Age-0 Crappie Research Articles

Factors Related to Crappie Indices of Abundance in a Large, Fluctuating Canyon Reservoir in Idaho

Crappie (Pomoxis spp.) populations are challenging to manage due to highly variable year-class strength; however, such variability has rarely been investigated in western North America, where crappie often occupy large, steep-sided reservoirs prone to severe drawdown. We investigated the influence that various factors had on crappie abundance, as indexed by long-term trawling for larval fish and long-term electrofishing for older fish. Our primary findings were that: 1) autumn age-0 crappie abundance was higher in years when larval abundance and reservoir flow were higher in the summer; 2) spring age-1 crappie abundance was higher in years when fish were larger and more abundant entering their first winter, when hydraulic residence time was reduced and the reservoir volume was higher during the winter, and when predatory-sized smallmouth bass (Micropterus dolomieu) were more abundant in the spring (though the latter relationship was likely not causative but rather a parallel response to mutually advantageous environmental conditions in the reservoir); and 3) age-0 crappie entering their first winter were larger in years with lower summer larval crappie abundance and warmer summer water temperature. We recommend autumn electrofishing to monitor crappie populations in large canyon reservoirs, where shorelines are often too steep to sample fish with trap nets, because it provides an index of age-0 crappie abundance and size at the onset of their first winter as well as data on older crappie year classes and sympatric species; it also requires less sampling effort than summer trawling.

Size of age-0 crappies (Pomoxis spp.) relative to reservoir habitats and water levels

Variable year-class strength is common in crappie Pomoxis spp. populations in many reservoirs, yet the mechanisms behind this variability are poorly understood. Size-dependent mortality of age-0 fishes has long been recognized in the population ecology literature; however, investigations about the effects of environmental factors on age-0 crappie size are lacking. The objective of this study was to determine if differences existed in total length of age-0 crappies between embayment and floodplain habitats in reservoirs, while accounting for potential confounding effects of water level and crappie species. To this end, we examined size of age-0 crappies in four flood-control reservoirs in northwest Mississippi over 4 years. Age-0 crappies inhabiting uplake floodplain habitats grew to a larger size than fish in downlake embayments, but this trend depended on species, length of time a reservoir was dewatered in the months preceding spawning, and reservoir water level in the months following spawning. The results from our study indicate that water-level management may focus not only on allowing access to quality nursery habitat, but that alternating water levels on a multiyear schedule could increase the quality of degraded littoral habitats.

Gradients of microhabitat and crappie (Pomoxis spp.) distributions in reservoir embayments

Embayments are among the most widespread littoral habitats found in Mississippi flood-control reservoirs. These macrohabitats represent commonly used nursery zones for age-0 crappies, Pomoxis spp., despite barren and eroded shorelines formed over 60–70 years of annual water level fluctuations. We tested if embayments displayed microhabitat gradients linked to the effect of water level fluctuations on riparian vegetation and if these gradients were paralleled by gradients in age-0 crappie distribution. Habitat composition changed longitudinally along the embayments with the most pronounced gradient representing a shift from nonvegetated mudflats near the mouth of embayments to herbaceous material upstream. The degree of habitat change depended on the water level. Similarly, catch rates of crappies increased upstream toward the rear of embayments, differing among water levels and reservoirs, but the longitudinal pattern persisted. Our results indicate that habitat composition gradients occur in embayments of northwest Mississippi flood-control reservoirs and that these gradients may influence a similar gradient in age-0 crappie distribution. While the biotic interactions behind the gradients may be less clear, we speculate that water level is the main factor influencing the observed gradients in habitat composition and fish. Management to benefit age-0 crappies may involve habitat improvement along embayment shorelines and water level regimes that foster growth of herbaceous plants.

Methods for Predicting Age-0 Crappie Year-Class Strength in J. Percy Priest Reservoir, Tennessee

Abstract We evaluated the precision and efficiency of larval townets and trap nets and correlated estimates to hydrologic parameters (temperature and spring discharge) during 1998–2002 to determine the best method for predicting year-class strength of age-0 white crappie Pomoxis annularis and black crappie P. nigromaculatus in J. Percy Priest Reservoir, Tennessee. Both larval townet and fall trap-net samples effectively sampled age-0 Pomoxis spp. and accurately indexed year-class strength. The geometric mean density of larval Pomoxis spp. in townet samples for the 3-week period bracketing peak density provided a more precise estimate of larval crappie density than the geometric mean of the 1-week peak. Larval density in May was correlated to age-0 catches in fall trap nets, so density of larval Pomoxis spp. was positively related to year-class strength. However, fall trap-net samples of age-0 Pomoxis spp. provided a more precise and cost-effective index of year-class strength than larval townet samples. M...

