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Bigmouth buffalo (Ictiobus cyprinellus) is a large-bodied planktivore inhabiting shallow waterways in North America and subjected to unregulated harvest throughout much of their native range. Despite high harvest pressure on some populations, we know little about the ecosystem-level effects of lowering bigmouth buffalo densities. To evaluate the effect of bigmouth buffalo density on lower trophic levels we added fish in ambient and harvested densities to a set of ponds and compared plankton dynamics to reference, fishless ponds. Zooplankton biomass declined in ambient density ponds after the fish addition while chlorophyll-a concentrations increased. In the harvested density treatment chlorophyll-a concentrations were similar to the reference ponds despite a decline in zooplankton biomass, likely due to larger zooplankton community size in the harvested ponds exerting greater grazing pressure. This experimental manipulation revealed density-dependent top-down control on lower trophic levels by bigmouth buffalo and the potential for cascading trophic interactions with the harvest of this species. These results point to the need for ecosystem-level studies of the effects of intensive harvest of bigmouth buffalo on water quality.

Summary Natural diets of tench (Tinca tinca L.), carp (Cyprinus carpio L.) and bigmouth buffalo (Ictiobus cyprinellus Val.) were studied to determine food competition among them in polyculture stocks of two different densities. Tench diet consisted mainly of zooplankton (43.8%) and bottom sediments (21.2%). In contrast, carp diet consisted mainly of bottom items including plant debris and detritus (68.8%), which dominated over zooplankton (19.1%). In bigmouth buffalo, most food bulk comprised zooplankton (80.7%). Thus, the resulting food competition (i.e. similarity) was most pronounced between tench and carp (60.8%) and between tench and bigmouth buffalo (47.4%). When comparing growth performance of the three cultured species, the ratios between stocking and harvesting size were: in normal stocking density (392 kg ha−1) 1.72, 3.67 and 2.13, and in doubled stocking density (777 kg ha−1) 1.07, 2.33 and 2.16 in tench, carp and bigmouth buffalo, respectively.

The complete mitochondrial genome of Ictiobus cyprinellus was first determined by a polymerase chain reaction-based sequencing method in this study. The mitochondria was 16,611 bp in length, including 13 protein genes, 2 ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes and 1 control region. All genes were encoded on the heavy strain except for ND6 and eight tRNA genes. The gene arrangement of I. cyprinellus was similar to those found in the other Catostomidae species. Base composition of the heavy strain was A (29.40%), T (24.86%), C (27.96%), G (17.78%) and with A + T bias of 54.26%.

The field study of the bigmouth buffalo (Ictiobus cyprinellus (Valenciennes)), conducted mainly in 1955 and 1956, was concentrated on two small eutrophic lakes in the Qu'Appelle River drainage of Saskatchewan. The bigmouth buffalo reaches its northern limit of range in the Qu'Appelle drainage. Migration into Saskatchewan was probably through postglacial connections at the headwaters of the Mississippi and Red River systems. In the lakes studied, the species prefers water shallower than 5 m.The relation of standard length to fork length and of fork length to weight is presented graphically, and the latter described by the equation: weight in pounds = (0.00097 fork length in inches)2.91. Length–frequency distributions and age determinations from scale reading show that the population studied was largely the very successful 1948 year-class, produced in a year of extensive flooding. Annulus formation occurred during the second or third week in June. Growth of the 1948 year-class in Pasqua Lake was extremely slow, probably influenced by the cool climate and population density here.Food of young buffaloes was mainly Cladocera and Copepoda. Larger buffaloes ate about 75% Entomostraca and 15% chironomids, the latter more important as the size of fish increased. Analysis of the living habits of the food eaten, and the feeding mechanism of the buffalo, shows that they occupy a food niche overlapping both bottom feeders and limnetic plankton feeders.Sexual maturation, especially of females, was extremely slow both in age and size as compared with southern populations. Examination of gonads suggests spawning occurs about May 18–25. Egg measurements indicate that females do not all spawn each year. The contention by other investigators that spawning is "triggered" by addition of fresh water analogous to normal spring floods of the Mississippi River is supported by the present study.The population in the Qu'Appelle drainage is probably dependent on the very sporadic production of strong year-classes. A more stable population would require association with regular spring floods of a nearby river or marsh. Commercial removal from the viewpoint of greatest productivity is most economical at the smallest marketable size, as yearly weight gains are probably more than offset by natural mortality.

