Crayfish Aquaculture Research Articles

Effects of different methods and times of 17β-estradiol treatment on the feminization success in the narrow-clawed crayfish Astacus leptodactylus (Eschscholtz, 1823)

Sex differentiation is a profitable technique in crayfish aquaculture. Most of the studies have focused on sex differentiation in crayfish by ablation or implantation of androgenic glands. There is no research on sex differentiation using hormones in crayfish. In the present study, the effects of 17β-estradiol (E2) injections (10−7 mol/crayfish) to females and baths (50 μg 17β-estradiol/L) to pleopodal eggs and stage1, 2, and 3 juveniles on the feminization of freshwater crayfish, Astacus leptodactylus were investigated. Results showed that E2 injection to females, bath to pleopodal eggs and bath to stage 1, 2, and 3 juveniles increased feminization rate significantly (p < 0.05) in comparison to the control in A. leptodactylus. Best feminization rate (male to female, 0.25:1) was observed after hormonal injection to the females combined with application of both for their both pleopodal eggs and stage 1, 2, and 3 juveniles. In conclusion, it is possible to obtain 75% females A. leptodactylus by E2 injection to females and bath to pleopodal eggs and stage 1, 2, and 3 juveniles. However, future studies are needed to investigate the mechanism of E2 in crayfish feminization and the sexual development of juveniles obtained from feminization.

Factors affecting the reproductive efficiency in crayfish: implications for aquaculture

In recent years, crayfish aquaculture industry has been developing rapidly in different regions of the world. Crayfish aquaculture is often carried out in dams, lakes and extensive pond systems. There is an increasing demand for crayfish juvenile in aquaculture sector. Therefore, it is important to know which factors affect reproductive efficiency in crayfish. In the present review, factors affecting the reproductive efficiency of crayfish are divided into two main sections, external and internal factors. Dietary lipids, phospholipids, highly unsaturated fatty acids, protein and amino acids, vitamins and carotenoids are important external factors affecting broodstock crayfish reproduction. In addition, various external (i.e. female size, stocking density, temperature, photoperiod, sex ratio) and internal (i.e. endogenous hormones) factors affect the reproductive efficiency in crayfish. This study reviews the present knowledge with the purpose of realizing the factors that are important to reach optimal crayfish nutrition, maturation and reproduction (i.e. pleopodal egg number and quality). This review will particularly be useful for crayfish farmers and crayfish hatchery units.

Characterization of microRNAs by deep sequencing in red claw crayfish Cherax quadricarinatus haematopoietic tissue cells after white spot syndrome virus infection

White spot syndrome virus (WSSV) is one of the most prevalent and widespread viruses in both shrimp and crayfish aquaculture. MicroRNAs (miRNAs) are crucial post-transcriptional regulators and play critical roles in cell differentiation and proliferation, apoptosis, signal transduction and immunity. In this study, miRNA expression profiles were identified via deep sequencing in red claw crayfish Cherax quadricarinatus haematopoietic tissue (Hpt) cell cultures infected with WSSV at both early (i.e., 1 hpi) and late (i.e., 12 hpi) infection stages. The results showed that 2 known miRNAs, namely, miR-7 and miR-184 play key roles in immunity. Meanwhile, 106 novel miRNA candidates were predicted by software in these combined miRNA transcriptomes. Compared with two control groups, 36 miRNAs showed significantly different expression levels after WSSV challenge. Furthermore, 10 differentially expressed miRNAs in WSSV-exposed Hpt cells were randomly selected for expression analysis by quantitative real-time RT-PCR. Consistent with the expression profiles identified by deep sequencing, RT-PCR showed a significant increase or decrease in miRNA expression in Hpt cells after WSSV infection. Prediction of targets of miRNAs such as miR-7, cqu-miR-52, cqu-miR-126 and cqu-miR-141 revealed that their target genes have diverse biological roles, including not only immunity but also transcriptional regulation, energy metabolism, cell communication, cell differentiation, cell death, autophagy, endocytosis and apoptosis. These results provide insight into the molecular mechanism of WSSV infection and highlight the function of miRNAs in the regulation of the immune response against WSSV infection in crustaceans.

