BULLETIN OF THE UNITED STATES FISH COMMISSION. 135 



DEVELOPMENT OF THE SPANISH MACKEREL (CITBIUM MACU- 



IiATUM). 



By JOH^' A. RYDER. 



The mackerel-batcliing operations at Mobjack Bay were conducted on 

 board the steamer Lookout and at Bosnian's Fish Guano TV^orks, New 

 Point Comfort, Va., from the 5th to the 13th of July, 1880. Spax^B and 

 milt were obtained in that vicinity from sixteen individuals ; the num- 

 ber of males and females was about the same. These ova were subjected 

 to as thorough and systematic an investigation as the limited time at 

 our disposal permitted. Some time pre\^ously Mr. R. E. Earll had 

 succeeded in taking some eggs in the vicinity of Crisfield which were 

 successfully fertilized and which hatched out in the amazingly short 

 period of twenty hours. In every case the eggs taken and cared for by 

 my assistant, Mr. W. P. Sauerhoff, hatched in twenty-four hours 5 it is 

 true that a few hatched somewhat sooner, but some left the egg-mem- 

 brane even later. I attribute this difference in the times of hatching in 

 the two cases to different methods of treatment of the ova or to a great 

 difference in the temperature of the water. The eggs taken and fertil- 

 ized at 4 o'clock p. m. were all hatched at the same hour the next day. 

 This season's experience at Cherrystone showed that when the tempera- 

 ture of the water was unusually low it would require nearly thirty-six 

 hours for the eggs to hatch, but the development was normal. 



The hatching operations for the season of 1881 were conducted at 

 Cherrystone Harbor, Northampton County, Virginia, in the earlier part 

 of the season, by the crew of the steamer Fish Hawk, but were after- 

 wards continued on Kimberley's wharf, under the direction of Col. Mar- 

 shall McDonald, commissioner of fisheries of Virginia. It was not the 

 good fortune, however, of the latter party, of which the writer was a 

 member, to obtain as large a number of ova as they had been led to 

 expect; this was in the main due to our iuabilitj^ to control the times of 

 fishing with the pound nets, which were the sources whence our supplies 

 of spawning fish were obtained ; also in part to their distance from our 

 hatching station, which, as our facilities for the prompt transportation 

 of the crew of spawn-takers by water was inadequate during the latter 

 part of the time we were engaged in our investigations, added not a 

 little to the disadvantages under which the work was conducted. Add 

 to this the fact that, although the number of ripe fish obtainable was 

 probably sufficient for our experiments, it was learned that they seemed 

 for the most part to discharge their spawn only in the evening or at 

 night, the times when by far the larger proportion of ova were obtained. 

 That this fish is nocturnal in its spawning habits was still further dem- 

 onstrated by Colonel McDonald while on a visit to Tangier Sound, 

 where the Spanish mackerel is taken at night in gill-nets, a mode of 



