Growth parameters of crayfish Cambarellus montezumae with the use of salix yeast as additives in the diet

The study of C. montezumae is of great significance due to its socio-economic and economic implications. Furthermore, laboratory production of this species is a relatively new issue, and definitive solutions to improve its commercial exploitation have not been established yet. Therefore, the objective of this study was to assess the growth of C. montezumae by incorporating additives in its diet to enhance its laboratory production.

Juvenile crayfish were collected, introduced in a recirculating aquaculture system, and randomly distributed into three treatments: shrimp-balanced food with willow extract, shrimp-balanced food with yeast, and shrimp-balanced food (control). The crayfish were measured and weighed once a week for 77 days to obtain growth parameters. Results revealed that the addition of yeast to the balanced food improved weight, length, biomass, periodic absolute increase for length (PAIL) periodic absolute increase for weight (PAIW), relative growth rate (RGRL) at day 70, and condition factor (K) at day 77. On the other hand, the addition of willow extract to the feed improved K at day 70. Moreover, both additives are suitable for obtaining lower FCF values than conventional foods, which implies the use of low amounts of food and a decrease in costs.

The weight (gr) and the length (mm) of fifteen individuals randomly chosen from each tub were measured weekly to obtain the following growth parameters:

Periodic absolute increase for length (PAIL) and for weight (PAIW):
PAIL= FL-IL and PAIW= FW-IW
where FL= final length, IL= initial length, FW= final weight and IW= initial weight.

Relative growth rate for length (RGRL) and for weight (RGRW):
〖RGR〗_L= (FL-IL)/IL and RGR_W= (FW-IW)/IW

Instantaneous rate of growth (IRG):
IRG= (LnFW-LnIW)/t
Where Ln= natural logarithm and t= time

Specific growth rate (SGR):
SGR=((LnFW-LnIW)/t)*100

Food conversion factor (FCF):
FCF= (food consumed)/((FB-IB) )
where FB= final biomass and IB= initial biomass

Condition factor, (Fulton index):
K=(weight/〖(length)〗^3 )*100