Luis H. Poersch

Use of different carbon sources for the biofloc system adopted during the nursery and grow-out culture of Litopenaeus vannamei

AbstractnThe carbon sources such as molasses cane sugar, dextrose and rice bran were tested in growing Pacific white shrimp, Litopenaeus vannamei, using the Biofloc Technology System, and the reduction in the concentration of total ammonia nitrogen in the experimental nursery and grow-out phases were assessed in tanks with a volume of 800xa0L at 35 and 70xa0days, respectively. In the nursery experiment, postlarvae with an average weight of 0.024xa0±xa00.01xa0g were stocked at 1200xa0m−2 and shrimp with an average weight of 4.09xa0±xa00.51xa0g and stocking density of 300xa0m−2 was used in the grow-out. The carbon sources used in the nursery were molasses (M) and rice bran (R) and in the grow-out were dextrose (D) and rice bran (R). In the nursery experiment, using molasses, the ammonia concentration was significantly lower (pxa0<xa00.05). In the grow-out experiment with dextrose, the ammonia concentration was significantly lower (pxa0<xa00.05), but performance data were significantly better (pxa0<xa00.05) in the rice bran treatment. The faster degradation of dextrose and molasses sources may have provided higher levels of carbon as a substrate for heterotrophic bacteria to use in metabolizing ammonia, thereby improving the water quality.

Unistellate spermatozoa of decapods: comparative evaluation and evolution of the morphology

Decapod unistellate spermatozoa are primarily characterized by the presence of a single appendage (spike) extending from the acrosome. Among decapods, this type of spermatozoon is found only in shrimps of the families Sicyoniidae, Penaeidae, and Solenoceridae (suborder Dendrobranchiata) and of the infraorder Caridea (suborder Pleocyemata). This review comparatively discusses the morphological diversity of unistellate spermatozoal ultrastructure among these decapods, as well as the role of the primary structures involved in the fertilization and spermatozoal capacitation. Furthermore, the use of the unistellate spermatozoal ultrastructure to support phylogenetic relationships and of the current phylogenetic evidences to investigate the evolution of spermatozoa of decapods is discussed. Morphologically, the main differences between caridean and dendrobranchiate unistellate spermatozoa are the shape of the main body (inverted cup-shaped, and spherical, bulged or elongate, respectively) and complexity of the acrosomal region. The latter is directly related to the type of fertilization. For example, dendrobranchiates have more complex acrosomal regions than that carideans, and fertilization involves a visible acrosome reaction, which is not observed in carideans. Ultrastructural changes of spermatozoa throughout capacitation are unknown in carideans, but for dendrobranchiates generally occur in the acrosomal vesicle and subacrosomal region throughout attachment of the spermatophore to the thelycum, enabling fertilization by the spermatozoa. Comparative evaluation of spermatozoal morphology and current phylogenetic evidences corroborates the hypothesis that the spermatozoal spike of carideans and dendrobranchiates is the result of convergent evolution.

Application of different doses of calcium hydroxide in the farming shrimp Litopenaeus vannamei with the biofloc technology (BFT)

The reduction in alkalinity and pH occurs due to the consumption of inorganic carbon by bacteria present in the biofloc. The objective of the study was to evaluate the effects of different doses of calcium hydroxide on the water quality and growth performance of the Litopenaeus vannamei in a biofloc system. The experiment consisted of four treatments with three repetitions for each treatment: Control treatment (TC), in which the pH maintained above 7.2 due to the application of 0.05xa0gxa0L−1 of calcium hydroxide, and treatments T10, T20 and T40, in which daily doses of calcium hydroxide equivalent to 10, 20 and 40xa0% of the total amount of feed offered to the shrimp, respectively, were added to the environment. Twelve experimental units (150xa0L) were stocked with 85 juveniles of L. vannamei (0.18xa0±xa00.06xa0g), corresponding to a density of 425 shrimpxa0m−3, and cultivated for 56xa0days. The values of alkalinity and pH for treatments TC and T10 were similar and significantly lower (pxa0<xa00.05) than those for treatments T20 and T40, which differed (pxa0<xa00.05) between each other. In terms of growth performance, TC, T10 and T20 performed significantly better (pxa0<xa00.05) than T40. There were no significant differences (pxa0>xa00.05) in the survival rates. The results obtained indicate that doses of 0.05xa0gxa0L−1 of calcium hydroxide or daily applications between 10 and 20xa0% of the total amount of feed offered to the shrimp can be used for the correction of alkalinity and pH.

The effect of different alkalinity levels on Litopenaeus vannamei reared with biofloc technology (BFT)

The initial stages of rearing marine shrimp using biofloc technology (BFT) involve the biofloc formation process. At the same time, there is an increase in the levels of total suspended solids and a decrease in alkalinity and pH. This reduction of alkalinity and pH occurs due to the consumption of inorganic carbon by the autotrophic bacteria present in the bioflocs and biofilms. The aim of this study was to evaluate the effects of different alkalinities on water quality and the zootechnical performance of the marine shrimp Litopenaeus vannamei in a BFT system. The experiment consisted of four treatments, with three replicates each: 75, 150, 225 and 300xa0mg CaCO3/L. To maintain the alkalinity at the established level, sodium bicarbonate was applied. For the experiments, twelve experimental units (areaxa0=xa00.20xa0m2) with an effective volume of 50xa0L were stocked with 30 juvenile L. vannamei (0.20xa0±xa00.07xa0g), to achieve a stocking density of 150 shrimps/m2 and were maintained for an experimental period of 49xa0days. The 75 treatment presented the highest levels of ammonia and nitrite throughout the study, compared to the 150 and 300 treatments. The results showed that higher alkalinity favors biofloc formation and the establishment of nitrifying bacteria.

