Native Fish Communities Research Articles

Non-native fishes homogenize native fish communities and reduce ecosystem multifunctionality in tropical lakes over 16 years

Non-native species are considered a major global threat to biodiversity, and their expansion to new ecosystems has recently increased. However, the effect of non-native species on ecosystem functioning is poorly understood, especially in hyperdiverse tropical ecosystems of which long-term studies are scarce. We analyzed the relationship between richness, biomass, and β-diversity of non-native and native fishes during 16 years in five hyperdiverse tropical shallow lakes. We further elucidated how an observed increase in the proportion of richness, biomass, and β-diversity of non-native over native fishes affect crucial multifunctional processes of lakes (decomposition, productivity). We found a general positive relationship between the richness and biomass of non-native and native fishes. However, the slope of this relationship decreased continuously with time, displaying an increase in non-native species richness and a decrease in native species richness over time. We also detected a negative relationship between the β-diversity of non-native and native fishes over time. Moreover, the increase in the non-native:native ratio of species richness, biomass, and β-diversity over time decreased ecosystem multifunctionality. Our results suggest that non-native fishes caused a homogenization of the native fish species over time, resulting in impoverishment of ecosystem multifunctionality; in part because non-native fishes are less productive than native ones. Therefore, focus on long-term effects and use of multiple biodiversity facets (α- and β-diversity) are crucial to make reliable predictions of the effects of non-native fish species on native fishes and ecosystem functioning.

Quantifying Consumption of Native Fishes by Nonnative Channel Catfish in a Desert River

AbstractThe establishment of nonnative predators can have devastating consequences for native fish communities, but predation rates are often difficult to quantify due to spatial and temporal variation in predator foraging behavior. Predation by Channel Catfish Ictalurus punctatus throughout the Colorado River basin potentially threatens the recovery of native fishes. Because Channel Catfish are highly opportunistic feeders, an understanding of how piscivory by this species impacts prey populations should help to guide management in invaded systems. We used laboratory observations to model temperature‐dependent stomach evacuation rates and combined those estimates with field‐collected diet data to derive annual consumption across a 152‐km reach of the San Juan River (New Mexico, Colorado, and Utah). In the field, stomach fullness increased with water temperature while the probability of observing fish prey in the diet increased with TL of Channel Catfish and water turbidity. Based on estimates of daily ration, diet composition, and Channel Catfish population demographics, we estimated the San Juan River population’s fish consumption to be 4.9 kg·ha−1·year−1 (95% CI = 4.0–6.1 kg·ha−1·year−1) in 2018 and 2.3 kg·ha−1·year−1 (95% CI = 1.8–2.8 kg·ha−1·year−1) in 2019. Native fishes accounted for 54% of the fish biomass consumed, which included two incidents of endangered Colorado Pikeminnow Ptychocheilus lucius consumption. Although these estimates should help managers to assess the predatory threat of Channel Catfish, additional information, such as the efficacy of nonnative control and prey population compensatory responses, will likely be necessary to develop robust management strategies aimed at reducing the predatory impacts of this nonnative species on native fish assemblages.

Marsela Fishing Habits (Parachromis managuensis) In Penjalin Reservoir Brebes, Central Java

Abstract. The presence of introduced fish populations in the Penjalin Reservoir is increasing, one of the dominant ones being caught is Marsela (Parachromis managuensis). It is feared that this fish population will continue to increase and will have a negative impact on other organisms, especially native fish communities. This study aims to determine the eating habits of Marsela fish, the composition of the type of food and its relationship to the abundance of plankton in the waters. This research was conducted in September-October 2018. The method used was CPUE with a sampling technique that is Simple Random Sampling. Sampling of fish in one day is done 6 times, namely at 05:00, 11:00, 17:30, 21:00, 00:00, and 03:00. Fish samples obtained are then grouped according to length and then an analysis of the contents of the stomach. The results showed that in the Penjalin Reservoir the percentage of phytoplankton presence was 96% with the highest abundance found in the Bacillariophyta group. Marsela is an omnivorous fish with popular foods are Chlorophyta and Charophyta. However, in adulthood Marsela fish also eat animals.Keywords: Marsela Fish (Parachromis managuensis), Fish Eating Habits, Penjalin Reservoir

Environmental DNA revealed the fish community of Hokkaido Island, Japan, after invasion by rainbow trout.

