Stomach Capacities of Six Freshwater Fishes

We investigated the relationship between stomach capacity and total body length in bluegill (Lepomis macrocirirus), spotted bass (Microplerus punctulatus), white crappie (Pomoxis annularis), black crappie (Pomoxis nigromoculatus), channel catfish (Ictalurus punctatus) , and white bass (Morone chrysops). The rate of change in stomach capacity for a given change in fish length was greatest for spoiled bass and channel catfish, which may indicate greater ontogenetic shifts in feeding strategies. Fish with larger stomach capacities should have more plastic diets because they are capable of consuming a wider range of prey sizes, particularly when they already have prey present in their stomach, compared to fish with smaller stomach capacities and similar feeding strategies

The influence of depth and velocity on age‐0 Scaphirhynchus sturgeon prey consumption: Implications for aquatic habitat restoration

After the pallid sturgeon (Scaphirhynchus albus) was listed as endangered in 1990, a variety of management actions focusing on early life history needs have been implemented to aid species recovery. Given the scarcity of age‐0 pallid sturgeon, managers and scientists have relied on sympatric congeners to evaluate the effectiveness of management actions in the short term; however, increased understanding of habitat requirements for age‐0 Scaphirhynchus sturgeon is still needed to appropriately focus management efforts. Recently, a lack of food‐producing and foraging habitats were proposed as potential limiting factors for pallid sturgeon, and the purpose of this study was to evaluate the current definition of these habitats at multiple spatial scales using data from age‐0 Scaphirhynchus sturgeon (shovelnose sturgeon [Scaphirhynchus platyrhynchus] or hybrid [shovelnose sturgeon x pallid sturgeon]). Results showed the water depths and velocities that currently define age‐0 pallid sturgeon foraging habitat had little effect on age‐0 Scaphirhynchus sturgeon prey consumption. Similar results occurred when evaluating the relationship between prey consumption and food‐producing habitat present 10, 20, and 30 days before capture. Assuming that individuals captured during this study were a valid surrogate, these results suggest that increasing foraging and food‐producing habitat as defined by the current depth and velocity criteria is unlikely to result in the desired benefits of increased growth and survival of age‐0 pallid sturgeon

Using consumption rate to assess potential predators for biological control of white perch

Control of undesirable fishes is important in aquatic systems, and using predation as a tool for biological control is an attractive option to fishery biologists. However, determining the appropriate predators for biological control is critical for success. The objective of this study was to evaluate the utility of consumption rate as an index to determine the most effective predators for biological control of an invasive fish. Consumption rate values were calculated for nine potential predators that prey on white perch Morone americana in Branched Oak and Pawnee reservoirs, Nebraska. The consumption rate index provided a unique and insightful means of determining the potential effectiveness of each predator species in controlling white perch. Cumulative frequency distributions facilitated interpretation by providing a graphical presentation of consumption rates by all individuals within each predator species. Largemouth bass Micropterus salmoides, walleye Sander vitreus and sauger S. canadensis were the most efficient white perch predators in both reservoirs; however, previous attempts to increase biomass of these predators have failed suggesting that successful biological control is unlikely using existing predator species in these Nebraska reservoirs. Le contrôle des poissons indésirables est important dans les écosystèmes aquatiques et l’utilisation de la prédation comme outil de contrôle biologique est une option attractive pour les biologistes des pêches. Toutefois, déterminer les bons prédateurs pour un contrôle biologique est crucial pour sa réussite. L’objectif de cette étude a été de tester l’utilité du taux de consommation comme indice de détermination des prédateurs les plus appropriés pour le contrôle biologique d’un poisson invasif. Les valeurs du taux de consommation ont été calculées pour neuf prédateurs potentiels de la perche blanche Morone americana dans les réservoirs Branched Oak et Pawnee, Nébraska. L’indice du taux de consommation est un moyen unique et perspicace pour déterminer l’effectivité potentielle de chaque espèce de prédateur dans le contrôle de la perche blanche. Les distributions de fréquences cumulées facilitent l’interprétation en donnant une représentation graphique des taux de consommation par tous les individus d’une même espèce de prédateur. Le bass à grande bouche Micropterus salmoides, les sandres Sander vitreus et S. canadensis sont les prédateurs les plus efficaces de la perche blanche dans les deux réservoirs. Toutefois des tentatives antérieures pour augmenter la biomasse de ces prédateurs n’ont pas réussi, suggérant que le contrôle biologique est improbable avec les espèces de prédateurs présentes dans ces réservoirs du Nébraska

