Publication Abstract

Common Dentex, a prime new species for aquaculture: Development of methods for reliable egg production.

Common Dentex, a prime new species for aquaculture: Development of methods for reliable egg production

By M Pavlidis, M Loir, L Greenwood, H Molsa, F Le Gac, J Laitinen, P Muje, B Mourot, M Paalavao, C Kokkari, F Le Menn, A Fostier, P Divanach, A.P Scott

The overall aim of the project is to provide a scientific and technical basis for effective and reliable reproduction of the common dentex (Dentex dentex), a prime new species for intensive fish farining. The main objectives of the project are: a) to provide basic knowledge on the repr delta uctive biology of this species, b) to investigate external factors likely to be used for manipulating the spawning period, c) to develop an appropriate and cost-effective methodology for synchronisation of spawning and increasing yields and quality of gametes, and d) to support the development of a new candidate species for aquaculture. D. dentex is a highly valued table fish in the Mediterranean region and elsewhere in the tropics and the continuously increasing catches suggest a high and unsatisfied demand for this sparid fish. Rearing experiments with juveniles have identified D. Dentex as highly suitable for intensive aquaculture. However, studies on this species are sparse and basic knowledge of the reproductive biology under intensive farmed conditions is extremely lirnited and conflicted. D'Ancona (1950) concluded that D. dentex is a gonochoristic sparid. However, Bauchot and Hureau (1986) and Glamuzina et al. (1989) stated that D. dentex was a protandric hermaphrodite, with sex reversal being unlikely to be obligatory. A recently field study (Morales-Nin and Moranta 1997) supports the initial information of D. Dentex as gonocoristic species. The project comprises four major tasks: (1) morphological, histological, endocrine and metabolic study of female and male sexual cycles in fish aged 3 months to 47 months (which covers three spawning seasons; (2) investigation of the role of melatonin, in conveying important information about diurnal and annual changes in daylength and investigation of the role of photo- and thermoperiod on the control of reproduction for out-of-season egg production; (3) spawning induction treatment and identification of the steroids synthesised by the gonads, as well as identification and measurement of the maturation- inducing steroid(s) or their metabolites in the water as a candidate marker for monitoring spawning success; (4) investigation on the importance of the sex ratio and interaction within sexes on the efficiency of spawning. Tasks are supported by quantitative and qualitative analysis of released eggs and sperm.

Reference:

M Pavlidis, M Loir, L Greenwood, H Molsa, F Le Gac, J Laitinen, P Muje, B Mourot, M Paalavao, C Kokkari, F Le Menn, A Fostier, P Divanach, A.P Scott, 1999. Common Dentex, a prime new species for aquaculture: Development of methods for reliable egg production. FAIR PL 95.406, Final Report. 246p

M Pavlidis, M Loir, L Greenwood*, H Molsa, F Le Gac, J Laitinen, P Muje, B Mourot, M Paalavao, C Kokkari, F Le Menn, A Fostier, P Divanach, A.P Scott*

FAIR PL 95.406, Final Report. 246p