Minimization of precocious sexual phase change during culture of juvenile ornamental shrimps Lysmata seticaudata (Decapoda: Hippolytidae)

Newly settled male phase Lysmata seticaudata (total length (TL) 6.9 ± 0.1 mm) were cultured individually and in groups of 100 or 200 individuals, at 18 and 26 °C, with or without water recirculation (WR). After two months, shrimps were classed as not commercial (NC) (TL < 20 mm) and commercial (TL > 20 mm) (sub-divided in tiny — TL > 20 mm and < 30 mm, and small (S) — TL > 30 mm and < 40 mm) and the presence of simultaneous hermaphrodites (SH) was recorded. Shrimps cultured individually at both temperatures with WR displayed the highest survival (100 ± 0.0%), while those cultured in groups of 200 individuals at 26 °C with no WR displayed the lowest survival (83.8 ± 3.5%). All shrimps cultured individually at 26 °C, with or without WR, reached S size, while those cultured in groups of 200 individuals at 18 °C displayed the lowest percentages of S size shrimps, (3.6 ± 1.1% and 2.6 ± 0.9% for shrimps cultured with and without WR, respectively). The percentage of shrimps changing from male to SH phase was significantly affected by rearing density (p < 0.0001) and water temperature (p < 0.0001), with a significant interaction (p < 0.0001) being detected between these two variables. All shrimps cultured individually at both temperatures (18 °C and 26 °C), with or without WR, remained as males. The highest percentage of sexual phase change, from male to SH, was recorded in shrimps cultured in groups of 100 individuals at 26 °C without WR (36.8 ± 2.8%). Not commercial shrimps at SH phase were only recorded in groups at 26 °C. The absence of sexual phase change in shrimps reared individually at both temperatures with WR (all shrimp shared the same water) and without WR seems to indicate that sexual phase change in L. seticaudata is only triggered if visual and/or tactile interactions are allowed. The occurrence of precocious sexual phase change can be minimized by lower culture temperatures, although this option may decrease growth rates and threaten profitability. The suppression of precocious sexual phase change can be achieved through individual shrimp culture or, if possible, through diet manipulation. However, these approaches may result in higher production costs, since individual shrimp culture is more laborious than communal rearing and grow-out diets specially formulated to prevent ovarian maturation will certainly be more expensive. Nonetheless, commercial viability will be improved by culturing this ornamental shrimp in less time and with higher survival rates.