Nigel P. Preston

Integrated treatment of shrimp effluent by sedimentation, oyster filtration and macroalgal absorption: a laboratory scale study

Effluent water from shrimp ponds typically contains elevated concentrations of dissolved nutrients and suspended particulates compared to influent water. Attempts to improve effluent water quality using filter feeding bivalves and macroalgae to reduce nutrients have previously been hampered by the high concentration of clay particles typically found in untreated pond effluent. These particles inhibit feeding in bivalves and reduce photosynthesis in macroalgae by increasing effluent turbidity. In a small-scale laboratory study, the effectiveness of a three-stage effluent treatment system was investigated. In the first stage, reduction in particle concentration occurred through natural sedimentation. In the second stage, filtration by the Sydney rock oyster, . Saccostrea commercialis Iredale and Roughley , further reduced the concentration of suspended particulates, including inorganic particles, phytoplankton, bacteria, and their associated nutrients. .

Nitrogen budget and effluent nitrogen components at an intensive shrimp farm

This study examined the operation of an intensive tropical shrimp farm in relation to the nitrogen (N) budget and the N components of the discharged effluent. Weekly samples were taken for total N (TN) concentration from the farm intake and discharge water over a 10-month period. A N budget was calculated based on TN data, continuous datalogger records of water exchange volumes, and farm records for feed addition, harvest and sediment removal. TN levels in the intake water were low throughout the 10 months and only contributed 5% of the N input to the farm. Most of the N (90%) entered the farm ponds as formulated shrimp food. Within the ponds, 22% of the input N was converted to harvested shrimp, 14% remained in the sediment, while most of the remainder (57%) was discharged to the environment. Only 3% of input N was unaccounted for, and assumed to be lost to the atmosphere via denitrification or volatilization of ammonia. More intensive sampling of effluent (three times a day) was done over 7-day periods in February (late summer) and July-August (winter) to provide detailed information on the N composition. All parameters varied substantially both within and between days. Forty-two to forty-five percent of the discharged N was in particulate form, mostly phytoplankton. The dissolved N fraction had two main components: dissolved organic N (DON), which comprised 37-43% of TN, and total ammonia N (TAN), which comprised 12-21% of TN. Comparison between the results of this and previous studies suggests that little progress has been made in improving nitrogen utilization efficiency of intensive Penaeus monodon shrimp farming over the past decade. Thus a major challenge facing this industry is to improve both environmental and economic performance by developing and implementing an integrated approach to reducing nitrogen waste.

The development and application of genetic markers for the Kuruma prawn Penaeus japonicus

Microsatellite and Amplified Fragment Length Polymorphism (AFLP) DNA markers have been characterised for use in establishing pedigrees, linkage mapping and identifying Quantitative Trait Loci (QTL) influencing commercially important traits in P. japonicus. Low efficiency of Microsatellite characterisation from P. japonicus genomic DNA, due to the high frequency and extended length of simple sequence repeats, make these DNA markers unsuitable for linkage mapping studies. Unique sequence flanking repeats necessary for PCR primer design were difficult to obtain due the extended lengths of the repeats. Microsatellites that were characterised displayed between 4-24 alleles and heterozygosities between 47-91% in unrelated animals. No P. japonicus derived microsatellite successfully amplified sequences in P. monodon, P. esculentus or P. stylirostris. AFLPs were developed as an alternative to microsatellites. Over 570 polymorphic loci were defined using different primer combinations. AFLPs are robust with some polymorphisms conserved across families. PCR amplification and sequencing of excised bands allowed development of Sequence Tagged Sites from AFLPs. A primary linkage map based on a three generation pedigree, genotyped at 246 AFLP loci has been constructed. It incorporates 129 markers in 44 linkage groups with an estimated genome coverage of approximately 57%.

Genetic mapping of the kuruma prawn Penaeus japonicus using AFLP markers

Abstract Amplified fragment length polymorphism (AFLP) analysis is a rapid, efficient technique for detecting large numbers of DNA markers for linkage analysis. We have used AFLP markers in a two-way pseudo-testcross strategy to generate genetic maps of a Penaeus japonicus family. A two-stage selective genetic mapping strategy was applied in this study. The initial stage involved the linkage mapping on 46 progeny from two tails (top and bottom 6%) of the size distribution of an intermediate cross family (F1 from HH×LL and F2 from HL×LH) using 54 pairs of AFLP primer combinations. The second stage of linkage mapping involved genotyping an additional 56 progeny (top and bottom 8%) of the same family with the same 54 primer combinations based on the framework map from the first stage. Of 535 polymorphic fragments scored in 46 progeny of the first stage, 355 segregated in a 1:1 ratio, corresponding to DNA polymorphisms heterozygous in one parent and null in the other. The other 154 markers followed a 3:1 Mendelian segregation ratio. Of 502 bands scored in 56 progeny of the second stage, 359 segregated in a 1:1 ratio and 138 in a 3:1 ratio. When the markers with a 1:1 segregating ratio were combined from both stages (401 in total), 217 markers were ordered into 43 linkage groups (1780 cM) of the paternal map and 125 markers in 31 linkage groups (1026 cM) of the maternal map. The average density of markers was approximately 1 per 10 cM. To investigate the homologies between two parental maps, we included 182 markers segregating 3:1 in the analysis. One homologous linkage group was recognised. The sex marker initially mapped on the maternal parent map was also confirmed in the second-stage mapping with more progeny information. The linkage data developed in these maps will be used to detect loci controlling commercially important traits.

