Early Sturgeon Sex Discrimination
Many commercially relevant fish species such as species of sturgeon have no externally visible sexual dimorphism, which makes breeding females only in aquaculture more difficult, minimises the production yield and increases the production costs. Up until now, no gender-specific marker has been identified for sturgeons as well as for many other commercial fish species.
The caviar industry is a particularly profitable aquaculture branch for a molecular-biological sex test for juvenile and adolescent sturgeons. Early sexual identification can significantly decrease the production costs by increasing the number of females (caviar production) only in the production facilities whilst maintaining a balance of male animals for intensive fattening (meat production) and use in continuous propagation. At the same time spin-offs genomic analysis may identify fast growth genes, increase meat production, or better egg quality for caviar.
At the present time, the ratio at normal production facilities is approximately 1:1 males to females through natural selection. If an early sex test is available, then this ratio could soon be manipulated, depending upon whether the production is required for either caviar or meat.
The search for sturgeon sex discrimination markers
TUNATECH and aquaFUTURE have a long history of collaboration on numerous projects ranging from salmon genetics and restocking of salmon in the river Rhine but especially in the field of sturgeon cultivation.
The search for sturgeon sex discrimination markers has also been carried out through research projects between TUNATECH, Heinrich-Heine-University of Duesseldorf and the Landesfischereianstalt in Born (Mecklenburg-Vorpommern), based on hormonal and histological changes in both adult and juvenile sturgeons. TUNATECH already invested considerable time and money into the research & development of a molecular-biological sex test for three sturgeon species.
The sampling was performed in Aquatir, one of the world largest and modern sturgeon farms, in which aquaFUTURE played a leading role in its implementation, where blood, tissue and mucus samples of sexually mature Belugas (Huso huso), Russian Sturgeons (Acipenser gueldenstaedtii) and Sterlets (Acipenser ruthenus) with known sex were taken.
Within TUNATECH's laboratories DNA and RNA were extracted from the preserved samples and a comprehensive analysis was performed for female and male Beluga, Sterlet and Russian Sturgeon samples, respectively. From these analyses female reference data were designed, onto which all other data were mapped.
With the help of this analysis, several putative sex specific markers were found and analysed further. Fortunately, through the latest results by a EU funded research project (STURGEoNOMICS), it has been possible to combine previous TUNATECH results and techniques with the new findings to produce an Early Sturgeon Sex Discrimination (ESSD) customised service for the industry.
The various steps of Early Sturgeon Sex Discrimination
This novel and customised solution for sex discrimination for multiple sturgeon species at early life stages will be made available in 2021 for a limited number of clients. Based on both laboratory and field experience in analysis, sampling and tagging using the range of products it has been made possible to provide a customised service package to suit all aquaculture facilities, be they large or small.
The commercial template developed by TUNATECH describes the various steps involved in applying our ESSD solution to a commercial environment. The initial step requires the marking or tagging of individuals usually with a passive integrated transponder (PIT) tag such that they can be recognised at a later stage.
TUNATECH and aquaFUTURE has over 20 years of experience in this field on numerous fish species. Secondly the process of obtaining DNA samples from individuals is then required using a tissue sampling unit followed by the molecular analysis to identify sex-specific markers based on recent scientific evidence and our own proof of concept.
A number of scenarios have been developed and have taken into consideration the large numbers of fish to be examined in some cases. A high throughput can be achieved in the first instance, followed by software analysis and combination of tagging and molecular results to provide a relatively automated sorting system for separation of males and females.
The techniques and tools used can be further applied in farm breeding programs to distinguish between fast growers and also single sex propagation scenarios (all females) with proof of concept/treatment within a short period of time. The ESSD template can be customised for commercial farms from small (500) to larger industrial production sites (10,000) according to the customer´s wishes.
Thorough testing in the laboratory of multiple samples from multiple species ranging from adult fish of 15 years of age down to juvenile sturgeons of approximately four months of age have indicated that the marker can be detected even at very early stages in the development.
Using knowledge gained from the successful development of eDNA tests for alien crayfish species and the detection of Atlantic salmon in rivers and streams, a modified non-PCR-based optical test is undergoing laboratory trials which will reduce measurement times down to 30 minutes without complicated laboratory instrumentation.
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