No abstract

No abstract

Semen conservation methods have been extensively studied for fish species over the last 60 years. Cryopreservation techniques can be divided into two types: one with slow cooling rates like traditional freezing and the other with ultrarapid rates as used in vitrification. These protocols increase the time over which semen samples can be used for reproduction or sperm quality analysis. Marine fish possess greater resistance than freshwater species to variations in osmolality. This favours the application of these methods, which produce better results after thawing and offer high biotechnological potential for aquaculture. In the last 15 years, sperm cryopreservation studies have been carried out in 32 marine species, but there are few analyses of the effects of freezing on the morphology and physiology of sperm cells. The object of this review was to provide recent data on semen cryopreservation in marine fish species and to suggest variables which may be applied in future research.

No abstract

No abstract

A comparison between water exchange and settling tank as a method for suspended solids management in intensive biofloc technology systems: effects on shrimp (Litopenaeus vannamei) performance, water quality and water use Abstract Biofloc systems rely on microbial processes in the water column to recycle animal waste products, reducing the need for water exchange. These increases biofloc concentration in the water and some form of removal is needed. An experiment was carried out to evaluate two management practices to control biofloc in Litopenaeus vannamei culture. Six tanks (48 m 3 ) were divided into two treatments: water exchange and solid settler. Shrimp were stocked at 164 shrimp m À2 and with 0.67 g of weight. After 61 days, shrimp under solid settler treatment demonstrated mean weight of 12.7 AE 0.5 g with survival of 73.8 AE 1.4%, and those under water exchange had a final weight of 10.1 AE 0.2 g and survival rate of 57.8 AE 11.1%. Total suspended solids did not differ between the treatments: 326.8 AE 24.9 mg L À1 for water exchange and 310.9 AE 25.3 mg L À1 for solid settlers. Settleable solids and productivity/respiration ratio was higher (P < 0.05) in water exchange treatment, indicating differences in physical and biological characteristics of bioflocs. Solids removal method influenced the water use, in which 1150 AE 249 L of water was necessary to produce one kilogram of shrimp using water exchange strategy, and 631 AE 25 L kg À1 with the use of settlers. Our results indicate that continuous operation of settlers can reduce variability in solids characteristics and water quality variables such as ammonia. Both strategies are efficient in controlling biofloc concentrations of the water; however, settlers can reduce water use and improve shrimp production.

Microalgae have great biotechnological potential but the high cost of traditional formulae culture media is one of the limiting factors to their commercial cultivation. As an alternative, the use of residual water from other activities has been proposed as a culture medium. The goal of this study was to produce Chaetoceros muelleri, Nannochloropsis oculata and Tetraselmis chuii biomass using residual water from an intensive Litopenaeus vannamei biofloc cultivation system and to verify the ammoniacal nitrogen, nitrite, nitrate and orthophosphate consumption. The microalgae cultures were developed until the second day of their stationary phase in the following treatments: 100% f/2 culture media; 100% residual water; residual water diluted 50% with marine water. T. chuii and N. oculata presented the best relative biomass average (576 mg L−1; 474 mg L−1)(P > 0.05). All the species completely assimilated the orthophosphate in 2 days. In 10 days, T. chuii and N. oculata assimilated 87% and 85% of nitrate respectively. It can be concluded that residual water from an L. vannamei biofloc cultivation system can be used as an alternative culture medium for T. chuii and N. oculata biomass production. Moreover, the microalgae biomass proved to be very effective in recycling the dissolved nutritive salts.

No abstract