154 REPORT OF THE SECRETARY OF COMMERCE 
son to determine to what extent changes in the offshore catch may 
represent merely changes in the distribution of mackerel. 
During the fiscal year 1938 a study was undertaken to determine 
whether a decline in abundance of flounders is in progress in the 
North Atlantic area. In order to interpret fluctuations in abundance, 
it was necessary to develop techniques for determining age and growth, 
the existence of separate races within the population, and the extent 
of migrations. 
Owing to the increased utilization of redfish, flounders, and other 
species of groundfish in addition to haddock, an investigation of the 
abundance of such fishes was begun during 1938. The central prob- 
lem is to assess total catch, fishing effort, and abundance in order to 
determine for each species whether it has already reached the point 
where an increase in yield will give a larger production only with 
detriment to future supplies. 
As a result of cooperation between the Bureau of Fisheries and the 
State of Maine, an investigation to test new methods of rearing 
lobsters, to determine the relative effectiveness of artificial and natural 
propagation, and to ascertain the condition of the lobster fishery on 
the coast of Maine has been added to other scientific fishery investi- 
gations being conducted in the New England area. The State has 
constructed a lobster-rearing plant adjacent to-the Bureau hatchery 
at Boothbay Harbor, with facilities for carrying on experimental 
work, and has assigned funds for the employment of a biologist. 
Experiments with larval lobsters and tagging of adults were begun 
during the spring of 1939. 
Middle and South Atlantic fishery investigations —At the request 
of the New York State Conservation Department, the Bureau par- 
ticipated in a biological survey of the marine fisheries of Long Island, 
acting principally in an advisory capacity. The survey was under- 
taken to provide a basis for improving or maintaining good fishing 
wherever the supply is controllable and to determine by a census of 
fishing activities the recreational and commercial value of the marine 
district of Long Island. Definite recommendations for the conser- 
vation of several species and for additional study have been included 
in a report to be published by the State. 
Evidence continued to accumulate which indicated an inadequate 
spawning escapement as the principal cause of the decline in abun- 
dance of shad along the Atlantic coast. Much of the field work of 
this investigation has been directed toward comparison of the spawn- 
ing escapement in the Hudson, where complete recovery of abundance 
has occurred, with the escapement in other rivers which are still 
severely depleted. The principal methods of study are tagging ex- 
periments, designed to estimate fishing intensity from the percentage 
of tags recovered, and studies of scales intended to estimate the per- 
centage escapement from the percentage of scales bearing spawning 
marks. 
Prior to recommending measures to insure an adequate number 
of spawners in the various coastal rivers, it was necessary to deter- 
mine whether shad return to spawn in their native rivers or whether, 
as many fishermen believe, there are extensive migrations. A direct 
attack on this problem has been made by tagging. Results of tag- 
ging experiments in North Carolina, the Chesapeake Bay, and the 
