Phenotypic plasticity in fish life-history traits in two neotropical reservoirs: Petit-Saut Reservoir in French Guiana and Brokopondo Reservoir in Suriname

Bernard De Mérona,Jan Mol,Paulo De Tarso Chaves,Régis Vigouroux

doi:10.1590/s1679-62252009000400018

Abstract

Fish species are known for their large phenotypic plasticity in life-history traits in relation to environmental characteristics. Plasticity allows species to increase their fitness in a given environment. Here we examined the life-history response of fish species after an abrupt change in their environment caused by the damming of rivers. Two reservoirs of different age, both situated on the Guiana Shield, were investigated: the young Petit-Saut Reservoir in French Guiana (14 years) and the much older Brokopondo Reservoir in Suriname (44 years). Six life-history traits in 14 fish species were studied and compared to their value in the Sinnamary River prior to the completion of Petit-Saut Reservoir. The traits analyzed were maximum length, absolute and relative length at first maturation, proportion of mature oocytes in ripe gonad, batch fecundity and mean size of mature oocytes. The results revealed a general increase of reproductive effort. All species showed a decrease in maximum length. Compared to the values observed before the dam constructions, eight species had larger oocytes and three species showed an increased batch fecundity. These observed changes suggest a trend towards a pioneer strategy. The changes observed in Petit-Saut Reservoir also seemed to apply to the 30 years older Brokopondo Reservoir suggesting that these reservoirs remain in a state of immaturity for a long time.

Highlights

The survival of a population in a given environment depends on the capacity of individuals to produce a number of descendants sufficient to maintain a viable population on the long term
The seasonal strategy characterized by late maturity, large fecundity and low juvenile survivorship would be associated with seasonal environments, the equilibrium strategy would be associated with relatively stable environments and the opportunistic strategy with stochastic environments
Condition Six species (Acestrorhynchus microlepis, Bryconops affinis, Curimata cyprinoides, Hemiodus unimaculatus, Auchenipterus nuchalis and Cyphocharax spilurus) were in better condition in Petit-Saut Reservoir than in the river and one of them (B. affinis) present in Brokopondo Reservoir showed a lower condition in the latter (Fig. 3)

Summary

Introduction

The survival of a population in a given environment depends on the capacity of individuals to produce a number of descendants sufficient to maintain a viable population on the long term. Individuals develop reproductive traits characteristic of life-history tactics which are essentially compromises between immediate reproduction and growth (expected future reproduction) (Stearns, 1993). This process is determined by two main elements: (1) the constraint of the genetic background, and (2) adaptation to short-term variability of the environment (Stearns, 1993). Life-history strategies of species are the result of an evolutionary process involving long-term variability of the environment as stated by the “habitat templet” concept (Southwood, 1977; Southwood, 1988; Townsend & Hildrew, 1994). The seasonal strategy characterized by late maturity, large fecundity and low juvenile survivorship would be associated with seasonal environments, the equilibrium strategy (low fecundity, high juvenile survivorship) would be associated with relatively stable environments and the opportunistic strategy (early maturation, low fecundity and low juvenile survivorship) with stochastic environments

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