Early male puberty is a significant economic problem in farming of several fish species in Europe. It is therefore necessary to develop strategies to delay puberty. These strategies should meet both, consumer acceptance and the economic interests of aquaculture. However, significant gaps exist in our knowledge as regards the physiological regulation of puberty, which preclude developing strategies to approach the problem. Similarly, although it is known already that differences in the genetic background within a species can result in differences in the timing and/or incidence of early male puberty, there is virtually no information on how genetic differences are reflected in differences in reproductive physiology. The same holds true for the potentially very interesting option of combining suitable genetic traits from identified sibling groups with certain photoperiod treatment regimes. Since photoperiod control appears to be one of the most promising techniques for controlling puberty in farmed fish, this project focuses on
1) improving the understanding of the physiological regulation of puberty
2) the interactions with factors such as the genetic background, nutrition and adiposity
3) notably to clarify how photoperiod affects the BPG axis during puberty. The aim is to further develop photoperiod protocols to be used on Atlantic salmon and sea bass, and also to provide a scientific framework for the future use of such (or similar) protocols in new farmed species such as cod, halibut and turbot.
Our overall objective is to develop improved photoperiod protocols for delaying first sexual maturation (puberty) in commercially farmed European fish species by:
· improved knowledge on the mechanisms of activation of the brain-pituitary-gonad (BPG) axis during puberty in fish, including development of new tools to study the BPG axis in salmon, rainbow trout and sea bass.
· improved understanding of the importance of differences in light intensity and spectral quality in affecting the BPG axis and the initiation/postponement of puberty, by assessment of pineal melatonin production in vitro and in vivo in salmon and sea bass.
· improved understanding of the interactions between photoperiod protocols, genetic background and adiposity in arresting/promoting puberty in salmon and sea bass.
The present project aims to:
Alter timing of puberty by use of different photoperiods, nutritional treatments and different sibling groups to:
1) more fully understand how these factors interact with the initiation/suppression of puberty by their effects on the BPG axis
2) further develop photoperiod protocols to reliably delay unwanted sexual development in salmon and sea bass under commercial farming conditions.
Identify the pineal sensitivity to light of different intensities and spectral compositions to determine threshold values for artificial light to control puberty in salmon and sea bass in outdoor fish farms/sea cages.
Further develop tools to study the roles of selected components of the BPG axis (gonadotropin-releasing hormones, gonadotropins, gonadal steroids and the receptors for these hormones) in determining puberty in fish by use of different model species as Atlantic salmon, rainbow trout and sea bass in order to fill gaps in our knowledge with respect to the activation of the BPG axis.
Define critical periods in the season and life-cycle, during which the timing of puberty might be altered by photoperiodic protocols and study, by in vivo and in vitro approaches, the endocrine changes that accompany enhanced/delayed puberty.
· Measure growth rate, body size and lipid stores in genetically defined sibling groups at assumed critical points in the life-cycle and season to identify putative thresholds for puberty.
The project aims to identify environmental and physiological key factors responsible for initiating puberty in fish along with the development of photoperiod protocols to reliably control puberty in farmed fish. The project will study a broad range of parameters during natural puberty, or in response to environmental treatments (photoperiod and nutrition), in the context of different, genetic backgrounds. Significant original information is expected from studies using different photoperiod treatments, diets and sibling groups to develop large differences in the incidence of early puberty. To combine this means with the thorough analysis of the endocrine processes during treatment-induced advancements or delays of pubertal development is the major innovative approach that characterises the experimental model used in this proposal. Significant progress is expected for both, applied and fundamental branches of aquaculture research, as well as for aquaculture industries.
FISHERIES AND AQUACULTURE
Scientist responsible for the project
Dr. Research Director OLE J. TORRISSEN
Nornesgt 50 Box 1870 Nordnes
Norway - NO
Phone: +47 55236371
Fax: +47 55236379
||INSTITUTE OF MARINE RESEARCH
||01 October 2002
||3 443 074 €
|Total EC contribution
||1 336 694 €
|Web address of the project