COUNCIL — SEPT. 1912 - APPENDIX K — 134 — 



tion to select, as far as possible, such lakes or ponds in which no eels were formerly 

 to be found, and where all fish leaving the water can be captured — otherwise the 

 results would be of little value. Where such waters are not available, artificial 

 ponds might be constructed for the purpose, such as for instance those used by 

 Bellini. Care must however be taken when applying the results obtained under 

 such artificial conditions to the question of fish living under natural conditions. 

 A number of specimens must from time to time be taken from among the fish 

 laid down, and carefully examined as to length, weight, age and sex, also as to 

 the time when the eels become silvery. With regard to this last factor, special 

 notice must be taken of the influence of artificial feeding in this respect, as also 

 with regard to the question of possible struggle for food between the eels and 

 other fish in the same water. 



In order to elucidate the question of setting out eel fry in natural waters, 

 whether lakes, rivers, fjords or coastal waters (for instance in the Baltic), and also 

 in the interests of Science, investigations should from time to time be made as to 

 the stock of eels in the waters, both with regard to small, undersized fish and 

 larger specimens. This should be done by means of determination of age, (in all 

 cases by examination of the scales, and for eels under 35 cm long also by 

 examination of the otoliths), growth, sex, size (breadth) of the ovaries and testes, 

 development of the breeding dress (silver eels) and stage of development of same. 

 Where possible, causes must be stated of the quicker or slower growth of the eels 

 at the various places of investigation, as temperature of the water at different 

 times of the year, approximate salinity, as well as purity or contamination of the 

 water, and amount of food stuff suitable for eels contained therein. In Denmark 

 an examination will in particular be made of the stock of eels in a lagoon, the 

 waters of which are entirely closed, as at Comacchio (Italy), an important object 

 of this being to check in some degree the reliability of the methods of determining 

 the age of the fish. 



If it is desired to stock closed inland waters with eels, investigation must be 

 made as to how far the biological and physical conditions are suitable for the eel. 

 It will here be of especial importance to consider whether the water in question 

 contains proper food for eels, or whether it could be used to greater advantage 

 by stocking with other fish. In view of the heterogeneous nature of the food stuffs 

 which suffice for the eel, it will be found that almost any water can be advantage- 

 ously stocked with eels, especially as the price paid for full grown eels is so high. 

 Should however the water already contain fish of equal value to that of the eel 

 (e. g. pike-perch) it will be necessary to determine how far the introduction of the 

 eel might prove harmful to the stock of other fish. 



