Fecundity of largemouth bass, Micropterus salmoides, Lac. reared and maintained on two diets was measured by use of a technique of collecting naturally-spawned eggs from nylon felt spawning mats. A volumetric measurement was made of the eggs in 10 spawns from Year Classes I, II and III pellet-fed fish for comparison with eggs from Year Class II bass fed forage fish. Average eggs per spawn for the Year Class I fish was 9,551; for Year Class II pellet-fed, 21,744; for Year Class III, 15,223 and for Year Class II fish-fed, 19,410. The lower number of eggs produced by Year Class III fish than Year Class II is thought to be related to influence of the diet given during the first 14 months of feeding when a ration of dry trout feed and ground frozen fish was fed to this lot. Other than this, the artificial ration used was Oregon Moist Pellet. Apparent viability of eggs from bass receiving artificial food was higher than that of eggs from those on a natural diet. This was not thought to be related to diet however. Egg size was comparable between the two diets, but color was better in eggs spawned by bass on a natural diet. Measurements of ovaries removed from selected specimens paralleled those of sample spawns except that the number of ova per pound of body weight was highest in Year Class I pellet-fed specimens. A noticeable amount of fatty tissue was present in the ovaries taken from two- and three-year-old fish which had been fed artificial food.
