EFFECTS UPON FISHES OF CHANGES IN SALINITY OF WATER. 67 



tiie change (in some lots a large majorit_y survived). These experiments show fur- 

 thermore that those fishes which survive the first few days after the transfer to salt 

 water may continue to liv(> in the latter for an indefinite period (one set observed as 

 much as 23 days). It is curious to relate that the survivors in experiment 32 (9 fishes 

 at the end of lit days), upon being transferred abruptly to fresh water, continued 

 alive for the next 10 days, after which their history was not noted. 



Several experiments with the white perch (Morone americana) indicate that an 

 al)rupt change from slightly brackish water to full-strength sea water is generally 

 fatal, under laboratory conditions at least. Here again a great deal depends upon 

 the condition of the fishes. During the present season, in several lots transferred to 

 salt water, the majority of individuals were dead within 24 hours. One experiment 

 during the preceding summer, however, gave difi'erent results. 

 Experiment 36. 



Ten fishes transferred to salt water survived s days, after whit'h they were 

 not observed. 



It must lie noted, however, that the brackish water was more saline in the latter 

 experiment, and consequenth' the change in density was not so great. 



Young of the chinook salmon {(hirorJii/ncInix fsr/iinri/fsc/ui), weighing from S 

 to 30 grams, which had been reared in fiesh water, were placed aluuptly in watei- of 

 density 1.013" without harm, but this is not surprising in view of the life history 

 of this species. 



A few species of exclusiveh' fresh-water fishes were likewise expewmented upon, 

 but it was not thought necessarj^ to do so with man}', since the commonly fatal efiects 

 of salt water upon these fishes are already well known. Three 3'ellow perch {I'erca 

 lf((i','sc( iik) and three sunfish {EKjuniiiifix (jiliho.siis) were dead after l-t hours (probaiily 

 much less) in the diluted salt-water supply nf the Nt^w York Aquarium (density 1.h1,5 

 at the time). One catfish (.1//// /«/'/x luliuhisiis) was found dead after 18 hours in 

 water of density 1.014. Several of this sp(>cies in another experiment were nearly 

 dead after two days, but in this latter case the density of tiie water was 1.010. Hence 

 the harmful efl'i^cts were naturally diminished. Four rudd (Zc/z'/.s, //.v , rijfJimjihfJKd- 

 iiuin), put directl}' into water of density 1.010, died some time iMtwiiii .'4 and 4S 

 hours after the change. In another case (experiment 50) S of these ti-lie- died within 

 24 hours in water of densit}' 1.011. 



Bert (1871, 1873, 1883) has discussed at consideraide length the fatal eflects of 

 transferring fresh- water fishes to salt water. He gives a list of species experimented 

 upon, with the avei'age time which elapsed before death in each case, ranging from 

 eighteen minutes for the "ablette" (a cyprinoid) to a period of from one daj' to a 

 month or more in the case of the eel. Bert points out the efiect of higher or lower 

 temperature in hastening or retarding the death of fishes under these conditions. 

 He likewise describes the sj'mptoms attending the death of a goldfish when it was 

 thrown into sea water: violent agitation, followed by quiescence; rise of the fish to 

 the surface, due to lower specific gravity; disturbances of respiration (at first accel- 

 erated, then retarded); changes in the color of the gills; opacit}' of the cr\-stalline 



"This was the density of tlie salt-water supply of the New York Aquarium at the time. It is likely that they would 

 have withstood the transfer to full-strength sea water equally well. 



