The effects of temperature on the growth, survival and biomass of different families of juvenile Penaeus japonicus Bate

Variation in the growth, survival and change in total biomass (termed biomass increase) of different families of juvenile Penaeus japonicus was investigated over a range of temperatures in controlled laboratory experiments. In the first experiment, the effects of temperature on six families of juveniles were examined over a broad range of temperatures (24 to 30 degreesC). In the second experiment, the effects of temperature on six more families of juveniles were examined over a narrower range of temperatures (27.5 to 31.2 degreesC). Over the broad temperature range, mean growth and biomass increase were highest at 27 degreesC and mean survival was highest at 24 degreesC. Mean growth was lowest at 24 degreesC, whilst survival and biomass increase were lowest at 30 degreesC. However, there was a significant interaction between family and temperature, with some families tolerating a broader range of temperatures than others. As a result, the ranking of families in relation to growth, survival and biomass increase changed at each temperature. This effect was more pronounced for survival than for growth. Over the narrower range, temperature significantly affected growth, survival and biomass increase, but there was no significant interaction between family and temperature. Growth, survival and biomass increase were significantly lower at 31.2 than at 27.5 and 29.2 degreesC. These results suggest that if grow-out conditions for P. japonicus vary by more than a few degrees, interactions between family and temperature could affect the efficiency of selection. The results also suggest that the family x temperature interaction may have a more pronounced effect on survival than on growth. Crown Copyright (C) 2002 Published by Elsevier Science B.V. All rights reserved

The effects of density on the growth and survival of different families of juvenile Penaeus japonicus Bate

Variations in the growth and survival of six families of juvenile (initial mean weight = 4.16 g) Penaeus japonicus were examined at two densities (48 and 144 individuals m(-2)) in a controlled laboratory experiment. Survival was very high throughout the experiment (95.4%), but differed significantly between densities and rearing tanks. Family, sex and family x density interaction did not significantly affect survival. Mean specific growth rate (SGR) of the shrimp was 18% faster at the low density (1.93 +/- 0.05% day(-1)) than at high density (1.64 +/- 0.03% day(-1)). However, there was a small but significant interaction between family and density indicating that growth of the families was not consistent at both densities. The inconsistent growth of the families across the two densities resulted in a change in the relative performance (ranking) of families at each density. Sex, rearing tank and rearing cage also affected growth of the shrimp. Mean SGR of the females (1.79 +/- 0.03% day(-1)) was 5% faster than males (1.70 +/- 0.03% day(-1)) when averaged across both densities. Shrimp grew significantly faster in rearing tank 3 than rearing tank 1 or 2 at both densities. Results of the present study suggest that family x density interaction could affect the efficiency of selection for growth if shrimp stocks produced from shrimp breeding programs are to be grown across a wide range of densities. Crown Copyright (C) 2004 Published by Elsevier B.V. All rights reserved

Reproductive dynamics of endeavour prawns, Metapenaeus endeavouri and M-ensis, in Albatross Bay, Gulf of Carpentaria, Australia

The spawning patterns of two penaeid prawns, Metapenaeus endeavouri (Schmitt) and M. ensis (De Haan), were examined from data collected at 45 stations between March 1986 and March 1992. An index of population fecundity based on the abundance, proportion and fecundity of sexually mature females was used as a measure of spawning output of the prawn stock. The population fecundity index for M. ensis was higher than that for M. endeavouri. The monthly population fecundity index for M. endeavouri varied markedly among years, while that for M. ensis was consistent among years. Spawning of M. endeavouri occurred year-round, while that of M. ensis was concentrated mainly in spring (September to November). For M. endeavouri, a minor spawning, derived from a relatively small number of summer spawners, occurred in the 20 to 30 m offshore waters in summer. In early summer (after May), the major spawning group consisted of large females from the winter-spawning cohort, and the spawning area shifted to depths of 30 to 60 m. In winter (July), the major spawning, derived from the winter-spawning cohort, occurred at depths of 20 to 40 m. For M. ensis, the major spawning, derived from the spring-spawning cohort, was observed in depths 40 m) by May and July, respectively, and return to shallow waters

