Clive M. Jones

Production of juvenile redclaw crayfish, Cherax quadricarinatus (von Martens) (Decapoda, Parastacidae) I. Development of hatchery and nursery procedures

Abstract Procedures were developed for the controlled production of juvenile redclaw crayfish, Cherax quadricarinatus in tanks over two seasons. These included broodstock handling methods and involved the definition of an in vivo ovary staging technique which permitted recognition of immature, maturing and mature females. Hatchery techniques were also defined which demonstrated that male:female ratios of up to 1:4 were equivalent for successful mating and spawning. Up to 97% of females spawned and carried eggs through to hatching when held in tanks at between 24.5 and 27.6 °C mean daily temperature and exposed to 14:10 hours light:dark day length. A sequential series of seven egg stages was defined from egg release through to hatching, based on morphological characteristics. The mean duration of each stage was measured and cumulative statistics calculated, indicating a mean incubatory period of 72.1 days (range 47 to 84) and 66.3 days (56 to 71), respectively, for the two hatchery runs. An exponential function was calculated which defines the relationship of fecundity and female size and which indicates that fecundity ranges from approximately 200 to 1000 eggs per female. Nursery procedures were developed which indicate difficulties with using the floating water plant Pistia as juvenile habitat, and the benefits of using artificial shelters. Newly hatched juveniles stocked at between 980 and 1842 m 2 , and fed a combination of formulated flake food and fresh zooplankton, survived well (mean 52%) and increased in size by between 500 and 900% over 28 to 50 days. The research demonstrates that C. quadricarinatus can be easily bred in captivity and juveniles reared successfully with relatively simple facilities and techniques.

Assessment of stocking size and density in the production of redclaw crayfish, Cherax quadricarinatus (von Martens) (Decapoda: Parastacidae), cultured under earthen pond conditions

Abstract Redclaw crayfish, Cherax quadricarinatus (von Martens) (Decapoda: Parastacidae),were cultured for 140 days within 24 net pens in a 0.2-ha earthen pond at densities of 3, 9 and 15 m−2, with mean stocking sizes of either 4.71 g or 16.89 g. Crayfish were fed a formulated supplemental pellet diet. An economic evaluation accounted for price paid per individual at stocking, value of the individual at harvest, and amount of food fed. There was no significant effect of density or stocking size on survival that ranged from 76.6% to 87.5%. As density increased, significant decreases in mean harvest size and specific growth rate occurred for both stocking sizes. Mean food quotients (FQs), yields, and economic returns significantly increased as stocking size and density increased, with large-stocked animals at 15 m−2 having the highest FQ, yield and economic return. This experiment shows that when stocking with well-advanced juveniles at densities between 9 and 15 m−2, yields in excess of 5 t ha are achievable in 140 days of culture.

Production of juvenile redclaw crayfish, Cherax quadricarinatus (von Martens) (Decapoda, Parastacidae) II. Juvenile nutrition and habitat

Newly hatched redclaw crayfish Cherax quadricarinatus were reared for 39 days in aquaria using various combinations of food and habitat. Food treatments were fresh zooplankton and a high protein formulated flake diet. Habitat treatments involved the presence/absence of a floating aquatic macrophyte, Pistia stratiodes. Both survival and growth of juveniles were significantly influenced by the type of food and habitat. Fresh zooplankton produced the best growth. An interactive effect between food type and Pistia resulted in differential survival. Use of aquatic macrophytes for habitat in intensive juvenile production systems is not recommended.

PRODUCTION OF JUVENILE REDCLAW CRAYFISH, CHERAX QUADRICARINATUS (VON MARTENS) (DECAPODA, PARASTACIDAE) III. MANAGED POND PRODUCTION TRIALS

Abstract Commercial-scale production of juvenile redclaw crayfish was conducted in earthen ponds. Based upon the results of previous experimental studies in tanks and aquaria, earthen ponds (1300 and 2600 m2) were furnished with juvenile crayfish shelters, and were prepared and managed to maximise availability of zooplankton. Juvenile redclaw were introduced by stocking ponds with egg-bearing females. Stocking density, as expressed by number of fertile eggs introduced, ranged from 74 to 326/ m2. Ponds were harvested after culture periods ranging from 45 to 62 days. Juvenile number at harvest ranged from around 6000 to over 36 000, representing a mean of 63.2 juveniles per maternal survivor. Mean size at harvest ranged from 0.31 to 1.00 g, representing growth of 9.7 to 36.9 mg/day. Results suggest that managed pond production of juvenile redclaw is commercially viable at the production rates achieved, and that a considerable increase in productivity is possible with increased availability of shelter and improved zooplankton management techniques.

