Reproductive biology of Galaxias maculatus (Jenyns 1842) in Río Ovando estuary, a high-latitude environment in southernmost Patagonia

BOY, C.C.; PÉREZ, A.F.; LATTUCA, M.E.; CALVO, J.; MORRICONI, E.

JOURNAL OF APPLIED ICHTHYOLOGY-ZEITSCHRIFT FUR ANGEWANDTE ICHTHYOLOGIE

Blackwell Verlag

Lugar: Berlin; Año: 2009

0175-8659

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:ES-TRAD; mso-no-proof:yes;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> This study establishes the reproductive cycle, batch fecundity and oocyte diameter of a diadromic population of Galaxias maculatus in the Río Ovando (54º S), the southernmost limit of its distribution. Given the short “favourable season” in relation to other populations of the species (in terms of temperature, photoperiod and food availability), the study also explores the trade-offs between feeding and oocyte production and between phases of growth and reproduction. The reproductive cycle was analyzed by the monthly evolution of the proportion of gonadal maturity stages (determined from microscopic examination of the gonads). Oocytes were measured using a micrometric ocular scales and clasified by diameter and morphological characteristics and absolute fecundity was established as total number of hydrated oocytes per ovary. Population studied axhibit a repetitive spawning strategy, given the coexistance of postovullatory follicles and hydrated oocytes in histological sections and the presence in ripe ovaries of an intermediate cohort of yolked oocytes ready for hydration. Individual fecundity is lower (1422 ± 422 oocytes/ovary) than in other populations, but the egg production increases trough individual repetitive spawnings during the protracted spawning period (from October to February). Females attain larger sizes than other populations in Southamerica (115 mm total length of the largest female) maximizing its potential fecundity. The present paper contributes to the knowledge of variability of reproductive traits of G. maculatus in relation to diadromic populations, given that the bulk of information in Southamerica refers mainly to landlocked populations.