Biofloc management with different flow rates for solids removal in the Litopenaeus vannamei BFT culture system

Different water flows for solids removal in the Litopenaeus vannamei BFT system were evaluated. One control (no solids removal) and two treatments using different water flows, high (3945xa0Lxa0h−1—HF) and low (1750xa0Lxa0h−1—LF), were used with no water replenishment after each process, and the total dry weight of the solids was measured. L. vannamei (0.18xa0±xa00.06xa0g; 350 individualsxa0m−2) were stocked in 35-m−3 tanks. For 17xa0weeks, the physical and chemical parameters were maintained within the recommended. To keep the total suspended solids concentrations at approximately 500–600xa0mgxa0L−1, clarifying was performed. The average water volume flowed by clarifiers was significantly different (pxa0<xa00.05) between HF (205xa0±xa034xa0m3) and LF (114xa0±xa024xa0m3). There was a significant decrease (pxa0<xa00.05) in the final tank volume in HF (28.09xa0±xa00.92xa0m3) and LF (28.62xa0±xa01.38xa0m3) due to the clarifying. Before clarifying (initial sample) and at the end of experiment (final sample) were not significantly different (pxa0>xa00.05) for crude protein, moisture or ash. The crude lipid of the LF in the final period was significantly lower (pxa0<xa00.05) compared to others in both periods. The survival, productivity and food conversion ratio were significantly better (pxa0<xa00.05) in the HF and LF treatments compared to those of the control. The best shrimp performance was obtained with solids removal. The lower flow in the clarifier facilitated particle settling, allowing adjustment of the flow.

The Effect of Ammonia, Nitrite, and Nitrate on the Oxygen Consumption of Juvenile Pink Shrimp Farfantepenaeus brasiliensis (Latreille, 1817) (Crustacea: Decapoda)

The pink shrimp Farfantepenaeus brasiliensis is native in southern Brazil and is potentially suited for aquaculture. Under intensive culture, the accumulation of nitrogenous compounds results from excretion by the shrimp and from the processes of feed decomposition and nitrification. The objective of this study was to evaluate ammonia, nitrite, and nitrate toxicity effects on oxygen consumption of juvenile pink shrimp. Shrimps (initial weight 0.7 ± 0.15 g) were exposed over a period of 30 days to 50%, 100%, and 200% of the safe levels of total ammonia (TAN = 0.88 mg/L), nitrite (NO2− = 10.59 mg/L), and nitrate (NO3− = 91.20 mg/L) for the species. The specimens were individually collected and placed in respirometry chambers, where the oxygen consumption was measured over a period of two hours. Throughout the experiment there was no significant difference (p > 0.05) among treatments in terms of survival and growth. The pink shrimp juveniles exposed to nitrogen concentrations of 200% of the nitrite and nitrate safe level showed the highest oxygen consumption (p < 0.05).

Short communication: Acute toxicity of hydrogen peroxide in juvenile white shrimp Litopenaeus vannamei reared in biofloc technology systems

Biofloc technology (BFT) has been used to rear white shrimp, Litopenaeus vannamei. In this culturing system, the absence of aeration causes a rapid drop in dissolved oxygen levels, and hydrogen peroxide (H2O2) can be used as an emergency source of oxygen. This study aimed to determine the lethal concentration and safe level of H2O2 applied as a source of oxygen for juvenile white shrimp L. vannamei in a BFT system. Juveniles (1.39xa0±xa00.37xa0g) were exposed for 2xa0h to different concentrations of H2O2 [29 (100), 58 (200), 116 (400), 174 (600), 232 (800), 290 (1,000) and 348 (1,200)xa0μLxa0H2O2/L (ppm H2O2-29xa0%/L)] in addition to a control group without addition of H2O2, and the survival rates were monitored for 96xa0h. The LC50 values and 95xa0% confidence intervals at 24, 48, 72 and 96xa0h were 235.5 (207–268), 199.1 (172–229), 171.1 (146–198) and 143.3 (120–170)xa0μLxa0H2O2/L, respectively. The safe level was 14.3xa0μLxa0H2O2/L, and the highest concentration with survival rates similar to the control group (NOAEC) was 29xa0μLxa0H2O2/L. In these concentrations, H2O2 can be used as a safe source of oxygen for L. vannamei reared in BFT systems.

Acute toxicity of carbon dioxide to juvenile marine shrimp Litopenaeus vannamei (Boone 1931)

ABSTRACT Elevated concentrations of dissolved carbon dioxide (CO2) and reduced pH levels are observed during the culture and transportation of aquatic organisms. Studies on the toxicity effects of CO2 in penaeid shrimp are scarce when compared to the amount of research in fish. The objective of the present study was to determine the lethal concentration and safety levels of CO2 for juvenile white shrimp Litopenaeus vannamei. Juveniles (1.76 ± 0.36 g) were exposed for 96 h to one of six concentrations of dissolved CO2 (14.5, 23.8, 59.0, 88.0, 115.0, and 175.0 mg/L) or a control condition (without the addition of CO2), and their survival was monitored for 96 h. The LC50 values with 95% confidence limits at 24, 48, 72, and 96 h were 130.05 (104.2–162.1), 77.2 (73.8–80.02), 69.65 (65.47–74.32), and 59.12 (53.08–66.07) mg/L of CO2, respectively. The calculated safety level was 5.9 mg/L of CO2, and the highest concentration that did not induce significantly higher mortality than that observed in controls (NOEC) was 23.8 mg/L of CO2. We recommend that CO2 levels should be kept below the safety level obtained in this study.