Growth–reproduction trade‐off and fecundity regulate population stability in Amazon floodplain fishes

Abstract

Understanding the factors that regulate temporal changes in population size is a core aspiration in ecology given the importance of population stability on the maintenance of species interactions, effects on local communities, the stability of ecosystems, and for biodiversity conservation. Understanding temporal trends in population size can support management practices as this may indicate demographic resilience for exploited species. Theoretical studies have long suggested that life‐history traits regulate population stability, but empirical support remains limited, especially for species‐rich environments. Additionally, harvesting has been suggested as an important factor increasing the fluctuation in the number of individuals in populations. In this study, we analysed population stability of 70 Amazonian floodplain fish species in relation to life‐history traits and the degree of fishing pressure. Our data covered a long time scale and broad geographical range of the Amazon floodplain. For that, we compiled datasets of two monitoring programmes, one comprising data from a single lake for 15 years and a second dataset with information from three floodplain lakes sampled over 5 years. The resulting geographical range spanned one of the most fished areas in the upper Amazon River, between the municipalities of Coari and Manaus, in the Brazilian Amazon. Temporal stability was measured as the coefficient of variation in species abundance. Population life‐history traits and the degree of fishing pressure were estimated at the species level. Population temporal stability had significant relationships with three life‐history traits: maximum body size, fecundity, somatic investment before sexual maturation (SIBSM), and the interaction of fecundity and SIBSM. Species with small body size, high fecundity, and low SIBSM displayed low stability; the opposite happened to species that invest highly in somatic tissue before the first reproduction and have large body size. Fishing pressure had no significant contribution to explaining population stability. However, the sampling technique employed and the set of species considered in the study do not represent main targets of fisheries. Here we stress the importance of life‐history traits in controlling an essential part of the population size variation in a complex and species‐rich fish assemblage in the Amazon floodplains. Our results highlight the importance of the trade‐off between growth and reproduction in controlling population stability and complement explanations on how life‐history functional traits underlie differences in population dynamics over time. Our results contribute to theoretical development and can be used to support fisheries and biological conservation management strategies. Specifically, our results point to the possibility of inferring demographic resilience based on life‐history information in the absence of high‐quality population data.

Life history speed, population disappearances and noise-induced ratchet effects

“…Consistent with this, empirical research has found negative correlations between population variability (one measure of stability) and both body size and generation time, and positive correlations between population variability and growth rates across multiple taxa and kingdoms [20][21][22][23]. Taken together, larger and slower organisms appear capable of buffering small perturbations better than small and fast organisms; however, especially when perturbations are reddened or auto-correlated, this same slow growth response may ensure that slow organisms are more likely to be pushed away from the equilibria.…”

“…In contrast to fast organisms, slow organisms, with longer lives, buffer noise and thus maintain high stability. Consistent with this, empirical research has found negative correlations between population variability (one measure of stability) and both body size and generation time, and positive correlations between population variability and growth rates across multiple taxa and kingdoms [13–16]. Taken altogether, larger and slower organisms appear capable of buffering noise better than small and fast organisms.…”

Intense droughts affect temporal stability of Amazonian stream fish assemblages

“…For the Xingu River basin, the results initially pointed to a similar outcome. However, the climatic and environmental stability experienced by Amazonian ichthyofauna (Oberdorff et al, 2019; Peres et al, 2010; Rodrigues‐Filho et al, 2018) and the results of recent studies (Borba et al, 2021; Freitas et al, 2013; Röpke et al, 2017, 2021) suggested that other factors may be influencing the restructuring of these assemblages after these recent flow interruption events.…”

“…Species selected as a function of the contribution to the differences of captures in SIMPER analysis. Red vertical lines indicate the flow interruption event et al, 2021;Freitas et al, 2013;Röpke et al, 2017Röpke et al, , 2021 suggested that other factors may be influencing the restructuring of these assemblages after these recent flow interruption events.…”

Effects of climate‐driven hydrological changes in the reproduction of Amazonian floodplain fishes

“…Most of the study species are classified as periodic life‐history strategists, represent multiple trophic categories and are under different types of fishing pressure (Table 1). Species were classified into categories based on fishing pressure: (1) not fished, (2) fished mainly for subsistence or (3) fished commercially and for subsistence purpose (modified from Röpke et al, 2021).…”