Latest Research News on catfish April 2021
 Structure and function in the catfish
The catfish (Siluroidei) appear to have evolved from an ancestor which, in most respects other than the form of its teeth, resembled primitive Characinoidei. In the first part of this paper it is shown that most of the numerous and profound anatomical changes which have occurred in the course of their evolution from this ancestor can be related to one or other of three basic changes: depression of the body in adaptation to bottom‐feeding habits, sensory modification in adaptation to nocturnal habits, and the evolution of defensive fin spines. Diplomystes is more primitive than other known catfish in the form of its maxilla and pectoral girdle, and in the posterior position of its dorsal fin.
The second part of the paper is concerned with some of the more specialized families of catfish (Mochokidae, Siluridae, Schilbeidae, Malapteruridae, Clariidae, Callichthyidae and Loricariidae). The specializations in each case are described, and related to the habits of the fish.
 Chemical Budgets for Channel Catfish Ponds
Budgets for water, nitrogen, phosphorus, chemical oxygen demand (organic matter), and dissolved oxygen (DO) were estimated over a growing season (March‐October) for three Alabama ponds used for culture of channel catfish Ictalurus punctatus. In addition to rainfall and runoff, 190 cm of water were applied from a pipe line to offset seepage and evaporation. Production of each kilogram of live fish required 1.32 kg of feed and released to the water in metabolic wastes 51.1 g nitrogen, 7.2 g phosphorus, and 1.1 kg chemical oxygen demand (COD). Metabolic wastes resulting from production of 1 kg of fish led to the synthesis of an additional 2.59 kg of COD in photosynthesis. Thus, 1 kg of live fish resulted in 3.69 kg COD. Fish harvest accounted for only 26.8% of nitrogen, 30.1% of phosphorus, and 25.5% of organic matter (COD) applied in feed. The remainder of the nitrogen and organic matter was apparently lost from ponds for no accumulation of these substances was detected in muds. Denitrification and ammonia volatilization apparently removed large amounts of nitrogen; organic matter was consumed in respiration. Most phosphorus not harvested in fish was apparently adsorbed by muds.
 The Effects of Frequency of Feeding on Culture of Catfish
In three studies on the effects of frequency of feeding on channel catfish (Ictalurus punctatus), optimal growth and food efficiency were obtained from groups fed to satiation two times per day. Gains in weight were substantially reduced in groups fed only one time per day and were not enhanced by feeding four times per day. The fact that food efficiencies were similar in fish fed one, two, and four times per day indicated that food intake and not utilization was the growth limiting factor. In a study with automatic feeders, fish fed 24 times per day had significantly poorer gains and food efficiencies than those fed four or eight times per day.
 Haematological and Blood Biochemical Changes in African Catfish, Clarias gariepinus Fed Walnut (Tetracarpidium conophorum Mull Arg) Leaf and Onion (Allium cepa Linn) Bulb Supplemented Diets
Juvenile Clarias gariepinus were fed diets containing Onion Bulb (OB) and Walnut Leaf (WL) residues at different graded levels: control (0%), OB2 (0.5%), OB3 (1.0%), OB4 (1.5%), OB5 (2.0%), WL6 (0.5%), WL7 (1.0%), WL8 (1.5%) and WL9 (2.0%). Packed Cell Volume (PCV), Haemoglobin (Hb) content, Red Blood Cells (RBC) and White Blood Cells (WBC) counts were measured in test fish after 84 days of feeding. Biochemical indices such as total protein, Albumin as well as blood serum, aspartate amino-transferase and alanine amino-transferase were investigated before and after the experiment. Data were analyzed using descriptive statistics and ANOVA at p = 0.05. The results obtained showed that packed cell volume and haemoglobin content were significantly different (p<0.05) among the treatments while red blood cell, white blood cell and mean cell volume and mean cell haemoglobin were not significantly different (p>0.05) among the dietary groups. There were increases in total protein and albumin but values of aspartate amino-transferase and alanine amino-transferase decreased though not significantly (p>0.05) among the treatments. However, fish fed the walnut leaves and onion bulbs residue- based diets recorded higher values in PCV, Hb, WBC and total protein compared to the values obtained before experiment and the control. The results of this study suggested that the dietary supplementation of walnut leaves and onion bulbs residues could be a potential, less expensive and positively affected haematological factor and boost immune response of cultured Clarias gariepinus juveniles.
 Molecular Characterization of Bacteria Isolates from Farm-Raised Catfish Clarias gariepinus (Burchell, 1822)
Selected bacterial isolates from skin, gut and gills of Clarias gariepinus were collected from five fish farms at Ijebu Ode. The isolates were assessed using 16S rRNA gene sequencing method to identify them and to construct the phylogenetic relationship. A total of 10 isolates were selected, their colonial morphology determined, thereafter the DNA of the isolates were prepared using CTAB method, PCR amplification of 16S ribosomal RNA gene of isolates was carried out using universal primer for bacteria, purification of the PCR product using ethanol precipitation, thereafter sequenced using an automated DNA sequencer. These sequence data were compared with other gene sequences in GenBank database (NCBI) using a BLAST search to find closely related sequences. 80% of the isolates belonged to different species of Pseudomonas, sharing 92% to 96% 16S ribosomal RNA identity with the respective type-strain, whereas the remaining 2 isolates belonged to Pediococcus acidilactici and Lysinibacillus fusiformis with 96% 16S ribosomal RNA homology.
 Alexander, R.M., 1966. Structure and function in the catfish. Journal of Zoology, 148(1), pp.88-152.
 Boyd, C.E., 1985. Chemical budgets for channel catfish ponds. Transactions of the American Fisheries Society, 114(2), pp.291-298.
 Andrews, J.W. and Page, J.W., 1975. The effects of frequency of feeding on culture of catfish. Transactions of the American Fisheries Society, 104(2), pp.317-321.
 Bello, O.S., Olaifa, F.E. and Emikpe, B.O., 2014. Haematological and blood biochemical changes in African catfish, Clarias gariepinus fed walnut (Tetracarpidium conophorum Mull Arg) leaf and onion (Allium cepa Linn) bulb supplemented diets. Journal of Experimental Agriculture International, pp.1593-1603.
 Akinyemi, A.A. and Oyelakin, O.O., 2014. Molecular characterization of bacteria isolates from farm-raised catfish Clarias gariepinus (Burchell, 1822). Microbiology Research Journal International, pp.1345-1352.