Abstract
The freshwater mugilids Joturus pichardi and Agonostomus monticola, have been documented on ecological and distribution aspects, mainly for Central American populations, nevertheless, little information is available on their reproductive aspects, specifically in Colombian freshwater environments. Reproductive biology of the mugilids J. pichardi and A. monticola from Sierra Nevada de Santa Marta (SNSM) rivers was studied between July 2005 and December 2006. A total of 14 specimens of J. pichardi and 320 of A. monticola were collected. The reproductive biology was analyzed by means of: sexual proportion, gonadosomatic index, and mean size at maturity, fecundity and oocyte diameter. Additionally, a bioassay was carried out to evaluate the effect of salinity on spermatic motility and its possible relationship with the species' spawning area. These mugilids share habitats with similar ecological characteristics, in which strong currents; clear water and stony areas stand out. Gonadal maturity indicators and indirect evidence are presented to support the relationship between reproductive maturity and higher rainfall levels in the area (September, October and November), as well as the catadromous migration of J. pichardi and A. monticola. This last species females outnumbered males with a sex ratio of 2.3:1. Females mean size at maturity was 172mm of their total length (TL) and 108mm TL for males. Fecundity (F) was 23 925 +/- 4 581 eggs per gram of gonad, and was related to size by the equation F = 395.1TL(1.281); besides, the mean oocyte diameter was 362 +/- 40 microm. Considering the salinity effect on sperm motility in both species, results suggested that J. pichardi spawned in estuarine environments but the species did not migrate to fully marine environments; however, A. monticola withstood a broad range of salinity, suggesting a spawning from intermediate to total saline environments. Both species have high culturing potentials, considering that their feeding is based on plant and macroinvertebrates, their meat quality and the size they are able to reach. These species represent an interesting resource to the fisher groups of the region and should be integrally assessed.
Highlights
La Sierra Nevada de Santa Marta, declarada por la UNESCO Reserva del Hombre y la Biosfera en 1986, es la formación montañosa litoral más alta del mundo (FPSNSM 1997)
Son abundantes los estudios sobre la biología, reproducción y alimentación de los mugílidos, la mayoría ha sido desarrollados en especies marinas y estuarinas, especialmente del género Mugil (e.g. Álvarez-Lajonchere 1976)
Los individuos fueron capturados en diferentes sitios y horas del día
Summary
Se realizaron muestreos mensuales entre julio 2005 y diciembre 2006, en los ríos Toribío (11°02’16” N - 74°12’16” W) y Piedras (11°17’8” N - 73°59’39” W), ubicados en la región noroccidental de la SNSM en el departamento del Magdalena y que drenan en el mar Caribe de Colombia. Se utilizó un análisis de varianza a una vía (previa comprobación de los supuestos de normalidad de los datos y homogeneidad de varianzas usando la prueba de Levene) para verificar diferencias entre los estados de maduración de los indicadores IGS1 e IGS2 y entre los tiempos de activación espermática y motilidad evaluados a partir del efecto de salinidad sobre las muestras de semen. Áreas de desove: No se logró la captura de ejemplares de J. pichardi durante los muestreos realizados entre la desembocadura y las partes baja próxima a esta zona, en los ríos de estudio en el periodo de septiembre, octubre y noviembre de 2005 y 2006. Posterior a la captura en estas zonas del río, se verificó que CUADRO 1 Características fisicoquímicas de los sitios de muestreo en los ríos Toribio y Piedras, SNSM, Colombia, julio 2005-diciembre 2006
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