Food Habits of Stunted and Non-Stunted White Perch (\u3ci\u3eMarone americana\u3c/i\u3e)

We studied food habits of white perch (Morone americana) from two populations with different stable states (stunted [Branched Oak Lake, Nebraska] and non-stunted [Pawnee Lake, Nebraska]) to determine if change in food habits of white perch is likely to occur in situations where a stunted while perch population is altered to a non-stunted state and vice versa. Three approaches were used to quantitatively describe seasonal (spring= March-May, summer= June-August, autumn = September-November) diets of white perch - 1) frequency of occurrence, 2) percentage of composition by volume, and 3) mean stomach fullness. White perch diets were dominated by cladocerans and dipterans in both reservoirs during all seasons. Fish egg predation was similar between reservoirs, and white perch rarely consumed fishes in either the stunted or the non-stunted population. Shifting a while perch population between stunted and non~stunted states will likely cause little or no change in food habits; fish in both Slates will primarily consume invertebrates

The effect of predation on stunted and nonstunted white perch

Predation is widely regarded as a means to prevent or minimise the establishment of a stunted (high density of slow growing individuals) population. We investigated the effect of predation on two different white perch Morone americana populations (stunted and nonstunted) by examining the stomach contents of piscivorous fishes. White perch and gizzard shad dominated piscivore diets in Branched Oak Lake, whereas white perch dominated piscivore diets in Pawnee Lake. White perch consumed in the stunted population (Branched Oak Lake) were larger and older than white perch consumed in the nonstunted population (Pawnee Lake). Many of the consumed white perch in the stunted population were sexually mature and had the opportunity to spawn at least once. In contrast, all of the consumed white perch in the nonstunted population were sexually immature. Predation may have reinforced the stunting of white perch in Branched Oak Lake through removal of the largest, oldest individuals

Stomach Capacities of Six Freshwater Fishes

We investigated the relationship between stomach capacity and total body length in bluegill (Lepomis macrocirirus), spotted bass (Microplerus punctulatus), white crappie (Pomoxis annularis), black crappie (Pomoxis nigromoculatus), channel catfish (Ictalurus punctatus) , and white bass (Morone chrysops). The rate of change in stomach capacity for a given change in fish length was greatest for spoiled bass and channel catfish, which may indicate greater ontogenetic shifts in feeding strategies. Fish with larger stomach capacities should have more plastic diets because they are capable of consuming a wider range of prey sizes, particularly when they already have prey present in their stomach, compared to fish with smaller stomach capacities and similar feeding strategies

Age-0 Sturgeon Accessibility to Constructed and Modified Chutes in the Lower Missouri River

Shallow-water habitat is hypothesized to provide nursery habitat for young fish. The construction of side-channel chutes to restore shallow-water habitat is common in the lower Missouri River; however, a recent adaptive management strategy document (developed by a multiagency, multidiscipline team), as well as previous research, has suggested that the accessibility of chutes to age-0 Scaphirhynchus spp. (sturgeon hereafter) may be limited. Access is a critical prerequisite for young fish utilizing chute habitat; thus, we investigated chute-specific accessibility for age-0 sturgeon at seven chutes (constructed and natural). Age-0 sturgeon were capable of accessing most chutes; however, accessibility appeared limited at sites with highly restrictive inlet structures. Our results suggest that future consideration of chute inlet designs that meet authorized Missouri River purposes while providing improved fish access is warranted. Additionally, capture sites for exogenously feeding age-0 sturgeon were usually deeper (\u3e1.5 m) and faster (\u3e0.5 m/s) than sites without sturgeon in chute and adjacent main-stem habitats. This finding is consistent with previous research that suggests that slow and shallow habitats may not be used by age-0 sturgeon as frequently as other habitat types in the lower Missouri River