Although once popular prior to the last century, the aquaculture of crucian carp Carassius carassius (L. 1758) in Sweden gradually fell from favour. This is the first genetic comparison of crucian carp from historic man-made ponds in the Scandinavian Peninsula. The aim was to identify old populations without admixture and to compare the relationship of pond populations from different provinces in Sweden. In total, nine microsatellite loci from 234 individuals from 20 locations in varied parts of Sweden were analysed. The genetic distances of crucian carp populations indicated that the populations in the southernmost province of Sweden, Scania, shared a common history. A pond population in the province Småland also showed a common inheritance with this group. In the province Uppland, further north in Sweden, the population genetic distances suggested a much more complex history of crucian carp distributions in the ponds. The data showed that there are some ponds with potentially old populations without admixture, but also that several ponds might have been stocked with fish from many sources.