title: Plasma estradiol-17beta levels and gonadosomatic index in tench (Tinca tinca L.) reared in natural and controlled conditions.
abstract: The plasma estradiol-17beta levels (E2-17beta) and gonadosomatic index (GSI) of female tench (Tinca tinca L.) reared outdoors and indoors were studied from December 1996 to April 1997. Water temperature and daylight were gradually increased (from 10 to 25 degrees C and from 9 to 16 hours per day, respectively) in the indoor group. Animals reared in natural conditions had similar plasma levels throughout the experiment but animals under controlled conditions experienced an increase in these levels in March in relation to previous months (4.81+/-0.73 ng/ml in March vs. 0.29+/-0.03 ng/ml and 0.99+/-0.31 ng/ml in January and February, respectively; P < 0.05) and in relation to animals reared outdoors (4.81+/-0.73 ng/ml vs. 0.47+/-0.19 ng/ml, respectively; P < 0.05). In April, a sharp decrease in estradiol-17beta in these animals was observed, probably associated with the end of vitellogenesis. GSI increased in both groups through the experiment and indoor animals showed greater values in March vs outdoor fishes (7.57+/-2.18 vs. 4.05+/-0.63; P < 0.05). No significant correlation was found between E2-17beta and GSI, (r = 0.35). It is concluded that manipulation of the photoperiod and temperature can modify gonadal development in tench, and this is similar to the situation in other Teleostei species. This research is the first step towards achieving, out of season, spawning in tench.
authors.affiliation: Dptos. Producción Animal, E.T.S. I. Agrónomos, UPM, Madrid, Spain.
authors.forename: P
authors.initials: P
authors.lastname: Martin
authors.forename: P G
authors.initials: PG
authors.lastname: Rebollar
authors.forename: L D
authors.initials: LD
authors.lastname: San Juan
authors.forename: J C
authors.initials: JC
authors.lastname: Illera
authors.forename: J M
authors.initials: JM
authors.lastname: Alvariño
mesh_terms: D000818:Animals; D003530:Cyprinidae / Q000097:blood* / Q000254:growth & development*; D004780:Environment, Controlled; D004958:Estradiol / Q000097:blood*; D005260:Female; D010053:Ovary / Q000254:growth & development; D017440:Photoperiod; D012621:Seasons; D012741:Sexual Maturation / Q000502:physiology*; D013696:Temperature; D014818:Vitellogenesis / Q000502:physiology
chemical_list: D004958:Estradiol