THE EMBRYOLOGY AND LARVAL DEVELOPMENT OF 

 BAIRDIELLA CHRYSURA AND ANCHOVIA MITCHILLI. 



By ALBERT KUNTZ, Ph. D., 

 School of Medicine, St. Louis University. 



INTRODUCTION. 



The present paper embodies the results of observations made on the eggs and larvae 

 of two species of teleosts, Bairdidla chrysura and An-chovia mitchilli. The work was 

 carried on at the United States Fisheries Laboratory at Beaufort, N. C, during the 

 summer of 191 3. 



It is not the purpose of this paper to discuss at length any of the merely technicallyi 

 interesting points in the development of pelagic fish eggs. Nor does it contribute any- 

 thing essentially new to our knowledge of the embryology of teleosts. The work was 

 undertaken for the purpose of securing a record as complete as possible of the time of 

 spawning and of the embryological and lar^'al development of fishes with pelagic eggs 

 breeding in these waters during the summer, one of the primary objects being to afford 

 a ready means of identifying either eggs or larval fishes at any time during embr>-ological 

 and larval life. 



Observations were made as far as possible on living material. The eggs were 

 collected in the tow net. The larval fishes were taken primarily in the stow net, the 

 bunt of which was provided with a hood of cheesecloth terminating at its apex in a large 

 collecting bottle. A small per cent of the larval fishes taken in this manner were brought 

 into the laboratory alive. The large majority of them, however, were dead before 

 being taken from the net. . 



Eggs collected at the same hour on successive days were found to be in approxi- 

 mately the same phase of development. Obviously, spawning occurs regularly each 

 day at approximately the same hour. Observations show that both species under 

 consideration spawn regularly in the early evening, probably before 8 o'clock. 



The eggs of these species are relatively small and contain but little yolk material. 

 Embryological development, therefore, proceeds very regularly and requires a relatively 

 short time. The eggs of Anchovia mitchilli require approximately 24 hours for hatching. 

 Those of Bairdiella chrysura hatch in approximately 18 hours. The time required for 

 hatching, doubtless, varies somewhat with the temperature of the water. The height 

 of the spawning season of Bairdiella chrysura occurs during the last week of June and 

 the first week of July. Anchovia mitchilli spawns freely during June, July, and August. 

 The height of the spawning season of this species, doubtless, occurs in July. The 

 average temperature of the water in the vicinity of the laboratory for the latter half of 

 June was 27.15° C. The average temperature for the entire month of July was 27.77° C. 

 These averages are based on daily readings taken at 5 o'clock p. m. 



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