An Exploration of Factors Influencing Crappie Early Life History in Three Alabama Impoundments

Abstract

Although black crappie Pomoxis nigromaculatus and white crappie P. annularis represent important sport fisheries in North America, we still know little about what influences their variable recruitment. Several abiotic (e.g., water level fluctuations) and biotic (e.g., prey abundance and size structure) factors have been suggested as important to crappie recruitment, but results have not been consistent among studies. We quantified adult characteristics, larval abundance, growth, diet, and postlarval juvenile abundance of crappies in three Alabama impoundments to determine factors consistently affecting crappie life stages across systems. Although adult condition (relative weight, Wr), fecundity, egg diameter, gonadosomatic index, and ovary weight differed among the three impoundments, the differences were not consistent with among-lake differences in chlorophyll-a concentration. Larval density was highest in the least productive system (Lake Martin), and larval production was not related to either adult condition or fecundity. Diet analysis indicated that larvae 4-14 mm in total length strongly selected the smallest prey available in all lakes but that larvae in Lake Martin consumed greater numbers and a higher biomass of crustacean zooplankton than those in Weiss and Jones Bluff lakes, probably because of the higher density of large zooplankton in Lake Martin. Despite the generally earlier presence in spring of crappie larvae in Lake Martin during both years, age-0 crappies in that lake were not larger than those in the other two lakes in summer. This is probably attributable to cooler early-spring water temperatures in Lake Martin. The catch of postlarval juvenile crappies was higher in the more productive lakes than in Lake Martin. Collectively, our results were not consistent with our expectation that lake productivity would positively influence the density of both zooplankton and age-0 crappies. The lack of a positive relationship between larval crappie density and system productivity or zooplankton size was an unexpected result that is probably important to the early life survival and eventual recruitment of crappies and that warrants further investigation.