Evaluation of Three Sorghums as Potential Alternative Forages for Crawfish Culture 1

Three cultivars of Sorghum bicolor (L.) Moench (grain sorghum, forage sorghum, and a sorghum sudangrass hybrid) were evaluated as planted forages for crawfish (Procambarus spp.) in two simulated culture systems, double cropping and crawfish monoculture. Based upon ease of culture, biomass production, and biomass degradation characteristics, grain sorghum and sorghum sudangrass exhibited great potential for either system. With the added advantage of grain production, grain sorghum represents the more attractive option and may provide farmers with a viable alternative to rice for double cropping with crawfish. The sorghum sudangrass produced large amounts of vegetative biomass and also represents a worthwhile forage option for the crawfish fanner. Either of these plants is conveniently incorporated into existing farm operations and could provide options as producers strive to integrate crawfish aquaculture with conventional agriculture.     

Characteristics of Rice Cultivars with Implications for Crawfish Double Cropping1

Twenty-five domestic rice (Oryza sativa L.) cultivars were evaluated in a simulated rice/crawfish double cropping system in southwest Louisiana during 1983 and 1984. Wide variation was observed among cultivars in parameters believed to be important for maximizing productivity in such a system. Mean maturity ranged from 99 (Labelle) to 118 days (Starbonnet), while height ranged from 76 (Bellemont) to 130 cm (Della, Nato). Significant differences in grain yield response were observed, with yields ranging from 4,101 (Bluebelle) to 6,665 kg/hectare (Newbonnet). Straw dry matter production varied greatly, from 3,831 (Bellemont) to 9,170 kg/hectare (Della), and was positively correlated with plant height (r = 0.64; P = 0.0001). Ratoon biomass production was negatively correlated with both grain yield (r = -0.39; P = 0.0001) and maturity group (r = -0.69; P = 0.0001). Plant senescence at grain maturity also varied greatly and appears to be a factor in post-harvest ratoon capability. Early or very early maturing cultivars with both proven grain production and good ratooning capability appear best suited. Cultivar selection should be based upon individual farm situations and currently employed agronomic practices.     

The influence of diel period on fish assemblage in the unstructured littoral of reservoirs

Abstract Diel changes in littoral fish assemblage were studied in four reservoirs in the Czech Republic (Central Europe). The sampling was performed by beach seining in an unstructured littoral zone. Perch, Perca fluviatilis L., roach, Rutilus rutilus (L.), bream, Abramis brama (L.), carp, Cyprinus carpio L., ruffe, Gymnocephalus cernua (L.), pikeperch, Sander lucioperca (L.), eel, Anguilla anguilla (L.) and A. brama × R. rutilus hybrids exhibited higher densities at night. Only bleak, Alburnus alburnus (L.) exhibited higher densities during the day. The number of species was higher in night hauls, and mean body size of roach and bleak was also higher at night. Diel changes in fish densities resulted in the change in species composition between day and night. The study has implication for the sampling design to assess littoral fish assemblages using beach seine netting and recommends night sampling for a representative assessment or sampling during both diel periods for a robust assessment.     

Is pearl colour produced from Pinctada margaritifera predictable through shell phenotypes and rearing environments selections?

The black‐lipped pearl oyster, Pinctada margaritifera, is the most important farmed mollusc species in French Polynesia. Donor oyster selection among wild P. margaritifera individuals, chosen according to their inner shell colour, makes it possible to obtain the broadest range of cultured pearl colours of any species. This study demonstrates the relative influence of using black [B] or red [R] outer shell phenotypes, combined with green [G] or yellow [Y] inner shell phenotypes, on pearl darkness level, colour categories and lustre. A large scale grafting experiment was designed and carried out over five grow‐out locations, covering three archipelagos: Tuamotus, Society and Gambier. Results revealed that the [B + G] phenotypes may be used as donors to produce dark green pearl, which suit the demands of the Asian market; whereas, phenotypes incorporating [R] and/or [Y] phenotypes may be used to obtain multicolour pearls of medium/light darkness, which suit the demands of the European market. From an environmental point of view, the 1) [B] phenotype showed no significant variation for light and other pearl colour production, and 2) [Y] phenotype produced both the same rate of pearl darkness level and green colour pearls whatever the grow‐out location. A classification tree model was built to predict, according to shell phenotype and culture location, the colour and darkness level of harvested pearls. Lustre was shown to be more influenced by the environment than by phenotype. These results should be taken into account in pearl farm production management and in selective breeding programmes.     

