Luís Henrique da Silva Poersch

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.

Perspectivas para o desenvolvimento dos cultivos de camarões marinhos no estuário da Lagoa dos Patos, RS

Shrimp production in Brazil has presented a significant increase in the last few years, especially in the northeastern region. Although climatic conditions in southern Brazil do not allow year-round production, considerable investments have been made in the region. In the estuarine area of Patos Lagoon, the culture of the native Farfantepenaeus paulensis in cages and pen enclosures, and of Litopenaeus vannamei in earthen ponds are being developed as new activities that will certainly produce social and economical development to the region. Nevertheless, the implantation of shrimp farming without proper ordination and control may generate serious environmental problems. The present paper presents an overview of the environmental characteristics of the area and describes the farming systems currently adopted. Furthermore, the main challenges faced by this new activity, such as the discussion of a legislation adapted to local conditions, and the definition of areas appropriate for farming are presented. Finally, the sustainable development of shrimp farming is discussed under social, economical and environmental perspectives.

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.

The Effect of Probiotics in a Litopenaeus vannamei Biofloc Culture System Infected with Vibrio parahaemolyticus

We analyzed the effect of commercial bacterial probiotics on a Litopenaeus vannamei biofloc culture system infected with Vibrio parahaemolyticus. Three replicates of two experimental treatments were conducted: a control system (without probiotic) and a system with the application of a multistrain probiotic containing Bacillus spp., Enterococcus spp., Thiobacillus spp., and Paracoccus spp. applied to the water and another multistrain probiotic containing Bacillus spp., Enterococcus spp., and Lactobacillus spp. added to the feed. Growth and survival rate were significantly higher in the probiotic treatment group (P < 0.05), and the shrimp in the probiotic group also had a lower (P < 0.05) FCR compared to the shrimp in the control group (1.4 vs. 2.7).

Rickettsia-Associated Mortality of the Yellow Clam Mesodesma mactroides (Bivalvia: Mesodesmatidae) in Southern Brazil

The yellow clam Mesodesma mactroides (Deshayes, 1854) is an intertidal sandy beach bivalve that is distributed from the southeast of Brazil (Ilha Grande, Rio de Janeiro State, 23°S) to Argentina (Isla del Jabali, Buenos Aires Province, 41°S) (Rios, 2009). Historically, the yellow clam had been considered an important economic resource (Coscaron, 1959). However, yellow clam populations collapsed as

A Comparison of the Reproductive Performance of the Wild Pink Shrimp Species Farfantepenaeus paulensis and Farfantepenaeus brasiliensis in Captivity

ABSTRACT The aim of this study was to compare the reproductive performance of the wild shrimp species Farfantepenaeus paulensis and Farfantepenaeus brasiliensis in captivity. The broodstocks were collected in offshore waters in Santa Catarina and transferred to the Marine Station of Aquaculture of the Federal University of Rio Grande. Broodstocks with a similar body weight between the two species were selected to measure reproductive performance. Females with mature ovaries were identified each day to obtain measures of reproductive performance. After spawning, fertilization rates were determined by microscopic examination. In addition, three samples of 100 eggs were collected to determine hatching rates, and three samples of 100 nauplii were collected to evaluate the rate of metamorphosis to protozoa. For males, spermatophores were manually extruded, weighed, and homogenized in 2 mL calcium-free saline solution, and 0.1 mL trypan blue was added. Sperm counts, abnormal cells (malformations of the main body or absence of the spike), and dead cells (blue coloration) were estimated with cell counts, using a hemacytometer under a light microscope. Spermatophore melanization was checked. The larval production of the two species was similar, but F. brasiliensis spawned in less time after unilateral eyestalk ablation. The spermatophore weight and sperm count were higher in the F. brasiliensis males, and none of the shrimp showed melanization.

Shrimp farming as an alternative to artisanal fishermen communities: the Case of Patos Lagoon, Brazil

The shrimp Farfantepenaeus paulensis is considered a suitable species for culture in the Patos Lagoon estuary, southern Brazil, where its catch has been decreasing in the last few years. Considering the potential of estuarine areas for shrimp farming, the application of low-cost structures to culture shrimp, such as the pen enclosures, is being proposed as an alternative source of income for artisanal fishermen and farmers living near Patos Lagoon. From an economical standpoint, these alternative systems present several advantages over the traditional pond-based culture systems since land, water pumping and artificial aerations are not required, high natural productivity is available and inexpensive materials are employed in the construction of grow-out structures. This paper reviews the farming of F. paulensis in the pen enclosures as an alternative to the artisanal fishing communities of the Patos Lagoon estuary. Particular emphases are placed on the development of culture systems, social and environmental impacts, constraints and perspectives.

