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What becomes of released fish ?
Does the stocking of fish in a keepnet before release cause serious losses? Dutch researchers have carried out a study which proves that it does not ! The use of a keepnet which is made from textile netting, and is very large both regarding diameter and depth has become commonplace over the years. It has even become compulsory in competitions as the catches are released afterwards. However extreme positions are sometimes adopted in other European countries. In October 1990 a German angler was prosecuted by the courts in Dusseldorf for having prolonged the suffering of fish kept in a net! Dutch fishermen are occasionally the target of indictments for cruelty brought before the courts by "animal lovers" Various researchers (Schulz and Van Klausewitz in particular) had already forewarned anglers against this practice. Their experiments can be called into question and result from a methodology which although meticulous does not correspond to what happens in reality : for example the fish were taken out of the keepnet at regular intervals. The follow up was carried out in aquariums, etc. The experiments conducted by the Dutch researchers (A.J.P. Raat, J.G.P. Klein Breteler and S.A.W. Jansen) between 1991 and 1999 were carried out under typical angling conditions. The fish were caught, placed in the keepnet for a certain amount of time, examined, weighed, measured and put back into a pond. Their survival and their development were compared to batches which had not been caught. During the keeping period vets measured the toxic substances produced by the fish. Five species were studied: carp, roach, rudd, orfe, bream. After several months the pond was emptied, the fish collected, observed and weighed and measured once again. During the collection of the fish it was noticed that: - the mortality of the orfe was slightly higher than that of the other species, - the mortality of the other species was hardly any different to that of the non-caught fish, - there was no correlation between the length of time they were kept in the keepnet and mortality, - there was no connection in relation to the seasons - the development of caught fish was not retarded by fishing. Even better, the caught carp had a higher growth rate than the others. Other researchers maintain that the fish are under stress and lose scales. No one denies that a few scales are to be found in the keepnet but from that to conclude that the fish are certain to die is not justifiable! A healthy fish renews its scales without any problem. Stress is well-known to humans, and also to fish, especially those in fish farms. It seems that the effort exerted by the fish during capture accelerates disturbances but the fish recovers quite rapidly. Horst Hoffman carried out video observations on fish in the keepnet and on others in aquariums in Stuttgart zoo. It appears that the fish swim in an erratic way for 1 or 2 minutes, they try to escape, then they calm down and display the same behaviour as the aquarium fish. Fine netting which keeps the fish in the dark is preferable. The experiments conducted show that mortality does not increase with the number of fish kept and also that keeping fish does not increase mortality compared to fish released directly after capture. So, please leave the anglers in peace!