A novel technique to save costs in caviar production

EM2 21 AQ Aquafuture workflowEarly Sturgeon Sex Discrimination (ESSD), a new diagnostic service for hatcheries and farms

This article was featured in EUROFISH Magazine 2 2021.

Sturgeon farmers producing fish for caviar would benefit hugely from a molecular-biological sex test for juvenile and adolescent sturgeons. Early sexual identification can significantly decrease production costs by increasing the number of females for caviar production while maintaining a balance of male animals for meat production and for use as brood stock.
Additional advantages from the genomic analysis to determine sex could be the identification of genes implicated in growth, meat production, or egg quality (caviar) which opens the door for improvements in these areas. Currently, the normal male to female ratio in production facilities is approximately 1:1 through natural selection. If an early sex test is available, then this ratio could be manipulated to favour the production of either caviar or meat.

Two aquaculture-focused companies with a tradition of working together

TunaTech, a life sciences company focused on aquaculture, and aquaFUTURE, a supplier of aquaculture equipment and consultancy services, have a long history of collaboration. Projects range from salmon genetics through restocking salmon in the river Rhine to sturgeon cultivation. Work on sturgeon sex discrimination markers based on hormonal and histological changes in both adult and juvenile sturgeons has also been carried out in research projects between TunaTech, Heinrich-Heine-University of Duesseldorf and the Mecklenburg Vorpommern Research Institute for Agriculture and Fisheries (Landesforschungsanstalt für Landwirtschaft und Fischerei Mecklenburg-Vorpommern) in Born.

TunaTech has already invested considerable time and money into the research and development of a molecular-biological sex test for three sturgeon species. The sampling was performed at Aquatir, one of the world’s largest and most modern sturgeon farms, in which aquaFUTURE played a leading role, where blood, tissue and mucus samples of sexually mature belugas (Huso huso), Russian sturgeons (Acipenser gueldenstaedtii) and sterlets (Acipenser ruthenus) of known sex were taken. At TunaTech’s laboratories DNA and RNA were extracted from the preserved samples and a comprehensive analysis was performed on the female and male samples from the three species. 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. From the latest results of an EU funded research project (STURGEoNOMICS1), 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.

EM2 21 AQ Aquafuture ESSD LogoA service tailored to the customer’s requirements

This novel and customised solution for sex discrimination at early life stages for multiple sturgeon species 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 is possible to provide a customized 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 the Early Sturgeon Sex Discrimination (ESSD) solution in 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 recognized at a later stage. TunaTech and aquaFUTURE have over 20 years of experience in this field with 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 by software analysis and combining tagging and molecular results to provide a relatively automated sorting system for separation of males and females. In the near future, the techniques and tools used will be further developed for application in farm breeding programmes to distinguish between fast growers, and also in single sex propagation scenarios (all females) with proof of concept. The ESSD template can be customised for commercial farms from small (500 individuals) to large sites (10,000 individuals).

Further trials to increase simplicity of testing procedure

Thorough testing in the laboratory of multiple samples from several species ranging from adult fish of nine years of age down to juvenile sturgeons of approximately four months has indicated that the marker can be detected even at very early stages in the animal’s 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 trials which will reduce measurement times down to 30 minutes without complicated laboratory instruments.

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