PROGRESS IN BIOLOGICAL INQUIRIES, 19 30 567 



ties ; the study of the migrations, in the hope of establishing whether 

 young flounders move out from the inshore grounds to populate the 

 offshore banks ; and the discovery of the source of the flounders that 

 concentrate in estuaries and on inshore shoals for the purpose of 

 spawning. 



A tag similar to the mark used on the plaice in European tagging 

 experiments has been attached to flounders held in captivity and 

 appears to be well suited to the purpose. Arrangements have been 

 made for the manufacture of a sufficient supply for an extensive field 

 trial to be undertaken early in 1931. 



MACKEREL 



Investigations of the mackerel fishery during 1D30 may be con- 

 sidered in two parts: (1) Observations of the commercial fishery; 

 (2) observations on the success of spawning and survival of the 

 young larvae. 



As in previous years the data on the commercial fishery collected 

 at the principal landing ports have been studied from the point of 

 view of the relative abundance of the mackerel on the various fishing 

 grounds, as compared with previous years, and the relative niuneri- 

 cal importance of the several year classes in the mackerel population. 

 The work continued under the supervision of O. E. Sette. Field 

 observations were made by Frank E. Firth at New York in May 

 and June, and at Boston from June to December; by Kobert A. 

 Goffin at Cape May, N. J., during April; by William C. Neville at 

 Newport during May; and b}' various field assistants engaged pri- 

 marily in the collection of data on the pound-net fisheries of the 

 Middle Atlantic region throughout the fishing season. 



Altogether, information was secured as to date, localit3^ and 

 quantity of 1,863 out of the total of 3,175 fares landed by the off- 

 shore fleet. Samples from about 1,500 fares were measured. These, 

 together with 5,652 mackerel measured by pound-net observers, make 

 a total of over 40,715 length measurements for the season. Scale 

 samples were taken from 930 mackerel. A considerable number of 

 vessel captains have continued to cooperate by the keeping of detailed 

 los-book records of their fishing activities. 



A final analysis has not been completed, but according to prelimi- 

 nary studies of the data, it appears that 3-year classes were tlie chief 

 contributors to the commercial catch of 1930. The class of 1923 

 (including a small percentage of older fish) furnished about 25,000,- 

 000 pounds; the class of 1928 furnished 12,000,000 pounds; and the 

 class of 1929 furnished 6,500,000 pounds out of the total catch of 

 43,500,000 pounds. 



The brood of 1923 has now been in the. fishery for six years, and 

 during this time it has made up the bulk of the yield. Its diminu- 

 tion in numerical strength has been very gradual. The approximate 

 number of mackerel of this brood in the purse-seine catch in each 

 successive year beginning with 1925, was 19, 24, 20, 14, 11, and 10 

 millions, respectively. This does not necessarily mean that the 

 relative abundance was exactly as indicated by the above figures for 

 the fishing effort has not been exactly equal during this period; but 

 we believe that they do express the abundance in an approximate 



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