Freshwater Pearl Culture Technology Development in India

ABSTRACT

Development of science and technology of cultured pearl production in a freshwater environment in India is described. Distribution of Indian pearl mussels, pond mussel Lamellidens marginalis, paddy field mussel L. corrianus, and riverine mussel Parreysia corrugata in relation to environmental variables such as type of soil, nature of sediment substratum, presence or absence of macrophytes (Eichhornia sp., Nechamandra sp., andNymphaea sp.) is described. Food and feeding of the mussels, together with density aspects in culture conditions are discussed. Mussel breeding including specificity in fish hosts, and mussel larval parasitic relationships are discussed. Basic steps involved in indigenous freshwater pearl culture technology are summarized. Pearl culture grafting procedures such as mantle cavity, mantle tissue and gonadal implantation along with different pearl products are also described.     

Suitability of different salmonid strains as hosts for the endangered freshwater pearl mussel (Margaritifera margaritifera L.)

• 1. The complex life cycle of endangered European freshwater pearl mussel Margaritifera margaritifera L. involves an obligatory parasitic phase on a host fish. Knowledge on the host–parasite interaction and on the suitability of different host fish species and strains is required both for the management of wild fish and mussel populations as well as for improving the efficiency of captive breeding methods.
• 2. In this study, the suitability of different salmonid strains for hosting glochidia was tested, including Danube salmon (Hucho hucho L.) and three brown trout (Salmo trutta L.) strains from inside and outside the freshwater pearl mussel distribution range. All brown trout strains as well as Danube salmon were successfully infected with freshwater pearl mussel glochidia and encystment of mussel larvae was detected.
• 3. One brown trout strain originating from the natural pearl mussel distribution range was identified as the most suitable host, revealing the highest fish‐weight‐normalized infection rates and highest glochidial growth rates, whereas endemic Danube salmon was least suitable. Under natural conditions, the role of Danube salmon may be attributed to the long‐distance dispersal of glochidia in the Danube system, whereas sedentary brown trout appear to be the most important hosts at a local scale.
• 4. Successful infection of suitable hosts and the maintenance of these host–parasite systems in calcareous water were demonstrated in this study. These results indicate that neither the infection process nor the encystment phase of freshwater pearl mussels is dependent on low lime concentrations.
• 5. The results of this study suggest that careful selection and management of appropriate host fish strains is mandatory for sustainable conservation management of freshwater pearl mussel populations. Copyright © 2010 John Wiley & Sons, Ltd.

     

ECONOMIC ANALYSIS OF LAND-BASED PRODUCTION OF CULTURED MARINE PEARLS IN INDIA

Land-based marine pearl culture is a novel technological concept suitable for all three important species of pearl oysters. Advantages include lack of fouling and avoidance of boring and predation. An economic evaluation of onshore marine pearl culture production was conducted to provide basic information about the practice. The average annual cost of production over the estimated 10-year period was $158,127 (U.S.), net operating income was $159,197 (U.S.) and the net income was $49,244 (U.S.). The average annual pearl production of 28 kg was higher than the break-even production of 15 kg. The break-even price was estimated at $6.60 (U.S.) per gram of pearl. Net Present Value (NPV) was estimated at $137,416 (U.S.) and the Benefit Cost Ratio (BCR) at 1.20 (20% discount rate). The Internal Rate of Return (IRR) was estimated at 28%.     

Molting,Mortality, and the Effects of Density in a Soft-Shell Crawfish Culture System 1

The molting and mortality patterns at a crawfish density recommended for commercial-scale soft-shell crawfish culture systems showed that, over a 116 day period, 74% of the crawfish molted, 22% died, and 4% remained in the system at the end of the study. Approximately three weeks of adaption to the system were required before molting rates of the crawfish began to increase. By the sixth week, the number of malted crawfish per day exceeded the overall mean and remained at this level until 10 days before moltable crawfish were depleted. In a second study, three density levels (3.7,4.9, and 6.1 kg crawfish/m²) were tested for 60 days. The lowest density produced significantly fewer (P < 0.05) molted crawfish. Mortality was significantly greater (P < 0.05) at the highest density compared with the lowest density. The highest density (6.1 kg crawfish/m²) showed a higher molting rate than the lower densities, but it was not significantly different (P < 0.05) from the molting rate of 4.9 kg/m².     