In freshwater ecosystems, invasive salmonid fishes can have a significant impact on native fish species. Detecting the invasion and its negative effects is critical for the conservation of native fish communities. We examined the species composition and seasonal changes in the freshwater fish community, including salmonids, on the Kamikawa Plain, Hokkaido Island, Japan, using environmental DNA (eDNA) metabarcoding. We detected 23 fish species in 176 samples collected from 16 sites over 12 months (October 2018 – August 2019). Between 11 and 20 species were detected at each site, including five native salmonids (Oncorhynchus masou, Oncorhynchus keta, Parahucho perryi, Salvelinus leucomaenis leucomaenis and Salvelinus malma krascheninnikova). The invasive alien rainbow trout Oncorhynchus mykiss was detected at all 16 sites and it was the most commonly detected salmonid. Although we found no obvious competitive exclusion of native salmonids by rainbow trout in the study area, the invasive species occurred more often and at more sites than any of the natives. We also determined the occurrence and seasonal changes in the fish community, classified as native salmonids, invasive rainbow trout, Cypriniformes and other benthic fishes. There were fewer species overall in winter, but the sites with higher species richness in winter were on the lower reaches of the river. In addition, we detected domestic invaders, such as the topmouth gudgeon, Pseudorasbora parva, although they were less prevalent than rainbow trout. These results show the effectiveness of eDNA metabarcoding, which can be used for surveying species richness at an ecosystem scale. In particular, the detection of the early stages of establishment and spread of invasive species can be achieved by eDNA monitoring.

Different refuge types dampen exotic invasion and enhance diversity at the whole ecosystem scale in a heterogeneous river system

Refuges that result from environmental heterogeneity within ecosystems have an important yet under-appreciated role in maintaining native community diversity in face of exotic invasion. The objective of our study was to determine if different refuge types constrain invasion impacts on native biodiversity at the whole ecosystem-scale of the Upper St. Lawrence River. We focused on the voracious round goby fish as a sentinel exotic species whose spatial distribution within this ecosystem is also representative of the species distributions of several other Ponto-Caspian invaders. We first explored if wetlands were acting as unknown refuges in reducing the local abundance of the round goby fish. We then tested the relative influence of a known broad-scale conductivity gradient compared with local wetlands on structuring the composition, diversity, and abundance of native macroinvertebrate and fish communities inside and outside each of these refuge types. We found that the two types of refuges, broad-scale conductivity gradient and local wetlands, limited round goby abundances at the whole ecosystem scale, and structured macroinvertebrate and fish community diversity. The broad-scale conductivity refuge was twice stronger than wetlands in limiting round goby abundance. Although wetlands were effective in constraining round goby abundance, the direct effect of wetlands rather than their indirect effects through limiting round goby abundance, were more powerful in explaining maintenance of macroinvertebrate and fish community diversity in invaded high conductivity waters. Our findings underscore the important role of environmental heterogeneity in producing different types of refuges that buffer invasion effects in freshwater ecosystems, and we advocate the preservation of wetlands as a part of this process.

Suckermouth-armored Catfish (Siluriformes: Loricariidae) of Central and Southern Vietnam

Presently, invasive fish species become dominant in some freshwater waterbodies and watercourses of Central and South Vietnam in terms of abundance, successfully competing with native species for ecological niches and environmental resources. This can ultimately reduce the diversity of native fish communities and cause their further transformation. Loricariids are considered the main group of invasive fish species being a serious threat to tropical and subtropical freshwater ecosystems. In this regard, the distribution and morphology of suckermouth-armored catfishes (Pterygoplichthys spp.) in different habitats of Central and South Vietnam were studied. A total of 54 reservoirs belonging to the basins of 15 large and small rivers were surveyed. Specimens were examined for 7 meristic and 34 plastic characters. The osteological analysis of the axial skeleton of fish conducted using radiography. Morphological differences and a number of developmental anomalies of morphology were found in different armored catfish populations from Vietnamese waters. It is noted that deliberate or accidental introduction of suckermouth-armored catfishes and their further spread can have negative consequences for the biodiversity of Vietnam’s aquatic ecosystems.

