World Aquaculture 61 ment with 16 females/tank and a 30- days nursery period was significantly different from all other treatments except stocked with 12 and 16 females/ tank and maintained for 40 days. Production in tanks stocked with 12 females and held for a 30day period was significantly greater from that of tanks stocked with 8 females and nursed for a 20-day or a 40-day period, and also greater than production in tanks stocked with 12 females and nursed for 20 days (Table 5). Treatments that had 12 females and were nursed for a 40-day period differed from treatments stocked with 8 and 12 females and nursed for 20 days. Also, tanks stocked with 16 females and had a 40-day nursery period gave different results than tanks stocked with 12 females and nursed for 30-days. Average weight of the 30- day nursery period group was superior to the 20-day period and similar to the 40-day period. Even if the results of survival had been similar to the 20-day period, the 53 percent average weight difference makes the 30-day period a better option as bigger juveniles would have a better survival rate when stocked into a growout tank or pond (Masser and Rouse 1997). Survival ranged between 17.6 and 36.1 percent. Only juveniles in the treatment stocked with 8 females/tank and nursed for 30-days survived better than juveniles in the treatment stocked with 16 females/tank with a 40-day period nursing period. Total juvenile production in tanks stocked with 16 females with a 30-day nursery period was significantly greater than juvenile production in tanks stocked with 8 females with 20-day or 40-day nursery periods and also significantly greater than production in tanks stocked with 12 females with 20-day nursery period (Table 5). There were no significant differences among other treatments. Survival had a tendency to decrease as the number of females stocked in the tank increased whereas total juvenile production tended to increase as stocking density of females increased. These observations were consistent with results of Experiment 2 at similar female stocking densities. A hatchery-nursery facility as the one used for the present study can produce approximately 1,400,000 juveniles/year, which stocked at 4/m2 can fulfill the juvenile needs of approximately 35 ha of farm ponds, and represents US$140,000.00 in sales for the owner of the hatchery. The development of good hatchery protocols and the creation of new profitable hatcheries will allow the current producers to increase their grow-out area and decrease the labor associated with the reproduction-nursery phase. Moreover, utilizing all pond space for grow-out instead of partitioning some for hatchery operations would increase total farm yield by at least 15 percent. Eliminating the need for a reproductionnursery phase would reduce the initial farm size needed for culturing redclaw profitably, previously considered 3.6 ha, and reduce the initial investment, broadening the redclaw Table 4. Juvenile production of redclaw, Cherax quadricarinatus, hatched in tanks and nursed for a 20-day, 30day or 40-day period. Nursery period (days) 20 30 40 Total weight of females (g) 721 713 764 Average weight of females (g) 60.21 60.04 63.28 Total juveniles hatched 5335 5279 5654 Biomass of females (g/m2) 250.35 247.71 265.31 Total Juvenile Production 1354a 1853b 1362a Juveniles/female 119a 159b 119a Juveniles/g/female 1.99a 2.65b 1.93a Biomass (g/m2) 121.53a 263.89b 203.85a Average weight of juveniles (g) 0.270a 0.413b 0.444b Survival % 25.4a 35.1b 24.1a 1Means within the same row with different superscripts are significantly different (P<0.05). Table 5. Juvenile production of redclaw, Cherax quadricarinatus, hatched in tanks from 8, 12 or 16 females and nursed for a 20-day, 30-day or 40-day period. Females Nursery Production Average Survival (%) period (days) weight (g) 8 20 1180a 0.31a,b,c 30.4 12 20 1393a 0.21a,b,c 26.0 16 20 1489a,b 0.29b,c 19.5 8 30 1445a,b 0.38a,b,c 36.1 12 30 1846a,b 0.45a,c 34.5 16 30 2269b 0.40a,b,c 30.9 8 40 1169a 0.45a,c 29.2 12 40 1427a,b 0.51a 26.4 16 40 1492a,b 0.37a,b,c 17.6 1Means within the same column with different superscripts are significantly different (P<0.05). industry to a larger spectrum of investors. Furthermore, this would allow small pond owners whose facilities were previously considered inadequate due to lack of the required pond area, to venture into redclaw aquaculture. Notes 1Administrator of the international outreach and education program at Auburn University department of Fisheries and Allied Aquaculture, Alabama, USA. 2Technical assistant at AGY Redclaw Hatchery and Farm of Megar S.A. de C.V. in Soto La Marina, Tamaulipas, Mexico 3Aquaculture lab manager at the biology department of the American University of Beirut. 4Associate professor of aquaculture at the American University of Beirut, Lebanon.
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