Substitution of Soybean Protein for Fish Protein in Formulated Diets for Red Swamp Crawfish Procambarus clarkii1

A 10 week laboratory growth trial was conducted with red swamp crawfish Procambarus clarkii to determine the amount of soybean protein that could be substituted for fish protein in formulated crawfish diets without reducing growth. Crawfish received 32% crude protein, isocaloric diets in which protein was supplied by soybean (soy) meal, menhaden fish meal or an isonitrogenous mixture of soybean and fish meal calculated to provide graded levels of each protein source. Dietary protein was provided as: 1) 100% soy protein; 2) 75% soy protein: 25% fish protein; 3) 50% soy protein: 50% fish protein; 4) 25% soy protein: 75% fish protein; and 5) 100% fish protein. Crawfish fed soy protein: fish protein (SP:FP) mixtures or fish protein alone exhibited better (P < 0.05) weight gain than crawfish fed a diet containing soy protein as the only protein source. Diets containing 25% soy protein: 75% fish protein (1:3 ratio) and 50% soy protein: 50% fish protein (1:1 ratio) produced greater (P < 0.05) weight gains than a diet in which fish protein was the sole protein source. Survival, feed efficiency ratio, maturation rate, net protein and energy retention, and body composition of crawfish did not differ (P > 0.05) among diets with SP:FP ratios of 1:3, 1:1 and 3:1. However, maximum (P < 0.05) weight gain occurred in crawfish fed the 1:3 SP:FP ratio. Although crawfish fed SP:FP ratios of 1:1 and 3:1 had lower weight gains in the laboratory than crawfish fed a 1:3 SP:FP ratio, SP:FP ratios of 1:1 and 3:1 might be adequate for supplemental diets fed to pond-reared crawfish that have access to natural sources of food.     

Effect of feeding different grain sources on the growth performance and body composition of tilapia, Oreochromis niloticus (L.)

Growth performance and body composition of tilapia Oreochromis niloticus (L.), fed isonitrogenous and isoenergetic diets containing different grain sources (maize, wheat, barley, sorghum and rice) at a level of 25% were studied for a period of 62 days. Fish fed a diet containing sorghum showed the maximum weight grain, highest specific growth rate (SGR, 2.23), the best feed conversion (FCR, 1.07) and protein efficiency ratio (PER, 2.42) in comparison with all other diets. The diets containing maize, wheat and rice did not show any significant (P < 0.05) differences between each other. The barley diet showed the poorest values (SGR, 2.05; FCR. 1.34; PER, 1.98: and NPR, 30.65) in comparison with others. Although the diet containing sorghum showed the best net protein retention (NPR, 36.21) values, the results did not differ (P > 0.05) among maize, wheat and sorghum diets. The sorghum diet produced fish with lower moisture but higher body fat contents as compared to others. The fish fed diets containing maize, wheat, barley and rice did not show any significant difference (P > 0.05) in their body moisture and fat contents. The source of grain in the diet did not affect the crude protein and ash contents of fish (P > 0.05). It is suggested that cereal grains at the 25% level can efficiently be utilized in tilapia diets, sorghum being the best.     

Efficacy of Vaccination Against Streptococcus iniae During Artificial Spawning of the Red-Tail Black Shark (Epalzeorhynchos bicolor,fam. Cyprinidae)

Artificial spawning may precipitate high mortalities of red-tail black shark (Epalzeorhynchos bicolor) broodstock from Streptococcus iniae infection. Two vaccine formulations (aluminum or oil adjuvant) were evaluated for effectiveness. Fish (mean weight 21.2 ± 5.7 g) were harvested, acclimatized, and vaccinated by intracoelomic injection. After 21 days, fish were moved to a biosecure laboratory and, one day later, simultaneously spawned and challenged by bath or by intracoelomic injection with S. iniae. Both formulations increased relative% survival (RPS) in unspawned (RPS [formulation]: 80 [aluminum]; 54 [oil]) and spawned fish (87–95 [aluminum]; 73–75 [oil]), suggesting that vaccination increases survival of red-tail black shark broodstock after spawning.     

In vitro Antifungal activity of essential oils from Tymbra,Origanum, Satureja species and some pure compounds on the fish pathogenic fungus,Saprolegnia parasitica

In the present study, the chemical composition and antifungal activity of the essential oils of the three Lamiaceae species, black tyme (Thymbra spicata L.), oregano (Origanum onites L.) and savory (Satureja tymbra L.) against Saprolegnia parasitica Coker strains (3) were evaluated. The composition of oils was analysed by gas chromatography/mass spectrometry (GC/MS). The major constituent of the oils was carvacrol (82.68% in Thymbra spicata, 82.24% in Origanum onites and 52.38% in Satureja tymbra). The antifungal activity of essential oils was determined by a tube dilution and disc diffusion method. All essential oils inhibited fungal strains at concentration of 100 μL mL^?1. The essential oil of O. onites and T. spicata was the most active (MIC 10 and 50 μL mL^?1, respectively). Thymol did not show inhibiting activity. The essential oils exhibited stronger inhibition than pure carvacrol. Essential oil derived from Tymbra, Origanum and Satureja species has the potential to be used as health control of rainbow trout (Oncorhyncus mykiss) against S. parasitica infection. This study describes the antifungal activity of three essential oils for developing alternative and native control methods against Saprolegniasis.     