Trials to visualize the effects of invasive rainbow trout on the native fish community in central Hokkaido, Japan ―HUE & Kobe U. Freshwater Biology Team―

Trials to visualize the effects of invasive rainbow trout on the native fish community in central Hokkaido, Japan ―HUE & Kobe U. Freshwater Biology Team―

Multiple stressor effects on alpha, beta and zeta diversity of riverine fish

We examined the effects of regional scale land use and local scale environmental and biotic stressors on alpha, beta and zeta diversities of native fish communities in wadeable streams and non-wadeable rivers in the Danube basin, Hungary. Relationships among land use and local scale environmental and biotic stressors were weak both in streams and rivers, suggesting that these stressors act relatively independently. Alpha diversity decreased strongly with increasing local scale environmental stressor intensity in rivers. On the contrary, its response to stressors was more obscure in streams, where the best-fit statistical model indicated the importance of the interaction between land use, local scale environmental and biotic stressors, while the secondly ranked model highlighted the negative impact of local scale environmental stressors. Analysis of variance using distance matrices provided evidence that stressors alone and in interactions explained compositional differences of pairs of study sites (beta diversity). Considering the degree of overall degradation, both local (alpha) and among-site (beta and zeta) diversity indices responded to increasing stressor intensity, generally negatively. Riverine fish communities showed higher degrees of similarity (lower beta and higher zeta) than stream fish communities. They also showed increasing similarity (i.e. homogenization) with increasing overall stressor intensity, unlike stream fish communities, which showed no relationship with overall stressor intensity. Our results suggest that the relationships between land use and local scale environmental and biotic stressors can be complex and so do their effects on biodiversity. While stressor specific indices can provide information on the role of specific stressors in some cases, the examination of overall stressor effects is needed to assess realistically the effects of anthropogenic disturbances on native fish diversity. Diversity indices that quantify among-site changes in species composition, such as measures of beta and zeta diversity, can be fruitful for better understanding the role of multiple stressors in structuring ecological communities.

Occupancy dynamics of rare cyprinids after invasive fish eradication

Abstract The eradication of invasive species is a management strategy implemented to eliminate adverse impacts of invaders on native species communities. After eradications, follow‐up studies are done to confirm eradication of the invasive species and the short‐term recovery of the native species, but long‐term monitoring to confirm full population recovery and stability is often not completed. In this study, long‐term monitoring of native fishes was carried out over 5 years after the eradication of an invasive fish from the Rondegat River, South Africa. Forty‐six sites distributed along four river sections were sampled for presence/absence using underwater cameras and snorkel surveys. Density data were collected by snorkel surveys. Using multi‐season occupancy models, the annual probability of colonization and local extinction of the native fishes and annual rate of change in occupancy along the river were estimated. Changes in native fish densities across time and across the control and treatment sections were analysed using Kruskal–Wallis analysis, followed by Dunn's post‐hoc test. Probability of colonization and local extinction differed for each native fish species and may have been affected by extrinsic factors, such as rainfall, and intrinsic density‐dependent factors, hypothesized from the density data. The occupancy rates of change revealed that the two Near Threatened fish species have reached an occupancy dynamic equilibrium but the Endangered fish has not, suggesting that other conservation efforts may be needed. Long‐term monitoring of native fishes after an eradication programme has confirmed the successful removal of the invader and the recovery and stability of the community. However, successful eradication was not sufficient for full recovery of all species; additional conservation management strategies are needed to secure the population stability and persistence of endangered fishes. We recommend that eradication programmes, regardless of locality, should employ long‐term monitoring to ensure full recovery of a native fish community.

Introduction of Bluefin Killifish (Lucania goodei) into the Sacramento–San Joaquin Delta

Biological invasion by non-native species has been identified as one of the major threats to native fish communities worldwide. The fish community of San Francisco Estuary is no exception, as the estuary has been recognized as one of the most invaded on the planet and the system has been impacted significantly by these invasions. Here, we summarize the introduction and probable establishment of a new species in the Sacramento–San Joaquin Delta, the Bluefin Killifish (Lucania goodei), as discovered by the US Fish and Wildlife Service Delta Juvenile Fish Monitoring Program (DJFMP). The DJFMP has conducted a large-scale beach seine survey since 1976, and it is the longest-running monitoring program in the San Francisco Estuary that extensively monitors the shallow-water nearshore habitat. Possibly introduced as discarded aquarium fish within the vicinity of the Delta Cross Channel, Bluefin Killifish is a close relative of the Rainwater Killifish (Lucania parva), another non-native fish species that has been present in the San Francisco Estuary system for decades. Studies in their native range suggest that Bluefin Killifish will fill a similar niche to Rainwater Killifish, albeit with a more freshwater distribution. The potential ecological impact of Bluefin Killifish remains unclear in the absence of additional studies. However, we have been able to track the spread of the species within the Sacramento–San Joaquin Delta through the existence of long-term monitoring programs. Our findings demonstrate the value of monitoring across various habitats for the early detection and proactive management of invasive species.

