African Catfish Clarias Gariepinus Research Articles

High genetic diversity and population differentiation in Clarias gariepinus of Yala Swamp: evidence from mitochondrial DNA sequences.

In order to improve the conservation and sustainable utilization of the African catfish Clarias gariepinus of the Yala Swamp in Kenya, genetic diversity and population structure of Lakes Kanyaboli and Namboyo populations of the species were studied using DNA sequences of the mitochondrial D-loop control region. Genetic diversity inferred as haplotype and nucleotide diversities and number of singletons and shared haplotypes was higher in the Lake Kanyaboli population (LKG) than the Lake Namboyo population (LNG) of C. gariepinus. Thirty-one haplotypes were inferred, of which 25 (80·6%) were private or singletons, while only six (19·4%) haplotypes were shared between LKG and LNG. Both populations were differentiated, with FST value that was significantly different from zero (P < 0·05). Two clusters were inferred both from the maximum likelihood tree and the spanning networks of phylogenetic relationships of haplotypes. Mismatch distribution for total sample was multi-modal but individually, distributions were uni-modal in LKG, but multimodal in LNG. The mean ± s.d. raggedness index for both populations was 0·085 ± 0·098 and not significantly different from zero (P > 0·05). Individual raggedness indices were 0·015 and 0·154 for LKG and LNG respectively. Fu's Fs was negative for both populations, with LKG recording -14·871, while LNG had -2·565, significantly different from zero for LKG (P < 0·05), but the value for LNG was not significant (P > 0·05). Tajima's D was negative for both populations, with LKG recording -1·734, while LNG had -1·136. Standardized square differences (SSD) were 0·001 for LKG and 0·048 for LNG and non-significant between them (P > 0·05). Values between all populations were also not significantly different (P > 0·05), mean ± s.d. SSD 0·025 ± 0·033.

Use of fluted pumpkin (Telfairia occidentalis) leaf powder as feed additive in African catfish (Clarias gariepinus) fingerlings

ABSTRACTThe effect of dietary Telfairia occidentalis leaf meal on growth, haematological profile, and body composition was investigated in African catfish Clarias gariepinus. Fingerlings of (5.12 ± 0.06 g) average weights were fed diets supplemented with four concentrations (5, 10, 15, and 20 g of T. occidentalis leaf powder/kg feed) for 56 days. Fish fed supplemented diets showed significantly improved growth performance, haematological parameters and feed utilization over the control (0 g T. occidentalis leaf meal/kg feed) treatment. The highest specific growth rate (7.33 ± 2.37% day−1) and best food conversion ratio (0.86 ± 0.06) were obtained in the 5 g T. occidentalis leaf meal/kg feed treatment. Protein efficiency ratio was higher in fish fed with T. occidentalis leaf meal and lowest in the control. No differences occurred in fish carcass moisture, protein, or ash content among the treatments (p > .05). The results suggest that dietary supplementation with T. occidentalis leaf powder improved the growth, feed utilization, and survival of C. gariepinus fingerlings.

Characterization of Antimicrobial Peptides Isolated from the Processing by-Products of African Catfish Clarias gariepinus

Antimicrobial peptides (AMPs) as components of innate immunity system have been isolated from fish and other species. In this study, the crude proteins extracted with gradient ammonium sulfate precipitation technique from the processing by-products of African catfish Clarias gariepinus (C. gariepinus) were purified by size-exclusion chromatography and all the four obtained fractions, Clarias antimicrobial peptides I(CAP-I), CAP-II, CAP-III and CAP-IV, showed antimicrobial activity. Among of these fractions, CAP-IV showed the highest antimicrobial activity against Staphylococcus aureus, Aeromonas sobria, Aeromonas hydrophila, Escherichia coli by agar diffusion plate test and the diameter of inhibition zone was 8.34, 9.27, 6.76, 6.13 mm, respectively. The molecular weight of main peptides of CAP-IV was around 4.1 KD by SDS-PAGE analysis. CAP-IV showed antimicrobial activity against both gram-negative and gram-positive bacterial pathogens at minimum inhibitory concentrations (MICs) ranging from 105 to 420 μg/mL. The antimicrobial activity of CAP-IV was stable at wide pH range, 3–11 and was also heat-stable when temperature was below 80 °C. Freeze-thawing treatment also only had slight effects on the antimicrobial activity of CAP-IV. Besides, CAP-IV was not sensitive to the hydrolysis by pepsin and trypsin, except for protease K. These results suggest that CAP-IV isolated from C. gariepinus is potential to be developed as a new antimicrobial peptide and may partially explain the high disease resistance of African catfish C. gariepinus.