Experimental inoculation of Louisiana red swamp crayfish Procambarus clarkii with white spot syndrome virus (WSSV)

The red swamp crayfish Procambarus clarkii represents an important aquaculture species responsible for over half of all commercial aquaculture profits in Louisiana, USA. White spot syndrome virus (WSSV) is highly pathogenic in crustacean species and induces mass mortality in aquaculture operations worldwide. Natural outbreaks of WSSV occur yearly in cultured populations of crayfish in Louisiana. The goal of this study was to better understand the infectivity of WSSV in P. clarkii, by determining the minimum lethal dose necessary to initiate infection and to measure the resulting cumulative mortality following infection with different doses. A real time quantitative PCR (qPCR) method was used to detect WSSV in DNA extracted from gill tissue to ensure P. clarkii study populations were WSSV-free before the start of trials. Viable viral particles were isolated from naturally infected P. clarkii gill tissue and quantified using a novel digital PCR approach. Three infectivity trials were performed, and WSSV inocula were created by serial dilution, generating 5 treatments per trial. Five crayfish (weighing ~25 g) per dilution per trial received viral inoculations. Mortality was monitored daily for the duration of the trial in order to construct a median lethal dose (LD50) curve, and probit regression analysis was used to determine LD50 concentrations of viral particles. Knowledge of the infectivity of WSSV in native crayfish populations is of critical importance to the management of the commercial crayfish aquaculture industry in Louisiana. This is the first study to investigate the infectivity and to determine the LD50 of the Louisiana strain of WSSV in native crayfish.

Antibacterial properties of extracts of Solidago canadensis and their potential use as dietary supplements in red swamp crayfish (Procambarus clarkii)

Canadian goldenrod (Solidago canadensis )i s one of the most destructive invasive weeds in South- eastern China. To evaluate its potential application as dietary supplement in red swamp crayfish (Procambarus clarkii), the antibacterial properties of aqueous and ethanol extracts of this plant against three major pathogenic bacteria in crayfish aquaculture were examined. Inhibition zone tests and determination of minimum inhibitory concentration revealed that the extracts had lower antibacterial activity than extracts from two traditional medicinal plants that possess antibacterial properties, garlic (Allium sativum) and cortex phellodendri (Phello- dendron chinense). However, they did exhibit greater antibacterial effects than extracts from another widely used medicinal plant, Sophora flavescens, and an aquatic weed, Alternanthera philoxeroides. Aqueous extracts of Cana- dian goldenrod gave greater inhibition than the ethanol extracts. Crayfish fed a diet with 2% these aqueous extracts exhibited significantly higher enzyme activity of alkaline phosphatase, catalase and phenoloxidase (P<0.05). Based on the results of this study, we conclude that aqueous extracts of Canadian goldenrod are highly promising for the development of new dietary supplement for use in crayfish aquaculture.

Pectin-based pellets for crayfish aquaculture: structural and functional characteristics and effects on redclaw Cherax quadricarinatus performances

Pectin is a promising candidate to be employed as binder for manufacturing pellets for crayfish feeding. In this study, the gelling properties of different types of pectin and their effects on Cherax quadricarinatus performances have been analysed. Pectins with different degree of esterification from apple and citrus were screened to select those with the best gelling properties to be employed in pellet manufacturing. Three pectins were selected: low esterification degree apple pectin (LEAP), low esterification citrus pectin (LECP) and high esterification degree apple pectin (HEAP). Scanning electron microscopy analysis, nutrient leaching and water uptake indicated that LEAP showed the best aggregating properties, followed by LECP and HEAP pellets. Cherax quadricarinatus performances were affected by the pectin type, with redclaw fed LEAP pellets showing the highest (P < 0.05) growth rate and amylase activity (P < 0.05) in the gastrointestinal tract. Altogether these results indicate that LEAP can be considered an excellent binder for feed pellets due to its gelling properties and its efficacy to improve growth and stimulation of digestive enzyme activity.

