Conflict between spotted-necked otters and fishermen in Hlan River,Benin

The spotted-necked otter (Lutra maculicollis) is believed to be declining across its range and, in Benin, has recently been listed as endangered. In Benin, the spotted-necked otter is largely restricted to the south of the country, where it is threatened by a number of factors, including conflict with fishermen. Understanding the nature and extent of this conflict, and the impact that it has on local fishermen, as well as identifying feasible mitigation strategies, represents a critical challenge for conservation managers.This study documents otter damage experienced by 30 fishermen in the Hlan River, in the Southern Benin wetlands. We performed hierarchical classification analysis using Ward distances to categorize fish species according to the level of otter damage suffered, and used generalized linear models to identify predictors that best explained otter damage. Our results suggest that of the 16 fish species commonly caught by fishermen in the Hlan River, otters favored the most valuable species (but these were also the most abundant in the catch). However, although otter damage was extensive, monthly total income loss attributable to spotted-necked otter damage (including fish loss and damage to equipment) was estimated at only 9% per fishermen (considerably lower than the 30% reported by a preliminary survey of 163 fishermen in the same area). Our model showed that otter damage increased significantly with the number of adult fish captured by fisherman while the cost of otter damage increased with the length of time that the fishing equipment was left unattended. We suggest that otter damage could be reduced if fishing equipment were checked at least twice a day by fishermen, and recommend a maximum interval between checks of 700 min (12 h). Long-term sustainable management of these conflicts will require an integrated approach taking into account socio-economic, political and environmental dimensions.     

Do non‐native fish as prey favour the conservation of the threatened indigenous Eurasian otter?

1. Biological invasions are considered a major threat to biodiversity. Most research has focused on the distribution, biology and impacts of non‐native species on native fauna and flora. However, few studies have explored their role as prey for native predators of conservation concern. 2. To assess the incidence and intensity of predation by the Eurasian otter Lutra lutra on established non‐native fish species, data were collated from the published literature. To be selected, studies had to cover at least 1 year, analyse more than 100 spraints and report the study period and percentage relative frequency (%RF) of all prey fish species. 3. To permit reliable, time‐related comparisons with %RF of non‐native fishes in otter diet, we also reviewed available information about both the distribution of non‐native fishes and history of their introductions to European countries, revealing a decrease with longitude in the number of naturalised non‐native fishes taken (ranging between 5 and 34) and their percentage in each fish assemblage. 4. Our selective criteria were met by 30 dietary studies from 44 study areas in 15 European countries during 1970–2010. The extent to which otters rely on non‐native fishes was almost negligible (mean %RF = 4.8), with the number of non‐native fishes preyed upon by otters decreasing with both latitude and longitude. 5. The %RF of non‐native fish in the diet increased slightly with time, with otters preying significantly more on non‐native fish in study areas where alterations of the fish assemblage had been highlighted in the reference papers. No relationship was found between otter diet breadth and the occurrence of non‐native fishes in their diet. 6. The current role of non‐native species in otter diet suggests that effective otter conservation management plans should focus on the maintenance and/or enhancement of native fish assemblages.     

Eurasian otter (<Emphasis Type="Italic">Lutra lutra</Emphasis>) diet and prey selection in Mediterranean streams invaded by centrarchid fishes

The diet of the Iberian otter (Lutra lutra) was determined by analysing 547 spraints collected at 28 sites within a wide area invaded by centrarchid fishes (pumpkinseed sunfish, Lepomis gibbosus and largemouth bass, Micropterus salmoides): the middle Guadiana basin (South-west Iberian Peninsula). Fish was the otters’ main prey, representing more than 60% of total individuals and more than 80% of total biomass. Otters preyed on most of the fish species captured in the field; however, the consumption of centrarchids was low compared to their abundance in the streams, and Jacobs’ index of preference showed a clear rejection of both species by the otter. Consumption of native fish genera (Squalius, Barbus and Chondrostoma) by otters increased in relation to their increase in the environment. In contrast, increasing numbers of L. gibbosus in the field was not reflected in otter consumption. The general decline of native freshwater fishes in Iberian rivers, the preferred prey of otters, together with the spread of exotic fish species (centrarchids and others) could put otter populations at risk.     

