PROGRESS IN BIOLOGICAL INQUIRIES, 1935 391 



Another distortion appeared in our measure of haddock abundance 

 on Georo-es Bank wlien in 1934 the fleet of hir^e trawlers shifted 

 a large part of their fishing activity to the Nova Scotian banks, 

 (xeorges was fished only when the yield was particularly good; 

 therefore, the catches of these boats give too high an average for 

 1934 and 1935. The extent of this distortion must be determined 

 before quantitative interpretation of the data is possible. 



If available knowledge is to be used to prepare for the fishing 

 industry a reliable forecast of the trend of the fishery for one or 

 more years in advance, one other type of datum is absolutely neces- 

 sary. ^ This is an annual evaluation of the abundance of young had- 

 dock in year classes below marketable size. These data also would 

 enable us to obtain a measure of the natural mortality rate of young 

 haddock. To secure such data requires considerable trawling with 

 special gear. Xo extensive work of this kind has been possible due 

 to lack of vessel facilities, but during the past year some exploratory 

 work was done on the Aflantis. made available by courtesy of the 

 Woods Hole Oceanograi)hic Institution. Only qualitative conclu- 

 sions are possible from the material so far collected. Quantitative 

 i-esults would require the use of a vessel equipped for regular trawling 

 and a number of com})rehensive cruises each year. 



Hydrography. — During the years 1931-34, hydrographic data were 

 collected and drift bottles released over an area covering Georges 

 Bank and Browns Bank. The cruises were made during the spring 

 of the year to obtain data for the study of ocean currents and their 

 effect on the drift of haddock eggs and larvae spawned in this region. 

 Although no field work of this kind was done in 1935, 25 drift bottles 

 were received from the April 1934 experiment and two from the 

 exj^eriment of June 1933. From the 1934 experiment there now is 

 a total of 91 returns from 629 released. Of these, 16 percent came 

 from west and south of Cape Cod, 42 percent from the Gulf of 

 Maine, 13 percent from the Nova Scotian and Newfoundland coast, 

 and 24 percent from Europe. One-half of the 1934 drift bottles 

 were painted a brilliant yellow and released alternately with clear 

 glass bottles. A red card was enclosed in the unpainted bottle. At 

 the end of 1935 returns from painted bottles were 27 percent higher 

 than from unpainted ones. 



Although attainment of the general objectives of the investigation 

 remains for the futm-e, certain lines of study have already yielded 

 results of immediate practical importance. Extensive field work in 

 1931-32 showed that the trawling fleet annually destroys great num- 

 bers of small haddock below marketable size. This number varies 

 according to the abundance of young fish on the banks and the num- 

 ber of boats fishing. In 1931 on Georges Bank it reached an esti- 

 mated total of more than 60,000.000 baby haddock comj^ared to a 

 catch of not much more than 30,000.000 of marketable size. Since 

 then the destruction has been less, not because the fishery has been 

 less destructive but because baby haddock have been less numerous 

 and the fishing intensity has been reduced by the diversion to the 

 Nova Scotian banks of a considerable part of fishing operation. 

 Nevertheless, the situation continues wherein every brood of young 

 fish is subject to a period of extensive destruction during its' early 

 years before it reaches marketable size. This loss of young haddock 



