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This 97‐day study, conducted during midwinter using a recirculating water system, was designed to evaluate the effect of light intensity and male and female eyestalk ablation on reproduction of P. vannamei and P. stylirostris. Four light intensities were established using various levels of fluorescent lighting (bright, 14.7 μEm‐2s‐1; moderate, 4.4 μEm‐2s‐1; dim, 0.6 μEm‐2s‐1; and dark, 0.0 μEm‐2s‐1) and the fifth consisted of artificial lighting supplemented with natural light through a translucent skylight (skylight, 4.7–9.3 μEm‐2s‐1). Unilateral eyestalk ablation was performed on all male P. vannamei in one of each pair of tanks within a treatment. In addition, half of the females in each tank were unilaterally ablated. Ovarian maturation, spawning, molting rate, and survival were monitored daily within each tank. Growth and gonad development were measured at termination. The optimum light intensity for P. stylirostris appeared to be lower than that for P. vannamei. P. stylirostris matured and spawned more frequently in the skylight and dim treatments than in the moderate, dark, and bright treatments. P. vannamei matured and spawned more frequently in the skylight, bright, and moderate treatments than in the dim and dark treatments. Natural light supplementation beneficially affected reproduction of both species. Male eyestalk ablation increased gonad size and doubled mating frequency of P. vannamei in comparison to unablated controls. This is the first documentation of increased penaeid shrimp reproduction by unilateral eyestalk ablation of males. Even more significant may be recognition that male gonadal development is a limiting factor in reproduction of shrimp in captivity.

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A variety of natural foods have been reported to induce ovarian maturation of penaeid shrimp. In this study, conducted from 19 June to 11 September 1980, four single‐food diets (clams, shrimp, squid, and worms) and one composite diet consisting of all four foods were fed to Penaeus vannamei in 3.7‐m diameter indoor circular tanks. The shrimp, averaging 28 g, were stocked at a rate of 6.9 m‐2 with a 1:1 male to female ratio. Unilateral eyestalk ablation was performed on half of the females in each tank. Tanks received one turnover of water volume daily and the water temperature and salinity averaged 27.0°C and 28.6 ppt, respectively. Daily photoperiod was maintained at 13 hours of light. Ovarian maturation, spawning, molting rate, and survival were monitored daily and growth and gonad size were measured at termination. The composite diet was the best overall diet, while squid was the best single‐food diet, followed by shrimp, worms, and clams. No maturation of unablated females was observed with the exception of one female that developed to stage 3. Although the size of the shrimp was considered marginal for spawning, 5 mated females were observed, but only one (squid treatment) produced viable nauplii. After termination of this study, all shrimp were fed the composite diet for 41 days. During this period, ovarian maturation and spawning occurred in the previously unproductive treatment receiving only clams, and growth rate of shrimp in all previously single‐food treatments increased 4 to 7 fold. The composite diet was also fed to two tanks of P. stylirostris (mean initial weight = 45.4 g) for a period of 118 days. During that time, 50 spawns were obtained with up to 3 spawns per female. A total of 4.3 × 105 P. stylirostris nauplii were produced.