A long-distance traveler: the peacock rockskipper Istiblennius meleagris (Valenciennes, 1836) on the Mediterranean intertidal reefs

In this study, we document the introduction of the Australian endemic Istiblennius meleagris into the Mediterranean Sea, probably via shipping, and its expansion along the Israeli coastline. Taxonomic confirmations were based on both morphological and molecular approaches. This is the first evidence of a non-indigenous benthic fish colonizing the rocky intertidal zone in the eastern Mediterranean, thus raising concerns regarding the future integrity of the native fish community in this ecosystem.

Conceptualizing alternate regimes in a large floodplain-river ecosystem: Water clarity, invasive fish, and floodplain vegetation

Regime shifts - persistent changes in the structure and function of an ecosystem - are well-documented for some ecosystems and have informed research and management of these ecosystems. In floodplain-river ecosystems, there is growing interest from restoration practitioners in ecological resilience, yet regime shifts remain poorly understood in these ecosystems. To understand how regime shifts may apply to floodplain-river ecosystems, we synthesize our understanding of ecosystem dynamics using an alternate regimes conceptual framework. We present three plausible sets of alternate regimes relevant to natural resource management interests within the Upper Mississippi River and Illinois River. These alternate regimes include: 1) a clear water and abundant vegetation regime vs. a turbid water and sparse vegetation regime in lentic, off-channel areas, 2) a diverse native fish community regime vs. an invasive-dominated fish community regime, and 3) a regime characterized by a diverse and dynamic mosaic of floodplain vegetation types vs. one characterized as a persistent invasive wet meadow monoculture. For each set of potential alternate regimes, we review available literature to synthesize known or hypothesized feedback mechanisms that reinforce regimes, controlling variables that drive regime transitions, and current restoration pathways. Our conceptual models provide preliminary support for the existence of alternate regimes in floodplain-river ecosystems. Quantitatively testing hypotheses contained within the conceptual model are important next steps in evaluating the model. Ultimately, the synthesis and evaluation of alternate regimes can inform the utility of resilience concepts in restoration and management on the Upper Mississippi River and Illinois River and improve our understanding of ecosystem dynamics in other large, heavily managed floodplain-river ecosystems.

Size, weight, and diet of the invasive lionfish Pterois volitans (Linnaeus, 1758) on the southern coast of Veracruz, Gulf of Mexico

The invasion of the Indo-Pacific lionfish Pterois volitans has produced detrimental impacts on the regional biodiversity and fisheries of invaded ranges. To understand the effect this lionfish may have on the native fish communities, it is necessary to understand its feeding habits. The objectives of this study were to report new distribution records of P. volitans along the southern coast of Veracruz (México), to document the feeding habits of the collected specimens, and to determine if there was a relationship between the diet, size, and weight of those specimens. The density of P. volitans in our study area was low. Diet composition for this species consisted of bony fishes (95.40%), crustaceans (4.20%), and mollusks (0.36%). Lionfish size and weight were positively correlated. We did not find statistical differences between the diet and the size/weight groupings; however, the smaller specimens seemingly had a more varied diet than the larger specimens.

Evaluating the role of predatory fish controlling the invasion of the Asian golden mussel Limnoperna fortunei in a subtropical river

Abstract The invasive Asian golden mussel Limnoperna fortunei is continuously expanding through South America, altering aquatic ecosystem structure and functioning. While several native fish species predate on this mussel, these interactions, and their consequences for the food web, have not been studied in depth. We combine a survey of the fish assemblage trophic structure using gut contents and stable isotope analysis with an in situ exclusion experiment in order to: (a) determine the main fish species predating on L. fortunei; (b) estimate the contribution of L. fortunei to the biomass of fish assemblage; and (c) evaluate the role of fish on the density and maximum shell length of L. fortunei in the lower Uruguay River (the Río de La Plata Basin). We found that about one third of fish species in the assemblage (28 out of 81 species) consumed L. fortunei, which was an important food item (>10% of the dietary volume and >30% of frequency of occurrence) for 11 fish species. Stable isotope mixing models consistently suggested that >14% of the total biomass of the fish assemblage was derived directly from carbon derived from L. fortunei tissues. In addition, the exclusion experiment demonstrated that fish predation reduces the mussel density by c. 70% and the mussel maximum shell length by c. 40%. Synthesis and applications. Our research suggests a top‐down effect of fish on the invasive Asian golden mussel's abundance. This work highlights the need to preserve the native fish communities, particularly in South America, where many vulnerable migratory fish are of key relevance as Limnoperna fortunei consumers. In the light of these findings, actions such as implementing efficient fish passage technologies in the actual (and projected) dams of the Uruguay River basin and elsewhere become essential to avoid local extinctions of these natural invasion controls upstream of the dams.

