Dennis R. DeVries

First-Year Recruitment of Largemouth Bass: The Interdependency of Early Life Stages

Four early life events (i.e., hatching, the ontogenetic diet shift to piscivory, fall lipid accumulation, and the first winter) are conceptualized as being critical to 1st-yr recruitment success of largemouth bass (Micropterus salmoides) via cause-and-effect as- sociations among them. Toward this end, we conducted a multiple life-stage investigation of largemouth bass to examine the functional dependency and significance to recruitment of these temporally separated early life events. Specifically, we quantified growth and survival of two largemouth bass year-classes in six Alabama ponds from hatching to the end of the first winter. The first winter was an important survival bottleneck with lower largemouth bass sur- vival in ponds with smaller largemouth bass (high-density ponds), relative to ponds with larger fish (low-density ponds). While cannibalism was not important, we found size- dependent first-winter mortality to be regulated directly by lipid reserves (i.e., triglycerides) accumulated during fall, and indirectly by both hatch date and the ontogenetic diet shift to piscivory during summer. Early-hatched largemouth bass attained an initial length ad- vantage, remaining large relative to late-hatched fish, despite the relatively higher growith rate of late-hatched fish during their first month of life. Enhanced size permitted early- hatched fish to become piscivorous before late-hatched fish, increasing their access to fish prey (i.e., sunfishes) during fall. This in turn elevated their fall lipid accumulation and winter survival above that of late-hatched fish. Our results indeed suggest that 1st-yr re- cruitment of largemouth bass in southern systems is governed by several functionally dependent critical events. Because each is likely vital to understanding recruitment vari- ability, we suggest that future recruitment studies should adopt a more synthetic (i.e., multiple life-stage) approach.

Use of a Split-Plot Analysis of Variance Design for Repeated-Measures Fishery Data

Abstract We present a repeated-measures split-plot analysis of variance (ANOVA) design that can be used to analyze fisheries data collected throughout time from fixed sampling stations. A high percentage (97%) of authors who published papers in the Transactions of the American Fisheries Society and the North American Journal of Fisheries Management during the past 10 years did not use repeated-measures ANOVA for analyzing their data when this technique was appropriate. When data are collected from fixed stations throughout time, the assumption that independent samples are randomly collected from the population is violated for simple ANOVA. Fixed stations may display population characteristics specific to that location, and environmental change or a management practice may influence stations differently. In addition, multiple measurements collected at a fixed station throughout time will likely be correlated. For a dependent variable of interest, a repeated-measures split-plot design will partition the var...

Manipulating Shad to Enhance Sport Fisheries in North America: An Assessment

Abstract Manipulating forage fish populations to enhance sport fisheries is a common management practice. Here we review the literature dealing with manipulations of gizzard shad Dorosoma cepedianum and threadfin shad D. petenense to assess whether or not this practice has been successful. Shad introduction has tended to enhance predators, such as white crappie Pomoxis annularis, black crappie P. nigromaculatus, and largemouth bass Micropterus salmoides, and negatively affect presumed competitors, such as bluegill Lepomis macrochirus. However, responses have not been consistent within a species: some studies document negative responses of predators or positive responses of competitors to shad introduction. Depending on the study, target species have experienced negative, neutral, and positive effects due to shad removal, making generalizations impossible. Inadequate statistical analyses coupled with problems with study design further complicated interpretation of these studies. In addition, because reside...

Prey Selection by Larval Fishes as Influenced by Available Zooplankton and Gape Limitation

Abstract Feeding success during the first weeks of life is critical to determining survival and ultimate year-class strength of fishes. To compare the relative influence of gape limitation and available zooplankton on prey size selection among the larvae of three species of freshwater fishes, we gathered data on fish gape size, prey size, and size-specific prey selection in lakes and reservoirs. These variables were compared among black crappies Pomoxis nigromaculatus from a lake that contained large zooplankton as prey and white crappies P. annularis and gizzard shad Dorosoma cepedianum (a potential competitor of white crappie) from reservoirs that contained small zooplankton. In three Ohio reservoirs (i.e., small-zooplankton systems), available zooplankton and larval stages of white crappies and gizzard shad were collected once per week during April through September 1987 and 1988. Although mean prey size of white crappies continued to increase with fish size, mean prey size of smaller-gaped gizzard sha...

Stocking Threadfin Shad: Consequences for Young-of-Year Fishes

Abstract Threadfin shad Dorosoma petenense are commonly introduced into reservoirs to supplement prey available to piscivorous fishes. To determine how early life stages of threadfin shad and their potential competitors and predators interact, we introduced this species into two Ohio lakes—Clark and Stonelick—and evaluated how its young of year influenced young-of-year bluegills Lepomis macrochirus and largemouth bass Micropterus salmoides. After adults were stocked in April, peak abundance of young-of-year threadfin shad occurred in August in both lakes. Bluegills generally spawned earlier than threadfin shad, which apparently reduced competition between young of these species. In Clark Lake, young-of-year threadfin shad did not reduce zooplankton populations, but in Stonelick Lake, peak abundance of young-of-year threadfin shad was followed by a precipitous decline in zooplankton. Data on cladoceran birth rates indicated this decline was due to increased predation by threadfin shad. Survival of bluegill...

