Observations of marks on channel catfish Ictalurus punctatus held for varying lengths of time in experimental ponds and on fish submitted for disease analysis suggested that aggressive biting among ...channel catfish may sometimes occur at relatively high rates in culture ponds. Studies in experimental pools indicated that larger fish sustained an average of 4 bites per fish while smaller fish sustained less than 1 bite per fish. Unfed catfish sustained an average of 12 bites per fish while fed fish sustained 7 bites per fish. No differences in the level of aggression were observed between genders. Mortality rates, apparently due to biting, ranged from 0% to 40% during the 2–4 week periods. Biting and subsequent infection of the wounds may contribute to the unexplained losses observed by producers.
This paper presents results of investigating the occurrence of spontaneous triploidy and tetraploidy in carp (Cyprinus carpio L.). The samples were taken from a fish farm and were 20-50 g of weight. ...Cytological tests were carried out, using leucocyte and "squash" techniques. The following was determined: -Chromosome number, both in the leucocytes and in the renal cells is 98. -Out of that, 54 are meta to submetacentric and 44 are subtelo to telocentric, with 152 chromosome arms. -The determined facts about the number of chromosomes and their arms do not coincide with results obtained by other researchers. -A triploid (147) and a tetraploid chromosome number (196) were discovered too. -On the basis of the determined triploid (147) and tetraploid (196) chromosome numbers, the conclusion is drawn that 98 is a diploid chromosome number, and not triploid, as had been assumed in some previous works.