Effects of Stargrass Hay Supplementation on Growth and Survival of Juvenile Redclaw Crayfish Cherax quadricarinatus

AbstractHay is used as supplementary forage for crayfish aquaculture in many farms around the world. However, our understanding of the relative contribution of hay to crayfish dietary requirements is limited. In the present work, 36 juvenile redclaw crayfish Cherax quadricarinatus were stocked into each of 28 tanks that received water continuously from a pond. Four replicate tanks were assigned to each of seven dietary treatments: commercial formulated feed (FF) only, at a ration calculated to produce optimal growth; 100% of the calculated FF ration plus the hay of stargrass Cynodon nlemfuensis added at 150 kg·ha−1·week−1; 75% of the FF ration plus hay; 50% of the FF ration plus hay; 25% of the FF ration plus hay; hay only; and no feed (control). At the end of 8 weeks, the crayfish were harvested, counted, and weighed. There were no significant differences in survival among treatments (α = 0.05), and crayfish growth did not differ among tanks that were offered FF. Redclaw crayfish in the hay‐only treatment grew less than those that were offered FF, but growth did not differ between crayfish that were offered only hay and crayfish in the no‐feed control. Although hay did not contribute to the growth of redclaw crayfish that were offered the high‐protein shrimp feed, it did allow for survival and minimal growth of crayfish that were not offered FF. Accordingly, hay might contribute to growth if a low‐protein, low‐energy diet is developed specifically for crayfish.

Peracetic acid (PAA) treatment is an effective disinfectant against crayfish plague ( Aphanomyces astaci) spores in aquaculture

We tested the efficacy of peracetic acid (PAA) and used 5 μm absolute filtration as an control on the disinfection or removal of crayfish plague ( Aphanomyces astaci) spores in aquatic environment. The laboratory tests indicated that a concentration of 10 mg L − 1 PAA inactivated A. astaci spore germination and was chosen to be tested as a disinfectant in infection trials on noble crayfish ( Astacus astacus). The same PAA concentration, 10 mg L − 1 , was effective, when crayfish were exposed to PAA treated spore solution while crayfish exposed to untreated spore solution died. We observed that a minimum time lag of 4 h was sufficient for the breakdown of PAA under practical conditions since there was a 100% crayfish survival in test groups over two weeks when exposed to PAA treated water after a treatment time lag of more than 2 h. Furthermore, the absolute 5 μm filtration used as control also removed all infectious A. astaci spores and resulted in high survival rate in the group exposed to filtered spore suspension, similarly to the control group. The tested treatments could be used in freshwater crayfish aquaculture to prevent A. astaci infections, since the substitute freshwater requirement in crayfish aquaculture is low and thus allows effective disinfection. The methods could also be applied to other aquaculture activities, such as treatment of stockling transfer water to prevent the spread of disease agents, especially A. astaci spores.

Rheological behavior of polysaccharide based pellets for crayfish feeding tested on growth in the crayfish Cherax albidus

Two algal polysaccharides: alginate and agar and one polysaccharide from fruit, pectin, have been used as food additives in relation to their structure and their rheological behavior, stability and interactions, to generate firm pellets to be employed in crayfish aquaculture. Three diets containing the same amount of nutrients (protein, lipid and carbohydrate) mixed with each of the three different polysaccharides were tested on male freshwater crayfish Cherax albidus growth. The aims of this study were to examine the effect of alginate, agar and pectin, on pellet stability in water, and on crayfish growth. The kinetics of water absorption and solute leaching of pellets were measured by immersing quadruplicate samples of the diets in water for 0.5, 2, 4 and 8 h. After the required immersion time, the samples were recovered, freeze-dried for 24 h and re-weighed. Recovered liquid was analyzed by Low Angle Laser Light Scattering Technique, which allowed the monitoring of the released particles in water during immersion. At the same time, the crayfish feeding response to firm pellets was monitored in feeding behavior and growth experiments.Our results show that pellets had good water stability, were preferred by crayfish and the presence of polysaccharides positively affected crayfish growth. Indeed, animals fed pellets showed a higher percentage of growth when compared to animals fed a fresh diet. In particular, pectin gave the best results, showing better water stability than alginate and agar and causing the best growth performance. Pellets are relatively low cost and easy to make and they may represent an advantage for those who want to farm crayfish under intensive conditions.

