USEFUL ALGAE — CHASE 409 



The stomachs were filled with small herring. The herring in turn 

 were gorged with two species of copepods; and the copepods were 

 filled with diatoms and algae. As Dr. Mann pointed out: "Very 

 clearly this chain of four links is equal to a sentence of four words. 

 No diatoms, no hake." 



Tiffany was able to identify 150 species and varieties of algae 

 in the digestive tract of Dorosoma cepedianum (gizzard shad) which 

 he observed to be a highly vegetarian fish. In a similar study made 

 by Coyle, 128 species of algae were determined in another fish, 

 Pimephales 'promelas (the fathead minnow). Two other species of 

 minnows, Notropis procue and Exoglossum maxillingua, are also 

 known to consume much vegetable matter including filamentous algae 

 and diatoms. These minnows are food for the game fish. 



The cultivation of Bangos in the Philippines has been described in 

 detail by Adams, Montalbin, and Martin. Lab-lab is the name 

 given to the food of the fry of the milkfish. It is composed of 

 unicellular, colonial, and filamentous blue-green algae, unicellular 

 green algae, diatoms, bacteria, protozoa, minute worms, and small 

 crustaceans. The pond bottom is cleaned two or three times by flow- 

 ing water freely into it and out of it. The pond is then exposed 

 to sunshine for 2 or 3 days. When the pond bottom is dry, water 

 is turned into it to a depth of 3 to 5 centimeters. The lab-lab 

 develops in 3 to 5 days, then the water is increased to a depth of 

 12 centimeters. The fry feed on the lab-lab and, when they are 

 older, on the filamentous green algae that develop over a depth of 

 12 centimeters. The algae thrive especially where the water is brack- 

 ish. Mullet also feed on the algae. 



Velasquez has studied the algae in the digestive tract of Dorosoma 

 cepedianum (the gizzard shad) in an effort to ascertain the ecological 

 balance of fish ponds in which vegetarian fish are an important part 

 of the fauna. He observed that the overstocking of fish ponds in the 

 Philippines is often followed by a great predominance of blue-green 

 algae which give the fish a bad taste. He found by culturing the 

 stomach contents of the fish that the digested algae which had been 

 present in the water supply but were not viable and so did not appear 

 in the cultures were Bacillariaceae (diatoms), Volvocaceae, Dino- 

 bryon of the Heterokontae, and filamentous green algae. On the other 

 hand, 30 species and varieties of Chlorophyceae, 12 species and varie- 

 ties of Myxophyceae, 4 species of Bacillariaceae, 2 species of Hetero- 

 kontae, and 1 species of Euglenophyceae passed undigested through 

 the digestive tract. His investigation indicates that one of the 

 sources of selective increase of certain algae in nature, and con- 

 versely, of the decrease of others, is due to the vegetarian fishes. 



