PROGRESS IN BIOLOGICAL INQUIRIES, 193 2 95 



Prior to 1929 the scup was generally considered a "summer fish " 

 and constituted an important product of the summer pound-net, trap, 

 and seine fisheries along the Atlantic inshore waters from the Chesa- 

 peake Bay to Cape Cod. However, with the rapid growth of a winter- 

 trawl fishery- off the Virginia Capes since the winter of 1929, an 

 additional strain has been placed on the species, and the question has 

 been raised whether or not it can withstand the year-round exploita- 

 tion to which it is now subject. Compilation and analysis of the 

 data bearing on this question were carried out by W. C. Neville. 



It was first necessary to determine whether the winter trawlers 

 and the summer pound-net, seine, and trawl fisheries were drawing 

 on the same stock of scup. Marking experiments have disclosed a 

 migration of scup in the fall from the summer fishing ground to the 

 winter fishing ground, and a spring migration from the winter grounds 

 ofiF Virginia to the summer area along New Jersey. Comparison of 

 the size and age composition of the catches of the summer and winter 

 fisheries disclosed that broods of scup that have contributed largely 

 to either the New Jersey, inshore, summer, pound-net fishery or to 

 the more offshore summer-trawl and seine fisheries have also been 

 prominent in the catches made by the trawl fishery in the following 

 winters. Thus, both fisheries appear to be drawing on the same 

 population. 



In order to determine whether the double strain on the stock w^as 

 affecting the yield in one or the other, or both of the fisheries, an 

 analysis was made of the changes in their yields. As indicated in 

 the first part of this report, the summer fishery gives no indication 

 of a decline in abundance to date, and this in spite of the fact that 

 the winter-trawl fishery of 1931-32 drew upon the same age groups. 



The total quantity of scup landed at Virginia ports by the winter 

 trawlers increased from approximately 1,600,000 pounds in 1930-31 

 to approximately 2,200,000 pounds in 1931-32. This increase, how- 

 ever, was caused entirely by increased fishing effort. Actually, there 

 was a decrease in availability, for the catch per trip declined from 

 7,900 pounds in 1930-31 to 2,800 pounds in 1931-32. It might appear 

 that this decline in the catch per trip, and the shift to smaller sizes 

 in the composition of the catch of the winter-trawl fishery, was perhaps 

 the first indication of depletion from overfishing; but this is not 

 necessarily true for other factors were responsible for these changes. 

 These are: (1) In the winter of 1931-32, scup were probably much 

 less readily available as a result of the schools scattering widely over 

 a larger expanse of coastal sea bottom; this because the bottom water 

 remained warm over a much larger area of the coastal plain in that 

 winter than in the preceding winter.^ (2) The change in the hydrog- 

 raphy of the region resulted in the greater availability of other 

 important food fishes, especially of sea bass, and probably caused a 

 diversion of fishing effort from scup to the more readily caught sea 

 bass. These conditions appear adequate to explain the decline in the 

 catch of scup per trip at sea in 1931-32. 



If the number of returns of tagged fish is indicative of fishing 

 intensity, there is little evidence that the scup fishery is being sub- 



' An account of this fishery is given in Winter-trawl Fishery off'the Virginia and North Carolina Coasts, 

 by John C. Pearson. Investigational Report No. 10, Bureau of Fisheries, 1932. 



' For a description of the changes in the hydrographic conditions between the winters of 1930-31 and 

 1931-32, see Temperature and the Southern Trawler by William C. Neville, Fishing, January 1933. 