Chemical and Microbiology Characteristic of Smoked and Seasoned African Catfish Fillet Affected by Canning Processing

African catfish (Clarias gariepinus) many cultivated by the farmers, however if not treated quickly&lt;br /&gt;damaged. One treatment that can maintain quality product african catfish is by smoked and canning. The&lt;br /&gt;aim of this study was to determine the chemical and microbiological characteristics of smoked African&lt;br /&gt;catfish fillet with seasoning packaged cans during storage. Preparation of research carried out by soaking&lt;br /&gt;the African catfish fillet into seasonings and liquid smoke concentration of 10% by immersion for 1&lt;br /&gt;minute, and then next process of curing and drying. Products that are ripe weighed 110 g and signed&lt;br /&gt;into cans sized Ø 301x205. Added medium brine concentration 5% and vegetable oil as much as 100&lt;br /&gt;ml, a process exhausting and seaming. The last stage is performed a sterilization process (126oC for 20&lt;br /&gt;minutes), cooling and incubation (24oC for 2 weeks). Observations deterioration of product quality of&lt;br /&gt;smoked African catfish fillet with seasoning performed at weeks 0, 2, 4, 6 and 8. Tests conducted include&lt;br /&gt;chemical test which includes test TVB, pH and peroxide value and microbiological testing in the form&lt;br /&gt;of TPC. The results showed that the combined treatment of the fumigation and the addition of medium&lt;br /&gt;(saline 5% and solution of vegetable oil) combined with treatment canning able to maintain product&lt;br /&gt;quality of smoked African catfish fillet with seasoning, based TVB, pH, peroxide value and TPC during&lt;br /&gt;storage.

Chemical and Microbiology Characteristic of Smoked and Seasoned African Catfish Fillet Affected by Canning Processing

African catfish (Clarias gariepinus) many cultivated by the farmers, however if not treated quickly&lt;br /&gt;damaged. One treatment that can maintain quality product african catfish is by smoked and canning. The&lt;br /&gt;aim of this study was to determine the chemical and microbiological characteristics of smoked African&lt;br /&gt;catfish fillet with seasoning packaged cans during storage. Preparation of research carried out by soaking&lt;br /&gt;the African catfish fillet into seasonings and liquid smoke concentration of 10% by immersion for 1&lt;br /&gt;minute, and then next process of curing and drying. Products that are ripe weighed 110 g and signed&lt;br /&gt;into cans sized Ø 301x205. Added medium brine concentration 5% and vegetable oil as much as 100&lt;br /&gt;ml, a process exhausting and seaming. The last stage is performed a sterilization process (126oC for 20&lt;br /&gt;minutes), cooling and incubation (24oC for 2 weeks). Observations deterioration of product quality of&lt;br /&gt;smoked African catfish fillet with seasoning performed at weeks 0, 2, 4, 6 and 8. Tests conducted include&lt;br /&gt;chemical test which includes test TVB, pH and peroxide value and microbiological testing in the form&lt;br /&gt;of TPC. The results showed that the combined treatment of the fumigation and the addition of medium&lt;br /&gt;(saline 5% and solution of vegetable oil) combined with treatment canning able to maintain product&lt;br /&gt;quality of smoked African catfish fillet with seasoning, based TVB, pH, peroxide value and TPC during&lt;br /&gt;storage.&lt;br /&gt;&lt;br /&gt;

Concentration of polychlorinated biphenyl (PCB) congeners in the muscle of Clarias gariepinus and sediment from inland rivers of southwestern Nigeria and estimated potential human health consequences