Latitudinal variation in diet and patterns of human interaction in the marine otter

The marine otter (Lontra felina) inhabits patches of rocky coastline from central Peru to southern Chile and is classified as Endangered by the IUCN. Given the limited information available about the species, we set out to assess marine otter diet with a view to detecting latitudinal differences, and to assess marine otter activity budgets and interspecific interactions (including anthropogenic) at Peruvian fishing villages and to compare results with similar Chilean studies. Nine study sites from central Chile to southern Peru were sampled for otter spraints to assess relative frequency of prey types and two fishing ports in southern Peru were monitored through focal and scan observations to assess activity patterns, interspecific interactions, habitat use patterns, and dive durations. Results indicate that toward the northern part of its range, crustaceans become less important and fish more important in the diet. Interactions were observed between marine otters and other species, including stray dogs and cats. The strong dependence of marine otters on the availability of safe rocky shelters, and the species’ apparent tolerance to living alongside humans raise conservation concerns about vulnerability to anthropogenic threats. These factors, if not correctly managed, could turn some of these rocky seashore patches into population sinks.     

Influence of occupation history and habitat on Washington sea otter diet

Habitat characteristics are primary determinants of nearshore marine communities. However, biological drivers like predation can also be important for community composition. Sea otters (Enhydra lutris ssp.) are a salient example of a keystone species exerting top‐down control on ecosystem community structure. The translocation and subsequent population growth and range expansion of the northern sea otter (Enhydra lutris kenyoni) in Washington State over the last five decades has created a spatio‐temporal gradient in sea otter occupation time and density, and acts as a natural experiment to quantify how sea otter population status and habitat type influence sea otter diet. We collected focal observations of sea otters foraging at sites across the gradient in varying habitat types between 2010 and 2017. We quantified sea otter diet composition and diversity, and long‐term rates of energy gain across the gradient. We found that sea otter diet diversity was positively correlated with cumulative sea otter density, while rate of energy gain was negatively correlated with cumulative density. Additionally, we found that habitat type explained 1.77 times more variance in sea otter diet composition than sea otter cumulative density. Long‐term diet studies can provide a broader picture of sea otter population status in Washington State.     

Commensal association of the common kingfisher with foraging Eurasian otters

Positive interactions between birds and mammals are a fascinating aspect of animal behaviour. Feeding associations may consist of local enhancement or facilitation, and in the latter case, of commensalism or mutualism depending on the benefits received by the facilitator. We report here on a previously undescribed feeding association between piscivorous birds and Eurasian otters Lutra lutra. In Spain, common kingfisher Alcedo atthis and grey heron Ardea cinerea were observed closely following foraging otters and benefited from feeding opportunities provided by these. Behavioural observations of otters in central Spain (28.4 hr; 19 days) revealed that an association with kingfishers occurred in 33% of otter foraging events (n = 92). Simultaneous observations in northern Spain (14.2 hr; 16 days) showed an association between otters and kingfishers or grey herons in 41.6% and 11.7% of otter foraging events (n = 77), respectively. The association probability between kingfishers and otters increased significantly when otters foraged closer to the shore and on small fish rather than other prey (crayfish or large fish). Birds fed on prey remain left by the feeding otters, on small fish captured by otters when these were satiated and playing, or on prey displaced by otters. Our observations are consistent with facilitation and commensalism: piscivorous birds gained feeding opportunities provided by the otters, with no apparent costs or benefits to the latter. Similar feeding associations have been described between other species of otters and piscivorous birds (kingfishers, herons, egrets, storks) in Asia, South America and Southern Africa, but had not yet been described in Europe. The occurrence of piscivorous bird–otter associations in different species and regions suggests that this commensalism may be often overlooked but widespread. We have shown that the association can be frequent and is context‐dependent, with benefits for associating birds depending on otters´ behaviour and targeted prey.     

Competition between Eurasian otter Lutra lutra and American mink Mustela vison probed by niche shift

