Optimal temperature and photoperiod for the spawning of blue crab, Callinectes sapidus, in captivity

Like all poikilotherms, the growth and reproduction of blue crab, Callinectes sapidus depends on temperature and season. Warmer water temperatures in the Chesapeake Bay allow for ovarian development and spawning, while colder water temperatures slow their metabolism and reproduction. The current study aimed to identify optimal environmental conditions for inducing reproduction in animals held in long-term captivity for year round production in aquaculture through environmental manipulations. Temperature and photoperiod were the main environmental factors tested for 25 weeks: 11 degrees C and 21 degrees C, with the following photoperiods: 0L:24D, 8L:16D, 16L:8D and 24L:0D. At 21 degrees C, the females increased spawning frequency, which was arrested at 11 degrees C. Shorter light exposure at 21 degrees C increased spawning frequency, while constant light inhibited and did not produce spawning. Constant dark (0L:24D) at 21 degrees C produced the most (86%) spawns, but yielded poor larval quality. At 21 degrees C with all photoperiod conditions except constant light, the first spawning took 94.8 +/- 32.4 days to occur (n = 17). With females producing multiple spawns, the intervals between the first and second spawns and the second and third spawns were 37.7 +/- 8.7 days (n = 6) and 31.0 +/- 7.1 days (n = 2) respectively. Analysis of our data using response surface methodology (RSM) predicts the following conditions: at 15-19 degrees C and 0-10 hr darkness for maximal survival and at 19-22 degrees C and 0-8 hr darkness for spawning. The number of larvae produced was positively correlated with size (weight) of the female C. sapidus, suggesting the importance of female size in reproduction.