Diet and ecomorphology of predator fish species of the Amazonian floodplain lakes

Abstract

Amazonian floodplain lakes host a high diversity of predatory fish which coexist and exploit the high diversity of available prey. Morphology could be the characteristic most closely associated with their preferred feeding sources (prey). However, it is unclear whether this association is direct or indirect. If it is indirect, swimming performance or preferential position in the water column could be the most evident characteristic. To examine the degree to which fish morphology of predator fish species is correlated to their dietary inputs, we compared the existence of morphological and feeding dissimilarity among eight predator species with the association between predator morphologies and preferred prey. We collected, measured, and sampled the stomach contents of fish from two lowland floodplain lakes associated with the Solimões River, Brazil, in May, August, and November of 2014. Of 187 collected fish across eight species, five species showed fish to be the most important item in their diets and three preferentially ate shrimp. Principal components analyses of ecomorphological attributes divided the species according to their ability to find the prey, swimming performance of the predator, and prey size. While there was significant distinction between the varying morphologies of predators, we were unable to distinguish between the specific diet of these species and did not find a correlation between morphology and feeding. These results are likely due to the fact that there is great abundance and diversity of available prey in the Amazonian floodplain lakes, so opportunistic feeding may be the primary foraging strategy of predator fish species living in these environments.

Trophic ecology of Acestrorhynchus falcirostris Cuvier, 1819 in island lakes on the lower stretch of the Solimões River, Amazon Basin

“…The generalist strategy found in the study corroborates with the reported in the literature for predatory fish (Cardoso et al, 2019;Jacobi et al, 2020;Mérona and Rankin-de-Mérona, 2004), since, in this seasonal phase, there is a greater supply of allochthonous items of animal and vegetable origin, such as winged insects, fruits and seeds that fall from the trees (Claro-Jr et al, 2004;Goulding, 1990) and serve as food for fish. This phase also aids the fish by allowing them to store fat until the low water period, when food becomes scarce.…”

“…The terminal mouth shape, large mandibular opening and huge canine teeth also help in capturing prey, as well as the gills rakers that are smaller and more spaced apart to trap food inside the oral cavity (Rotta, 2003;Ramírez et al, 2015;Cardoso et al, 2019). Another factor that facilitates the type of intake is the bag shape (or pisciform) of the stomach of A. falcirostris, with elastic musculature to accommodate the whole prey in the celomatic cavity (Rotta, 2003), since Trophic ecology of Acestrorhynchus falcirostris most of the fish consumed by A. falcirostris are of fusiform shapes, such as Triportheus spp., which aids the entire prey intake when compared to rhomboid-shaped fish.…”

“…In fact, the high-water period provides an increase in the diversity of food items, in which fish species, including those of predatory fish, benefit from the quantity and quality of available items. This creates and Rankin-de- Mérona, 2004), effects of seasonality on energy acquisition (Neves dos Santos et al, 2008), energy allocation for reproduction (Neve dos Santos et al, 2010), the relationship between their feeding strategy and hydrology (Röpke et al, 2019) and diet and morphological relationships (Cardoso et al, 2019). However, studies on the niche breadth, fractional trophic position and feeding strategy for A.…”

Niche partitioning of two piscivorous fish species in a river in the western Brazilian Amazon

“…The greater consumption of pelagic fish by H. scomberoides can be explained by the ecomorphological traits of the species. In general, H. scomberoides is able to eat whole prey due their large mouth with underslung jaw (Beaumord, 1991;Cardoso et al, 2019), but have also been shown to capture their prey using their long canine teeth (Howes, 1976). Due to their large and upward-oriented mouths, these species focus prey-capture at the water surface or at the limnetic zone (Saint-Paul et al, 2000).…”

Do fish isotopic niches change in an Amazon floodplain lake over the hydrological regime?

“…Although the link between higher influx of allochthonous resources during the flood season and increases in niche width seems intuitive, some studies have shown narrower niche breadth in this season (Walker et al., 2013) and others have shown no consistent pattern of niche breadth during the flood pulse (Correa & Winemiller, 2014). Even though trophic ecology of Amazonian fishes has been extensively studied (Arauajo‐Lima et al., 1986; Leite et al., 2002; Mortillaro et al., 2015; Rejas, 2018; Cardoso et al., 2019), there is no defined pattern of seasonal variation of fish trophic niche width in floodplain lakes (Mérona and Rankin‐de‐Mérona, 2004). Understanding the natural seasonal variation in trophic niche dynamics is an important step towards Amazonian fish conservation.…”