Influence of pH upon the activity of glycosidases and proteinases of intestinal mucosa,chyme and microbiota in fish

It is shown that amylolytic and proteolytic activity of the intestinal mucosa, the chyme and the intestinal flora in the fishes, zander Zander lucioperca (L.), perch Perca fluviatilis L., bream Abramis brama (L.) and roach Rutilus rutilus (L.), belonging according to their feeding habits to different ecological groups at the same pH values as well as in the pH range from 5.0 to 10.0 considerably varies. The glycosidase pH optimum of the mucosa and intestinal microbiota is 7.0, whereas that of the chyme varies from 6.0 (in roach) to 8.0 (in bream). pH optimum of the mucosa proteinases in all fish species is 10.0, whereas that of the chyme and the bacterial flora can be observed in all the range of pH values.     

Contribution of donor and host oysters to the cultured pearl colour in Pinctada martensii

Cultured free round pearls are produced by implanting a spherical nucleus with a small piece of nacre‐secreting mantle graft from a donor oyster into the gonad of a recipient oyster (host). To examine the possible contribution of host and donor oysters to the colouration of the harvested pearls, the CSE‐1 Imaging and Color‐Measuring System were used to quantitatively measure the L*a*b* values of donor and host shells and the produced pearls in Pinctada martensii. Results showed that the colour of pearls had significant positive correlation (r = 0.1–0.22, P = 0.00) with that of donors, but had no correlation with that of host oysters, thus convincingly confirmed the contribution of nacre colour of donor to the realization of pearl quality of colour. To further clarify the relationship between the donor and the pearl colour, the donors from pearls of good and poor colour quality were further compared and the results demonstrated the significant difference in L* values (P < 0.05) and insignificant difference in a* and b* values, suggesting the necessity of selecting donors with bright and lustrous nacre in pearl production.     

A new record of the freshwater pearl mussel Margaritifera margaritifera L. (Bivalvia,Unionoida) from the River Narcea (Asturias,north‐western Spain)

1. A population of the freshwater pearl mussel Margaritifera margaritifera L. was found in the River Narcea in the province of Asturias (north‐western Spain). Primary analysis of the population shows that it is well distributed along the river and is particularly abundant in shady river banks with a gravel substrate. 2. The length of living mussels ranges between a minimum of 22 mm and a maximum of 116 mm, with most in the size class between 65 mm and 70 mm. There is a good proportion of young mussels, although no fertile females were found in the course of the investigation. 3. Although there is no specific legislation in Spain for the protection of M. margaritifera, it has recently been proposed to include M. margaritifera in the Spanish List of Threatened Species as ‘vulnerable’. 4. Although the River Narcea seems to provide suitable conditions for the pearl mussel (water quality, available salmonid hosts, etc.), the main conservation measures must be directed at avoiding river fragmentation from dams, channelization and organic enrichment from individual farms or towns situated close to the river bank. Copyright © 2000 John Wiley & Sons, Ltd.     

Growth response of indigenous and exotic carp species to different protein sources in pelleted feeds

Three indigenous carp species, Catla catla (Ham.), Labeo rohita (Ham.) and Cirrhinus mrigala (Ham.), and two exotic carp species, Cyprinus carpio L. and Hypophthalmichthys molitrix (Val.), were stocked together at a total density of 6000 fish ha^-1 in the ratio of 11:22:14:14:11, respectively. Three pelleted feeds, maize gluten (MG), cotton seed (CS) and fish meal (FM), were fed at 5% of the body weight of fish per day. The crude protein content of each feed was different. Growth rates for exotic species were significantly higher (P < 0.05) on all feeds than growth of indigenous species. The best growth for both exotic and indigenous carps was achieved on fish meal. Supplemental feeds made from locally available materials can enhance fish culture in Pakistan.     

