PROGRESS IN BIOLOGICAL INQUIRIES, 19 30 609 



The bright colors of fish fed a salmon-egg ration opens up great 

 possibilities. A number of States have adopted the policy of rear- 

 ing all trout to legal size before they are liberated, and there is no 

 doubt that this practice will soon be foUoAved in other sections. The 

 most serious drawback to this practice is the fact that hatchery-fed 

 fish invariably have a much duller coloration than wild fish and, 

 therefore, can be readily recognized by the discriminating angler. 

 This difficulty can be eliminated by feeding the fish a ration rich in 

 salmon eggs for a short time before they are to be distributed. Not 

 only do they (juickly assume the bright colors of wild fish but they 

 also show remarkable vigor and resistance to disease. It thus be- 

 comes possible to artificially rear fish that are indistinguishable 

 from those which have spent their lives in open waters. 



Steam-dried menhaden meal also gave good results when fed in 

 combination with beef liver and Avas found to be superior to the 

 flame-dried product. It is becoming increasingly evident in these 

 experiments that properly prepared fish meals and dried milks form 

 a valuable addition to the diet of trout. Not only do the fish do fully 

 as well, or even better than on a straight meat diet, but there is 

 also a considerable saving in the cost of the food. At current prices 

 the cost of the food required to raise trout to a certain size on a diet 

 containing a large percentage of dry salmon eggs or menhaden meal 

 is about 40 per cent less than when they are fed straight beef liver. 



A set of experiments was also run to determine the relative value of 

 pig melts as a troiut food. Owing to its low price this product is 

 being fed in considerable quantities at a number of hatcheries. It 

 was found that pig melts, either alone or in combination with other 

 meals, are considerably inferior to beef liver as a growth producer 

 but are superior to beef melts which are also fed at some hatcheries. 



The experiments showed that in general the rations which produced 

 the most rapid grow^th were also the most economical even though 

 the actual cost of the ration might be somewhat higher than that of 

 the poorer rations. This is due to the fact that with the poorer 

 rations a larger amount of food is required to produce an equal 

 amount of fish flesh. For instance, with the salmon egg rations about 

 3 pounds of food were required to produce 1 pound of fish, Avith 

 straight beef liver about 4 pounds of food were required to pro- 

 duce the same amount of fish, Avhile the pig melts it was necessary to 

 feed approximately 6 pounds of meat to produce the same result. 



Breeding experhments. — The work in selective breeding was contin- 

 ued along the same lines as in previous years. Each season a number 

 of select fish are mated and the progeny of each pair reared sepa- 

 rately during the following summer. In selecting these fish special 

 emphasis is placed on rapid groAvth, vigor, fecundity, body symmetry, 

 and coloration. Since it is obviously impossible to rear the progeny 

 of each pair to maturity separately only the young which excel in the 

 characteristics noted above are retained for experiment during the 

 second season. In this Avay it is the confident expectation that within 

 a few years a stock of exceptionally vigoi'ous and rapidly growing 

 fish will be built up. 



During the fall of 1930 eggs were taken from 45 pairs of selected 

 fish, and the young are now being held in separate compartments 