Parentage determination of Kuruma prawn shrimp Penaeus (Marsupenaeus) japonicus using microsatellite markers

The application of microsatellite markers for parentage determination is gaining both acceptance and popularity in aquaculture. In this study we used simulations and controlled matings to examine the potential of microsatellite markers in assigning parentage to Kuruma shrimp (Penaeus japonicus) progeny. Simulations based on allele frequency data from a captive population of P. japonicus demonstrated that at least five loci would be required to assign progeny to their correct maternal parent (with 95% confidence) when drawn from a breeding population of 30 dams and 150 putative sires. Based on this information, nauplii from 22 matings where maternal parents were known were typed at six microsatellite loci and subjected to parentage analysis. Assignment success of progeny to their “true” mother was lower than predicted by the simulations, with only 47% of progeny assigned correctly. Null alleles and allelic dropout resulting from poor quality DNA contributed to this disparity. The benefits of DNA parentage analysis as a tool to retain pedigree information in shrimp selective breeding programs are discussed

Response to selection and heritability for growth in the Khuruma prawn, Penaeus japonicus

Divergent selection for High (H) and Low (L) growth was carried out for a single generation with the aim of measuring response to selection and heritability of growth in Penaeus japonicus H and L growth (weight at 6 months of age) parents were selected from a commercial prawn pond which had been stocked with post-larvae from wild caught broodstock. Offspring of H x H, L x L and reciprocally mated (H x L, L x H) parents were reared and grown out in laboratory tanks. The direct response to one generation of selection averaged 107%, being 8.3% for high growth and 13.1% for low growth. Responses at other ages averaged 5.7, 69 and 7.9% at 3, 4 and 5 months, respectively The average realised heritability for weight at 6 months of age was 23 4% which did not differ significantly from the estimate from the regression of offspring on mid parent of 27.7% It was concluded that the heritability of growth in P. japonicus is moderate but that rates of response to selection will be high largely due to the high levels of natural variation

Application of DNA parentage analyses for determining relative growth rates of Penaeus japonicus families reared in commercial ponds

The ability to track large numbers of individuals and families is a key determinant of the power and precision of breeding programs, including the capacity to quantify interactions between genotypes and their environment. Until recently, most family based selective breeding programs for shrimp, and other highly fecund aquaculture species, have been restricted by the number of animals that can be physically tagged and individually selected. Advances in the development of molecular markers, such as microsatellite loci, are now providing the means to track large numbers of individuals and families in commercial production systems. In this study microsatellites, coupled with DNA parentage analyses, were used to determine the relative performance of 22 families of R japonicus reared in commercial production ponds. In the experimental design 6000 post-larvae from each of 22 families, whose maternal parents had been genotyped at 8 microsatellite loci, were stocked into each of four I ha ponds. After 6 months the ponds were harvested and a total of 6000 individuals were randomly weighed from each pond. Mean wet weight of the shrimp from one pond was significantly lower than that of the other three ponds demonstrating a possible pond effect on growth rate. The representation of families in the top 10% of each pond's weight distribution was then determined by randomly genotyping up to 300 individuals from this upper weight class. Parentage analyses based on individual genotypic data demonstrated that some families were over-represented in the top 10% in all ponds, while others were under-represented due to slower growth rates. The results also revealed some weak, but significant, male genotype x environment (G x E) interactions in the expression of shrimp growth for some families. This indicates that G x E effects may need to be factored into future R japonicus selective breeding programs. This study demonstrated the utility of DNA parentage analyses for tracking individual family performance in communally stocked shrimp pond populations and, its application to examining G x E effects on trait expression under commercial culture conditions. Crown Copyright (c) 2005 Published by Elsevier B.V. All rights reserved

Developing techniques for enhancing prawn fisheries, with a focus on brown tiger prawns (Penaeus esculentus) in Exmouth Gulf. Final Report to FRDC for project FRDC 1999/222.

