Variation in characteristics among gizzard shad populations: The role of impoundment size and productivity

Small impoundments (hereafter, "lakes") provide close-to-home fishing opportunities for many anglers but do not always provide quality fishing, especially for panfish. Often, these lakes contain populations of slow-growing Bluegill Lepomis macrochirus and crappies Pomoxis spp. The presence of abundant Gizzard Shad Dorosoma cepedianum and Common Carp Cyprinus carpio is known to negatively influence these populations. Chemical and mechanical removal of these nuisance species requires intensive effort, is costly, and usually results in only short-term benefits. An alternative approach is to stock piscivores that prey on these species and reduce their abundances. Hybrid Striped Bass (Striped Bass Morone saxatilis × White Bass Morone chrysops) alone or in combination with Flathead Catfish Pylodictis olivaris were stocked into small lakes to consume Gizzard Shad and Common Carp. To evaluate the success of this approach, I determined whether stockings of hybrid Striped Bass and Flathead Catfish were (1) associated with a consequent reduction in abundances and changes in size structure of Common Carp and Gizzard Shad, (2) related to improved growth rates and size structure of Bluegill and crappie populations, and (3) associated with changes in Largemouth Bass Micropterus salmoides demographics and aquatic macrophyte coverage. Nine treatment lakes were each paired with a reference lake, and fish population variables and macrophyte coverage were analyzed with a before-after, control-impact design. With a few exceptions, additions of piscivores were largely unsuccessful in reducing Gizzard Shad and Common Carp abundances and in improving growth of panfishes and the additions had little effect on Largemouth Bass or macrophyte coverage. A multi-pronged approach combining several methods (e.g., stocking of piscivores, reducing nutrients, and mechanical or chemical removal) may be necessary to effectively reduce the abundances of Gizzard Shad and Common Carp in these small lakes.

Section: Discussionmentioning

confidence: 99%

Bolstering Piscivore Abundance to Restructure Small Impoundment Fish Communities

Michaletz

2020

“…In Midwestern and southern impoundments, crappies commonly prey on clupeids, such as Gizzard Shad Dorosoma cepedianum , when those prey are small enough to consume (Ellison 1984; Muoneke et al 1992; Michaletz et al 2012a). However, within the small study impoundments, the occurrence of suitably sized clupeid prey was highly sporadic within and among years owing to large variation in annual abundances of age‐0 Gizzard Shad (Michaletz, in press) and their rapid growth rates (Michaletz 2017). For example, electrofishing mean CPUE of age‐0 Gizzard Shad in midsummer ranged from 0 to 1,949 fish/h among the study lakes and among years (Michaletz, in press), and juveniles grew to an average of about 140 mm TL by age 1 (Michaletz 2017), which is too large for most crappies to consume (Michaletz et al 2012a).…”

Section: Discussionmentioning

confidence: 99%

“…However, within the small study impoundments, the occurrence of suitably sized clupeid prey was highly sporadic within and among years owing to large variation in annual abundances of age‐0 Gizzard Shad (Michaletz, in press) and their rapid growth rates (Michaletz 2017). For example, electrofishing mean CPUE of age‐0 Gizzard Shad in midsummer ranged from 0 to 1,949 fish/h among the study lakes and among years (Michaletz, in press), and juveniles grew to an average of about 140 mm TL by age 1 (Michaletz 2017), which is too large for most crappies to consume (Michaletz et al 2012a). Consequently, Gizzard Shad were not consistently available as prey, so crappies frequently had to rely on other prey resources that were probably less desirable for maintaining good growth (Ellison 1984; Muoneke et al 1992; Michaletz et al 2012a).…”

Section: Discussionmentioning

confidence: 99%

Variable Length at Age for Black Crappies and White Crappies in Missouri Small Impoundments

Michaletz

2020

I observed exceptionally variable TL at age for both Black Crappies Pomoxis nigromaculatus and White Crappies P. annularis in several small impoundments in northern Missouri. I used linear mixed models to assess the relative influences of sex, juvenile growth (back-calculated lengths at age 1 [L1] and age 2 [L2]), and age in explaining variation in TL of age-3 and older crappies. I also examined the potential effects of TL, age, and sex on body condition (relative weight W r) and TL, age, and W r on reproductive investment (gonadosomatic index [GSI]) of females. Models with various combinations of explanatory variables were compared with Akaike's information criterion. The most supported model explained over 60% of the variation in TL at age of age-3 and older fish and included age, L2, and sex for both species. For White Crappies, the L2-only model explained more variation in TL than the age-only model, but the opposite was true for Black Crappies. Logistic regression using TL and L2 as independent variables revealed that crappies of both species had less than a 50% probability of reaching 229 mm TL-a common minimum TL limit-by age 5 if L2 did not exceed 150 mm, indicating the importance of juvenile growth in determining adult size. The best model for W r included TL, age, and sex for both species but explained less than 19% of the variation in this variable. Likewise, the best models for GSI explained less than 10% of the variation and included TL and W r for Black Crappies and TL, W r , and age for White Crappies. Because of the importance of juvenile growth in determining sizes of adult crappies, future studies should focus on processes that influence growth rates during the juvenile phase.

“…Furthermore, we caution management biologists to monitor water quality by measuring dissolved oxygen and temperature at different depths throughout the year to ensure that introduced trout will die from thermal stress. Due to gape limitation of stocked trout, its likely they will only control age‐0 Gizzard Shad, so suitable levels of Gizzard Shad reproduction may still prevent adequate predatory control by trout of Gizzard Shad populations that have fast growth, large adult biomass, and limited abundance of age‐0 fish (Michaletz ). However, managers should be careful to ensure Rainbow Trout cannot survive in thermal refugia during summer or they may become difficult to control and simply trade one problem for another.…”

Section: Discussionmentioning

confidence: 99%

Effects of Wintertime Stocking of Rainbow Trout on the Forage Community of an Oklahoma Impoundment

Snow¹,

Shoup

Porta³

et al. 2019

Rainbow Trout Oncorhynchus mykiss are sometimes stocked to create put-and-take fisheries in small impoundments. Information about the effects of these stockings on existing piscivores is poorly understood. Therefore, we performed a study to evaluate the forage consumption by Rainbow Trout stocked in Lake Carl Etling, Oklahoma. A creel survey during the 2014-2015 trout season determined that angling pressure was low, which left the majority of stocked trout in the lake until their thermal maximum was exceeded in late May-June. Rainbow Trout stomach contents were collected monthly from November through April annually (2015-2018) via gastric lavage. Gizzard Shad Dorosoma cepedianum were consumed during most months, but their occurrence in Rainbow Trout stomachs was highest in January and December. A sharp decline in Gizzard Shad consumption was followed by an increase in detritus consumption each year. Using either Gizzard Shad numbers observed in monthly Rainbow Trout diets or the estimated monthly abundance of Rainbow Trout, we postulated that Rainbow Trout substantially affected age-0 Gizzard Shad biomass (reducing it by 66.7 or 54.6 kg/ha, respectively), potentially negatively affecting growth rates of other piscivores in the system. This study demonstrates the unintended consequences of stocking an additional predatory fish into small impoundments and the importance of evaluating angler harvest of these stocking programs to ensure the stocked species receives sufficient angler harvest to match stocking rates and prevent negative impacts on the fish community (both forage and other piscivorous species).