A synthesis of dominant ecological processes in intensive shrimp ponds and adjacent coastal environments in NE Australia

One of the key environmental concerns about shrimp farming is the discharge of waters with high levels of nutrients and suspended solids into adjacent waterways. In this paper we synthesize the results of our multidisciplinary research linking ecological processes in intensive shrimp ponds with their downstream impacts in tidal, mangrove-lined creeks. The incorporation of process measurements and bioindicators, in addition to water quality measurements, improved our understanding of the effect of shrimp farm discharges on the ecological health of the receiving water bodies. Changes in water quality parameters were an oversimplification of the ecological effects of water discharges, and use of key measures including primary production rates, phytoplankton responses to nutrients, community shifts in zooplankton and delta15N ratios in marine plants have the potential to provide more integrated and robust measures. Ultimately, reduction in nutrient discharges is most likely to ensure the future sustainability of the industry.

Managing the development of sustainable shrimp farming in Australia: the role of sedimentation ponds in treatment of farm discharge water

Abstract In Australia, the shrimp farming industry operates within strict environmental guidelines applied at national and state government levels. In this paper, we briefly review the current status of the development of an ecologically sustainable shrimp farming industry in Australia and the future research priorities to assist in maintaining sustainable development. The broad objectives of the current regulations governing shrimp aquaculture in Australia are to achieve appropriately sited and operated facilities. However, there are differences amongst the various jurisdictions, and these need to be reconciled. Currently, shrimp farm discharge regulations are based on permissible characteristics of discharge water quality. These parameters are highly variable over short time frames, and this presents a significant barrier to the development of cost-effective sampling strategies that accurately reflect trends in farm discharges. Furthermore, water quality parameters may provide little information about the effect of discharges on the ecology of the receiving waters. We describe more sophisticated indicators of the potential impacts of shrimp pond discharges, including the δ 15 N-nitrogen isotopic ratios in marine plants, which integrate the high variability in water quality parameters. In many shrimp-farming countries, including Australia, there is an increasing trend towards the use of sedimentation ponds (=settling ponds, settling basins) for treating pond effluent prior to discharge or recirculation. Despite this trend, the performance of such systems has rarely been studied at farm scale, and therefore their effectiveness is poorly understood. We have examined the nutrient reduction performance of sedimentation ponds on a commercial farm over an entire production season. The results demonstrated that the sedimentation ponds were effective in reducing discharges of suspended particulates, but were less effective in reducing nutrient concentrations. Total suspended solids (TSS) were reduced by 60% with residence time of 0.7 day. The best reductions of total phosphorus (TP) and total nitrogen (TN) (35% and 23%, respectively) were in a sedimentation pond with 2 days residence time. The pond with the longest residence time, 4.6 days, had poorer removal rates for each of the three parameters. Although sedimentation ponds alone are a useful strategy, we advocate that sustainable development of shrimp farming requires an integrated approach involving appropriate planning, regulation and effective monitoring protocols by governments, and reduction of the volume of effluent and mass loadings of nutrients from shrimp farms. The key future challenges are to continue to improve feeds and feed utilization efficiency; reduce water usage through recycling and reduced exchange; and improve treatment of discharge water to remove nutrients.

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.

Growing backwards: an inverted role for the shrimp ortholog of vertebrate myostatin and GDF11

SUMMARY Myostatin (MSTN) and growth differentiation factor-11 (GDF11) are closely related proteins involved in muscle cell growth and differentiation as well as neurogenesis of vertebrates. Both MSTN and GDF11 negatively regulate their functions. Invertebrates possess a single ortholog of the MSTN/GDF11 family. In order to understand the role of MSTN/GDF11 in crustaceans, the gene ortholog was identified and characterized in the penaeid shrimp Penaeus monodon. The overall protein sequence and specific functional sites were highly conserved with other members of the MSTN/GDF11 family. Gene transcripts of pmMstn/Gdf11, assessed by real-time PCR, were detected in a variety of tissue types and were actively regulated in muscle across the moult cycle. To assess phenotypic function in shrimp, pmMstn/Gdf11 gene expression was downregulated by tail-muscle injection of sequence-specific double-stranded RNA. Shrimp with reduced levels of pmMstn/Gdf11 transcripts displayed a dramatic slowing in growth rate compared with control groups. Findings from this study place the MSTN/GDF11 gene at the centre of growth regulation in shrimp, but suggest that, compared with higher vertebrates, this gene has an opposite role in invertebrates such as shrimp, where levels of gene expression may positively regulate growth.

The use of enriched 15N as an indicator of the assimilation of individual protein sources from compound diets for juvenile Penaeus monodon

Abstract We examined the potential of using an enriched stable isotope ( 15 N) to trace the assimilation of individual protein sources from compound aquaculture diets by juvenile Penaeus monodon . We used the marine diatom Chaetoceros muelleri as a source of plant protein and the brine shrimp ( Artemia ) as a source of animal protein. The diatoms were labelled by replacing 5% of the nitrogen in their culture nutrient media with 15 N enriched KNO 3 . The Artemia were labelled by feeding them 15 N enriched diatoms. The 15 N enriched diatoms and Artemia were each incorporated into a standard compound pelleted diet. The pellets were fed to juvenile P. monodon (weight range 2 to 5 g) in the laboratory and in enclosures at a local prawn farm. Analysis of the percentage 15 N in the abdominal muscle of juvenile prawns demonstrated rapid assimilation of the enriched isotope from diatoms and Artemia . There was a progressive increase in the percentage 15 N in the abdominal muscle during the 4-week experiment. Application of a simple mixing model showed that the relative assimilation rate of enriched nitrogen from Artemia was approximately 4.3 times that of the diatoms after 2 weeks and approximately 3.6 times that of diatoms after 4 weeks. The results demonstrated that enriched stable isotope tracers can provide rapid and direct information about the assimilation and retention of nitrogen from individual protein sources in compound diets for shrimp.