Abstract
The high mortality of maternally incubated eggs represents a serious problem that prevents the development of noble crayfish (Astacus astacus) farming in Italy. In this experiment, formaldehyde bath technique has been tested with maternally incubating females. The survival rate of maternally incubated eggs, exposed to progressively reduced concentrations of formaldehyde (4000, 3000, 2000, 1000, 1500 and 500 mg l−1), has been compared with that of untreated controls for two consecutive years (2010 and 2011). The formaldehyde treatments were administered as disinfection baths, for a period of 15 min, twice a week. A concentration of formaldehyde of 500 mg 1−1, or greater, was found to be effective in controlling egg mortality, without apparent harming the female broods.
Highlights
In Italy, crayfish farming is principally based on a few extensive family managed farms (Quaglio et al 2008)
Dead eggs can be invaded by aquatic fungi, e.g., Saprolegnia sp. and other oomycetes, which often spread to the surrounding eggs, and may result in 100% mortality in the worst cases (Edgerton et al 2002; Kouba et al 2013)
The effect of disinfection in 2010 was clearly positive, and the difference between the disinfected groups and the control was significant (Fig. 1), there were no differences between the three formaldehyde concentration treatments at the end of the experiment (Table 1)
Summary
In Italy, crayfish farming is principally based on a few extensive family managed farms (Quaglio et al 2008). The main problem of crayfish rearing in Italy is the high incidence of aquatic mycosis during egg incubation, which has two main consequences: the hampering of the diffusion of crayfish farming and the increasing environmental impact of crayfish farms. Other oomycetes, which often spread to the surrounding eggs, and may result in 100% mortality in the worst cases (Edgerton et al 2002; Kouba et al 2013) The diffusion of this mycosis takes on an important ecological relevance as the disinfectants used in rearing conditions can contaminate output waters and the farms can become direct vectors of disease in natural ecosystems. This fungal disease is usually controlled by manually removing dead
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