Effects of Gender and Size on Feed Acquisition in the Pacific White Shrimp Litopenaeus vannamei

Abstract

Pacific white shrimp, Litopenaeus vannamei, are sexually dimorphic for growth, where subadult and adult females typically are larger than males of the same age. This character may be attributed to physiological and/or behavioral differences between the sexes. To determine if growth differences are the result of a more aggressive feeding behavior by females, four concurrent feeding trials were conducted to study the effects of gender and size on feed acquisition time. Feeding trials consisted of tanks (three replicate tanks per trial) stocked with (1) all females with small‐ and large‐size groups, (2) all males with small‐ and large‐size groups, (3) a random selection of males and females (resulting in larger females than males), and (4) males and females of equal size. Depending on the trial, tanks were stocked with either an equal number of males and females or small and large shrimp. Shrimp were fed a limited ration of squid, and the total feeding time (TFT) of shrimp between groups within a tank was compared. Results show that both gender and size are important factors in TFT as large shrimp out‐competed small shrimp in both all‐female and all‐male feeding trials. Gender is more important than size as males out‐competed females for feed even when they were smaller than competing females. These results suggest that sexual growth dimorphism is not the result of more aggressive feeding by females. In fact, males have a competitive advantage over females in acquiring feed. These results are counterintuitive because females typically are larger than males. Additional research is needed to investigate the physiological basis for sexual growth dimorphism in this commercially important shrimp.

Effects of androgenic gland ablation on growth, sexual characters and spermatogenesis of the white shrimp,Litopenaeus vannamei(Decapoda: Penaeidae) males

“…In L. vannamei , a previous study (Pérez‐Rostro, Ramírez & Ibarra ) indicated that after 160 days of culture, the growth rate was significantly different between females (18.09 g) and males (16.96 g). Complementarily, Pérez‐Rostro and Ibarra () observed that the weight for growth divergence between sexes is affected by the environment, and Moss and Moss () reported that sexual dimorphism for growth in L. vannamei is not the result of feeding behaviour, suggesting a physiological advantage.…”

The importance of behaviour in improving the production of shrimp in aquaculture

“…; Vega‐Villasante et al . ; Moss & Moss ; Table ). This cyclic behaviour of nonfeeding is termed ‘physiologic fast’ and may be caused by nonfunctionality of some structures such as the mouth, oesophagus or stomach when an individual sheds the exoskeleton (Vega‐Villasante et al .…”

“…; Campos‐Ramos et al . ; Moss & Moss ; Gopal et al . ) due to a greater gain in mass per moult cycle (Hansford & Hewitt ).…”

“…) and L. vannamei (Moss et al . ; Moss & Moss ) suggest that female monosex cultures grow faster than mixed‐sex cultures or male monosex cultures. However, there are very few studies in penaeids that relate variation in behaviour to sexual differences.…”

“…However, there are very few studies in penaeids that relate variation in behaviour to sexual differences. Moss and Moss () observed that L. vannamei males were more active swimmers than females, which normally spent most time on the bottom of tanks. Moreover, males presented more aggressive behaviours than females when competing for food.…”