The original breeder bluegill males became sexually mature earlier than the males of 

 the 1938 brood. In the March collection, 75 per cent of the young males appeared immature, 

 while the older specimens were classed as poorly developed. In the May collection, 64 per 

 cent of the old males were in spawning condition or partly spent, while only 10 per cent 

 of the young were in the same condition. During late August there was a higher percentage 

 of ripe fish among the young males than among the old males, but all were spent after 

 September 18. In the females, however, this difference was not marked, and both the old 

 and young were in spawning condition at about the same time. Two old females taken on 

 June 16 showed atrophied gonads, suggesting complete loss of reproductive capacity. 



Bluegill nests were first observed on May 28 (average water temperature at 3 feet, 

 77 degrees F.). On June 5, 40 nests were counted and nearly all contained eggs. A few 

 bluegill fry were taken with a minnow seine on June 22, but most of the yoimg had dis- 

 appeared by June 28. On June 30, after an extensive search, only two young could be found. 



On July 25, all nests were occupied by spawning bluegllls. Many largemouth bass 

 yearlings loitered about the nests. Whenever an opportunity offered, these bass entered 

 the nests and fed—presumably on bluegill eggs or young fry. A few yomg bluegllls were 

 observed at this time among mats of Potamogeton foliosus. 



On August 28, several bluegllls occupied nests on the north side of the lake near the 

 spillway. At this time bluegill fry were numerous and ranged in length from 0.50 to 1.25 

 inches. Young were still numerous along the shores on September 18. The largest were 2 

 Inches long. Occupied bluegill nests were seen. During the period October 25-30, no young 

 were seen along the edges of the lake. 



FOOD OF THE BASS AND BLUEGILL 



An abundant food supply is essential for rapid growth in fishes. The amount of food 

 available must exceed the amount necessary to maintain the bodily processes, or there will 

 be no growth at all. Most fish foods are developed within the body of the lake Itself, 

 although terrestrial insects and adult aquatic insects are taken by fish in numbers from 

 the water's sxirface. Apparently, it is possible to maintain fish of assorted sizes and 

 fish spawned year after year because the items of food also occur in graded sizes. Al- 

 though there is some variation in the choice of foods selected by the kinds of fishes 

 inhabiting small lakes, the item that is most abundant at any one time is usually the one 

 most often eaten. Seasonal changes in food habits seem to depend upon changes in abundance 

 of certain foods. 



The optimum fish population is one that includes the kinds and numbers of fish to 

 make the best use of all available foods without too keen competition for food of any one 

 type. Since the food preferences of a fish change as it grows, a fish population includ- 

 ing a wide range of sizes and ages is more efficient in utilizing the available food 

 supply of a lake than one composed of fish of about equal sizes. Stunting is often the 

 result of large broods competing for the same foods. 



Stomachs were preserved from a large proportion of the bass and bluegllls collected 

 from Fork Lake each month — ^March through November, 1939. They were preserved in alcohol 

 and data recorded on length, weight, sex, age, etc., of the individuals from which they 

 were taken. Later, these stomachs were opened, the volume of the contents measured, and 

 estimates made of the volume and number of each item. The data cover 671 bluegill 

 stomachs and 299 largemouth bass stomachs. The piu'pose of this work was to learn what 

 the bass and bluegllls were eating and to follow changes in the diet from month to month. 

 We are particularly interested in learning whether or not there Is much competition 

 between bass and bluegllls in small lakes. 



The volume of the stomach contents was determined by one of two methods: (1) by 

 displacement of water in a graduated, conical, centrifuge tube; (2) by comparison with a 

 series of blocks of graduated sizes from one-five-hundredth cubic centimeter to 2 cubic 

 centimeters glued in a shallow box. The latter method was devised by the late R. E. 

 Richardson. 



The percentage, based on volume, of each item in each stomach was determined, and 

 these percentages were averaged for each monthly collection of yearling bass, yearling 

 bluegllls and old bluegllls. This procedure tends to reduce the Importance of large items 

 like crayfish, which were Infrequent, and to increase the importance of smaller forms, such 

 as Insects commonly found in most stomachs. 



Since most of the Fork Lake fish were taken in hoopnets which were set from 1 to 3 

 days before being lifted, these results are not strictly representative of what the fish 

 were eating. Small items like bluegill fry, or small worms, digest rapidly. Large fish 

 and crayfish require days to digest, even in warm weather. In cool weather, digestion 

 may extend to a week or more. Heavily chitinized insects are Included in the data, even 



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