A hematological study was made based on 10 specimens each of the buffalofishes Ictiobus cyprinellus and I. bubalus (Catostomidae). Average results of analyses of selected blood characteristics of I. cyprinellus and I. bubalus, respectively, were: hemoglobin content, 7.8 and 8.5 g/100 ml; erythrocyte count, 1.08 and 1.28 millions/mm2; hematocrit, 34.6 and 32.9%; mean corpuscular hemoglobin, 67 and 64 μμg; and leucocyte count, 23916 and 29004 cells/mm3. Types of leucocytes noted were lymphocytes, neutrophils, "secretory granulocytes," eosinophils, and thrombocytes. No basophils were found. The secretory granulocyte is apparently derived from the neutrophil series. The status of the secretory granulocyte in buffalofishes is discussed with reference to pertinent literature.

Food habits and food selectivity of bigmouth buffalo, Ictiobus cyprinellus, in Lake Poinsett, South Dakota were studied from January through November 1968. Food of bigmouth buffalo fry ranging from 12.5 to 21.0 mm total length was primarily benthic organisms. Food of sub-adult and adult bigmouth buffalo ranging from 236 to 833 mm total length was primarily zooplankton. Most planktonic organisms were consumed in about the same proportion as they were available. Selectivity was greatest for adult Daphnia pulex, the largest food item present, and least for calanoid copepods. The bigmouth buffalo in Lake Poinsett might best be described as an indiscriminate planktivor throughout most of its life history.

The paper deals with some results of experimental acclimatization of American channel catfish and bigmouth buffalo in U.S.S.R. waters. Attention is focused on the biological characteristics such as growth, nutrition, maturation, etc. of the species, under new environmental conditions. Consideration is given to biotechniques for rearing the introduced species in Ukrainian inland waters.

Although the pace of senescence varies considerably, the physiological systems that contribute to different patterns of senescence are not well understood, especially in long-lived vertebrates. Long-lived bony fish (i.e., Class Osteichthyes) are a particularly useful model for studies of senescence because they can readily be aged and exhibit some of the longest lifespans among vertebrates. In this study we examined the potential relationship between age and multiple physiological systems including: stress levels, immune function, and telomere length in individuals ranging in age from 2 to 99 years old in bigmouth buffalo (Ictiobus cyprinellus), the oldest known freshwater teleost fish. Contrary to expectation, we did not find any evidence for age-related declines in these physiological systems. Instead, older fish appeared to be less stressed and had greater immunity than younger fish, suggesting age-related improvements rather than declines in these systems. There was no significant effect of age on telomeres, but individuals that may be more stressed had shorter telomeres. Taken together, these findings suggest that bigmouth buffalo exhibit negligible senescence in multiple physiological systems despite living for nearly a century.

The River Niger is blessed with diverse fish species and aquatic life. The study of the fish fauna and biodiversity along the River Niger was conducted from October 2016 to December 2018. A total of 35 species belonging to 18 families were obtained from this study. New to this River as regards literature are the family Solidae and Catostomidae. The sole fish (Solea solea) (0.16%) with only 1 representation while the Catastomids were represented by 3 species; Ictiobus niger (1.73%), Ictiobus cyprinellus (2.20%), Ictiobus bubalus (2.52%). Other species obtained were the Mormyrus rume 3.93%, Polyterus bichir (2.99%) and Protopterus annectens (7.08%). The most abundant of species observed was Gymnarchus niloticus (8.49%) of the family Gymnarchidae while the least was Solea solea (0.16%). The biodiversity indices revealed that Station 2 had the most evenly distributed species and the most of diverse species though Station 1 had the most number of species. Station 3 however had the least of species obtained. It is concluded the River Niger is still productive and in good condition, capable of maintaining and managing fish species according to condition factor.

Mortality of fish early life stages was measured in a pressure vessel to simulate vertical displacement within the water column. Mortality was measured for three pressure regimes for four fish species: larval bigmouth buffalo Ictiobus cyprinellus, larval blue catfish Ictalurus furcatus, juvenile bluegill Lepomis macrochirus, and juvenile largemouth bass Micropterus salmoides. The maximum pressure‐change tested, 344.8 kPa, equivalent to a 35.2 m displacement of fish within the water column, did not cause significant mortality of larvae or juveniles. Since 32.5 m exceeds depths in most inland navigation channels and possibly the depth to which rapid propeller induced water mixing occurs, the range of pressure changes that could be experienced by early life stages during towboat mixing of the water column will not result in significant mortality.