Influence of restricted access to floodplains on life-history patterns in fish: implications for conservation

Natural selection has tailored the developmental characteristics of animals to the natural ranges of variation of their environments, so that human restriction of those environments tends to restrict the range of variety within species dependent on them. Understanding how restricting access to the floodplain through river engineering for flood management may affect fish species requires understanding their life history strategies, which in turn requires understanding their reproductive processes, and specifically understanding the maturation process itself. Maturation is treated here as a problem of allocation of surplus energy, proceeding in parallel with rather than in competition with somatic development, influenced by genetic endowment (physiological efficiency) and environmental opportunity, and regulated by inhibition. Insights from the effects of exploitation on variation in other fishes, and on the consequent stability of their populations, are used to consider some potential implications of river management on floodplain species. Among floodplain fishes, more information is needed on genetic and spatial structure of populations, on internal and external environmental regulation of developmental timing, and on the nature of the process of inhibition of maturation, to ensure protection of the integrity of these species populations in environments being modified.