Correlations among flesh and shell yields and morphometric characteristics of Macrobrachium rosenbergii (de Man, 1879) collected from different reservoirs in Sri Lanka.

Abstract

Macrobrachium rosenbergii, generally known as giant freshwater prawn (GFP), is a key crustacean species broadly cultured in the world due to its rapid growth rate, ability to grow in a wide range of salinity levels, high consumer preference and market price. Although GFP culture is at a preliminary stage of development in inland aquaculture of Sri Lanka, their post larvae are regularly stocked in irrigation reservoirs to develop a culture-based fishery. Due to high market value of GFP, it plays an important role in the local economy. Assessing the relationships of flesh and shell yield with morphometric characters of GFP help support stakeholders at the value chain when marketing the product. Therefore, present study was aimed at evaluating the flesh and shell yield of GFP, in relation to their body weight and carapace length, which are the morphometric parameters that can be easily obtained in the field. Variations due to sex, and the size of the inhabitant reservoirs were considered. Three hundred GFP specimens (150 blue claw males and 150 females) were collected from the culture-based fishery harvest at major (>800ha), medium (200-800ha) and minor (<200ha) perennial reservoirs in northcentral and southern provinces. After taking morphometric parameters, specimens were dissected, degutted and flesh and shell parts were weighed separately. Significant correlations between flesh yield (%) and body weight was found in both male (r=-0.3920, p value<0.0001) and female GFP (r=-0.2170, p value=0.0076), but not between the shell yield and body weight. Correlations between flesh yield (%) and carapace length was also ascertained in both male (r=-0.2930, p value=0.0002) and female GFP (r=- 0.1590, p value=0.0051). Of the size categories of GFP caught from reservoirs, strongest relationships were ascertained for both sexes from major perennial reservoirs. Albeit, there was no significant difference (ANOVA: p>0.05) in flesh and shell yield amongst the three reservoir categories. Thus, study concluded that the flesh yield of male and female GFP can be predicted using either body weight or carapace length, which might be useful in processing industry.