Verifying Residuals from Catch Curves to Detect Recruitment Variation in Largemouth Bass and Crappies

Residuals associated with catch-curve regressions can represent variable recruitment in fish populations, but the use of this method to quantify recruitment variation has not been verified. I computed age-0 and age-1 catch rates of crappies Pomoxis spp. collected with trap nets set in the fall in three Alabama reservoirs and the age-1 catch rate of largemouth bass Micropterus salmoides captured with electrofishing during spring over a 13-year period in a single Georgia reservoir. These indices of juvenile abundance were correlated (r = 0.52–0.81, P < 0.01) to residuals generated from catch-curve regressions for electrofishing data collected when these same year-classes recruited to the fishery at age 3 and older. At higher age-0 crappie and age-1 largemouth bass catch rates, these relations became curvilinear, and improved fit was computed with data transformation and nonlinear fits to the data. An asymptotic relation was observed between age-0 and age-1 catch rates for the same crappie year-classes, and an inverse relation was evident between mean length at age 1 and juvenile crappie catch rates. This result suggested that density-dependent growth suppression and mortality occurred, as age-0 fish did not proportionally recruit to the age-3+ fishery. However, the age-1 crappie (about 18 months old) catch rate was linearly related (r2 = 0.48–0.55; P < 0.01) to residuals when data were compared separately for each reservoir, which suggested that full recruitment to the population occurred at this age. For largemouth bass, mean length at age 1 was positively related to age-1 catch rate, and recruitment of strong year-classes to the fishery appeared proportionally greater than for abundant age-0 crappies. Residuals generated from catch-curve regressions can serve as a useful quantitative index of juvenile crappie and largemouth bass abundance that can be used in subsequent analyses to explain recruitment variation. However, in some instances, initial strong year-class abundance may not be fully expressed in the fishery later in life.

Factors Influencing Recruitment of Crappies in Chautauqua Lake, New York

Abstract Black crappies Pomoxis nigromaculatus and white crappies P. annularis were introduced to Chautauqua Lake from Sodus Bay of Lake Ontario (New York) in the late 1920s to establish a recreational fishery. The abundance of both species rapidly increased, and an intensive recreational fishery developed. Anecdotal accounts from the recreational fishery and catches in pound nets indicate that both species remained at high levels of abundance until the 1970s. However, the catch of age-2 crappies in gill-net samples has declined since 1978. Index trawling from 1978 to 1999 indicated that the year-class strength of black and white crappies was synchronized and fixed between fall of age 0 and fall of age 1. Age-0 crappie abundance was positively associated with the biomass of walleye prey (yellow perch Perca flavescens, sunfish Lepomis spp., and white perch Morone americana) and negatively associated with that of walleye Stizostedion vitreum, showing that availability of alternative prey affects walleye pre...

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

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.

Early Life History Characteristics of Age-0 White Crappies in Response to Hydrology and Zooplankton Densities in Normandy Reservoir, Tennessee

Age-0 white crappies Pomoxis annularis were collected in 1994 and 1996–1998 in cove samples from Normandy Reservoir, a 1,307-ha flood control impoundment on the upper Duck River in southcentral Tennessee. Age-0 crappies were measured (TL, mm) and weighed (g); otoliths were removed and hatch dates and daily growth rates determined for the aged fish. Across years, crappies hatched as early as 13 April and as late as 6 June. Hatch date and length-frequency distributions were unimodal in all years. The first hatch date and mean hatch date of white crappies were positively correlated with the first day the reservoir achieved full pool. Growth ranged from 0.41 to 0.90 mm/d; it did not appear to be affected by the density of white crappie larvae but may have been affected by that of crustacean zooplankton. Within each year, earlier-hatched fish grew at slower rates than later-hatched fish, probably owing to the warmer water temperatures experienced by later-hatched fish. However, year-classes that hatched earlier grew faster on average, perhaps due to reduced competition from fish species that spawned later than white crappies. The growth of age-0 white crappies appeared to be little affected by spring or summer water level events, but it may have been influenced by hatch date and zooplankton density.

Quasi-cycles in crappie populations are forced by interactions among population characteristics and environment

Crappie (Pomoxis spp.) populations have been characterized as cyclic, with strong year-classes recurring at 2- to 4-year intervals. We evaluated the potential for cyclic trends in crappie populations using a population model that included a density-dependent stock recruitment function and random environmental variation. Slow, medium, and fast growth were simulated over 100 years. The model predicted highly variable recruitment that was strongly influenced by environmental fluctuation at low and intermediate stock densities. At high stock density, recruitment was low, even if environmental conditions were favorable. Significant quasi-cycles occurred, but they were not sustained throughout the time series due to random environmental fluctuation. Quasi-cycles occurred because intermediate stock density and favorable environmental conditions occasionally combined to produce a very strong year-class that greatly increased stock density in the following 1–3 years and produced low recruitment, even if environmental conditions were favorable. Empirical data from 32 years of sampling age-0 crappies at Ross Barnett Reservoir showed trends similar to the simulated fluctuations. We conclude that crappie populations likely do not exhibit true cycles but may show quasi-cycles as a result of the interaction between random fluctuations in environment and density-dependent mechanisms. The frequency of such quasi-cycles may be enhanced by rapid growth and high exploitation.