Interspecific competition is one of several constraints that might prevent an individual from maximising its energy intake. When an interspecific competitor is introduced, an individual is often forced to shift its diet according to the intensity of the competitive pressure. In this paper, we explore whether the introduced American mink ( Mustela vison Schreber) shifts its diet when the density of its potential competitor, the Eurasian otter ( Lutra lutra L.), is increased. We compared the diets of otter and mink at the same location but at two moments in time when the relative densities of these two species were different while controlling for the abundance of aquatic prey. Mink and otters are semi-aquatic mammals belonging to the same guild of mustelids and otters are expected to be the dominant competitor because they are larger and better at hunting underwater. The diets of otters and mink overlap to a great extent but while otters specialise mainly on aquatic prey, mink are able to exploit both aquatic and terrestrial prey. These observations prompted the hypothesis investigated in this work that at higher otter densities the diet of mink should change to include a higher proportion of terrestrial items. This hypothesis was supported by the data and at higher otter densities mink diet was observed to consist of a higher proportion of mammals and birds while fewer fish were present, although this pattern was present only in winter while no changes were observed in spring. Meanwhile the diet of otters remained basically unchanged. In the second part of the study, we investigated whether niche breadth and niche overlap between otter and mink changed at different otter densities. We found that niche overlap declined as the density of otters increased, in agreement with the prediction of habitat selection theory.     

Feeding habits of the otter and the American mink in Bialowieza Primeval Forest (Poland) compared to other Eurasian populations

Diets of the otter Lutra lutra and the American mink Mustela vison were studied by scat analysis on five woodland rivers and streams in eastern Poland. Fish constituted 51% of food biomass consumed by otters in spring‐summer and 40% in autumn‐winter, with common fish (perch Perca fluviatilis, pike Esox lucius, and roach Rutilus rutilus) being captured most frequently by the otters. Amphibians (mainly Rana temporaria, which also dominated in the living community) made up 34% of otters’ food biomass in spring‐summer and 58% in autumn‐winter. American mink relied on three prey groups: fish (40% in spring‐summer, and 10% in autumn‐winter), frogs (32% and 51%, respectively), and small mammals (21% and 36%). Out of available Micromammalia, mink strongly selected the root vole Microtus oeconomus. The cold season diet of both otter and mink depended on river size. On small rivers with forested valleys, otters and mink fed nearly exclusively on amphibians (72–90% of food biomass). With size of a river increasing and riverside habitat becoming more open (sedge and reed marshes instead of forests), otters shifted to catching predominantly fish (up to 76% in diet) and mink to preying on small mammals (up to 65% in diet).
Review of literature on otter and mink in Eurasia showed that their diets did not change with latitude (as indicators of climate severity and duration of water freezing) but they depended on habitats. In otter diet, the mean share of fish declined from 94% (SE 1.7) on sea shores, to 71% (SE 2.9) on lakes and fish ponds, to 64% (SE 2.8) on rivers and streams. The roles of amphibians and crustaceans increased in the same gradient (from 0 to 15%, and from 3 to 7%, respectively). On inland waters, the abundance of crayfish was the essential factor differentiating otters’ diet composition. In Eurasia, the staple food types of American mink on rivers and streams were fish (on average, 27% in diet, SE 3.9), mammals (30%, SE 5.0), and amphibians (17%, SE 4.8), whereas on lakes and ponds mink fed predominantly on birds (on average, 33% in diet, SE 10.1) and fish (28%, SE 9.5). In the Palaearctic region, over a wide gradient of habitats, otters appeared strongly specialised on prey taken from water, whereas American mink was a typical generalist capable of utilising several prey groups originating from both water and land.     

Determinants of Eurasian otter (Lutra lutra) diet in a seasonally changing reservoir

Otter diet in reservoirs is known to experience seasonal changes. We selected a reservoir with a large population of exclusively wintering great cormorants and seasonal changes in stored water volume to test the relative influence of abiotic and biotic factors on otter foraging ecology. DNA metabarcoding of otter spraints revealed a dietary change from autumn to winter. Otters had a diet dominated by the exotic goldfish in autumn, but predated intensively on the native northern straight-mouth nase in winter. This change was likely caused by predation of cormorants on goldfish and to fish biology. Secondly, macroscopic analysis of spraints revealed that otters shifted from a diet dominated by fish (in terms of biomass) to a diet dominated by red swamp crayfish during spring–summer, when the latter became overabundant. As revealed by modelling, this second shift was most likely influenced by the sudden increase in stored water volume in spring, but also by the cumulative effect of cormorant predation on fish during autumn–winter. Macroscopic analyses of otter spraints collected in a second reservoir with no cormorants revealed a lack of seasonality. Hence, the combined influence of both biotic and abiotic factors explained otter diet seasonality in a lentic-water novel ecosystem.

