INVESTIGADORES
ACHA eduardo marcelo
artículos
Título:
Reproduction of Jenyns´s sprat, Ramnogaster arcuata, a winter spawner in the temperate waters of the Río de la Plata estuary (Argentina – Uruguay).
Autor/es:
RODRIGUES, K.A.; MACCHI, G.J.; ACHA, E.M.; MILITELLI, M.I.
Revista:
JOURNAL OF THE MARINE BIOLOGICAL ASSOCIATION OF THE UNITED KINGDOM
Referencias:
Año: 2008 vol. 88 p. 423 - 429
ISSN:
0025-3154
Resumen:
The reproductive biology of the Jenyns´s sprat Ramnogaster arcuata in the Río de la Plata area (Argentina-Uruguay) was studied using macroscopic and histological analysis of ovaries. Samples were collected during two research surveys carried out in June 1998 and June 1999. In addition monthly occurrence of this species from historical data were analysed. Jenyns´s sprat specimens were mainly observed in open waters of the estuary during winter months. Most of the females collected during June 1998 and 1999 were in spawning stage. This pattern differs from those of the fishes that reproduce in the estuarine waters of the Río de la Plata, which spawn during spring and summer. These results suggest that conditions of productivity and larval retention in the estuary also remain during winter months. This characteristic may be useful for R. arcuata in avoiding competition with other estuarine spawners during the early life stages. Jenyns´s sprat is a multiple spawner with indeterminate annual fecundity. A preliminary estimate of spawning frequency indicated a daily percentage of females with postovulatory follicles of 17.5%, which suggests that this species spawns on average once every six days. Batch fecundity, estimated from counts of hydrated oocytes, ranges from 669 to 2,026 hydrated oocytes in 1998 and from 570 to 1,834 hydrated oocytes in 1999. Batch fecundity was fitted to a linear function of total length and total weight (without ovary). The dry weight of 100 hydrated oocytes ranged between 3,9 and 6,3 mg, being these values significantly higher than those estimated for other species of the Río de la Plata estuary.