found near the edge of the Continental Shelf 

 in depths 40 fathoms or more and particularly 

 in the southern part of the ground (easterly 

 of Bodic Island) in depths 25 to 50 fathoms. 

 When relatively less cooling occurs, scup are 

 generally scattered over the central part of 

 the general fishing area (easterly of Chesa- 

 peake Lightship) in depths 20 to 40 fathoms. 

 Usually better catches are made in a "cold 

 winter", because the scup are more con- 

 centrated and available in a relatively small 

 part of the fishing ground. 



5. Discarding at sea of large quantities of 

 small scup in some winters suggests the need 

 for practical gear modification to correct this 

 wasteful practice. 



TAGGING STUDIES 



Accurate appraisal of the general stock of 

 scup and proper understanding of the impor- 

 tance and causes of fluctuation in catch involve 

 the determination of whether or not separate 

 population units exist, and the extent of the 

 availability of each to the general fishery or 

 to the separate fisheries in certain localities 

 of the general range. The identification of 

 separate units can often be traced by a com- 

 parison of age and size composition in the 

 catch, varying fluctuations in yield, and more 

 directly by tagging experiments. 



In the preceding discussion of the fluctua- 

 tions in the catch of the summer and winter 

 fisheries, evidence from the analysis of age 

 and size composition, together with changes 

 in catch, suggests that the summer and winter 

 fisheries draw on the same general stock, 

 since the catch of each has included the same 

 broods of fish, and that fish available to the 

 summer fisheries at various parts of the 

 coast apparently migrate in the autumn to the 

 region of the winter fishery and mix. Direct 

 evidence of this was obtained from the results 

 of tagging. 



From 1931 to 1934 inclusive, 7,160 scup 

 were tagged and released in the summer and 

 winter fisheries. In the summer fishery, scup 



were tagged near the northern and southern 

 ends of the range; namely. Woods Hole, Mass., 

 and Wildwood, N.J. In the winter trawl fishery, 

 scup were tagged at a sufficient number of 

 locations as to be representative of the general 

 region being fished by the majority of the 

 fleet. Several types of tags were used, the 

 best results being obtained with a modified 

 type of Scottish plaice label (external tag) 

 and the "belly tag" (Internal tag). Modification 

 of the plaice label and development of the 

 belly tag is credited to Robert A. Nesbit of 

 the Bureau (Nesbit, 1933). The external tags 

 consisted of two lamenated celluloid disks, 

 25/1000-inch thick and 1/2-Inch diameter. 

 These were attached to the mlddorsal region 

 by a pin of pure nickel wire, .032 inch in 

 diameter. One of the disks was white and 

 numbered; the other was red with printed 

 instructions of return address and notice of 

 reward ($1). The Internal tag used In the earlier 

 experiments consisted of a strip of bright red 

 celluloid 25/1000-lnch thick, 1-1/4-Inch long, 

 1/4-inch wide, and printed and numbered (fig. 

 13). In later experiments, tags 1-1/4-lnch long 

 and 5/16-inch wide were used — one side bears 

 a number, instructions for return, and notice 

 of reward; and the other side bears a request 

 for additional information on locality and date 

 of capture and length of the fish. The internal 

 tag was inserted in the body cavity through 

 a small incision in the body wall. To date 

 (January 1, 1937), 113 tags have been returned 

 (1.6 percent). Releases and recaptures of 

 tagged scup from these experiments are listed 

 in tables 20, 21, and 22 and charted in figure 

 14. 



From these experiments. It was definitely 

 learned that the scup migrate in the autumn 

 from the summer fishing grounds along the 

 shores of southern New F.ngland and New 

 Jersey to the winter fishing grounds off the 

 Virginia Capes and In the spring, make a 

 return migration from the winter grounds 

 to the summer area. Thus, it was demon- 

 strated that the winter fishery draws on all 

 contingents of the stock available to the 

 summer fishery. 



Doubt, however, whether the entire summer 

 fishery draws on a common stock was raised 



47 



