Factors Affecting Recruitment of Black Crappies in South Dakota Waters

A biotelemetry study was undertaken during spring 1995 to identify black crappie Pomoxis nigromaculatus nest sites in one South Dakota impoundment (Richmond Lake) and one natural lake (Brant Lake). Individually coded ultrasonic transmitters were implanted into the body cavity of 15 adult male black crappies in each water body prior to spawning. Available habitat characteristics were recorded at 75 random sites within each water body, and habitat characteristics at nest sites were recorded for each male black crappie believed to be nesting. Of the habitat characteristics analyzed, only shore gradient and substrate firmness did not differ between water bodies. In Richmond Lake, black crappies selected nest sites with live cattails Typha spp. that were protected from prevailing south winds. In Brant Lake, they selected nest sites with vegetation (usually woody debris) and silt substrate that had warmer water and were protected from wind and waves. It appeared that black crappies nested in the most protected areas available. An observational study was undertaken to contrast the early life history of black crappies in an impoundment (Richmond Lake) and a natural lake (Brant Lake) during 1994-1996. I expected variable recruitment (i.e., missing year classes) in the natural lake, and more consistent recruitment in the impoundment. Age-0 black crappies were collected with a 500-μrn mesh ichthyoplankton trawl, 1.6-mm mesh trawl, and 13-m.rn bar mesh trap nets. Zooplankton was collected with a 2m tube sampler and then filtered through a 80-μm mesh net. Diets of age-o black crappies collected with the ichthyoplankton net were analyzed. Otoliths of age-0 black crappies collected· in trap nets were examined to estimate hatch date of these fish. Larval black crappie abundance was always higher in Richmond Lake than Brant Lake. Abundance of larval black crappies was highest during 1994 in both waters. Peak abundance of larval black crappies in 1994 also occurred earlier than in 1995 or 1996, likely a result of water temperatures warming earlier during 1994. Hatch dates estimated from black crappie otoliths showed a similar pattern. Larval abundance did not correspond with fall trap net catch per unit effort (CPUE) of age-o fish. Fall age-0 black crappie CPUE in trap nets was highest during 1995. This suggests that recruitment of crappies in South Dakota waters is not simply a function of the number of hatched larvae. The zooplankton and diet assessments showed nothing unique about 1995 that produced the highest abundance of fall age-o black crappies. The ichthyoplankton trawl and trap nets had similar trends in catches for both water bodies during 1994-1996, suggesting that broad environmental factors may have similarly affected reproduction and recruitment at the natural lake and impoundment. Given that the effects of turbidity on fishes are highly variable, a controlled aquarium study was conducted to determine the effects of physical (i. e., colloidal clay) turbidity on the survival of juvenile black crappie. Suspending clay was added to 16 randomly selected 60-L tanks each containing 20 fish using a randomized-block experimental design. Turbidity levels were no turbidity (mean turbidity level = 8 nephelometric turbidity units; NTU), low turbidity (94 NTU), medium turbidity (185 NTU), and high turbidity (218 NTU). The feeding regime was newly hatched Artemia franciscana provided once daily for 38 d. No juvenile black crappies survived in the low turbidity tanks after 33 d. Survival was highest (mean = 99%) for fish held in no turbidity and moderate for fish held in both medium and high turbidities (73% and 60%, respectively). Juvenile black crappie did not grow in length. Surviving black crappie in both medium and high turbidities exhibited weight loss, while the weight of black crappie in no turbidity remained constant. Thus, colloidal turbidity was detrimental to juvenile black crappie survival. saugeyes (d sauger Stizostedion canadense x i walleye s. yitreurn hybrids) have been used effectively as a predator to reduce recruitment and improve growth and size structure for overabundant crappie Pomoxis spp. populations. Saugeyes were stocked into 336-ha Richmond Lake, South Dakota, an impoundment that contained an overabundant black crappie population. Small fingerling (circa 3-4 cm) stockings in 1992 and 1993 had relatively low survival; fall electrofishing CPUE values for age-0 saugeyes were 5/h and 3/h. In 1994 and 1995, larger (circa 14-19 cm) fingerlings were stocked, and fall CPUE values were 185/h and 33/h. In addition, the fingerlings stocked in 1994 were collected during fall 1995 electrofishing as age-1 fish at a rate of 41/h. At northern latitudes, small fingerling saugeyes grow slowly and likely remain vulnerable to predation by and competition with overabundant black crappie populations. Stocking larger saugeye fingerlings may overcome this problem