     

Diet composition of the Eurasian otter Lutra lutra in different freshwater habitats of temperate Europe: a review and meta‐analysis

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Hand‐rearing and rehabilitation of orphaned wild giant otters,Pteronura brasiliensis,on the Rupununi river,Guyana, South America

From 1985–2003, 34 orphaned giant otters, Pteronura brasiliensis, (22 males, 12 females) were hand raised for eventual return to the wild at The Karanambu Cattle Company Limited Ranch (Karanambu), on the Rupununi River, Guyana, South America. The orphans ranged in age from 2 weeks to 9 months old; most were 8–10‐week‐old cubs. Feeding, housing, exercising, veterinary care, and rehabilitation protocols for young giant otters were developed during this period. Six cubs died during hand‐rearing; of these, four died from illness or injury, and two were killed, one by a caiman and one by another orphaned otter. Of 34 giant otters brought to Karanambu, 28 (82%) were reared successfully to an age and condition suitable for rehabilitation, and 18 (53%) returned to the wild. Ten otters survived hand‐rearing but died either before or during the process of rehabilitation. These hand‐reared giant otters were killed by people (3 known, 2 presumed) or other giant otters (5), including one male otter that remained at Karanambu for several years. During rehabilitation, young giant otters chose to spend increasing amounts of time on the Rupununi River away from human care, often interacting with wild giant otters. Although long‐term monitoring was not possible, Karanambu staff observed most (15 of 18) of the rehabilitated otters repeatedly, for as long as 4 years after their return to the river. The giant otter rehabilitation program at Karanambu generated new knowledge about this species, and offered visitors the opportunity to observe them. Zoo Biol 24:153–167, 2005. © 2005 Wiley‐Liss, Inc.     

Indirect food web interactions: sea otters and kelp forest fishes in the Aleutian archipelago

Although trophic cascades—the effect of apex predators on progressively lower trophic level species through top-down forcing—have been demonstrated in diverse ecosystems, the broader potential influences of trophic cascades on other species and ecosystem processes are not well studied. We used the overexploitation, recovery and subsequent collapse of sea otter (Enhydra lutris) populations in the Aleutian archipelago to explore if and how the abundance and diet of kelp forest fishes are influenced by a trophic cascade linking sea otters with sea urchins and fleshy macroalgae. We measured the abundance of sea urchins (biomass density), kelp (numerical density) and fish (Catch per unit effort) at four islands in the mid-1980s (when otters were abundant at two of the islands and rare at the two others) and in 2000 (after otters had become rare at all four islands). Our fish studies focused on rock greenling (Hexagrammos lagocephalus), the numerically dominant species in this region. In the mid-1980s, the two islands with high-density otter populations supported dense kelp forests, relatively few urchins, and abundant rock greenling whereas the opposite pattern (abundant urchins, sparse kelp forests, and relatively few rock greenling) occurred at islands where otters were rare. In the 2000, the abundances of urchins, kelp and greenling were grossly unchanged at islands where otters were initially rare but had shifted to the characteristic pattern of otter-free systems at islands where otters were initially abundant. Significant changes in greenling diet occurred between the mid-1980s and the 2000 although the reasons for these changes were difficult to assess because of strong island-specific effects. Whereas urchin-dominated communities supported more diverse fish assemblages than kelp-dominated communities, this was not a simple effect of the otter-induced trophic cascade because all islands supported more diverse fish assemblages in 2000 than in the mid-1980s.     

Prey selection in coastal Eurasian otters Lutra Iutra

Prey preferences and dietary differences between sex and age categories of Eurasian otters were studied in coastal Norwegian habitats Relative to their trapping frequency potential prey species with hard, spiny exoskeletons (crabs and sea urchins) or otherwise tough, spiny integuments (Labridae) were much less frequently found in spraints than fish species with soft integuments Spines did not protect fish with otherwise soft integuments from otter predation The number of non-fish taxa per otter stomach did not vary significantly between otter age categories despite presumed differences in hunting abilities (small cubs large cubs and subadults, adults) Relative frequency of occurrence of crabs and sea urchins was < 5% in the stomachs in each of these otter categories Anadromous, katadromous and freshwater fish species were infrequently eaten The coastal otter population during the study period probably had access to an adequate, and preferred, supply of marine fish prey
At the otter population level no prey size selection was conclusively demonstrated within the range of fish sizes sampled However, fish sizes eaten differed significantly between otter sex and age categories The fish sizes per stomach were on average larger in males than in females, regardless of age Adult males tended to eat the largest fishes Among the self provisioning age categories (subadult and adult otters) fish lengths differed significantly between otter males and females, but not between the otter age categories, and did not covary significantly with otter body length Fish eaten by females with old placental scars (potential mothers of fisheating cubs) were significantly smaller than those eaten by small cubs, provisioned by their mothers     

