196 



FISHERY BULLETIN OF THE FISH AXD WILDLIFE SERVICE 



Figli.io 10. — Scale from an unusually large shad, a female, measuring L!i!.7 inches and weighing 7 pounds !' ounces. 

 Roman numerals VI through X represent spawning marks. Unfortunately, in this illustration the posterior por- 

 tion of tlie scale is obscured so that the fifth annulus cannot be seen as separate from the first spawning mark just 

 below the baseline in the posterior portion. 



spawning mark should each be counted as a year. 

 We were fortunate in obtaining, through our tag- 

 ging program in the Connecticut River during 

 1951, direct evidence of the amount of absorption 

 occurring while the shad is in fresh water. Shown 

 in figure 12 is a scale taken from a shad at the 

 mouth of the Connecticut River during a tagging 

 operation: it shows five distinct annuli and a space 

 to the edge of the scale representing the growth 

 during the sixth year. This shad was just enter- 

 ing the river on its migration to the spawning 

 grounds as is evidenced by the smooth scale 

 margin. A scale was taken from this same tagged 

 fish when it was caught 51 days later off the coast 



of Massachusetts by a trawler : this fish apparently 

 had spawned in the Connecticut River and then 

 migrated out of the river and northward into the 

 Atlantic Ocean. The second scale is shown in 

 figure 11. One year's growth has almost been 

 eroded away, leaving only pieces of the fifth an- 

 nulus to be seen around the anterior periphery of 

 the scale. The fifth annulus can still be clearly 

 seen near the baseline just inside the ragged edge 

 of the scale. 



The amount of erosion, or absorption, during 

 the first spawning migration appears to vary with 

 the age at first spawning. For example, the scale 

 of a shad spawning for the first time at 6 years 



