Previous work with centrarchid fishes suggests that recruitment success is higher for fish hatched early in the spawning season. Similar recruitment patterns have been shown for bluegills Lepomis macrochirus, but only in piscivore-free waters and at the northern extent of their range. We investigated the role of predation and first-winter mortality in governing bluegill recruitment. Spawning date distributions for larval bluegills taken in ichthyoplankton tows were compared with distributions for juveniles in shoreline rotenone samples from the fall and the following spring. Daily otolith rings were used to determine ages and spawning dates for bluegills in Ridge Lake, Illinois, during 3 years. Spawning took place from mid-May to mid-August of each year and produced several peaks in larval abundance. Differences between the spawning date distributions of larval bluegills and juveniles surviving to fall suggested that fish spawned early in the season experienced higher mortality than those spawned later. Extensive field sampling and bioenergetic model estimates of age-0 bluegill consumption by largemouth bass Micropterus salmoides indicated that predation was an important source of mortality for early-spawned fish. Estimates of bluegill abundance and size structure in fall and spring showed that losses over the first winter were high (75% to 88%); however, unlike in studies at more northern latitudes, there was little evidence of size-specific mortality. Our results suggest that predation is an important mechanism regulating the recruitment success of young bluegills and that early cohorts produced during protracted spawning must endure high mortality to become spring yearlings.
|Original language||English (US)|
|Number of pages||15|
|Journal||Transactions of the American Fisheries Society|
|State||Published - Mar 2003|
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Aquatic Science