fish that were retained and landed. This part of the program was started 

 in June 195l, 2 years before the regulation came into effect. This sampling 

 at sea is continuing. Tvjo reports of catch analyses made under this program 

 during the pre-regulation period have already appeared (Premetz 1953, 

 Premetz et al. 195U) • 



A later part of the testing program was the licensing of a few vessels 

 to fish with small-mesh nets, in order to provide an index of abundance of 

 2-year-old fish comparable with that obtained before regulation. This index I 

 is necessary for appraising the ultimate benefits from use of the larger mesh.. 



This group of "study boats" has made possible a very valuable comparison' 

 of catches of vessels using large-mesh nets and of those using sma.ll-mesh j 

 nets. For convenience, these two groups of vessels will be referred to in • 

 the text and tables as "large-mesh vessels" and "small-mesh vessels." I 

 Through the cooperation of the fishermen, biologists have made frequent tripd 

 to sea on vessels of both groups. 



The purpose of the present paper is to report upon the quantities of 

 small fish protected by the regulation and to present an evaluation of the 

 effects of the regulation upon the quantities and sizes of fish landed from 

 Georges Bank during the first year of regulation. 



Analysis of Catch 



The initial effect of increasing mesh size depends upon the level of 

 selection of the new net rate in relation to the level at which the fishermen 

 have been culling, and upon the relative abundance of sizes lying within the 

 selection range of the new net at the time its use is begun. 



Before regulation, the fishermen had been discarding fish less than 3U 

 to 35 cm. in length (Premetz 1953, Premetz et al. 19Sh) . The 5o-percent 

 point on the selection curve of the i4-l/2 inch mesh is about 37.5 cm., that 

 is, half the fish 37.5 cmi in length will escape through cod-end meshes that 

 average U-l/2 inches inside measurement. Thus the new mesh permits the 

 escape of some fish that would normally be caught and marketed. The loss 

 to the fisherman will be greatest when fish of 37.5 cm. in length are most 

 abundant. Georges Bank haddock are this length when they are about 2-1/2 

 years old. Since they are spawned from Februarj'' to March, they attain this 

 age and size in the fall of their third year of life. 



Since the strengths of the year classes of haddock vary extremely, 

 there will be an abundance of fish of this critical size only in fall seasons 

 when a dominant year class reaches the age of 2-1/2 years. When the mtsh 

 regulation was put into effect in June 1953, fish nearest this age were the 

 195l year class. Since 1951 was a very weak year class, the loss of small 

 fish during the summer and fall of 1953 was very light. 