Effect of density on growth and survival of ornate rock lobster, Panulirus ornatus (Fabricius, 1798), in a flow-through raceway system

Juvenile ornate rock lobsters (Panulirus ornatus) (3.240.09 g; 13.80.13 mm CL) captured from the wild were stocked at three densities (14, 29, and 43 m–2) within each of four 4000-L fibreglass raceway tanks with flow-through seawater supply. Lobsters were provided with shelters consisting of opaque polyethylene platforms, 600 mm × 600 mm, supported on six 100-mm legs and were fed continually through the night with a commercial penaeid prawn (P. japonicus) pellet supplemented with prawn flesh once per day. Growth and survival were monitored by means of a monthly sample of 20 lobsters from each experimental unit. After 272 days, density treatments did not differ significantly in survival, which averaged 52.5% (2.8). Lobster size was also unaffected by density, and mean size for all lobsters was 225.34.68 g (61.84.7 mm CL) at harvest. Mortality was consistent through time and was almost entirely attributable to cannibalism of postmoult individuals. The cannibalism may have been due to inappropriate shelter and feeding strategy. Despite higher mortality than anticipated, growth was rapid, representing a specific growth rate of 1.56% day–1, sufficient to permit growth from 3 g to 1 kg within 18 months. The experiment confirmed the excellent potential of P. ornatus for commercial aquaculture.

Advances in the culture of lobsters.

Commercial aquaculture of marine lobsters is an attractive proposition, as most species are high value with established market demand, and fishery production is static or diminishing. Nevertheless, achievement of commercial success will necessitate resolution of technical difficulties associated with on-growing of aggressive species (clawed lobsters) or with rearing the larvae, which for spiny and slipper lobsters is generally a painstaking and protracted process. Notwithstanding these technical challenges, increasing market demand for the product is driving a substantial research and development effort around the world to develop commercial lobster farming technology. This chapter reports on the status of that effort, the successes and obstacles.

Reproductive cues in Panulirus ornatus

Abstract Two experiments were performed to assess the effect of photoperiod and temperature on spawning of Panulirus ornatus. In experiment 1, sexually mature lobsters taken from the wild during summer were held at one of two photoperiods, winter (13 Light: 11 Dark) and summer (14.5 Light:9.5 Dark). Additionally, lobsters were also exposed to either summer (29°C) or winter (24°C) average water temperatures. Spawning was significantly greater when animals were exposed to summer photoperiod than to winter photoperiod, irrespective of temperature. Although a higher percentage of lobsters spawned when placed under a higher temperature, this trend was not statistically significant. In experiment 2, sexually mature lobsters were taken from the wild during winter and exposed to the same two photoperiods as in experiment 1, at a summer equivalent temperature of 29°C. Breeding started earlier and was more successful at the summer photoperiod. Time to first breeding was 17 weeks after exposure to summer photoperiod, compared with less than 1 week in experiment 1, and did not occur until individuals had moulted. Moulting occurred in 81% of lobsters, primarily after an increase in temperature to 29°C. The time between moulting and mating was varied and there was no significant difference in moult frequency between the two experimental photoperiods. After the lobsters had moulted, breeding success was reached earlier if photoperiod was lengthened. Results suggest photoperiod is the primary cue for the onset of gonad maturity and mating activity, with temperature playing a less important role. Physiological rest and possibly a moult may be required between breeding seasons before spawning can occur. Furthermore, temperature may be an important cue for pre‐reproduction moulting.

Oceanographic Currents and Local Ecological Knowledge Indicate, and Genetics Does Not Refute, a Contemporary Pattern of Larval Dispersal for The Ornate Spiny Lobster, Panulirus ornatus in the South-East Asian Archipelago

Here we utilize a combination of genetic data, oceanographic data, and local ecological knowledge to assess connectivity patterns of the ornate spiny lobster Panulirus ornatus (Fabricius, 1798) in the South-East Asian archipelago from Vietnam to Australia. Partial mitochondrial DNA control region and 10 polymorphic microsatellites did not detect genetic structure of 216 wild P. ornatus samples from Australia, Indonesia and Vietnam. Analyses show no evidence for genetic differentiation among populations (mtDNA control region sequences ΦST = -0.008; microsatellite loci FST = 0.003). A lack of evidence for regional or localized mtDNA haplotype clusters, or geographic clusters of microsatellite genotypes, reveals a pattern of high gene flow in P. ornatus throughout the South-East Asian Archipelago. This lack of genetic structure may be due to the oceanography-driven connectivity of the pelagic lobster larvae between spawning grounds in Papua New Guinea, the Philippines and, possibly, Indonesia. The connectivity cycle necessitates three generations. The lack of genetic structure of P. ornatus population in the South-East Asian archipelago has important implications for the sustainable management of this lobster in that the species within the region needs to be managed as one genetic stock.

Chemical Communication and Aquaculture of Decapod Crustaceans: Needs, Problems, and Possible Solutions

Chemical communication has received very little attention in the field of crustacean aquaculture research. It has been investigated mainly with regard to the extent that chemical cues might be involved in social control of growth, which results in growth suppression and size variation among individuals under culture conditions, but no consistent conclusion has emerged that stimulated further development and application of solutions based on this knowledge. Implementation of knowledge on chemical communication in crustacean aquaculture has not gone further than some preliminary trials of the incorporation of pheromones as feeding attractants or of their use to facilitate trapping. In this review we attempted to identify those aquaculture procedures in which knowledge of chemical communication might be implemented, to indicate possible uses and to suggest possible solutions related to various aquacultured crustaceans. In most cases solutions based on chemical communication could probably be integrated into current culture techniques and would serve to enhance their efficiency. To achieve this aim, pheromones and potent chemical components that mediate behavioral and physiological processes relevant to aquaculture should be identified and synthetic versions and technical means for their efficient application should be developed.