MARINEGGS
Genetic identification of fish eggs by species-specific DNA markers for use in stock biomass Assessments and Detection of Commerical Fraud

Many species of fish within a group show overlapped distributions and spawning periods, and their eggs can be confounded in plankton surveys. In this project, it is proposed to improve a fisheries-independent method of fish spawning stock biomass estimation by developing genetic-based methods for the accurate identification of the early stages of the eggs of 12 commercially important marine species. The species are Trachurus Trachurus, T. Mediterraneus, T. Picturatus and Macrorhamphosus Scolopax (a species with eggs similar to horse mackerel eggs); Scomber Scombrus and S. Japonicus (species with eggs similar to mackerel eggs); Gadus Morhua, Melanogrammus Aeglefinus and Merlangius Merlangus (a species with eggs similar to cod eggs); Merluccius Merluccius, Lepidorhombus Whiffiagonis and L. Boscii (species with eggs similar to hake eggs). Probes will be also be developed for eight more species (hakes) for commercial fraud identification.

Objectives
The objectives of this project are:
1) to determine the most suitable method of preserving fish eggs to allow both visual sorting and DNA recovery
2) to develop species-specific mtDNA and nDNA probes for Atlantic horse mackerel, Mediterranean horse mackerel, snipe fish, Atlantic mackerel, Spanish mackerel, cod, haddock, whiting, hake, Argentinean hake, austral hake, black hake, Chilean hake, Patagonian hake, Cape hake, Boston hake, Megrim whiffiagonis and Megrim boscii
3) to develop PCR-based protocols for gene probe identification of fish eggs
4) to assess the degree of improvement of the new PCR-based methods for egg identification of horse mackerel, mackerel, cod and hake with respect to the visual method of egg identification
5) to validate the method for the detection of commercial fraud in the European hake markets.

Progress to Date
At the start of the fourth year, objectives 1, 2, 3 and 5 had been completed.

Results
The project has identified that 4% formaldehyde is the best product for visual identification of fish eggs.
Different protocols for successful DNA recovery from formaldehyde-fixed eggs have been developed.
Variation at mitochondrial and nuclear sequences provided species-specific markers for genetic identification of formaldehyde-fixed eggs of the four groups of species.
Successful identification of the species was achieved in fresh and pre-cooked hake commercialised for human consumption.
In its final year, the project has been assessing the degree of improvement of the new PCR-based methods for egg identification with respect to the visual method.

Classified in NON-FOOD PRODUCTS, FISHERIES AND AQUACULTURE

Scientist responsible for the project