[5] PROPAGATION OF CODFISH. 787 



Subjoined will be found the report of Mr. James Carswell, who was 

 in charge of the manipulation of the eggs and of the water observations. 



EEPOET OF ME. CAESWELL. 



As desired, I submit the following report of cod-hatching for the 

 winter of 18S6-'S7. 



On my arrival at the station, on the 29th of November, I found in the 

 hatchery a few cod eggs and fry. Some of the latter I put in an aqua- 

 rium, but all got drawn upon the siphon bag and were lost. This I 

 attributed to their sickly conditiou when put in. 



On the 9th of December the Grampus arrived with 273 live codfish, 

 and a smack, on the 11th of the same month, with 170, all of which were 

 put into the live cars, and all proved to be good spawners. The first 

 eggs taken were a small lot on the day of arrival, but these and the 

 two following lots turned out badly, not hatching over 50 per cent. At 

 the time they were taken I did not think they were likely to turn out 

 well, because they scattered too much in the water when put in the hatch- 

 ing jars. Cod eggs when taken should at once rise to the surface of 

 the water after being impregnated, and remain there until hatched; 

 although in the case of very low temperature, when a long time is taken 

 to hatch, the eggs will sometimes get coated with a very fine sediment 

 and sink. Still, if they are far enough advanced for the young fish to 

 be seen with the naked eye, they will hatch out, notwithstanding they 

 have sunk to the bottom. 



The codfish in live cars were examined every other day with varied 

 success, the smallest number of eggs taken being 75,000, and the largest 

 3,200,000. All the eggs taken from the 13th to the 31st of December— 

 about 18,000,000 — turned out well, the average loss, as near as I could 

 estimate, being about 20 per cent., but in several instances it did not 

 exceed 5 per cent. I think the cod-hatching apparatus now In use at 

 the Wood's Holl Station will compare favorably with any apparatus 

 known to me and which is used for the hatching of other species of fish. 



Experience has proved that it is not advantageous to have the tem- 

 perature of the water above 40°. In warmer water the eggs hatch out 

 too rapidly, the fry are weak and sickly, and a very large percentage 

 of them die after hatching. I consider the best temperature to be from 

 31° to 3S°, when the eggs will take from eighteen to twenty-five days in 

 hatching; then the fry straighten out soon after hatching, look strong 

 and vigorous, and invariably stay on the surface of the water. My ex- 

 perience is, the stronger the fry the nearer the surface they will remain. 



From the 13th to the 31st of December I made several experiments in 

 trying to keep the young fry alive in aquaria. First with the usual 

 siphon-bag as in shad work; but in every case this resulted in drawing 

 all the fry onto the cheese-cloth, where they would remain until they 

 died. Next I fitted up three aquaria (see plans) and applied the tidal 

 motion in three different ways, but this also resulted in the death of 

 the fry after a time; not, however, on account of their sticking to the 