Quantifying trophic interactions and niche sizes of juvenile fishes in an invaded riverine cyprinid fish community

Quantifying feeding interactions between nonindigenous and indigenous fishes in invaded fish communities is important for determining how introduced species integrate into native food webs. Here, the trophic interactions of invasive 0+ European barbel Barbus barbus (L.) and the three other principal 0+ fishes in the community, Squalius cephalus (L.), Leuciscus leuciscus (L.) and Phoxinus phoxinus (L.), were investigated in the River Teme, a River Severn tributary in Western England. B. barbus has been present in the River Teme for approximately 40 years. Analyses of stomach contents from samples collected from three sites between June and September 2015 revealed that, overall, fishes displayed a generalist feeding strategy, with most prey having low frequency of selection. Relationships of diet composition versus body length and gape height were species‐specific, with increasing dietary specialisms apparent as the 0+ fishes increased in length and gape height. The trophic niche size of invasive B. barbus was always significantly smaller than S. cephalus and L. leuciscus and was significantly smaller than P. phoxinus at two sites. This was primarily due to differences in the functional morphology of the fishes; 0+ B. barbus were generally restricted to foraging on the benthos, whereas the other fishes were able to forage on prey present throughout the water column. Nevertheless, the invasive B. barbus were exploiting very similar prey items to populations in their native range, suggesting these invaders were strongly pre‐adapted to the River Teme and this arguably facilitated their establishment and invasion.     

When should pearl oyster,Pinctada margaritifera (L.), spat be transferred from the hatchery to the ocean?

Hatchery propagation of pearl oysters is relatively new and optimal hatchery protocols are still being developed. While in the hatchery, pearl oyster spat are supplied a constant and reliable food source and are protected from fluctuations in environmental conditions and predators. This study investigated the hypothesis that retaining blacklip pearl oyster, Pinctada margaritifera (L.), spat in the hatchery for longer periods, prior to transfer to the ocean, would improve growth and survival during early nursery culture. Results showed that the longer spat were retained in the hatchery, the smaller their average size at grading (3.5 months of age). At grading, spat transferred 3 weeks after settlement had a mean dorso–ventral shell height (DVH) of 9.2 ± 0.4 mm with 34% of individuals retained on a 10‐mm mesh. However, spat retained in the hatchery until 5, 7 and 9 weeks after settlement, had a mean DVH of 9.0 ± 0.4, 7.8 ± 0.3 and 6.3 ± 0.4 mm respectively. Only 10% of spat transferred 9 weeks after settlement were retained on a 10‐mm mesh at grading. The results probably reflect superior nutrition available in the ocean and indicate that pearl oyster spat should be transferred from the hatchery as soon as possible after settlement in order to maximize growth.     

Assessing Potential for Aquaculture Development with a Geographic Information System

Comprehensive analyses of aquaculture potential are required for policy formulation and planning for aquaculture development. A computer-automated geographical information system (CIS) was assessed as a tool to analyze the complex spatial and attribute data sets needed to locate aquaculture potential. The state of Louisiana, USA, was the study area. Areas for the further development of catfish and crawfish culture and crawfish-rice and crawfish-grain sorghum double cropping were identified. The CIS showed that there were ample opportunities for the expansion of catfish farming on flatlands based on soil suitability and length of the growing season. Parishes in which crawfish are already raised occupy most of the best suited soils and include those with the longest growing seasons. The potential to further integrate crawfish with rice and with grain sorghum in double cropping systems was good. The results demonstrated that a GIS can be used to aid large-area aquacultural development planning.     

Effects of Water Quality,Weather and Lunar Phase on Crawfish Catch1

The relationship between water quality, weather, lunar phase and daily changes in crawfish (Proearnbums clurkii) catch per unit effort (CPUE) was determined in five experimental crawfish ponds from March through May, 1984 and 1985. Air and water temperatures, solar radiation, dissolved oxygen, wind velocity, barometric pressure, precipitation and lunar phase were recorded daily during the harvesting phase of the study. Crawfish CPUE (g/trap/24 h) was significantly correlated with water temperature, dissolved oxygen, lunar phase, barometric pressure, wind velocity and the relative density of harvestable size crawfish. Most statistically significant environmental or climatological variables explained less than 20% total daily variation in crawfish CPUE. The nine environmental variables were reduced to four factors—temperature-harvestable crawfish, cold fronts, rain showers, and lunar phase—with principal-components analysis. Eighty-five percent of the variation in daily crawfish catch was attributed to water temperature and relative density of harvestable crawfish, and 7.1% was explained by lunar phase. Rain showers and cold fronts accounted for 4.8 and 2.5% of the daily variation in crawfish CPUE, respectively. Crawfish catch increased with an increase in water temperature and relative abundance of harvestable crawfish, and with short duration rain showers. Conversely, crawfish CPUE declined with the approach of full moon and with passage of cold fronts.