The intestinal microbiome (IM) or the community of commensal and pathogenic microbes that inhabit the intestinal tract of fish has long been of interest in aquaculture because of its hypothesized role in nutrient digestion and fish immunity. Artificial improvement to the IM of fish with pre- and probiotics has been shown to have benefits in some studies; however, the mechanisms behind these supplements are poorly understood because of a lack of knowledge on the basic structure of the IM of fish. The research described here aims to characterize the IM of the highly studied and commercially important Icatlurid catfish, channel catfish Ictalurus punctatus and blue catfish I. furcatus. In this study we evaluated differences between the homeostatic IM, across genotype (Objective 1) and developmental ontogeny (Objective 2), using high-throughput sequencing of 16S rRNA gene amplicons. We compared the IM of four selected strains of blue catfish and three selected strains of channel catfish at 193 days post-hatch (DPH) in Objective 1 (n = 40); while the influence of developmental ontogeny was evaluated by observing the IM of a single family of channel catfish at 3, 65, 125, and 193 DPH Objective 2 (n = 20). The bacterial phyla Fusobacteria, Firmicutes, and Proteobacteria were detected in all fish strains and developmental time points; however, at the genus level the abundances of different bacteria varied among experimental units, as well as being rather variable between individuals. At 3 DPH (n = 5) the IM of channel catfish sac-fry larvae showed the most variation between individuals; with bacteria from the genus Bradyrhizobium dominating the IM of two sac-fry (84% and 88%), and Flavobacterium, Lactobacillus, Comamonadaceae dominating the IM of the remaining three sac-fry analyzed (86%, 99%, and 97% respectively). The dominant bacteria in the gut of all other fish analyzed (n = 55), was Cetobacterium somerae (mean ± SD, 41.4% ± 36%), a commensal microbe that is known to produce vitamin B12. Statistical differences in the abundance of three different bacteria within the order Clostridiales (P ≤ 0.039) were detected in Objective 1, with more of these OTUs inhabiting the gut of channel catfish than that of blue catfish. Statistical differences in the abundance of Edwardsiella, a genus of bacteria known to cause disease in catfish, were detected across the two species of Ictalurid catfish in Objective 1 (P = 0.038), and across developmental ontogeny in Objective 2 (P = 0.021); however, these bacteria were detected at low abundance (0.002% - 0.004%). Comparisons of beta diversity showed significant differences between many strains of Ictalurids, with a highly significant difference between channel catfish and blue catfish (P = 0.001); however, few differences were detected when comparing beta diversity across the four time points over the first 193 DPH in Objective 2, with only 3 DPH and 125 DPH showing significant differences (P = 0.022). Overall these data suggest host-genotype, and to a lesser extent developmental ontogeny, influence the structure of the IM of Ictalurid catfish. As the first study to be conducted on the IM of these fish species, these results have performance implications on the culture of these commercially important catfish, while also enhancing our basic knowledge on the dynamics of the fish microbiome.

No description available.

No description available.

Distribution of the orangefin madtom (Noturus gilberti) was determined from 347 sites sampled in Virginia and North Carolina. This species inhabited 264 stream kilometers, over twice the reported range, in the following systems: Craig Creek, Roanoke River, Dan River, Big Chestnut Creek, South Mayo River, Pigg River, and Smith River. The orangefin madtom was somewhat common; 33% (Dan River) to 70% (Craig Creek) of the sites sampled were occupied. Negative interspecific associates of orangefin madtoms included chubs, mountain redbelly dace, rosyside dace, crescent shiners, and crayfish; only Roanoke darters were considered positive associates. Sand and silt levels were significantly lower at sites with N. gilberti, while percentage of small cobble, local gradient, and depth were significantly higher. Discriminant function analysis identified large gravel, local gradient, silt, and occurrence of rosyside dace and crayfish, as significant predictors of the occurrence of the orangefin madtom. Seasonal samples from Craig Creek consisted of three age groups. The smallest individual captured was 33 mm total length (TL) and the largest was 111 mm TL. Mortality appeared moderate from age I until summer of the third year, when most individuals apparently died shortly after spawning. Spawning habitat of orangefin madtoms in Craig Creek appeared to be fast-water riffles dominated by small cobble substrate. Attempts to induce N. gilberti spawning in the laboratory were unsuccessful due to high mortality of captive fish. Field-collected margined madtom egg masses, however, were successfully hatched, and subsequent survival was significantly greater for fry fed ground trout chow versus live brine shrimp nauplii. / Master of Science

North American freshwater catfishes (Ictaluridae) is family of freshwater catfishes and includes 7 genera and 48 species. Original habitat of those family is Northern and Central America, but some species were to be introduced to the other regions inclusive Europe. In Czech Republic was recorded occurrence of two species of genus Ameiurus. Brown bullhead (Ameiurus nebulosus) imported by J. Šusta in 1890, and black bullhead (Ameiurus melas), which was imported in 2003 as an admixture to load of Common carp stocking material from Croatia. Distribution of these species is restricted on a small areas in the Elbe river basin and Třeboň pond system in Southern Bohemia. These species are very similar and their resolution is possible only on the basis morphometrics and anatomical diversity (number of fin rays, serration of spine on pectoral fin). Therefore was necessary carry out detailed measuring of both species with the aim of find out appropriate next differences. We measured 63 measurements by digital slide gauge and next we quantified number of fin rays. Totaly was processed 90 black bullheads and 52 brown bullheads.