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Logistic regression adjusted for the proportion of mature Cichla kelberi by total length (LT) at 3 cm intervals. Males and females are indicated in black and light blue, respectively. Estimation of L50 is shown in the dotted red lines
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The reproductive strategy of the non‐native predator cichlid Cichla kelberi was determined to explain its success after more than 60 years of being introduced into an isolated reservoir in southeastern Brazil. This was one of the first‐known translocations of the genus Cichla out of its natural range. Macro‐ and microscopy characteristics of the go...
Citations
... They inhabit both lentic and lotic environments (Jepsen et al., 1997) and are generally sedentary, although they exhibit potential for longer-distance movements (Hoeinghaus et al., 2003). Notably, they employ an equilibrium reproductive strategy, with both parents actively participating in nest building and offspring care (Guedes et al., 2021). Peacock basses have been and continue to be introduced worldwide since the 1940s, being already detected in the Americas, Europe, Oceania, the Middle East, Asia and Africa (Franco, Petry, Tavares, et al., 2022;Sastraprawira et al., 2020). ...
... We used the cannibalism biomass (i.e., the weight of the Cichla item) observed in the diet of each C. ocellaris specimen captured in the Lajes reservoir as the response variable. We used as potential predictors a set of explanatory variables related to the phenotype (body size), environmental conditions (temperature and transparency), hydrology (rainfall and water level), time since introduction, gonadosomatic index (GSI-proxy for reproductive period; Guedes et al., 2021), the abundance of C. ocellaris in the environment (proxy for intraspecific competition), abundance of other piscivorous fish in the environment (proxy for interspecific competition; e.g., Hoplias malabaricus Bloch, 1794), and availability of resources in the environment (abundance of the main prey consumed in the diet). The ML models were applied to: (i) determine the effects of all relevant explanatory variables, rather than just the non-redundant ones; and (ii) detect nonlinear and interactive relationships between the variables. ...
... However, the distribution of non-native species is asymmetrical within the lentic environments; for example, peacock bass and tilapias reached higher densities in shallow (0-7 m) and physically complex littoral habitats, whereas deep areas harbour lower densities of these species . Equilibrium strategy cichlids (sensu Winemiller, 1989) are often found in higher abundances near complex and hydrologically stable habitats which they use for nesting and parental care (Guedes et al., 2021;Mims & Olden, 2012). It is precisely here that cannibalism-a behaviour that seems antagonistic to care-begins. ...
The strategies that allow invasive alien species to perpetuate themselves in the long term are still poorly understood in invasion science. Considering top predators, a key issue is how they overcome the prey decline which they have caused during the invasion process. We investigate factors related to the persistence, impacts and long‐term success of the emerging peacock bass (Cichlidae: Cichla ) invasion, a fish native to the Amazon biome that has been introduced globally.
We analysed a robust temporal database that includes comparisons (1994–2002 vs. 2015–2017) on the diet of Cichla ocellaris , the abundance of this invader, its prey and competitors in a human‐modified ecosystem. In addition, we compare the frequency of cannibalism (presence or absence) between native versus non‐native populations, and between natural versus human‐modified ecosystems in the American continent. Four hypotheses were tested: (i) prey and competitor populations decrease through time as a result of predation impacts; (ii) cannibalism is size‐ and density‐dependent, and increases after native prey decline; (iii) cannibalism is more frequent in non‐native populations; and (iv) the abundance of invader decreases over time because of reduced resources and increased cannibalism.
Our results revealed that the impacts of introducing this predator into communities are temporally cumulative and continue to evolve even after 70 years since its introduction. These impacts have led to dramatic reductions in prey availability, resulting in widespread cannibalism. Adult individuals preying on juveniles in areas with higher abundances of peacock bass indicated that cannibalism is size‐ and density‐dependent. Cannibalism was more frequent in non‐native populations and in human‐modified ecosystems. A complex feedback process (reproduce and cannibalise frequently) may be responsible for overcoming long‐term resource scarcity, and the cannibalism may not be a regulatory force strong enough to surpass the reproductive success of the population.
Our findings at the local and continental scale converge to confirm the cannibalism as an adaptive invasiveness strategy that facilitates the invasion process and makes populations self‐sustainable in the long term, which may jeopardise the efficacy of management actions for these top predators introduced globally.
A new approach for visual fish survey in reservoirs using underwater drones (remotely operated vehicle- ROV) is presented. The ROV was applied to identify abiotic gradients and to compare fish assemblages on the steep slopes in a tropical reservoir. The tested hypothesis is that fish are concentrated in the littoral zone due to the better physicochemical and habitat conditions, compared to deep and hypoxic layers. Twelve species were recorded (seven native, five exotic), with all species occurring in the littoral zone, seven species in the transition, and four in the profundal zone. A greater fish abundance and richness was found in the littoral zone corroborating the main hypothesis. The littoral zone was dominated by exotic cichlids (Cichla spp., Coptodon rendalli), while native catfish (Loricariichthys castaneus, Pimelodella lateristriga) occupied deeper areas. The fish distribution seems to be driven by local factors, such as oxygen availability and habitat structure. The preference for the littoral zone by alien cichlids may have led to the extirpation/decrease of native characids and induced catfishes to occupy deep habitats. Underwater drones can be a valuable tool for the simultaneous collection of abiotic/biotic data, especially in deep reservoirs with complex habitats, resulting in advances in the environmental monitoring.
Supplementary information:
The online version contains supplementary material available at 10.1007/s10750-021-04790-9.