Predation and the distribution and abundance of a pulmonate pond snail

SummaryThe abundances of a freshwater pulmonate snail, Lymnaea elodes were studied in a temporary pond and a permanent, more productive pond in northeastern Indiana, USA. When snails from both populations were reared in each of the ponds in containers excluding predators, snails grew to be 1.3 to 2 times as large in the more productive pond, and laid 9 times as many eggs. However, field sampling data showed adults to be more abundant in the temporary pond. The only obvious difference between the two ponds was the presence of the molluscivorous central mudminnow (Umbra limi) in the permanent pond. These fish fed upon L. elodes when eggs and juvenile snails were abundant. In an experiment in the temporary pond, addition of mudminnows lowered egg and juvenile snail survival in pens where snail abundances had been increased. We suggest that vertebrate predators like the mudminnow can be significant sources of mortality for thin shelled species like L. elodes, possibly excluding them from habitats like lakes and rivers.

First-Summer Survival of Largemouth Bass Cohorts: Is Early Spawning Really Best?

Abstract Previous work has demonstrated that survival of largemouth bass Micropterus salmoides through the first year of life can be size dependent, favoring larger individuals. Because size, diet biomass, lipid accumulation, and ultimately overwinter survival of juveniles are typically positively related to age, early spawning is clearly advantageous. However, a true understanding of which largemouth bass cohorts contribute to the new year-class remains somewhat unclear because these conclusions have largely been based upon fish collected during summer rather than fish collected during spring. Conceivably, even earlier hatched cohorts of largemouth bass could have existed in many of these studies, and these fish may simply not have survived to the summer collection period. In order to assess this possibility, we quantified first-summer survival of largemouth bass cohorts collected during 1992 and 1993 in Auburn, Alabama, ponds (which were 2–5 ha each). Our results indicate that it is early-hatched cohort...

Regulation of Growth and Mortality in Larval Bluegills: Implications for Juvenile Recruitment

Abstract Factors related to growth and survival of 10-d cohorts of larval bluegills Lepomis macrochirus were examined in two small impoundments via daily growth increments on otoliths. Successful spawning occurred from April through September, producing peak larval densities greater than 360 fish/m3. Larval bluegill density was negatively correlated with zooplankton density in both ponds, suggesting that larvae reduced zooplankton abundance via predation. Several variables were related to larval growth and mortality. Cohorts whose larval densities were low tended to have faster growth and higher survival than cohorts with high larval densities. The mechanism responsible for this density-dependent relation was not clear in all instances; however, some evidence suggested that control occurred via intraspecific competition for zooplankton. Relative survival of larval bluegills to the juvenile stage was negatively correlated with limnetic larval fish density; however, no relations were detected between larval...

Habitat Use, Diet, and Population Structure of Adult and Juvenile Paddlefish in the Lower Alabama River

Abstract We quantified habitat use, diet, and population characteristics of paddlefish Polyodon spathula in the lower Alabama River, Alabama, in an effort to determine whether juveniles and adults differ in their seasonal use of three types of habitats (oxbow lakes, backwater areas, and channel areas) and to identify differences in population characteristics between fish from the Alabama River and those from other drainage systems. Both juveniles and adults used backwater and channel areas. Paddlefish used backwater areas primarily during summer and fall and channel habitats during winter and spring. Juvenile paddlefish that were present in backwater areas migrated with prespawn adults, whereas juveniles in the oxbow habitat did not. Juvenile paddlefish used oxbow lakes as nursery areas, remaining there until sexual maturity. Paddlefish in the lower Alabama River had shorter life spans than those previously studied further north, suggesting a latitudinal gradient in fish survival. Although fecundity rates...

Paddlefish in the Alabama River Drainage: Population Characteristics and the Adult Spawning Migration

Abstract Paddlefish Polyodon spathula were sampled by boat-mounted electrofishing and gill netting in the Tallapoosa and Cahaba rivers and in oxbow lakes of the Alabama River floodplain, Alabama, during January–June of 1992 and 1993. Tagging studies, characterization of spawning migrations, and comparative analyses of catches suggested that paddlefish in the Tallapoosa and Cahaba rivers represented functionally discrete populations that reside in the adjacent reservoirs. Variation in population characteristics appeared to be related to differences in the hydrologic and thermal regimes of the two study rivers and to differences in historical exploitation of populations in the two resident reservoirs. Growth (calculated via back-calculated body length at age) differed between populations in the upper and lower Alabama River, probably reflecting the relatively lentic (upper) and lotic (lower) nature of habitats in these two reaches. Life history characteristics of paddlefish in the Alabama River drainage dif...