Wilson Wasielesky

Importance of biofilm for water quality and nourishment in intensive shrimp culture

Abstract Experiments were conducted to test the usefulness of biofilms—a microbial consortium associated with extracellular polymeric substances attached to submersed surfaces—in reducing the levels of ammonium and phosphate of rearing system water, and as a food source for the shrimp Farfantepenaeus paulensis . A mature biofilm, which is able to keep ammonium and phosphate at low levels, occurred 10–15 days after tank cleanup, and was characterized by chlorophyll- a concentration around 5 μg/cm 2 . It was mainly composed of pennate diatoms ( Amphora , Campylopyxis , Navicula , Sinedra , Hantschia and Cylindrotheca ; ca. 9×10 4 cells/mg of biofilm) and filamentous cyanobacteria ( Oscillatoria and Spirulina ; ca. 2×10 5 cells/mg), though bacteria (max. 1.48×10 7 /mg), flagellates (max. 1.08×10 3 /mg) and ciliates (max. 3.51×10 2 /mg) were also present. Pennate diatoms and filamentous cyanobacteria were responsible for the largest uptake of ammonium from the water, but nitrifying bacteria also played an important role. The presence of a biofilm lead to reduced exportation of phosphorus (33% less phosphate) and to a higher output of nitrate+nitrite, instead of ammonium. Biofilm was also an important complementary food source for the shrimp, increasing their growth.

Acute toxicity of ammonia to various life stages of the São Paulo shrimp, Penaeus paulensis Pérez-Farfante, 1967

Each life stage of the Sao Paulo shrimp, Penaeus paulensis, was exposed to ammonia in a series of acute toxicity tests, by the semistatic method, at 25 °C and salinity at 28 ppt. A pronounced sensitivity was observed in the egg stage. In this phase, 0.30 mg/l NH3-N caused death of 50% of the embryos. The 24-h LC50 values for nauplii, zoeae, myses and postlarvae were, respectively, 102.30, 22.93, 74.87 and 24. 19 mg/l total ammonia-N (4.25, 1.79, 2.91 and 1.40 mg/l NH3-N). The 96-h LC50 values for zoeae, myses and postlarvae were 9.39, 21.98, 5.49 mg/l total ammonia-N (0.73, 0.85 and 0.32 mg/l NH3-N). The LC50 of ammonia for juveniles (5.45 ± 0.4 g mean live-weight) and for adults (31.43 ± 1.3 g mean live-weight) were also measured. The 24-h LC50 values for juveniles and adults were, respectively, 51.87 and 61.63 mg/l total ammonia-N (1.47 and 1.59 mg/l NH3-N) and the 96-h LC50 values were 38.72 and 42.49 mg/l total ammonia-N (1.10 and 1.06 mg/l NH3-N). An analysis of variance showed that there was no direct relationship between shrimp development and its tolerance to ammonia (P > 0.05) and that eggs, zoeae and postlarvae are very sensitive to ammonia:. The “safe level” for rearing P. paulensis was estimated to be 0.03 mg/l NH3-N. In general, P. paulensis is less resistant to ammonia than other species of shrimp.

Comparative Analysis of Pink Shrimp, Farfantepenaeus paulensis, and Pacific White Shrimp, Litopenaeus vannamei, Culture in Extreme Southern Brazil

ABSTRACT Culture potential of the native pink shrimp, Farfantepenaeus paulensis, and exotic Pacific white shrimp, Litopenaeus vannamei, was analyzed in extreme southern Brazil. The experiment was conducted at the Marine Aquaculture Station, University of Rio Grande, Rio Grande do Sul State. After nursery, pink shrimp (0.16 g) and Pacific white shrimp (0.17 g) juveniles were transferred to a 450 m2 earthen pond internally divided into six circular (21 m2 each) experimental pens. Pens were randomly assigned to a treatment (pink shrimp or Pacific white shrimp) and stocked at 15 shrimp/m2. Shrimp growth was monitored during 102 days in the summer. Feed was composed of a commercial diet and a fresh frozen mixture (fish and crustacean). After 30 days of culture, Pacific white shrimp showed significantly higher increases in mean weight, reaching at-harvest weight of 12.52 g compared to 11.17 g for pink shrimp. Water quality parameters presented optimal growing conditions for both species, except for lower temperatures (19°C) during the last two weeks of culture, which resulted in a drastic decrease in the growth rate of Pacific white shrimp. These results indicated a better tolerance for lower water temperatures on the part of shrimp. Although the lower temperatures resulted in a reduced number of cycles (1 or 2 per year), the estimated yield for pink shrimp (1,451 kg/ha) and Pacific white shrimp (1,790 kg/ha) suggested that the production per cycle in extreme southern Brazil is comparable to that in the other Brazilian States. Despite the more favorable results for Pacific white shrimp, the culture of pink shrimp is also recommended, but further studies are necessary to improve its growth performance under culture.

