FISHEBY INDUSTRIES. 



35 



6 per cent, were sea run, i. e., had gone to sea as fry. Either the 

 loss during the growth to maturity is very much greater ui that 

 portion of the young seeking the sea the first season or that portion 

 is very much smaller than the portion remaining a year in fresh 

 water. In 1903 and 1904, when a comparatively small number of 

 fry was being put out by the hatchery on the Naha, it was found 

 that few went to sea as fry. It was suggested then that upon greatly 

 increasing the number planted in that stream a certain surplus 

 might go to sea as fry and thereby be largely lost. Unfortunately, 

 as yet no exammation has been made to find whether such a result 

 occurs. If there is such a result from the large plants the failure of 

 the Naha as yet to build up beyond its natural productivity may be 

 accounted for. 



A further suggestion was made, as a result of the studies of 1903 

 and 1904 on the Naha, that the food resources of the lake might be 

 overtaxed by the heavy plants of fry and the young become unthrifty. 

 Measurement of some 80 yearlings of the 1911 fish from this stream 

 revealed the astonishing fact that they were in better condition 

 and larger than fish of corresponding age measured in 1903 and 

 1904. The stomachs of most of these were empty, but in two were 

 found salmon fry. Nearly all the intestines contained a black 

 substance that is believed to be mainly the indigestible substances 

 derived from fry ingested some time previously, the digestible ele- 

 ments having been absorbed. This evidence of cannibalism sug- 

 gests another possible check upon results from the increased plants. 

 Fry planted as soon as hatched, or even as soon as free swimming, 

 arrive in the lake when it is still populated with the yearlings of 

 the previous season's plant. The old rule that big fish eat little 

 ones finds no exception among salmon, and overpopulation of the 

 waters must be. an active stimulus to this natural instinct. 



It has been shown that the salmon return at 4 and 5 years of 

 age, perhaps in about equal numbers, probably varying in different 

 seasons. Taking Yes Bay and Naha streams together as a unit, 

 there were liberated in the two hatcheries in 1906, i. e., from 1905 

 spawn, 74,000,000 fry. The adults from these fry were due to 

 return in 1909 and 1910. To the two streams there may be accred- 

 ited for those two years 445,000 fish, and half of these should be 

 credited to the 74,000,000 fiy of the 1905 eggs. Constructing a 

 table on these bases for the three years now completed and esti- 

 mating the fourth, we have: 



