Populations of Spotted Sunfish and Florida Largemouth Bass in a Constant-Temperature Spring

Abstract

Populations of spotted sunfish, Lepomis punctatus punctatus (Valenciennes) and Florida largemouth bass, Micropterus salmoides floridanus (LeSueur) have been studied in the fertile biotic communities of Silver Springs, Florida. This large limestone spring has a constant temperature, nearly constant chemical environment, and stable biological communities, but a seasonal change in light intensity and general productivity. Studies of the scales of these two species have shown rings which are possibly rhythmic but not related to temperature. Strong rings in spotted Sunfish are apparently too numerous to be annuli and their formation is not correlated with the time of year. The spotted sunfish population reproduces mainly in spring and summer, although there is evidence for some scattered winter breeding. Age groups do not stand out distinctly in length-frequency diagrams. Reproduction by Florida largemouth bass appears to be chiefly limited to spring and summer. Thus, even with a constant temperature, there are apparently cycles in the life history of these fishes which cause the periods of increased reproduction to coincide with periods of greater food production. Recaptures of tagged bass and measurements of spotted sunfish in cages within the springs indicated moderate growth rates. Tagging with individual color combinations for visual study indicated little movement by the spotted sunfish, hut a high mortality. Data are included on the length-weight and body-scale relationships, degree of scale regeneration, and food. The seasonal activities of centrarchid populations are adjusted to make use of the maximum flow of productive energy in spring and summer and are thus correlated with the photoperiodic cycle.