602 U. S. BUREAU OF FISHERIES 
The seales and measurements are placed in books numbered the same as the 
tags. 
4 metal tag is used. Various metals were tried, none of them entirely un- 
satisfactory, but monel metal was adopted finally as being noncorroding and 
comparatively cheap in price. 
One of the chief difficulties in using tags of. any description is the effects of 
an irritation set up around the point of attachment. After several months, 
or more, many of the tags will pull through the softened tissue, oyt along the 
membrane of the tail, and be lost. It is estimated that 60 per cent of the tags 
are lost in this manner within the first year. The irritation of the tag does 
not appear to affect the physical condition of the fish except at the point of 
attachment, and in some cases the wound heals nicely. 
About 1,700 tagged cod have been reported recaptured, of which 350 were 
taken by our vessels Halcyon and Albatross, most of them a month to a year 
after the fish were tagged. These latter records are of particular value, for 
with them it is possible to determine the rate of growth with reasonable ac- 
curacy and to note how this increased growth is registered on the scales. 
Locality records, the condition of the fish, and other data are more precise when 
we make our own recaptures. 
The percentage of tag returns depends largely on the intensity of fishing and 
the locality of tagging, whether close to land, on a cod ground of restricted 
area, or offshore, where the grounds may be a thousand times as large. For 
example, as many as 20 to 35 per cent of the cod tagged on certain cruises 
have been recaptured off Mount Desert Island, Me.; whereas we have not 
yet received a single return from 1,000 cod tagged last August on Georges 
Bank, 150 miles from our shores. 
The results of the tagging have several points of particular interest. Ac- 
cording to tag returns it was found that cod east of Cape Ann, Mass., do not 
migrate south toward Cape Cod, except as stragglers; but quite a few Maine 
fish migrate east to Canadian waters. Of about 10,000 cod tagged east of Cape 
Ann, only 1 has been reported recaptured south of Cape Cod, and we caught 
that fish ourselves; and of nearly 18,000 tagged on Nantucket Shoals, we have 
only one reliable recapture record from as far east as Maine. Between Maine 
and southern Massachusetts we have tagged a few cod in Massachusetts Bay, 
and recaptures of these fish have been made both to the eastward and to the 
southward. ' 
The most impressive cod migration that we have found occurs each fall from 
Nantucket Shoals to Rhode Island, Long Island, New Jersey, and Delaware. 
Our most southerly recapture record was off Cape Henlopen, Del., but we know 
that cod migrate as far south as North Carolina. Within the region west and 
south of Rhode Island virtually no cod are present in summer. In the fall 
the first cod appear off western Long Island and off New Jersey the last week 
of October. The first recaptures of our tagged fish have occurred each year 
in this region between October 27 and November 4, and the last during April. 
In Rhode Island waters cod are rather abundant from fall to spring, and a 
few fish remain over the summer, but not enough to support commercial fishing. 
Speaking of all localities along the New England coast where we have tagged 
it was found that cod may remain for long periods in one immediate locality, 
Sometimes for as long as 1 or 1% years. We have tagged fish very close to 
buoys and lighthouses or other convenient marks and returned one year later 
to recapture the fish in exactly the same locality. Not only has this happened 
to individual fish, but small pods of cod have shown a tendency to remain 
intact for a considerable time. We have more than one record where nearly 
consecutive numbers were taken a year later in the same locality on the same 
day ; and we have several records of consecutive numbers taken within a few 
minutes of each other several months after the tagging date. 
Scale samples have been taken from all fish tagged since 1924, inclusive. 
When a fish was recaptured by our vessels it was again scaled, of course, and 
measured, The data obtained from these recaptures are of great importance 
for it is our only positive method of learning how growth is registered on the 
scales. The scales from these recaptured fish prove that an annulus is formed. 
What is usually called a zone of winter growth on the cod scale might better 
be termed “zone of retarded growth,’ for I have noted that the so-called 
“winter rings” begin to form as early as September and October. 
Over 10,000 scales have been mounted, and of these about 10 per cent have 
been studied. Scale study has not been pushed vigorously because of an uncer- 
tainty existing as to the early growth. The long spawning period of the cod 
