60 Ht'LLETIN (IK THK BITRKAI' OF KISHKRIKS. 



It will l.r vvraWvd that in cxpcriincnt n the /''. -//-//-//^o/'/.v tiiially MK'cuinhcd to 

 the ctlccts of tiic fivsii watci-, tiiuiiuli mitlix inj;'. on the average. I.oth of tlie otiier 

 .spefics. The death of this species in fi-esh water was very surprising, since tin' 

 specimens here used came from a hi'ackish water pond (Tashmoo Pond. Mart li:i- 

 Vinevard) having a specific gravity of only 1.005 (corrected), and had been kept in 

 the laboratory prior to the experiment in water of about the same specific gravity. 

 It is to be rememt)ered, too, that tiiis species occurs in nature in fresh-water lakes 

 and streams. The above results, how(>ver. wen- sustained by further experiment. 

 Experiment 15. 



Woods Hole, September, 1!H)4. 'Pwenty-tive h(!altli_y specimens of F. diiij>h- 

 amix, from a lot which had been kept in tiie laboratory (water I.0i»4 to l.oni;i 

 for 11 days, put directly into running freshwater. Fishes fed throughout . 

 Two fishes died within -24: hours; 16 (04 per cent) died within 8 days, when tlie 

 experiment was discontinued. Meanwhile, in a control tank of brackish water 

 containing large numbers of this species, very few died. 

 ('i/j>/-t/i('(/>>/i I'lirixjiitux, a brackish and salt-water fish belonging to the same 

 family as Fund nl us. was chosen as a subject for similar experiment. 

 ■" F.,/,rr!w,„f in. 



Wo.xls Hole, .\ugust, l'.»n4. Two W(>ll-fed specimens of C r,irn,i,tiiis from 



salt water placed directly in fresh water. Both were dead on the following 



morning. 



The "white perch" {Mannn- (inu ricdiut)^ as is well known, may occur either in 



fresh, salt, or brackish water. It is not certain, however, that in nature the clian^c 



is abruptly nmde. 



F.prriim-nt 17. 



Woods Hole, September. 1H04. Of K) specimens of J/i^wwe from brackish 

 water (1.004 to 1.000), which were transferred to fresh, 4 had died and 1 sick- 

 ened within 8 days, when the e\i)eriment was discontimiefl. Experiment Mtj 

 (p. 67) serves as a good control. 

 Experiments with F. diiiphuiius and the white j)ercii during tiie summer of l!»(i."i 

 show that tlie capacity of difien-nt individuals to endure transfer either to fresh or to 

 salt water vari(>s greatly, depending upon the condition of the fishes. It seems likely 

 that a white perch from brackish water may in some cases survive indefinitely after 

 transfei- to fresh water, though this is certainly not true of all speciinens. Those 

 which surviv(> the initial period of mortality seeiu (pialified to resist the harmful 

 effects. 



Of the typically marine tishes few were tested as to their ability to withstand 

 abrupt transfer to fresh water, since this is well known to result fatally in the case of 

 most species. Soup {Stenotomnx chry-'topst) were found to die in from 1 to 3 hours, the 

 fishes being taken from water of a specific gravity 1.023 and temperature about 20- C. 

 Two jiufiers (.s)'//'/v//(A.s ///</( ///.^/(/.v) died within 3 hours under the same conditions. 

 Some cunners { 'r(iiito<jolid<rnx ndsp, rxiix) were dead at end of 12 hours (perhaps much 

 less), and of 2 tautog {Taidixjn miifix) 1 died within 12 and a second within 24 hours. 

 Sculpin {Myti.roccplialuii octod, diiisjduusii.^), sea I'aven {Ifcinitripferioi (diiej'icanm). and 

 sea bass {d idrapristea xtrudKn) aW died witliin a day (probably nmch less)." The 