This project has been successful in developing new approaches for the production of juvenile prawns at high densities (> 2,000 prawns.m-3) at both experimental and semi-commercial scales in Exmouth Gulf. This new production technology could lead to a 3 phase approach to the production of prawns: hatchery, nursery and grow-out. Surveys of benthic habitats and juvenile prawns and their predators, combined with information from fishery independent surveys, identified seagrass beds in the southern and south-eastern Exmouth Gulf as the best potential release sites for juvenile prawns. These surveys also found that the extensive loss of seagrass following Cyclone Vance is likely to have led to very low catches in the tiger prawn fishery and future work will investigate estimating the extent of the seagrass nursery habitat for inclusion as an environmental variable in evaluating stock recruitment relationships. Eight reliable microsatellite markers have now been developed for P. esculentus and tested to determine their effectiveness for identifying released (“domesticated”) from wild prawns using new statistical methods. Results showed that these eight loci alone would not enable reliable discrimination between released and wild prawns unless the identity of the released-stock’s fathers could be determined. This could be achieved in a cost-effective manner if the fathers’ genotypes could be deduced by genotyping a single mixed batch of larvae from each spawning, given the maternal genotypes. The results from the bio-economic model show that enhancement is only “profitable” about 50% of the time (excluding capital costs and depreciation), but highlighted that little is known of the values for density-dependent mortality and mortality due to harvest, transport and immediately after release

The influence of water renewal rates on the reproductive and molting cycles of penaeus paulensis in captivity

The present study analyzed the reproduction of wild-caught Penaeus paulensis in relation to its molt cycle. The experimental design consisted of two treatments (continuous water flow and batch renewal) with two replicates. The stocking density in experimental tanks (1.50 x 0.96m) was approximately 7 animals/m2, resulting in 4 males (23.9 2.3 g) and 6 females (52.0 5.5 g) per tank. Shrimp had their uropods cut for individual marking and femalematuration was induced through the unilateral eyestalk-ablation. The intermolt period of females and males (17.4 3.2 and 17.8 4.6 days, respectively), number of days between molting and the first spawn (6.9 2.8 days) andnumber of spawns in the intermolt period (1.4 0.5), presented no significant differences (P>0.05) between treatments. No influences on molt cycle or reproductive performance parameters could be related to differences in water quality parameters, especially nitrogenous compounds, suggesting a trend towards reduce water exchange in shrimp maturation. However, a relative decrease in the number of eggs per spawn was observed. This possibly wasdue to the smaller maturation tanks. The results of P. paulensis molt cycle could be useful for accompaniment and better planning of the reproduction in captivity.O presente estudo foi proposto para analisar a reprodução de um estoque selvagem de Penaeus paulensis em relação ao seu ciclo de mudas. O desenho experimental foi composto por dois tratamentos em duplicata (fluxo contínuo e com renovação). A densidade de estocagem nos tanques experimentais (1,50 x 0,96m) foi de aproximadamente 7 camarões/m2, resultando em 4 machos (23,9 2,3 g) e 6 fêmeas (52,0 5,5 g) portanque. Os camarões tiveram seus urópodos cortados para marcação individual e a maturação das fêmeas foi induzida por ablação unilateral do pedúnculo ocular. O período intermuda de fêmeas e machos (17,4 3,2 e 17,8 4,6 dias, respectivamente), número de dias entre a muda e primeira desova (6,9 2,8 dias) e número de desovas no período intermuda (1,4 0,5), não apresentaram diferenças significativas (P>0,05) entre os tratamentos. Nenhuma influência no ciclo de muda ou nos parâmetros de performancereprodutiva foram relacionadas a diferenças naqualidade de água, principalmente no que se refereaos compostos nitrogenados, sugerindo uma redução nas taxas de renovação de água em sistemas de maturação. Contudo, uma diminuição no número de ovos por desova foi observado. Este fato parece estar associado as pequenas dimensões dos tanques utilizados. Os resultados do ciclo de muda de P. paulensis podem ser úteis para oacompanhamento e melhor planejamento da reprodução desta espécie em cativeiro