ABSTRACTThe distributions of polychlorinated biphenyl (PCB) congeners were determined in sediment and muscle of the African sharptooth catfish (Clarias gariepinus) from the Ogun and Ona rivers, southwest Nigeria. In addition, the effect of PCB congeners on condition factor (CF) and associated human health risk was assessed using muscle levels for a noncarcinogenic hazard quotient (HQ) calculation. Elevated concentrations of high-molecular-weight (HMW) PCB congeners were detected in sediment and fish downstream of discharge points of both rivers. A significant reduction in fish body weight and CF was observed to correlate with high PCB congener concentrations in the Ona River. A principal component (PC) biplot revealed significant site-related PCB congener distribution patterns for HMW PCB in samples from the Ogun River (71.3%), while the Ona River (42.6%) showed significant PCB congener patterns for low-molecular-weight (LMW) congeners. Biota-sediment accumulation factor (BSAF) was higher downstream for both rivers, presenting PCB congener-specific accumulation patterns in the Ona River. Significant decreases in fish body weight, length and CF were observed downstream compared to upstream in the Ona River. The non-carcinogenic HQ of dioxin-like congener 189 downstream in both rivers exceeded the HQ = 1 threshold for children and adults for both the Ogun and Ona rivers. Overall, our results suggest that industrial discharges contribute significantly to PCB inputs into these rivers, with potential for significant health implications for neighboring communities that utilize these rivers for fishing and other domestic purposes.

Effects of dietary Lactobicillus plantarum on the growth, carcass quality, and immune response of African catfish (Clarias gariepinus) challenged with Salmonella typhi

ABSTRACTAn experiment was conducted to investigate the effects of Lactobacillus plantarum on the production of African catfish (Clarias gariepinus). Five experimental diets containing 0, 103, 105, 107, and 109 CFU of Lactobacillus plantarum g−1 diet (T1–T5 treatments respectively) were fed to African catfish (Clarias gariepinus) (9.20 ± 0.1 g initial body mass), for 70 days. Results indicated significantly lower growth performance in the fish fed diet without probiotics and in those fed diet with the least probiotic level. Treatments with probiotics significantly improved the blood profile and carcass protein but significantly reduced the carcass fat (P < 0.05); these treatments also marginally improved the carcass minerals in comparison with the treatment without probiotic (P < 0.05). Challenging the fish fed the experimental diets with Salmonella typhi showed higher immunity of fish fed the probiotic diets than those fed the nonprobiotic diet. Duncan’s multiple range test showed that the best fish performance was observed with 103 CFU g−1 L. plantarum for very parameter measured. However, regression analyses showed the optimum level of the bacteria to be 104.13–105 CFU g−1

Morphological re-description and new geographical records for three digenean parasites infecting African sharptooth catfish Clarias gariepinus (Pisces: Clariidae) in Egypt.

Sixty specimens of African sharptooth catfish Clarias gariepinus (Clariidae) were collected during the period of March 2014-February 2015 from boat landing sites and fishermen of the River Nile at Beni Suef Governorate, Egypt, and examined for the presence of digenean parasites. The morphology of these parasites was studied by using light microscopy to describe morphological and morphometrically measurements for different body parts. Three digenean species belonging to three different genera were collected from various organs within the examined fish species. A certain degree of site specificity was also observed, with Thaparotrema botswanensis being found only in the gall bladder of C. gariepinus, while both Pseudoholorchis clarii and Glossidium pedatum were found only in the intestine and thus seem to occupy a certain niche within their host. This study represent as the first record of T. botswanensis and G. pedatum from C. gariepinus, as well as the first report of the genera from the River Nile in Egypt. In addition, re-description of P. clarii clarifies measurements for some body parts.