Effect of low salinity on the yellow clam Mesodesma mactroides

The aim of this study was to determine the lethal salinity (LC50) for the yellow clam Mesodesma mactroides (Bivalvia: Mesodesmatidae) and identify histopathological alterations that could be used to diagnose structural changes in clam tissue. Clams in two size classes (adults and juveniles) were placed in 10 L chambers and exposed to salinities of 35, 30, 25, 20, 15, 10, and 5 g/L. There were triplicate chambers with seven clams each for each salinity. The LC50 values for a 48 h exposure were 6.5 g/L and 5.7 g/L for adults and juveniles, respectively. For a 96 h exposure, the LC50 values were 10.5 g/L for adults and 8.8 g/L for juveniles. The histological examination of yellow clams exposed to 10 g/L for 96 h showed intercellular oedema and necrotic foci in the epithelium of the digestive gland and occlusion of the lumen of the digestive gland. In conclusion, M. mactroides can be characterised as a moderately euryhaline species, tolerating salinities from 35 to 15 g/L.

The use of different aerators on Litopenaeus vannamei biofloc culture system: effects on water quality, shrimp growth and biofloc composition

This study evaluated the effects of different aeration types on water quality, shrimp growth and biofloc composition in a Litopenaeus vannamei culture. The study was conducted with three treatments: (1) PR—propeller aspirator pump aerator; (2) VP—vertical pump aerator; and (3) BL—diffused air blower. The study was performed in a greenhouse with nine 35,000-L rectangular tanks. Water quality parameters (temperature, salinity, dissolved oxygen, pH, ammonia, nitrite, nitrate, settleable and suspended solids) were measured along the 33 experimental days. Moreover, samples were collected to quantify the microorganisms present in the tanks. At the end of the study, samples of the biofloc of each tank were collected to proximal analysis. Throughout the experiment, the temperature, pH, salinity and alkalinity were maintained within the recommended levels for L. vannamei. The propeller treatment showed a concentration of total ammonia above the recommended levels and lower densities of ciliates and flagellates, most likely because of inadequate biofloc formation in this treatment. The final weight was higher in the blower and propeller treatments. However, survival was lower in the propeller treatment compared to the other treatments. The results of this study suggest that diffused air systems (air blower) improve the formation of biofloc and growth performance of L. vannamei.

The Challenge of Sustainable Aquaculture: Effects on the Environment of the Patos Lagoon Estuary

Abstract Over the last ten years, catches of the pink shrimp Farfantepenaeus paulensis by artisanal fishermen in the Patos Lagoon Estuary (southern Brazil) have been decreasing. This has created economic and social problems for approximately 3500 families, who rely on this activity as their main source of income. In an attempt to solve these problems, the Mariculture Laboratory of the University of Rio Grande (FURG) has developed a technological package for the pen culture of this species in the estuarine area. This culture system requires low investment, is easy to manage and allows fishermen to continue their normal activities. This study evaluates the influences that this culture may have on the macrobenthic communities surrounding the enclosures. The experiment was carried out around a 0.3 ha pen placed in the estuarine area adjacent to Marinheiros Island (Rio Grande county). This area has a central channel over 5 meters deep and shallow areas less than 1.5 meters deep near the shore, where the pen was installed. Two linear transects were carried out in opposite directions parallel to the shoreline, starting from the edge of the pen. Monthly water and sediment samples were collected 5, 15, 30 and 100 m from the pen to evaluate oxygen consumption, chlorophyll-a, total phosphorus and total nitrogen concentrations. Characterization of the macrobenthic community revealed the presence of Laeonereis acuta, Nephtys fluviatilis, Neanthes sp., Kalliapseudes schubartii, Callinectes sapidus, Erodona mactroides, Heleobia australis, Heteromastus similis and isopods. Significant differences in the diversity and abundance of the species were detected between the samples, especially at the closest point to the pen, where more H. similis specimens were found. No significant differences in oxygen consumption, total nitrogen or total phosphorus concentrations were found between the sampled points. These results demonstrate that this kind of culture system does not influence water quality in the surrounding area. The higher abundance of H. similis near the pen (1 m) demonstrated a very limited impact on the macrobenthic community. Organic matter accumulation zones created by the presence of the pen might favor the presence of H. similis, which is a deposit feeder. This result could become more significant if the culture conditions are intensified or more pens are installed.