A multidisciplinary approach using genetic markers and biological tags in horse mackerel (Trachurus trachurus) stock structure analysis

Objectives of the Project

The overall objective of this project is the biological stock identification of the horse mackerel (Trachurus trachurus) throughout its whole range, from North-eastern Atlantic to Mediterranean Sea. This goal will be achieved integrating both established and innovative approaches such as genetic markers, other biological tags (morphometry, parasites), tagging experiments and life history traits (growth, reproduction and distribution). The proposed research will therefore set-up an improved multi-disciplinary tool for fish stock identification, and an exhaustive knowledge of horse mackerel stock structure, in order to allow an enhanced management of this resource in EU waters in short, medium and long term.

To achieve the overall objective the following complementary goals will be pursued:

• Identification of horse mackerel populations and stocks from the Mediterranean Sea and North-east Atlantic using different molecular genetic markers (allozyme electrophoresis, mitochondrial DNA sequencing, DNA microsatellite, SSPC)

• Evaluation of the levels of genetic variability in the identified populations.

• Estimation of the genetic divergence and assessment of the genetic relationships among stock units.

• Estimation of gene flow between populations and stocks by means of indirect methodologies based on genetic data, in order to highlight the degree of population subdivision.

• Evaluation of parasitic infection levels by means of epizootiological parameters (prevalence, mean intensity and/or abundance of metazoan infection) in the horse mackerel samples.

• Interpretation of the parasitology results in terms of host population biology (e.g.: migration routes, feeding and spawning areas).

• Application of the geometric morphometrics on the horse mackerel body and otoliths, as a tool for the identification of intraspecific variation.

• Testing of body and otolith shape differences among areas, by applying multivariate statistical techniques.

• Evaluation of the viability in the application of internal and external tags in the horse mackerel.

• Use of physical tagging in selected areas to infer patterns of movement and degree of mixing among horse mackerel stocks or populations.

• Examination of the different population parameters: growth rate, maturity ogive, fecundity, age structure, distribution and abundance, to identify horse mackerel management units.

• Assessment on the effects of the extrinsic factors (fishing pressure), the space and time, in the population parameters observed.

• Correlation between host population biology data, tagging results, genetic data and parasitic fauna composition in the identified horse mackerel units.

•Guidelines drawn from the obtained results for the management of horse mackerel, aimed at maintaining genetic diversity and demographic structure of the resource in EU waters.

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