Yolk Sac Damage of Hatched Fry
The yolk sac is a delicate structure and its various tissues are susceptible to damage. Spongiotic and proliferative dermatitis, which presents as multifocal punctate white lesions on the yolk sac surface, can develop after exposure to chemotherapeutics. Connective tissue oedema around the yolk commonly occurs in sac fry during a number of infectious and non-infectious disease episodes. This imparts an opaque to bluish colour change, and hence the term 'blue-sac' disease. Terms such as 'pinched...
General Risk Factors for Infectious Diseases in Intensive Aquaculture and
There has been considerable interest in defining the methods of transmission of infective agents, specifically whether an agent is vertically, congenitally or horizontally transmitted between fish Fig. 12.3 . When vertical or congenital transmission has been identified as a possible route, considerable effort is spent in broodstock and progeny screening to selectively remove carriers. However, in most fish disease outbreaks i.e. rapidly escalating rates of morbidity and mortality , horizontal...
Common Water Chemistry Diseases in Aquaculture Associated with Water
Water chemistry and quality problems in aquaculture are frequently more significant to morbidity and mortality than all infectious disorders combined. Fig. 12.13. Marked abdominal distension due to marked gastric dilation - 'water belly syndrome'. Photo courtesy of Dr D. Groman, Atlantic Veterinary College. Fig. 12.13. Marked abdominal distension due to marked gastric dilation - 'water belly syndrome'. Photo courtesy of Dr D. Groman, Atlantic Veterinary College. With the popularity of water...
Reduced Hatchability of Fertilized Eggs
Successful egg rearing can be markedly inhibited by water quality problems such as gas bubble disease, oxygen deficiency, and high iron levels in inflow water iron precipitates onto the egg surface . Several common management factors can also reduce hatchability, although usually less dramatically than those factors previously cited. For example, Fowler and Banks 1990 noted that iodophor baths, which are commonly used during and after egg hardening to reduce the congenital transmission of viral...