The effects of salinity on acute and chronic nickel toxicity and bioaccumulation in two euryhaline crustaceans: Litopenaeus vannamei and Excirolana armata.

We investigated the influence of salinity (5 ppt versus 25 ppt) on acute (96-h LC(50)) and chronic toxicity (15-30 day LC(50)) of Ni in two euryhaline crustaceans, the shrimp (Litopenaeus vannamei) and the isopod (Excirolana armata). 96-h LC50 values were 41 μmolL(-1) and 362 μmolL(-1) for L. vannamei and 278 μmolL(-1) and >1000 μmolL(-1) for E. armata at 5 ppt and 25 ppt, respectively. Speciation analysis demonstrated that complexation with anions such as SO(4)(2-), HCO(3)(-) and Cl(-) at 25 ppt had a negligible effect on reducing the free Ni(2+) ion component in comparison to 5 ppt. The salinity-dependent differences in acute Ni toxicity could not be explained by differences in Ni bioaccumulation. Therefore, differences in physiology of the organisms at the two salinities may be the most likely factor contributing to differences in acute Ni toxicity. Chronic LC(50) values (2.7-23.2 μmolL(-1)) were similar in the two species, but salinity had no significant effect, indicating that water chemistry and osmoregulatory strategy do not influence chronic toxicity. However chronic (15-day) mortality in both species could be predicted by acute (96-h) Ni bioaccumulation patterns.

NURSERY OF LITOPENAEUS VANNAMEI REARED IN A BIOFLOC SYSTEM: THE EFFECT OF STOCKING DENSITIES AND COMPENSATORY GROWTH

ABSTRACT The purpose of this study was to evaluate the effect of stocking density and the occurrence of compensatory growth in the white shrimp Litopenaeus vannamei in the nursery phase reared in a biofloc culture system. Two experiments were performed in a recirculating water system with 12 experimental tanks (microcosm), each with a bottom area of 0.5 m2. The tanks were supplied by a matrix 70-m2 biofloc technology water tank (macrocosm), where a shrimp biofloc technology systems culture was maintained concurrently. The water was returned to the system by gravity, providing a daily renewal rate of approximately 4,800%. During the first experiment, L. vannamei postlarvae with an initial weight of 0.003 g were cultured for 30 days at densities of 1,500, 3,000, 4,500, and 6,000 shrimp/m2. The cultures reached significantly different final weights (P < 0.05) of 0.45 g, 0.33 g, 0.30 g, and 0.23 g, respectively. Mean survival rates were greater than 87.6% in all treatments. To evaluate the occurrence of compensatory growth in L. vannamei after a period of enclosure stress, the second experiment was organized in 2 phases. During the first, shrimp postlarvae were reared at densities of 1,500, 3,000, 4,500, and 6,000 shrimp/m2 for 35 days. The shrimp were then restocked at a density of 300 shrimp/m2 and were maintained until compensatory growth was observed. In 20 days, the shrimp showed full compensatory growth. The mean final weight and survival rate did not differ significantly (P > 0.05) between the treatments. The results confirm that the strategy of enclosure rearing can be applied to the culture of L. vannamei.

Long-term ammonia toxicity to the pink-shrimp Farfantepenaeus paulensis.

Juvenile pink-shrimp Farfantepenaeus paulensis were exposed (75 days) to NH(3) (0.016-0.287 mg L(-1)) under static condition with water renewal every 24h. Experiments were performed at 20 degrees C, at a water salinity of 15 ppt, and at pH 7.8. Endpoints analyzed were survival, growth and predation rates. After 75 days of exposure, survival was >or=90% in all concentrations tested. However, growth (carapace length and wet body mass) was reduced after exposure to NH(3) concentrations as low as 0.033 mg L(-1), while the relative growth (dry body mass and ash content) was reduced after exposure to the highest NH(3) concentration (0.287 mg L(-1)). Predatory activity was inhibited after exposure to 0.144 or 0.287 mg L(-1) NH(3). Post-larvae exposed (75 days) to 0.301 mg L(-1) NH(3) under the same experimental conditions also showed a reduced growth (wet body mass) and relative growth (dry body mass). In addition, they showed decreased body lipids content and increased body glycogen and glucose contents. However, no changes in body protein, chitin and uric acid contents were observed. Also, NH(3) did not affect post-larvae feeding response. Altogether, findings suggest that F. paulensis reduces its food intake to limit the internal accumulation of nitrogenous waste products when exposed for long time to high levels of ambient ammonia. As a consequence, shrimp show a marked change in energy metabolism, characterized by a decreased content of body lipids paralleled by an increased content of body carbohydrates, resulting in a significant reduction in growth.

