The Effect of Stocking Eel in Selected Marine and Freshwater Habitats of Denmark

The effect of eel stock enhancement was studied in a semi closed brackish fjord and in the upper parts of River Gudenå. At both locations the seed stock used was glass eels imported from France on-grown in heated culture to a size of 3 and 9 gram. Prior to release the stocked eels were tagged with coded wire tags. In collaboration with fishermen on the fjord catches were examined in the years from 2000 -2006 and a total of 1834 tagged eel were recaptured. The stocked eel did well with growth rates in the range of 3 - 7 cm annual, sex ratios on yellow eel were ca. 1/3 mails and 2/3 females.  Survival of the stocked cohort was estimated to be 18 %. In River Gudenå post stock monitoring was done using a Wolf trap catching migrating silver eels. The first silver eel arrived in the trap in 2007 seven years after stocking. Until year 2013 a total of 339 silver eels have been trapped of which 50 % were females. So far less than 1 % of the stocked cohorts have emigrated from River Gudenå suggesting marine areas are more cost-effective to stock.