Fishing‐down within populations harms seed dispersal mutualism

Abstract

Large fish are often the most effective seed dispersers, but they are also the preferred target for fisheries. We recently started to comprehend the detrimental impacts of the extirpation of large frugivorous fish species on natural forest regeneration, but we lack a general understanding of how intraspecific size‐selective harvest affects fish–fruit mutualism. Our literature review demonstrated that large individuals within populations positively affect diverse aspects of seed dispersal, from consuming a higher diversity of seeds to enhancing germination. Furthermore, we filled a research gap by studying how individual size variations within two small frugivorous fish species (<16 cm) affect seed dispersal in flooded savannas. Even within small‐bodied species, large individuals swallow a higher number of intact seeds, but not necessarily a higher proportion. Overall, our results demonstrate the disproportional role of large‐bodied individuals as key seed dispersers in flooded habitats. Consequently, fishing‐down within both large‐ and small‐bodied species can negatively affect seed dispersal and natural regeneration in overfished wetlands.

Plant Dispersal in a Temperate Stream by Fish Species With Contrasting Feeding Habits: The Role of Plant Traits, Fish Diet, Season, and Propagule Availability

“…This may reflect ontogenetic differences in diet as small juvenile cyprinids feed mostly on invertebrates and switch to a more herbivorous diet as they grow (e.g., Nurminen et al, 2003). This result is in accordance with the findings of Galetti et al (2008) and Costa-Pereira et al (2017) for tropical fish. However, in temperate streams a larger dispersal potential of larger fish might apply only to small, relatively hard seeds.…”

Frugivoria de Peixes em Áreas Úmidas Neotropicais: Passado, Presente e Futuro de uma Interação Única

“…Another major knowledge gap in our understanding of fish-forest interactions is assessing reciprocal dynamics between forests and fishes in floodplain ecosystems. So far we know that fishes provide important seed dispersal services which likely have contributed to shape and maintain Fish Frugivory in Neotropical Wetlands forest diversity in South American floodplains (Correa et al 2015b, Correa et al 2017. Very few studies, however, have examined how floodplains forests contribute to maintain fish productivity and diversity.…”

“…The protein provided by canopy arthropods that fall into the water during the flood season support diverse fish assemblages in floodplain forests of oligotrophic rivers (Correa and Winemiller 2018). Fruits also are a dependable and valuable food resource to fishes due to the community-wide synchrony in fruit production with the flood season (Correa et al 2017) and their high nutrient content (Waldhoff et al 1996, Waldhoff andMaia 2000). As such, fruits constitute a resource pulse that facilitates the coexistence of ecologically similar fish species (Correa and Winemiller 2014).…”

“…Large fish within and among species tend to swallow more seeds intact, therefore the rates of seed dispersal, relative to seed predation, increase with body size (Galetti et al 2008, Anderson et al 2009, Correa et al 2015a. Furthermore, large fish have big stomachs with a greater capacity to consume fruits, possess a greater mouth-gape which allow them to consume small-and large-seeded fruits, and are more mobile, which increases the probability of encountering the fruits of more plant species and dispersing seeds farther distances (Anderson et al 2009, Correa et al 2015a, Costa-Pereira et al 2017. The passage of seeds through the digestive tract of fishes can have positive, neutral or negative effects on germination success (reviewed in Correa et al 2007, andHorn et al 2011).…”

Seed consumption by small fish follows peak seed availability in a tropical dry forest river

“…In turn, physiological, morphological, and behavioral adaptations in fish correlate with the consumption of fruits and seeds (Correa et al., 2007; Costa‐Pereira et al., 2011; Drewe et al., 2004). Although large‐bodied frugivorous fish species are commonly the effective seed dispersers (Anderson et al., 2009; Correa, Costa‐Pereira, et al., 2015; Galetti et al., 2008), small‐ or medium‐sized fishes play an important role as dispersers of small‐seeded plants (Costa‐Pereira et al., 2011, 2017; Silveira et al., 2019; Silveira & Weiss, 2014).…”