Figure 1. — The Great Lakes RV Kaho of the Bureau of Commercial Fisheries Branch of Exploratory Fishing and Gear Research. 



All drags throughout this study were made with a 

 52-ft (headrope) Gulf-of-Mexico type, semi-balloon 

 fish trawl described by Gordon and Brouillard 

 (1961). An additional seven drags during Cruise 4 

 and eight drags during Cruise 1 1 were made for 

 studies of mesh-size selectivity with a "trouserleg" 

 cod end. The results of that study have been sum- 

 marized by Reigle (1966). 



Drags lasted 30 min, unless shortened because of 

 rough bottom, snags, gear malfunctions, or station- 

 ary fishing gear (gill nets, pound nets, and trap nets) 

 set within the area of operation. Dragging speeds 

 averaged 2.5 miles per hour with the net held as 

 closely as possible to a constant depth by dragging 

 along the bottom contour. Catches were recorded by 

 species and weight. Additional observations on 

 weather, sea conditions, bottom conditions, and 

 water temperature were recorded at all drag loca- 

 tions. 



For this study, evaluations of fishing results are 

 based on two methods of calculations: 1) Catch 

 rate — which is pounds produced per unit effort for 

 all drags in a particular evaluation and 2) average 

 catch for effective fishing effort — which is pounds 

 per unit effort for only those drags that contained 

 the species being evaluated (Reigle 1969a, b). Effec- 

 tive fishing effort as well as the analysis of fishing 

 statistics in the Great Lakes has been discussed by 

 Hile (1962). All analyses of catch rate and average 

 catch for effective fishing effort are based on a one- 

 half hour of fishing time. Total fishing time was 

 adjusted into '/2-hr periods, thus drags, which were 

 shorter than one-half hour due to snags or for other 

 reasons, were adjusted and are included in all evalu- 

 ations. 



Prior to each survey cruise, fishing sites were 

 selected in such a way as to provide information 

 from representative areas over a range of depths 



