CXXIV REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



biological investigations being carried on by Mr. J. Percy Moore, of 

 the University of Pennsylvania. 



The earliest catch of Spanish mackerel at Cape Charles City was 

 reported on May 26, but stormy weather interfering with fishing oper- 

 ations and keeping the water at a relatively low temperature, only 

 small numbers were obtained in the beginning, and, in fact, they were 

 not at all abundant at any time during the season. The first ripe fish 

 were not taken until June 17, but from that date up to July 31 from 

 1 to 8 mature females were secured on each of twenty-five days, the 

 total number of fish from which eggs and milt were obtained amounting 

 to 97 females and 121 males. From 1,000 to 330,000 eggs were fertilized 

 each day, or a total of 2,494,000 eggs for the season, and an average of 

 25,711 eggs to each female. Several entire lots of spawn, amounting t<» 

 516,000 eggs, died before hatching. From the balance 829,000 embryos 

 were secured, making tlie proportion of eggs hatched 41.9 per cent. 

 There was considerable variation among the different lots in this respect, 

 however, some yielding only 4 per cent of fry and others as high as 63 

 per cent; the proportion was seldom less than 25 per cent, and gener- 

 ally above 30 per cent. The period of incubation up to the time when 

 hatching began ranged from 21 to 29^ hours, and for all the lots averaged 

 24f hours. The rate of development of the embryos was found to be 

 greatly affected by temperature and amount of sunshine, and electrical 

 conditions seemed also to have their influence, but to what extent could 

 not be ascertained. 



Temperature and density observations were kept up during the prog- 

 ress of the work, but as corresponding observations for the period just 

 preceding the appearance of the ripe fish are lacking it is not possible 

 to determine what relations the spawning functions bear to changes 

 in the physical condition of the water. The surface-water temperature 

 was subject to considerable and often sudden variation, corresponding 

 to fluctuations in the air temperature, dependent upon the time of day, 

 conditions of weather, etc. Four observations were made daily, namely, 

 at 6 a. m., noon, 6 p. m., and midnight. On June 18 the water tempera- 

 tureatthese hours was 77.5°, 80°, 78°, and 78°, respectively. The record 

 for the entire season shows that the temperature at 6 a. m. ranged from 

 72° to 80°; at noon, from 72° to 82°; at 6 p. m., from 73° to 84°; and at 

 midnight, from 74° to 81°. The densities, corrected to 60° F., ranged 

 from 1.0134 to 1.0186, being, of course, greatly influenced by the tides. 



The fish made use of in connection with these experiments were 

 obtained from the different traps distributed between Hungers Wharf 

 and Butlers Hole, the catch from which is mostly marketed at Cape 

 Charles City. Spawn-takers were on hand whenever the traps were 

 hauled, and it is gratifying to acknowledge the hearty cooperation which 

 they received from the fishermen. Mr. Moore always accompanied one 

 of the parties, and was thus enabled to greatly extend the scope of his 

 observations. The following notes are based mainly upon a preliminary 

 report which he has furnished: 



