EFFECTS T'VOX FISHES OF CHANGES IN SALINITY OF WATER. 73 



((•) Fishes put inrn water averaging- about 1Jm»1 (ranging t'nun a halt' point 

 below to a half point aliove this tigure). 



April S. 248. 6 



9 250. 9 



10 24(i. 9 



11 240. 5 



12 244.7 



i:5 24:?. 2 



15 242.9 



17, 5.15 p. lu 241.5 



Fishes then put into 1.0:^5 water. 



.\pril 17. (i.l5 p. Ill 239.6 



l^-l'-i" ---- - 228.5 



Ui 225. 6 



Fish in good condition up to this time. 



Results: In water of density 1.001, a gain of nearly 1 per cent in lirst day; 

 a loss of 2.2 per cent in 2 days, of 3.7 per cent in 8 days. After change to 

 salt water, a loss of O.tj per cent in 2 days. 



(d) Water of density 1.015 (sea water from Sandy Ho(jk. slightly diluted). 

 Loss of 1.3 per cent in 2 days, of 3.1 per cent in 11 days. The tishes remained 

 in perfect health throughout. It is not at all prohahle that the decrease 

 during the lirst 2 days is significant. 



(') Water of density 1.025 (Sandy Hook water, strengthened by addition of 

 commercial .sea .salt). This particular lot of water had, for some reason, a 

 harmful effect upon the fishes. It! of them being removed dead or in a dying 

 condition during the first 9 days. The results are none the less worth record- 

 ing: Loss of 1.3 per cent during first hour; of-t.l per cent during first day; 

 of S.3 per cent during first 2 daj's. After this the decrease was far le.ss rapid. 

 At the end of 9 da3's the 9 remaining fishes were put into the salt water of 

 the aijuarium .supply (now 1.010). The weight remained practically stationary 

 (lo.ss of less than 1 per cent) during the next 3 days. 

 Comparison of c with i figures is interesting, the gain following transfer to 

 this slightly saline water being much less than that in fresh water. It is also to be 

 recorded that no deaths occurred in the 9 days during which the fish were in the 

 slightly saline water, while 11 fi.shes were in this time removed, either dead or sick, 

 from the fresh water. The absence of fungus from the.se fi.shes .seems to be due not 

 ^o much to the fatal effect of the salts upon the fungus (for the latter will thrive in 

 water of much greater salinitj', see p. p9) as to a salutary effect upon the fishes them- 

 selves. It is well known that fishes which are in good health are mo.st resistant to 

 fungus, while tho.se which are in poor condition most readily succumb to it. 



The loss of weight in i^. Ju'ti-rodltun when changed from diluted sea water (1.013) 

 to nearly full strength sea water (1.023) is shown once more in the case of the fishes 

 u.sed in experiment 86; but in this case no harmful effects resulted to the tishes. and 

 the experiment is therefore of greater significance. The loss of weight here was 2 

 per cent during the first day. 