Connectivity but not recruitment: Response of the fish community to a large‐scale flood on a heavily regulated floodplain

AbstractRecent environmental flow management in the Murray–Darling basin, south‐eastern Australia, has centred on restoring natural flooding regimes to meet ecological requirements, including the promotion of native fish recruitment, despite uncertainty about the effectiveness of managed environmental flooding. This study investigated recruitment responses of small‐bodied native and non‐native fish species to a large natural flood, supported by managed environmental flows in the Macquarie Marshes of the Murray–Darling basin. We surveyed the fish community within the heavily regulated, dryland floodplain system of the marshes, the year after breaking of the Millennium drought (2002–2009). During the spring–summer of 2010, the Macquarie Marshes experienced a one‐in‐10‐year flood, sustained by two environmental flow allocations, flooding 174,000 ha of floodplain. Five native species were collected across the nine study sites. Two non‐native species were particularly abundant during the flood, outnumbering the five native species in a ratio of 32:1, with Gambusia holbrooki the most abundant species, comprising 87% of all native and non‐native individuals captured. There was no marked effect of flood stage on the total abundance of small‐bodied native or non‐native fishes, but the composition of the fish community varied between surveys of the rising and falling phases of the flood. We did not capture any larval or post‐larval fish despite using a variety of suitable sampling methods. The lack of larvae in the Macquarie Marshes, following extensive flooding, most likely reflected the overall poor condition of native fish communities and low standing stocks of mature fish, resulting from deleterious long‐term effects of flow regulation exacerbated by drought. A gradual rebuilding of ecosystem health, fish health, and resilient fish populations by active management of environmental flows to impose more natural boom and bust dynamics may be needed to restore fish reproduction and recruitment in this regulated river.

Changes in Primary Producer and Consumer Communities in Response to Upstream Nutrient Addition in the Kootenai River, Idaho

The purpose of this study was to assess potential effects of nutrient addition in the previously unassessed lower Kootenai River (Meander Reach), 44–155 km downstream from the nutrient dosing site. We hypothesized that downstream periphyton and plankton densities would increase due to nutrient spiraling and organismal drift following seasonal upstream nutrient addition. Liquid inorganic ammonium polyphosphate fertilizer (10:34:0, N:P:K) was added to the Kootenai River in Idaho immediately downstream from the Idaho-Montana border with an in-river target concentration of 3.0 µg L-1 total dissolved phosphorus for 16 weeks (01 June–01 October) from 2006 through 2012. As predicted, mean periphyton, phytoplankton, and zooplankton densities increased significantly (P < 0.05) post-nutrient addition. Periphyton density increased 5.1 times (pre: 685.1 mm-2, post: 3501.0 mm-2), phytoplankton densities increased 1.7 times (pre: 1775.9 L-1, post: 3005.4 L-1), and zooplankton densities increased by 49% (pre: 67.0 L-1, post: 99.7 L-1). While nutrient uptake, water chemistry, algal and chlorophyll accrual, periphyton, macroinvertebrate, and native fish community responses to nutrient addition have been previously published, including results from upstream reaches of the Kootenai River, this study provides the first published account of lower trophic level responses at considerable distances downstream from the dosing site in altered, low velocity habitats which are very different from the upstream gravel-bed reaches reported in other studies. Results of this study add to the growing body of empirical knowledge regarding the use of nutrient addition for restoring large culturally denutrified rivers in the Pacific Northwest and provide valuable new insights regarding the longitudinal patterns of response magnitude.

What is needed to restore native fishes in Australia’s Murray–Darling Basin?

The Murray–Darling Basin (MDB) is Australia’s food bowl, contributing 40% of agricultural production and supporting a population of over 4 million people. Historically, the MDB supported a unique native fish community with significant cultural, subsistence, recreational, commercial and ecological values. Approximately one-quarter of the MDB’s native species are endemic. Changes to river flows and habitats have led to a &amp;gt;90% decline in native fish populations over the past 150 years, with almost half the species now of conservation concern. Commercial fisheries have collapsed, and important traditional cultural practices of First Nations People have been weakened. The past 20 years have seen significant advances in the scientific understanding of native fish ecology, the effects of human-related activities and the recovery measures needed. The science is well established, and some robust restoration-enabling policies have been initiated to underpin actions. What is now required is the political vision and commitment to support investment to drive long-term recovery. We present a summary of 30 priority activities urgently needed to restore MDB native fishes.

