The trap was a simple box-like frame i3(> inches by U8 inches 

 by U8 inches) of 2 inch by k inch lumber covered with l/li-inch 

 mesh hardware cloth and built as a single movable unit. Its 

 funnel, fabricated of hardware cloth and a 2 inch by k inch wood 

 frame, was removable after insertion of a closing baffle on the 

 front of the trap. This facilitated taking out both lampreys 

 and fish. 



The original structure without the subsequent improvements 

 ■was fabricated and installed in two working days by four men. 

 Problems in construction were minimized by low water levels and 

 the relatively small size of the stream. The sill and flashing 

 of hardware cloth which was substituted for sheet piling proved 

 very satisfactory and is strongly recommended for semi-permanent 

 structures on those sites triiere the nature of the bottom prevents 

 the driving of pilingj it is inexpensive to fabricate and very 

 easily installed. 



On or about August 1 of each intervening summer, all of the 

 weir except the steel upri^t parts and the sills and flashing was 

 removed from the creek and stored overvrinter until reinstallation 

 just prior to the beginning of the sea lamprey runs in the early- 

 spring. 



The basic requirements of an effective sea lamprey weir are 

 that it be strong enough to withstand the impact of maximum flood 

 waters and that it be high enou^ and wide enough to remain fish- 

 tight under like conditions. The Carp Creek weir withstood severe 

 flood conditions on three occasions. On May 31, '^9h7} the north 

 wing partly buckled due to improper bracing during a period of 

 very high water. This wing was completely removed and rebuilt on 

 May 31 and June 1, 19U7. 



The weir in its final form was essentially lamprey-tight. I 

 consider that over 99 percent of the sea lamprey run was captured 

 in the years 19h7 and 19U8 and that the complete run was captured 

 in 19U9« 'W^e discovered early that a sea lamprey will find and 

 make use of the smallest, and perhaps only, aperture in a large 

 barrier. Consequently, we continually checked all possible loci 

 of escapement with our hands as part of the routine vi.sits to the 

 weir. On May 9, H, lU, 29, and July Ij 19U7, the creek was 

 patrolled from Carp Lake to the weir. On all but the last date, 

 no trace of sea lampreys was found. On July 1, I found five nests 

 about three-quarters of a mile above the weir. Eggs were found in 

 tiro nests and promptly destroyed. The other three nests contained 

 no eggs although they had evidently been completed for several 

 weeks. I suspect that the escapement accounting for all these 

 nests, which probably did not exceed ten individuals, occurred 

 during the period May 31-June 1 while the north wing of the weir 

 was being repaired. 



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