562 Memoir Sears Foundation for Marine Research 



at first. Once hatched they rise close to the surface and drift downstream. On the average, 

 they grow to 17 or 18 mm during their first month, to 27—34 mm during the second 

 month, and to about 40 mm after 3.5 months, when we have seined several hundred 

 fry of 30-40 mm at Mt. Desert Island, Maine; and the schedule is about the same 

 in European waters, the precise rate of growth depending on temperature. 



By the time larvae of the Elbe River in Europe have grown to 8 mm, the yolk sac 

 is mostly absorbed; at 15 mm all the fins are more or less developed, but the caudal 

 is still rounded; and by 45 mm the formation of scales has begun. We see no reason 

 to suppose that development proceeds otherwise in America." 



In their second spring, when one year old, the fry average about 86 mm (data for 

 Great Bay, New Hampshire). From scale studies it appears that they average as follows: 



Figure 132. Osmerus eperlanus mordax, larva, 26 mm long, from Portland Harbor, Maine, July 31, 1912. 

 Drawn by Mrs. E. B. Decker. 



at two years about 145 mm (5.7 in.) and about 0.6 of an ounce, at three years 171 mm 

 (6.7 in.) and about i.i ounces, at four years 220 mm (8.7 in.) and about 2 ounces. 

 The largest measured was 230 mm (about 9 in.). At this locality at least, four or more 

 year-classes are represented in the commercial catches. Those taken in Crystal Lake, 

 Michigan, where they were introduced, grow somewhat faster, reaching 6—8 inches 

 at two years, up to 9 inches at three years, up to 10 inches at four years, and 10.75— 

 12 inches at five years {ij: 401—424), with a maximum recorded length of 14 inches, 

 probably for a six-year-old. Doubtless they grow much more slowly in other lakes that 

 harbor stunted races. 



Spawning Habits. The marine fish normally spawn in fresh water, and as a rule 

 they do not travel far upstream ; they may go only a few hundred yards above the head 

 of tide. Some spawn in the tidal zone and some even spawn in brackish water behind 

 barrier beaches. But they never spawn in salt water, for flooding with the latter, as some- 

 times happens, kills the eggs. They spawn on pebbly bottom where there is a current, 

 and often in water only a few inches deep. Most often the spawners are two years old, 

 or older. Spawning takes place in late winter or early spring, depending on the temper- 

 ature of the water. According to data from hatchery operations, the chief production 

 of eggs takes place in temperatures of 50°— 57°F in Massachusetts, and of about 45°— 

 50° F in Grand River, Quebec, representative of the northern part of their range. 

 The spawning period lasts 10-14 days and is completed ordinarily by mid-May in 



10. For excellent accounts and illustrations of the smelt of the Elbe River, see Ehrenbaum {2$: append. 3, pi. i), whose 

 illustrations have been reproduced by Kendall {$6: fig. 25). For the embryology and early larval development of 

 the American Smelt, see Rice [86: 57-76, pis. 1-5). 



