FOR THE ANGLER Smaller Trout If Eels Absent

Press, Volume CII, Issue 30294, 21 November 1963, Page 20

FOR THE ANGLER Smaller Trout If Eels Absent

[Specially written for “The Press” by J. SIERS]

For some years the Fisheries Laboratory has been experimenting with eels and trout in Canterbury. The first stage of the south branch work shows that when eels are removed the number of trout increases. Later there is a corresponding loss in the size of; the average trout You get more trout, but they are smaller. Obviously, the next deduction would be that eels eat trout and when eels are removed there are more trout but less trout food. In the eyes of the cautious scientist there is only one basis for conclusion: facts. And in the next series of experiments, the field team will try to determine whether eels actually compete with trout for food, and if so what is the most popular food of both species. If it is found the removal of the eels has not made extra food available to trout, the experiment could well show that in most cases there is little cause to build costly control measures to try to stop eels from getting into trout water. What the fisherman has to decide is essentially this: Is he prepared to tolerate eels in a trout stream? Their presence will mean there will be fewer trout in the same

water, but they will be bigger and will reach their larger size faster; or, does he want more trout of a much smaller size and possibly poorer condition? In the test tection of the south branch, experiments have shown that where the eels were removed the population of trout has increased up to five times. In another section where eels were removed, the trout population has increased nine times. But comparison shows that to one section where the eels were removed it takes the trout one and a half years longer to reach the size of the trout living with eels.