Nuclear Markers of Danube Sturgeons Hybridization

Acipenseriformes are composed of 25 sturgeon species and two paddlefish species distributed exclusively in the northern hemisphere. The Danube River and the Black Sea were originally inhabited by six sturgeon species but two are extinct and only four are still reproducing currently in the Lower Danube: Huso huso, Acipenser stellatus, A. gueldenstaedtii and A. ruthenus. Sturgeon species hybridize more easily than other fish and the determination of pure species or hybrid status is important for conservation and for breeding in fish farms. This survey demonstrated that morphological determination of this status is not reliable and a molecular tool, based on eight microsatellites genotypes is proposed. This method, based on three successive statistical analyses including Factorial Correspondence Analysis (FCA), Structure assignation and NewHybrids status determination, showed a high efficiency in discriminating pure species specimens from F1, F2 and two kinds of backcross individuals involving three of the four reproducing Lower Danube sturgeon species

Managing Polyploidy in Ex Situ Conservation Genetics: The Case of the Critically Endangered Adriatic Sturgeon (Acipenser naccarii)

While the current expansion of conservation genetics enables to address more efficiently the management of threatened species, alternative methods for genetic relatedness data analysis in polyploid species are necessary. Within this framework, we present a standardized and simple protocol specifically designed for polyploid species that can facilitate management of genetic diversity, as exemplified by the ex situ conservation program for the tetraploid Adriatic sturgeon Acipenser naccarii. A critically endangered endemic species of the Adriatic Sea tributaries, its persistence is strictly linked to the ex situ conservation of a single captive broodstock currently decimated to about 25 individuals, which represents the last remaining population of Adriatic sturgeon of certain wild origin. The genetic variability of three F1 broodstocks available as future breeders was estimated based on mitochondrial and microsatellite information and compared with the variability of the parental generation. Genetic data showed that the F1 stocks have only retained part of the genetic variation present in the original stock due to the few parent pairs used as founders. This prompts for the urgent improvement of the current F1 stocks by incorporating new founders that better represent the genetic diversity available. Following parental allocation based on band sharing values, we set up a user-friendly tool for selection of candidate breeders according to relatedness between all possible parent-pairs that secures the use of non-related individuals. The approach developed here could also be applied to other endangered tetraploid sturgeon species overexploited for caviar production, particularly in regions lacking proper infrastructure and/or expertise

Design and operational characteristics of a Tilapia rearing system for temperate regions

Typescript (photocopy).A small-scale spawning and rearing facility for the production of Tilapia aurea fingerlings was constructed in a polyethylene-covered greenhouse. Spawning and fry rearing during the winter extended the growing season by two months. Fish averaging 3.0 cm total length were stocked in ponds during April. Lights and small immersion heaters were used to regulate spawning conditions in 1,100 liter fiberglass tanks. T. aurea broodfish were stocked and allowed to spawn. The fry were subsequently collected and treated with synthetic testosterone producing only male fish. Fry hormone treatment was done in a small recirculating system to maintain temperatures above 20 C. After sex-reversal, fry were held indoors in tanks until outside water temperature stabilized at 20 C. The fish were then stocked into two 0.1 hectare ponds. Over a 66 day period, 59 broodfish spawned, resulting in 2,348 fingerlings being produced. After 191 days of pond culture, 2,130 fish weighing an average of 518 g were harvested. No fry were recovered from the ponds, indicating that the hormone-treatment was successful. Total construction and operating costs of the fingerling production system were used in a computer budget simulation model to estimate the profitability of the system. A small facility such as the one described and equipped for research purposes would produce fingerlings at an estimated unit cost of $0.83. Reducing equipment requirements to reflect those of an individual or commercial operator lowered production costs to$0.27 per fingerling. A system that could produce 120,000 fingerlings over six months would reduce costs to $0.18 per fingerling. A telephone survey of tilapia producers in the United States provided information on current production methods and market problems. Assessing market demand and providing a steady source of fish to retailers appear essential to the establishment of a successful tilapia operation

Design and operational characteristics of a Tilapia rearing system for temperate regions

Typescript (photocopy).A small-scale spawning and rearing facility for the production of Tilapia aurea fingerlings was constructed in a polyethylene-covered greenhouse. Spawning and fry rearing during the winter extended the growing season by two months. Fish averaging 3.0 cm total length were stocked in ponds during April. Lights and small immersion heaters were used to regulate spawning conditions in 1,100 liter fiberglass tanks. T. aurea broodfish were stocked and allowed to spawn. The fry were subsequently collected and treated with synthetic testosterone producing only male fish. Fry hormone treatment was done in a small recirculating system to maintain temperatures above 20 C. After sex-reversal, fry were held indoors in tanks until outside water temperature stabilized at 20 C. The fish were then stocked into two 0.1 hectare ponds. Over a 66 day period, 59 broodfish spawned, resulting in 2,348 fingerlings being produced. After 191 days of pond culture, 2,130 fish weighing an average of 518 g were harvested. No fry were recovered from the ponds, indicating that the hormone-treatment was successful. Total construction and operating costs of the fingerling production system were used in a computer budget simulation model to estimate the profitability of the system. A small facility such as the one described and equipped for research purposes would produce fingerlings at an estimated unit cost of $0.83. Reducing equipment requirements to reflect those of an individual or commercial operator lowered production costs to$0.27 per fingerling. A system that could produce 120,000 fingerlings over six months would reduce costs to $0.18 per fingerling. A telephone survey of tilapia producers in the United States provided information on current production methods and market problems. Assessing market demand and providing a steady source of fish to retailers appear essential to the establishment of a successful tilapia operation

The effects of stocking density on two Tilapia species raised in an intensive culture system

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Biblioraphy: leaves 48-55.Not availabl