COD EGGS IN MASSACHUSETTS BAY, 1924-1925 



263 



ever, due to the need of increasing the number of stations (thus prolonging the 

 cruises), and to the frequent delays that were inevitable during the severe winter sea- 



son, the 



interval between trips was increased later to two weeks. 





Cruise 



Date 



Cruise 



Date 



1 



Dec. 3, 1924. 



8 



Mar. 10, 1925. 



2 



Dec. 9-11, 1924. 



9 



Mar. 12, 1925. 



3 



Dec. 16-17, 1924. 



10 



Mar. 25, 1925. 



4 



Dec. 22-23, 1924. 



11 



Apr. 7-8, 1925. 



5 



Jan. 6-7, 1925. 



12. _ 



Apr. 21-23, 1925. 



6 



Feb. 6-7, 1925. 



13 



. May 20-22, 1925. 



7 



Feb. 24-28, 1925. 



14 June 16-17, 1925. 



EQUIPMENT AND METHODS 



The collections made at each station consisted of a vertical haul, two 20-minute 

 surface hauls (one coarse and one fine net), and a 20-minute haul near the bottom 

 with a coarse net. In order to facilitate the work, advantage was taken of the very 

 extensive data on temperature and salinity variations in the Gulf of Maine previously 

 obtained by Doctor Bigelow, and only such physical observations were made as were 

 necessary to interpret the existing conditions and to serve as a basis for comparison 

 with previous years (see Table 15). These consisted of temperature readings from 

 various levels and, at times, salinity determinations. Most of the latter were com- 

 puted by Richard Parmenter from hydrometer readings. Greene-Bigelow water 

 bottles, with reversing deep-sea thermometers (Riehter and Schmidt- Vossberg), were 

 used. 



Vertical hauls were made with a Michael Sars meter net, the upper 13^ meters 

 (nearest the large opening) being of No. 00 silk bolting cloth and the lower three 

 meters of No. 2 silk. The fine surface net of No. 20 silk was 1 foot in diameter at 

 the opening and 3 feet long. Michael Sars meter nets of the same type as the vertical 

 nets were used for surface and bottom towing. 



Drift bottles were set out at various places in order to supplement the evidence 

 of water movement indicated by the cod eggs. (Figs. 14 and 15.) 



Between November 12, 1924, and June 17, 1925, more than 650 net collections 

 were made and the distribution of the eggs was plotted by trips. Considerable 

 error, no doubt, has entered into the results, but this is unavoidable in work of this 

 type, where so many hauls and such large quantities of eggs are involved. The 

 use of horizontal nets for quantitative work may be criticized, but, as has been 

 pointed out often (Bigelow, 1917; Fish, 1925, etc.), unless the desired species are 

 present in extremely large numbers, the catches with a vertical haul are too small 

 to be of any value; and even when abundant, they are so unequally distributed 

 usually that the results are more likely to be misleading than helpful. Again, con- 

 clusions based entirely on surface hauls might prove equally erroneous if the eggs 

 were concentrated at the lower levels. Had there been ample time and funds, 

 more accurate figures might have been obtained, and the difficulties arising from 

 "streaky distribution" overcome to some extent by greatly increasing the number 

 of stations and plotting results based on vertical hauls alone. This was not possible 

 at the time, however; therefore the sum of the yields of one vertical haul and one 

 20-minute surface haul from each station has been used in preparing charts on the 