Diseases of yabbies ( Cherax albidus) in Western Australia

Routine disease testing of yabbies ( Cherax albidus) in Western Australia for over 10 years revealed only few diseases of significance to freshwater crayfish aquaculture. The most serious of these are the recent discoveries of an introduced microsporidian Thelohania sp. and a previously undescribed virus that has been associated with mortalities in yabby dams but has a widespread distribution with low prevalence (<5%). Other parasites and ectocommensals have been recorded from C. albidus in Western Australia including temnocephalans, cilliates, Psorospermium sp. and the nematode Gammarinema sp. However, these appear to have little effect upon the host other than lowering their market value. Testing for crayfish plague ( Aphanomyces astaci) since 1989 has shown that this disease is not present in Western Australia. Although many farmers feed lupin seeds ( Lupinus angustifolius) to crayfish in Western Australia, this practice can result in mortalities due to enterotoxaemia.

Hybridization in Australian Freshwater Crayfish—Production of All‐Male Progeny

Abstract.— In freshwater crayfish aquaculture high densities can result from uncontrolled reproduction. Hence some farmers manually sex yabbies Cherax albidus and stock only mate crayfish in farm dams or ponds. Although male‐only yabby populations produce an estimated 70% increase in gross income, hand sexing is time consuming and prone to error. A hybridization experiment using freshwater crayfish from the yabby species complex, collected from geographically isolated regions throughout Australia, revealed a hybrid between Cherax rotundus females and C. albidus males which consistently produces only male progeny. This has been confirmed in nine crosses of the same two species. The reciprocal cross of C. albidus females ×C. rotundus males produces both male and female progeny. The consistent production of only male progeny by hybridization has not been recorded previously for a crustacean.

Genetic implications of broodstock selection for crayfish aquaculture in the Midwestern United States

The commercial culture of crayfish has recently gained popularity in many regions of the United States. This popularity has led to the development of culture strategies in several Midwestern states, where a number of crayfish species are being examined in order to determine those best for culture in this region. Some crayfish species seem better adapted to the climactic conditions of the Midwest, and therefore perform better in an aquaculture setting than others. The reasons for these differences may be connected to genetic variability. However, the extent of genetic variation both within and among crayfish species is not well known. We examined genetic variation within and among populations of the Northern ( Orconectes virilis) and White River ( Procambarus acutus acutus) crayfishes using protein electrophoresis. Allele frequencies are reported for four populations of O. virilis and P. a. acutus and single populations of O. nais and O. immunis. Among the O. virilis populations, significant variation in allele frequencies was observed at several loci, and fixed allelic differences were detected at three loci. P. a. acutus populations also exhibited a similar diversity of allele frequencies, and these differences appear related to geography. This study demonstrates that O. virilis and P. a. acutus are genetically heterogeneous, even over relatively small geographic distances. Intraspecific genetic variability in crayfish appears to be quite extensive and should be considered by aquaculture specialists when selecting brood stocks. Therefore, we recommend that local stocks be chosen for aquaculture operations commencing in the Midwest and that the introduction of non-native species (or populations) be limited in order to conserve native crayfish gene pools.

Freshwater crayfish aquaculture in North America, Europe, and Australia: families Astacidae, Cambaridae, and Parastacidae

ContentsIntroduction * I. Cultivation of Freshwater Crayfishes in North America * Freshwater Crayfish Culture * Freshwater Crayfish Processing * Diseases of Louisiana Crayfish * II. Cultivation of Freshwater Crayfishes in Europe * Introduction * The Crayfish and Crayfish Production in Europe * Crayfish Culture * III. Cultivation of Freshwater Crayfishes in Australia * Introduction * Phylogeny * Distribution of Parastacids in Australia and Their Suitability for Aquaculture * The Yabbie, Cherax destructor * The Marron, Cherax tenuimanus * Redclaw, Cherax quadricarinatus * Economics * Marketing * Status of Australian Crayfish Culture, 1989?90 Season * Index