Human–wildlife conflicts at pond fisheries in eastern Poland: perceptions and management of wildlife damage

Wildlife occurring at aquacultural sites can ignite conflicts over resources managed by humans. A telephone survey concerning nuisance wildlife occurrence, perceptions of inflicted damage, and use of preventive measures at pond fisheries was conducted in 2003–2004 in eastern Poland. Significant economic losses to wildlife were reported by 80% of the respondents, with 41% claiming severe losses to more than one species. Serious damage was attributed primarily to otters Lutra lutra (56% of farms), cormorants Phalacrocorax carbo (26%), grey herons Ardea cinerea (23%), and beavers Castor fiber (21%). Two alien species, mink Neovison vison and muskrat Ondatra zibethicus, were widespread, but rarely blamed for causing substantial harm. Lethal controls were the most popular means of damage reduction and were more likely to be deployed at fish farms reporting significant losses. Cormorants, shot at half of the farms visited, were the most widely persecuted. Both otters and beavers were culled, notwithstanding their protection status and compensation payments available for beaver damage to ponds. The survey indicated poor cooperation between conservation authorities and fish farmers in managing wildlife concerns. Monitoring conflict interactions, i.e., wildlife occurrence and alleged damage at fish farms vs damage management processes, is an essential step toward conflict alleviation. Considering the wide range of species interacting with fisheries, adoption of more flexible policies to address the conflicts than a single-species conservation approach is recommended.     

Spatial distribution and diet of the Neotropical otter<Emphasis Type="Italic">Lontra longicaudis</Emphasis> in the Ibera Lake (northern Argentina)

The seasonal spatial distribution and diet of the Neotropical otterLontra longicaudis (Olfers, 1818) were studied on Ibera Lake within the Esteros del Ibera, an important wetland of NE Argentina (Ramsar site no. 1162). Twelve lake perimeter sites were regularly checked for otter tracks and signs. The amount of signs was compared to environmental parameters to test their influence on otter presence and movements. A positive correlation was found between the amount of signs and the physical structure of the littoral areas, as well as vegetation structure. Lakeside otter presence decreased during the summer sampling throughout all sites. In order to determine otter diet, 205 spraints were examined. Otters fed mainly on fish (mostly Cichlidae), but also on crustaceans and molluscs. Other fish consumed were Characidae, Synbranchidae, Loricariidae and Erythrinidae. Seasonal variation was observed in diet composition: in summer, diet crustaceans and vertebrates other than fish increased. A higher percentage of benthic fish species was also observed in summer, while pelagic and benthopelagic species increased in winter. Such dietary changes may be explained by the different habitat use of otters in different seasons, from the lake coast (winter) towards more internal marshy areas of the wetland (summer).     

Foraging strategies and prey switching in the California sea otter

Summary Southern sea otters (Enhydra lutris nereis), in recovering from near extinction, are gradually extending their range to include areas from which they have been absent for more than one hundred years. This study took advantage of the otters' relatively sudden arrival in the area near Santa Cruz, California, to monitor their prey selection in the first two years of residence there. Foraging observations revealed that sea urchins (Strongly-locentrotus franciscanus) were heavily preyed upon initially, but virtually disappeared from the diet after one year of sea otter residence. The disappearance of sea urchins was accompanied by an increased use of kelp crabs (Pugettia producta) and the appearance of clams (Gari californica) in the otters' diet. Abalones (Haliotis rufescens) and cancer crabs (Cancer spp.) remained fairly stable as dietary items throughout the two year period. An electivity index was used to quantify sea otter preferences, which corresponded closely with a ranking scheme based on energy intake/unit foraging time calculated for each major prey species. As predicted by optimal foraging theory, sea otters prefer food species of high rank and replace depleted dietary items with those of next highest rank. The process of dietary switching was analyzed with respect to foraging success rates, and it appears that poor success rates, associated with predation on an increasingly rarer prey species (sea urchins), drive sea otters to hunt for different prey. Both patch selection and search image formation appear to function in this process. The potential effects on community structure and stability of predators exhibiting a preference for the most profitable prey are discussed.     