Differential Growth and Survival of Weekly Age-0 Black Crappie Cohorts in a Florida Lake

Black crappies Pomoxis nigromaculatus exhibit highly variable survival to adulthood because of their varying larval and juvenile abundance, growth, and mortality during early life. We examined how growth and mortality changed with hatch date, prey density, and water temperature for 7-d cohorts of juvenile black crappies in Lake Wauberg, Florida (a 150-ha hypereutrophic natural lake) during spring and summer 1998. Fish were collected once per week from March through June and twice per month during July and August by means of an otter trawl. Based on daily otolith rings, hatching occurred over a 12-week period (1 March−18 May). The mean daily growth rate (DGR) was positively related to water temperature, which increased over the hatching season. Common prey taxa included calanoid copepods, Daphnia and Bosmina spp., and cyclopoid copepods. The total density of these taxa did not differ significantly among collection dates. Mean hatching date shifted from mid-March for fish collected in mid-April to early April for fish collected in late May. Early-hatched fish had lower DGRs (0.72 mm/d, compared with 0.76 mm/d for fish hatched in midseason and 0.82 mm/d for those hatched late in the season), higher mean daily instantaneous mortality rates (0.25, compared with 0.09 for the other two groups), and lower survival to the end of the first summer. As a result, the 1998 year-class of black crappies in Lake Wauberg was probably dominated by middle- and late-hatched individuals by the end of the first summer.

Effects of Shad Density and Reservoir Hydrology on the Abundance and Growth of Young-of-Year Crappie in Alabama Reservoirs

ABSTRACT We studied five Alabama reservoirs during 1992 through 1994 to explore the influence of both reservoir hydrology and larval shad (Dorosoma spp.) on young-of-year crappie (Pomoxis spp.) recruitment. Mean relative abundance of age-0 crappie was slightly and negatively correlated with larval gizzard shad (D. cepedianum) density but not with that of larval threadfin shad (D. petenense). Alternatively, age-0 crappie growth was positively correlated with threadfin shad density but not with gizzard shad density, which indicated that shad were not adversely affecting young crappie growth via competition for food. Neither crappie abundance nor growth was related to the dates of peak larval gizzard shad or threadfin shad occurrence. Age-0 crappie abundance was positively related to mean summer (June-August) retention time in four short retention time (< 15 d) reservoirs. However, when gizzard shad density was included into the analysis, this variable was no longer a significant predictor of crappie abundance, indicating that the relation between larval gizzard shad density and age-0 crappie abundance was overridden by the influence of mean summer retention time. Our findings indicate that the potential for interactions between young crappie and shad is certainly viable, but any impacts that larval shad might have had on age-0 crappie abundance and growth were not detected.

Hatching Time and Early Growth of Age-0 Black Crappies, White Crappies, and Their Naturally Produced F1Hybrids in Weiss Lake, Alabama

Abstract Extensive natural hybridization occurs between black crappie Pomoxis nigromaculatus and white crappie P. annularis in Weiss Lake, Alabama. First-generation (F1) hybrids have faster annual growth than black crappies and white crappies in this reservoir. However, no information exists on hatching date and early growth differences among black crappies, white crappies, and F1 hybrid offspring. We collected age-0 crappies in early August 1992–1994 from Weiss Lake and identified species and their hybrids with starch gel electrophoresis. Hatching date and early growth were determined from otoliths. Swim-up dates of F1 hybrids peaked about a week earlier than those of parental species. The growth rate of F1 hybrids (0.86 mm/d) was significantly higher than those of black crappies (0.67 mm/d) and white crappies (0.72 mm/d). Back-calculated lengths at ages 10, 20, and 30 d were higher for F1 hybrids compared with black crappies. Thus, the faster growth of F1 hybrids starts just after hatching and continues...

Effect of Environmental Variables upon Crappie Young, Year-Class Strength, and the Sport Fishery

Abundance of juvenile crappies Pomoxis spp. was positively related to floodwater storage in Rathbun Lake, Iowa, from 1972 to 1980. Regression analysis showed that age-0 crappies less than 15 d old increased by 1,330/acre for each million acre-feet–days of water stored above conservation pool from April through August. However, this relationship did not hold for data collected from 1981 to 1989. Abundance of crappies less than 15 d old was also positively related to numerical catch in the sport fishery 2–4 years later. Effects of temperature, wind, substrate, and turbidity on catch of age-0 crappies in townets from 1980 to 1983 were investigated. Once a spawning threshold temperature was attained, turbidity was most influential in determining age-0 crappie densities. About 50% of the variability in larval crappie abundance was explained by turbidity, exclusive of water level. The relationship between substrate firmness and larval crappie abundance was best described by a parabolic function; moderate firmness was associated with highest crappie numbers. Wind was intercorrelated with substrate firmness such that windswept shores provided hostile spawning habitat both in terms of molar action and extremely hard substrate. The 150-mi shoreline at Rathbun Lake was classified to identify prime spawning areas and thereby provide a basis for preserving and enhancing crappie production areas at the lake.