Eel Farm
BACKGROUND
Scandinavian Silver Eel AB (SSE) is a daughter company of Kemira Kemi AB, Kemwater in
Helsingborg, Sweden.
SSE started as a waste energy project in 1985 to exploit warm brackish cooling water, pumped from Öresund, produced by three sulphuric acid plants. The abundant quantities of water available meant that farming eels in a through-flow system at 25oC was an economically viable proposition because at this temperature the eels grow to consumption size within 18 months.
The results from the pilot plant operating during the period 1982-85 were very encouraging and led directly to the construction of our commercial plant. The commercial plant became operational in the spring of 1986 and by 1988 SSE had reached the production target of 100 tonnes of consumption eels per year.
FARMING TODAY AT SSE
In order to compensate for a reduction in free energy SSE altered the
existing farm
from a through-flow system
Small tanks
using brackish water to a recirculated system using freshwater. The initial step was to connect the fingerling unit (40 tanks, 2 X 2m) to a separate trial recirculation system, where after leaving the tank water is first mechanically filtered in a drumfilter, then biologically filtered and finally oxygenated before being pumped back to the fish tanks. The sludge, faeces and any feed waste collected during mechanical filtration is used as a fertiliser.
The biological filtration (nitrification) process occurs in concrete tanks filled with water and where small plastic rings are kept in motion by strong aeration.
After installing the recirculation system in the fingerling unit the growth and feed
conversions were significantly improved despite having higher stocking levels.
Recirculation unit
The success of the trial recirculation system meant that a second system was installed for the on-growing unit (28 D-ended tanks, 3 X 11m). The standing stock of SSE now varies between 80-90 tonnes and the production of consumption eels is around 150 tonnes/year.