Habits of the Bluegill 815 



A STUDY OF THE PRODUCTIVITY AND BREEDING 



HABITS OF THE BLUEGILL, LEPOMIS 



PALLIDUS (MITCH) .^ 



Lowell T. Coggeshall, Indiana University. 



The bluegill, Leponiis pallidus (Mitch.), one of the most common 

 Centrarchids, has never been studied with regard to the number of young 

 produced in a definite area under natural conditions. The method 

 used w^as to count the entire number of nests in the lake and to collect 

 and count the embryos in a few typical nests. The average per nest 

 multiplied by the total number of nests gave the approximate number 

 of young produced each year. An attempt was made to determine the 

 total population of bluegills although this was very difficult because of 

 the many varying factors concerned. This work was done during June, 

 July, and August of 1921, 1922, and 1923, with a few observations 

 during the months of March and October. The work was essentially 

 the same for the three summers and was all done on Eagle (Winona) 

 Lake. 



Nests. — The nest of the bluegill is like that of the bass and several 

 other Centrarchids. It is made by the male, which, by standing almost 

 vertically over the nest and flipping the tail, brushes the lighter debris 

 aside leaving shells, roots, or gravel for a solid bottom. The nature 

 of the bottom regulates the depth and size of the nest; if the bottom 

 of the nest is made up of thick roots it is always very shallow, never 

 more than three or five centimeters in depth and more often just a 

 clean place on the bottom. If the nest is located in marl it is much 

 deeper with sloping sides, oftentimes 15 centimeters deep. The nests 

 located in marl always have the bottom covered with dead shells and 

 if the shells are thinly distributed the male makes a much deeper cavity 

 in order to get enough shells to form the bottom of the nest. The nests 

 average 28 inches across with some as wide as 36 inches. 



The location of the nest is determined by the character of the bot- 

 tom. As the nesting sites are observed from year to year it seems that 

 the same places are selected again and again with only a little varia- 

 tion. Practically all of the nests are found at the edge of the two 

 meter contour line where the water rapidly becomes deeper so that, when 

 the bluegill is alarmed it may dart rapidly out to deeper water. Only 

 a very few instances were noted where the nests were found at a depth 

 of one half meter or less. They are found rarely in the Potamogetons 

 unless these plants are unusually short and scattered. Nests were 

 never found where the Potamogetons extend to a depth of 12 to 15 feet 

 and are continuous with the spike rushes (Scirpus americanus) to the 

 shore line. The bays in the lake are more densh/ populated than the 

 shallower points. 



Nests are almost always found in clusters, nly three instances 

 being noted where a single nest was found enti oly apart from any 



^ This study was n-^cle at the suggestion and under i;.o supervision of Dr. Will 

 Scott, Director of the Indiana University Biological Station, Winona Lake, Indiana. 



"Proc. Ind. Acad. Sci., vol. 33, 1023 (1924)." 



