Figure 2.--Holding pockets used in testing the Maine sardine tag. The lower pocket contains untagged fish; 



the upper, tagged fish. 



Herring selected for tagging were in the 

 5- to 6-inch total length group. Fish of that 

 size group are especially sought by the sardine 

 fishery and, when tagged in the late summer 

 and autumn, offer an opportunity for over- 

 wintering and recovery the following year. 

 The dorsal musculature of a 5- to 6-inch 

 herring is well-formed and holds the tag 

 well, whereas smaller fish of about 4 inches 

 show distress and inability to sound when the 

 tag is attached. 



Herring that showed abrasion or considerable 

 scale loss were discarded. Under average 

 field conditions a three-man team could main- 

 tain records, load needles, and tag fish at a 

 rate of about 100 per hour. It was impossible 

 to apply the tag without removing some of the 

 scales, and herring that appeared sluggish in 

 the holding pocket were replaced. 



To test tag retention 50 tagged herring were 

 mixed with 50 unmarked fish in a small hold- 

 ing pocket and pumped through a descaling 

 machine into the hold of a carrier vessel. To 

 simulate the second pumping operation that the 

 fish undergo when being unloaded for 

 processing, the entire test lot was subjected 

 to another pumping by the carrier vessel. 

 None of the tags was detached by the descaling 

 and pumping processes. 



The tendency of tags to cause mortality 

 was tested under aquarium conditions by 

 releasing 20 tagged fish and 20 untagged fish 

 in a 1,500-gallon tank of circulating sea water. 

 It is apparent that the tag did affect the 

 mortality of the test fish, particularly in the 

 early weeks of the experiment, although the 

 gap between the mortalities of tagged fish and 

 controls lessened with time (table 1). The 