Impact of the invasive alien topmouth gudgeon (Pseudorasbora parva) and its associated parasite Sphaerothecum destruens on native fish species

The Asian cyprinid Pseudorasbora parva is considered to be a major threat to native fish communities and listed as an invasive alien species of European Union concern. Our study aims to gain evidence-based knowledge on the impact of both P. parva and its parasite Sphaerothecum destruens on native fish populations by analysing fish assemblages and body condition of individuals of native fish species in floodplain water bodies that were invaded and uninvaded by P. parva. We explored the use of environmental DNA (eDNA) techniques to detect S. destruens. Prevalence of S. destruens in native fish species was assessed. Fish samplings showed significantly negative correlations between the abundance of P. parva and the native Leucaspius delineatus, and Pungitius pungitius and three biodiversity indices of the fish assemblages (Simpson’s diversity index, Shannon–Wiener index and evenness). Contrastingly, the abundances of the native Gasterosteus aculeatus and P. parva were positively related. In nearly all isolated water bodies with P. parva, this species is outnumbering native fish species. No effect of P. parva presence was found on body condition of native fish species. Sphaerothecum destruens was demonstrated to occur in both P. parva and G. aculeatus. Gasterosteus aculeatus is suggested to be an asymptomatic carrier that can aid the further spread of S. destruens. Analysis of eDNA proved to be a promising method for early detection of S. destruens, here showing that S. destruens presence coincided with P. parva presence. The ongoing invasion of both P. parva and S. destruens is predicted to pose a significant risk to native fish communities.

Salinity tolerance during early development of threatened Murray hardyhead (Craterocephalus fluviatilis) to guide environmental watering

Abstract The worldwide reduction in wetlands has led to the large‐scale decline of wetland‐dependent species. In Australia, to redress some of the decline, partial restoration of the hydrology of a small number of wetlands has been attempted using allocations of environmental water. A common goal of the watering is the maintenance and enhancement of native fish communities, which historically have included populations of the salt tolerant Murray hardyhead (Craterocephalus fluviatilis), a small, short‐lived fish, endemic to the lower Murray–Darling Basin. Despite the addition of environmental water to several sites at which the species is known to persist, populations continue to decline. This decline is, at least in part, suspected to be a consequence of salinities that conflict with the breeding ecology and survival of early life stages. Here the effect of salinity on egg hatch rate and the upper salinity tolerance of larval and juvenile Murray hardyhead was determined under laboratory conditions. It was found that eggs were vulnerable to elevated salinities, whereas juveniles were capable of tolerating salinities up to 105 ppt. Based on the results of the experiment, brackish wetlands managed for Murray hardyhead should be maintained, where possible, between 12 and 45 ppt. Such a salinity regime will necessitate less intensive management of salinity, and a reduced volume of environmental water, providing both environmental and fiscal benefits. The research highlights the benefits of investment in targeted research.

Impact of the non-native locariid fish Pterygoplichthys pardalis in native fish community on a seasonal tropical floodplain in Mexico

The present study reports the seasonal dynamics of the fish community structure in the presence of a non-native fish (Pterygoplichthys pardalis) in tropical waterbodies of southern Mexico. The studied floodplain existed in both connected pools and disconnected pools “to the Palizada river”. Local fish fauna showed consistent assemblages across seasons, but among the 17 local fish species recorded, the non-native species P. pardalis showed the highest percentage of contribution to the fish community (ca. 20%). Conversely, the frequency of occurrence and density of the non-native species showed variation in relation to the type of waterbody and seasonality; its density was approximately four times higher in disconnected pools than in connected pools in the rainy season and its predominant size class in both pool types was 21-30 cm in standard length. Interestingly, the diversity of the native species was negatively related to the density of the non-native species, indicating that the presence of P. pardalis can be a factor involved in the decline of native fish diversity in these local communities. Currently, the possible impacts of the presence of P. pardalis on local fish diversity at the regional scale are unknown, but our results suggest that hydrological dynamics regulate the establishment of the non-native species in this region. However, future studies are needed to provide insights into the actual scenario of P. pardalis distribution in Yucatan Peninsula and the possible impacts on the native fish fauna in southern Mexico.