Seasonal changes in oocyte development, growth and population size distribution of Percilia gillissiand Trichomycterus areolatus in the Itata basin, Chile

Abstract

Seasonal changes in oocyte development, growth and population size distribution of Percilia gillissi and Trichomycterus areolatus in the Itata basin, ChileCambio estacionales en el desarrollo de oocitos, crecimiento y distribución de talla poblacional de Percilia gillissi y Trichomycterus areolatus en la cuenca del río Itata, Chile GUSTAVO ABSTRACTThere is scarce basic biological data on native freshwater fi sh species from Chile and next to zero on growth, gonad development and reproduction, which are critical for the purposes of the conservation of their natural populations. Seasonal analysis of sub-individual (oocyte development) and population (length frequency, growth rates) endpoints in Trichomycterus areolatus and Percilia gillissi were evaluated from February 2007 to January 2008. Oocyte development has a marked seasonality for P. gillissi, with mature eggs in October and declining frequency of mature oocytes into January. For T. areolatus we found some mature eggs in July, with highest number of mature eggs in October, coincident with previous data on maximum gonad size. Both species showed a multiple spawning reproductive strategy, with a long spawning season starting in spring to early summer. Increased numbers of juveniles were observed during mid-summer for P. gillissi,and during the end of the summer and beginning of autumn for T. areolatus. Juveniles had a higher growth coeffi cient (K) (0.56-0.38 mm month-1) than adults (0.29-0.15 mm month-1), and almost all juveniles in the population reached maturity before the spring (>50 mm for T areolatus and >40 mm for P. gillissi) and were incorporated into the population as a new recruitment cohort. Knowledge of the seasonal variability of these individual and population level responses can help better understand the biology of the species, and simultaneously improve the management and conservation of freshwater biota in Chile. KEYWORDS:Seasonal cycles, native fi sh Chile, oocyte development, multiple spawning reproductive strategy, population size-structure. RESUMENExisten escasos datos de biología básica sobre las especies de peces nativas chilenas de agua dulce y casi ninguno en sobre el crecimiento, el desarrollo gonadal y reproducción, que son fundamentales para los propósitos de la conservación de sus poblaciones naturales. El análisis estacional de los parámetros sub-individuales (desarrollo de oocitos) y poblacionales (frecuencia de tallas y tasa de crecimiento) en Trichomycterus areolatus y Percilia gillissi fueron evaluados entre febrero de 2007 y enero de 2008.El desarrollo de los oocitos posee una marcada estacionalidad en P. gillissi con oocitos maduros en octubre y una disminución de estos estados maduros hacia enero. En T. areolatus encontramos oocitos maduros en Julio, pero con una mayor abundancia durante octubre, coincidente con datos previos de máximo desarrollo de la gónada. Ambas especies mostraron una estrategia reproductiva de desoves multiples, con una temporada de desove que comienza en primavera hasta principios de verano. Amb...

The South American and Australian percichthyids and perciliids. What is new about them?

“…Information concerning the biology and behavior of both species is incompletely known. There are a few reports about the reproduction and behavior of Percilia gillisi (Kilian, Campos, 1969;Chiang et al, 2011;Chiang et al, 2012) and ontogenetic changes of P. irwini (Aedo, Habit, 2009). There is concern about the present situation of the two species, which are currently catalogued as threatened in Chile.…”

Endocrine Disruptor Impacts on Fish From Chile: The Influence of Wastewaters

“…Bahamonde et al (81) point out that intersex can occur, as we already mentioned, spontaneously in gonochoristic species exposed to EDCs. This fact together with the evidence of Chiang et al (67,80) who did not observe this phenomenon and could determine the size of first sexual maturation for both sexes separately, suggests that the specimens found by Riffo (83) in the "Peuco" stream (southern limit of the province of Santiago, an area of high agricultural use and pesticides with potential ED) are the first evidence of EDCs in Chile.…”

“…It is necessary to understand that fish are constantly subjected to environmental stress (21,22) before planning EDC effect studies, including changes in temperature, hypoxia, sediment loads, flow rate, among others. To understand and to have the ability to extrapolate the effects observed in the individual organism with a chemical or mixture of chemicals having endocrine disruptive properties, cellular and physiological seasonal variations associated with changes in metabolic rates and fish reproductive status must be taken into consideration when evaluating the impacts on individuals and populations (9,21,33,(66)(67)(68)(69)(70)(71)(72)(73)(74)(75)(76)(77)(78)80).…”

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Hydrological connectivity drives longitudinal movement of endangered endemic Chilean darter Percilia irwini (Eigenmann, 1927)

“…It is worth noting that much of the movement detected was directional upstream movement, which could support this hypothesis. Furthermore, a study investigating oocyte development of a closely related species ( Percilia gilissi ) found that this species has an extended spawning season, spanning from the middle of austral winter (July) to the start of summer (December) (Chiang et al ., 2012). This period also corresponds to higher flow regime in the region, which could make upstream movement more difficult because of high water velocity, but could also facilitate such movements by improving upstream connectivity, especially in part of the catchment subjected to seasonal drought.…”