Breder. — Marine Fish Culture. 213 



If three survived the new generation would be 50 per cent greater 

 in number than that of the parents, and so on. Codfish are no 

 doubt perfectly promiscuous in habit, and as the sexes seem to 

 vary greatly in relative frequency from time to time we will as- 

 sume there are two males to every female. While this is giving 

 an overabundance of males this liberal allowance may be used 

 here as a basis without doing great violence to the point to be 

 made. Accordingly, then, in a spawning school each female 

 would have available the milt of two males to fertilize her ova, 

 and therefore an average of three eggs from every female 

 would have to be successful to maintain the said status quo. In 

 order to draw a sharp mental picture of what this means re- 

 course may be made to one of the much overworked methods 

 used by statisticians to bring home the point. As cod eggs aver- 

 age one-eighteenth of an inch in diameter a medium sized 

 "market cod" could lay a string of eggs which if placed in a 

 single straight line would be over one and one-quarter miles in 

 length. ^ Of this mileage only one-sixth of an inch would have 

 to reach "maturity" to keep the number of cod in the sea at a 

 constant figure. An inspection of a certain report ^ shows that 

 77,659,000 fry were liberated from the Woods Hole hatchery dur- 

 ing the winter of 1917-18. Assuming for the sake of the discus- 

 sion that the naturally spawned eggs lost twice as many of their 

 numbers between the time of ovaposition and the day their ar- 

 tificially incubated relatives were liberated, than did the latter, 

 due to non-fertilization and the vicissitudes of early life in open 

 water, and also that after this time the cultured fry now being 

 subjected to like conditions, equalled the naturally spawned fish 

 in losses, then a net initial advantage of 100 per cent would be 

 possessed by the fry hatched in cod boxes. As cod are certainly 

 not increasing perceptibly in numbers, according to simple pro- 

 portion it may be said that the total effective output of the station 

 for the year would, by these figures, be about 311 fish, available 

 of course to the fishermen some years later. This figure is far 



* Cod 61^ pounds In weight deposit on an average 1,500,000 eggs which 

 number if arrayed as described would reach for that distance. By "market 

 cod" fishermen mean all under 10 and over 2% pounds in weight, which excludes 

 the very small or scrods and the very large, the latter of which form the bulk 

 of their catches. 



' Report of the U. S. Commissioner of Fisheries for the fiscal year 1918 

 with appendices — Hugh M. Smith, Commissioner. Appendix I — The distribu- 

 tion of fish and fish «ggs during the fiscal year 1918, Document 863, p. 75. 