Understanding the inter-specific dynamics of two co-existing predators in the Tierra del Fuego Archipelago: the native southern river otter and the exotic American mink

Knowledge about interactions between endangered native southern river otters (Lontra provocax) and introduced American mink (Neovison vison) is essential for effective management of both species. We evaluated competition for spatial and trophic niches between otter and mink in overlapping and non-overlapping areas, comparing distribution, habitat preference, diet and mink marking behavior. We surveyed otter and mink signs along 250 km of Beagle Channel coastline. Habitat suitability models were constructed based on species presence/absence and habitat characteristics, using generalized linear models. Feces were collected for diet analyses. Otters used forested coasts with 12°–32° shoreline slope and without human influence, and our evidence suggests they were not affected by mink presence. Mink preferred forested and shrubland coasts with 10°–28° shoreline slope. Neither human influence nor otter presence affected mink habitat occupation, but in the presence of otters, mink left fewer signs. Otters consumed more aquatic prey than mink, and mink modified their diet in the presence of otters, consuming more exotic small terrestrial mammals and less fish as well as shifting to smaller and shallower fish species that are less consumed by otters. Mink showed more plastic, generalist behavior than otters, being more tolerant of human presence, using more habitat types and having greater diet breadth. At the same time, otters apparently affect mink adversely and could help limit their invasion in sympatric areas. Conservation and recovery of otters, therefore, may produce a secondary benefit of simultaneously reducing the effect of mink, thereby providing an additional way to control this exotic predator’s population.     

Ethnobiology of snappers (Lutjanidae): target species and suggestions for management

In this study, we sought to investigate the biology (diet and reproduction) and ethnobiology (fishers knowledge and fishing spots used to catch snappers) of five species of snappers (Lutjanidae), including Lutjanus analis, Lutjanus synagris, Lutjanus vivanus, Ocyurus chrysurus, and Romboplites saliens at five sites along the northeast (Riacho Doce, Maceió in Alagoas State, and Porto do Sauípe, Entre Rios at Bahia State) and the southeast (SE) Brazilian coast (Paraty and Rio de Janeiro cities at Rio de Janeiro State, and Bertioga, at São Paulo State.). We collected 288 snappers and interviewed 86 fishermen. The stomach contents of each fish were examined and macroscopic gonad analysis was performed. Snappers are very important for the fisheries of NE Brazil, and our results indicated that some populations, such as mutton snapper (L. analis) and lane snapper (L. synagris), are being caught when they are too young, at early juvenile stages. Local knowledge has been shown to be a powerful tool for determining appropriate policies regarding management of target species, and artisanal fishermen can be included in management processes. Other suggestions for managing the fisheries are discussed, including proposals that could provide motivation for artisanal fishermen to participate in programs to conserve resources, such as co-management approaches that utilize local knowledge, the establishment of fishing seasons, and compensation of fishermen, through 'payment for environmental services'. These suggestions may enhance the participation of local artisanal fishermen in moving to a more realistic and less top-down management approach of the fish population.     

Feeding Ecology of the Giant Otter,Pteronura brasiliensis1

The food habits of the giant otter, Pteronura brasiliensis, were determined by analyzing fecal samples collected year–round from communal latrines at Xixtiaú Creek (00°48'S, 61°33'W), Jauaperi River (central Brazilian Amazon) between 1993 and 1994. Communal latrines were also sampled during the low water season at Aquidauana River (19°32'S, 56°40'W), Pantanal of Mato Grosso do Sul (central Brazil). Fragments of vertebrae, mandibles, teeth, scales, and fin spines provided an estimate of the diet composition. Remains of fish were present in all of the samples. The main fish groups found at Xixuaú Creek were Perciformes, represented specifically by Cichlidae (97.3% of all samples), Characiformes (86.5%) and Siluriformes (5.4%). The Characiformes were represented mainly by E, rythrinidae (Hoplias sp. 90.6%), followed by Serrasalmidae (28%). The Anostomidae occurred with a frequency of 18.7 percent, while Characinae, Bryconinae, and Cynodontidae were only observed in 3.1 percent of the Characiformes records. At Aquidauana River, the Characiformes were the most frequent fish group, represented in 100 percent of all samples, followed by Siluriformes (66.6%) and Perciformes (33.3%). The fish from the main groups identified in the diet of the giant otters prefer riverbanks, lakes, and flooded forests. The feeding habits of Pteronura brasiliensis are probably influenced by the vulnerability and abundance of the prey consumed by this carnivore.