Effects of Water Temperature, Photoperiod, Eyestalk Ablation, and Non-Hormonal Treatments on Spawning of Ovary-Mature Red Swamp Crayfish

Abstract This study evaluated the temperature and photoperiod requirements of spawning in ovary-mature red swamp crayfish Procambarus clarkii and examined the feasibility of inducing spawning in them by inexpensive and practical, nonhormonal treatments. In a spawning induction experiment lasting 20 d, four water temperature gradients (12–14°C, 16–18°C, 20–22°C, 24–26°C) and four photoperiods (completely light [CL], 16 h light: 8 h dark [16L:8D], 12 h light: 12 h dark [12L:12D], and completely dark [CD]) were evaluated. Spawning in ovary-mature red swamp crayfish could be observed in a relatively broad temperature range, from 16°C to 22°C. A period (5–14 d) of low temperature (16–18°C) significantly induced spawning in ovary-mature females (p < 0.01), but hibernation began to occur and spawning could not be observed when the temperature was below 14°C. Spawning occurred in both CD and CL circumstances, but long-period light-groups showed a higher spawning rate—68.9 ± 10.2% (mean ± SD) for CL and 69.6 ± 6.4% for 16L:8D—than that in short-period light-groups—53.3 ± 5.7% for 12L:12D and 33.3 ± 8.3% for CD (p < 0.05). In another spawning induction experiment lasting 3 d, eyestalk interventional stimulating with a high concentration of Na+ combined with a low concentration of Ca2+ induced spawning with a high survival rate (SR = 95.8 ± 7.3% [mean ± SD]) in ovary-mature females. A high concentration of K+ combined with a high concentration of Ca2+ caused no spawning and a high mortality rate (SR = 20.8 ± 19.0% [mean ± SD]). In this study we also observed that water removal or removing from water can be a stimulating factor of inducing fast and synchronous spawning in ovary-mature crayfish, inducing 46 (16.0%) of 288 ovary-mature red swamp crayfish spawned in 10–185 s.