Growth and survival of pink shrimp (Farfantepenaeus paulensis) postlarve in cages and pen enclosures

Um pacote tecnologico para o cultivo do camarao-rosa em estruturas alternativas de baixo custo, gaiolas e cercados, vem sendo aplicado em conjunto com pescadores artesanais do estuario da Lagoa dos Patos, no extremo sul do Brasil. Embora a tecnologia para o cultivo intensivo de pos-larvas (PL) em laboratorio ja esteja bem documentada, informacoes referentes a sobrevivencia e crescimento desses organismos na fase de bercario ainda sao escassas para cercados e gaiolas no ambiente natural. Em virtude destes fatos, o objetivo do trabalho foi comparar o crescimento e a sobrevivencia de pos-larvas de F. paulensis durante a fase de bercario em gaiolas e cercados no ambiente. Para o desenvolvimento do trabalho, foram utilizadas seis gaiolas (2,0 ´ 2,0 ´ 1,4 m) com malha de poliester revestida de PVC com abertura de malha de 1,5 mm. Em cada unidade foram estocadas 800 PL26. Para verificar a influencia do substrato, foram espalhados uniformemente 10 cm de sedimentos da propria enseada dentro de tres gaiolas, simulando um cercado. A taxa de sobrevivencia dos camaroes obtida nas gaiolas foi de 92,2% e nos cercados de 88,7%, nao sendo detectadas diferencas (P > 0,05). Porem, o peso medio final dos camaroes nos cercados (1,05 ± 0,05 g), foi superior (P < 0,05) ao peso dos camaroes nas gaiolas (0,88 ± 0,12 g). A especie pode ser cultivada na fase de bercario em gaiolas ou cercados sem prejuizo a sobrevivencia final. Entretanto, recomenda-se que a fase de bercario seja realizada preferencialmente em cercados.

The role of lipoic acid in the protection against of metallic pollutant effects in the shrimp Litopenaeus vannamei (Crustacea, Decapoda).

The effects of cadmium (Cd) and arsenic (As), dosed alone or in combination have been poorly investigated in crustaceans. Besides, it is not known if dietary supplementation of exogenous antioxidants, like lipoic acid (LA), might prevent or even reverse toxic effects of Cd and As. The objective of the present study was to evaluate the role of lipoic acid in modulating biochemical responses after Cd and As exposures in Litopenaeus vannamei. Muscle from shrimp exposed to Cd alone or Cd+As showed a decrease in glutathione (GSH) levels, while the pre-treatment with LA reversed this situation. In this tissue, the pre-treatment with LA also induced an increase in glutathione-S-transferase (GST) activity in all groups. In hepatopancreas it was observed a marked accumulation of Cd and As, a decrease in the reactive oxygen species (ROS) concentration in response to Cd exposure alone (-LA); concomitant in the same group it was observed an increment of metallothionein-like content. As exposure induced an increase in GSH levels but LA reversed this increase. Also, LA showed to increase the GST activity in all groups treated. Besides, in this organ LA showed to augment total antioxidant competence. Obtained results indicate that LA can be used as a chemo-protectant against oxidative insults in shrimp.

Recent developments on broodstock maturation and reproduction of Farfantepenaeus paulensis

Esta revisao constitui a primeira iniciativa de reunir em um so documento os recentes desenvolvimentos/estudos sobre maturacao e reproducao de Farfantepenaeus paulensis em cativeiro. O objetivo do presente estudo foi revisar informacoes que poderao colaborar para a producao sustentavel de nauplios de F. paulensis em cativeiro. Foi dada enfase aos estudos que vem sendo realizados na ultima decada no Laboratorio de Maricultura, Fundacao Universidade Federal do Rio Grande, RS. A discussao aborda aspectos relativos ao ciclo reprodutivo, maturacao ovariana, sistemas de maturacao e desova, inseminacao artificial, performance de reprodutores e manutencao de reprodutores em cativeiro.

Nursery of Pink Shrimp Farfantepenaeus paulensis in Biofloc Technology Culture System: Survival and Growth at Different Stocking Densities

ABSTRACT Farfantepenaeus paulensis postlarvae were reared at different stocking densities during the nursery phase in a biofloc technology (BFT) culture system without water exchange. An experimental system comprising a 70-m3 macrocosm tank containing shrimp cultured in the BFT system at 300 shrimp/m2, with a productivity of 2.7 kg/m2 was used, which supplied twelve 0.5-m2 tanks at densities of 500, 1,000, 1,500, and 2,000 shrimp/m2 through pumping. The experiment lasted for 30 days. The water was recirculated 48 times a day from the macrocosm to the microcosm tanks. The growth rate, final weight, survival, and productivity of the shrimp were analyzed. There were no significant differences in the water quality parameters among treatments because the water input and output from the macrocosm tank to the experimental units was constant. There were also no significant differences (P > 0.05) in survival. However, the final weight and productivity were significantly different (P < 0.05) among treatments. The treatments with the lowest stocking densities were associated with the highest weights, whereas the treatments with the highest stocking densities presented the highest productivities. The study demonstrates that the use of a BFT culture system may enable the culture of this species at high stocking densities in nurseries. The results also demonstrate the possibility of using a high stocking density for commercial culture and restocking programs.