52 Mr. J. J. Armistead on Fish Culture^ [Feb. 14, 



quantity of water in the rivers, largely lessens the quantity of fresh 

 water which is poured into the estuaries into which the rivers flow 

 during times of drought. Then, on the other hand, we get the 

 contrary during floods, when an enormous bulk of fresh water is 

 poured into the salt water in the sea, and in a shall )w estuary, such 

 as the one upon which I live, and which is represented roughly here, 

 we find that, with these rivers flowing into it (the watershed of the 

 firth is I think something like nearly ten times greater than the firth 

 itself, and the firth is a very shallow one) that the specific gravity 

 of the water, the temperature of the water, and other things, are 

 tampered with to such an extent that some of the fish actually 

 deserted it about forty years ago, which, I think, would be somewhere 

 about the time that the hill drainage commenced. The herring is 

 one fish that has deserted the firth, and since that time it has never 

 to any extent come into it. Sometimes some herrings for a short time 

 will come in, but they are very soon out of it again, which shows 

 that when favourable conditions occasionally occur the fish will come 

 into the water ; whereas, owing to this drought altering the specific 

 gravity, we find the fish keeping away. 



All these matters are of the greatest importance with regard to 

 the regulation of our fisheries, both marine and fresh water, and they 

 want looking into. I think that, perhai)s, one of the greatest delights, 

 or the greatest delight, of fish culture is that there is so much to 

 be learnt, and that we are always finding out something new, and 

 that there is always a field to which we can turn for searching out 

 the hidden mysteries of nature and increasing our knowledge, and 

 learning more about the fishes that we have been talking about. 



I would have liked to say a little about the diseases of fish, but 

 I am afraid that there is no time. We have already over thirty of 

 these diagnosed, and, ^vhat is more, we have found out the means of 

 cure for a number of them, and we have been helping fish culture 

 very much in this way. Many of the diseases are parasitic, and we 

 find j)arasites which afiect the fish which were not known to fish- 

 culturists years ago. One is a curious protozoan which gets on the 

 bodies of the fish, and has been known to kill them in large numbers. 

 It can be destroyed in a rather peculiar way*, by placing the fish in a 

 tank with a current of water flowing through it, the bottom strongly 

 impregnated with salt, a saturated solution of salt. The fish keep in 

 the upper water, which is fresh. These curious little j^rotozoaus at 

 certain times leave the fish and go down to the bottom. There they 

 divide, and they are multiplied by division and produce enormous 

 numbers. These free-swimming little creatures get into the water and 

 swim about, and are taken up by the fish again. We find that by 

 having a saturated solution of salt at the bottom of the water and a 

 current of fresh over it, the fish live in the fresh water, and the 

 parasites, when they leave the fish and go down to the bottom, are not 

 able to reach the fish again, because they are killed at once by the 

 salt. 



[J. J. A.] 