Genotoxicity assessment and oxidative stress responses in freshwater African catfish Clarias gariepinus exposed to fenthion formulations

Fenthion is one of the most widely used organophosphate insecticides for the control of many varieties of pests in Nigeria. The genotoxic effect of the pesticide was evaluated in the blood erythrocytes of Clarias gariepinus using the micronucleus (MN) test. The oxidative stress parameters were also studied in the liver and gill tissues. Fish were exposed to 2.0, 4.0, and 8.0 mgL−1 of fenthion and sampling was done on days 1, 7, 14, 21 and after 7-day recovery. Micronuclei induction was highest (7.55) on day 14 at all concentrations in the peripheral blood cells. Oxidative stress was evidenced by increased lipid peroxidation (LPO). Maximum LPO values of 62.47% and 71.17% were observed in the gill and liver tissues respectively in C. gariepinus exposed to 8.0 mgL−1 concentration of fenthion. There were alterations in the values of reduced glutathione (GSH), glutathione reductase (GR), glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase (CAT) during the exposure and recovery periods. The 7-day recovery period was not adequate to eliminate fenthion-induced changes as LPO, CAT, and GR activity remain elevated. However, MN frequency and activity of SOD, GSH, and GPx (except at 8.0 mgL−1) recovered. The present findings give further credence on the integrated use of MN test and oxidative stress parameters in risk assessment of pollutants in aquatic ecosystem.

First report of monogenean flatworms from Lake Tana, Ethiopia: gill parasites of the commercially important Clarias gariepinus (Teleostei: Clariidae) and Oreochromis niloticus tana (Teleostei: Cichlidae).

BackgroundLake Tana is the largest lake in Ethiopia and the source of the Blue Nile. The lake harbours unique endemic cyprinid fish species, as well as the commercially important endemic Nile tilapia subspecies Oreochromis niloticus tana and the North African catfish Clarias gariepinus. Its endemicity, especially within the Labeobarbus radiation, its conservation importance and its economic indispensability attract scientific interest to the lake’s ichthyofauna. Fish parasites of Lake Tana, however, are hitherto poorly known, and no formal report exists on its monogenean flatworms. For sustainable aquaculture and fisheries development, it is essential to study monogenean fish parasites in these economically most important fish species. Moreover, it remains to be verified whether this unique ecosystem and its endemicity gave rise to a distinct parasite fauna as well.ResultsNile tilapia and North African catfish hosts were collected from Lake Tana in 2013. Nine species of monogenean parasites of two orders, Gyrodactylidea Bychowsky, 1937 and Dactylogyridea Bychowsky, 1937, were recovered. Gyrodactylus gelnari Přikrylová, Blažek & Vanhove, 2012, Macrogyrodactylus clarii Gussev, 1961, Quadriacanthus aegypticus El-Naggar & Serag, 1986 and two undescribed Quadriacanthus species were recovered from C. gariepinus. Oreochromis niloticus tana hosted Cichlidogyrus cirratus Paperna, 1964, C. halli (Price & Kirk, 1967), C. thurstonae Ergens, 1981 and Scutogyrus longicornis (Paperna & Thurston, 1969).ConclusionsExcept for M. clarii, all species represent new records for Ethiopia. This first study on the monogenean fauna of Lake Tana revealed that the lake’s North African catfish, as well as its endemic Nile tilapia subspecies, harbour parasites that are known from these host species elsewhere in Africa.

Interpopulation crossbreeding of farmed and wild African catfishClarias gariepinus(Burchell 1822) in Indonesia at the nursing stage

Introduced African catfish Clarias gariepinus (Burchell 1822) have been cultivated in Indonesia since 1985 and have made a significant contribution to aquaculture production. Unfortunately, the rapid development of catfish farming was not accompanied by proper genetic improvement of broodstock and this led to poor production performances. A method that can potentially provide rapid improvement in the genetic quality of broodstock is the crossbreeding technique. The present study evaluated growth and survival performances up to 81 days post-hatching (nursing stage) of reciprocal interpopulation crossbreeds generated from five existing introduced African catfish populations in Indonesia, i.e. from Indonesia, Egypt, Kenya, the Netherlands and Thailand. Artificial spawning was applied to form five purebred populations and 20 crossbreed populations. There were significant differences in body length growth (specific growth rate – SGR), survival rate (SR) and number of over-size fish (OS) averages. The Egypt female × Netherlands male (EN) crossbreed showed the best performance with cumulative SGR, SR, and OS of 9.69 ± 0.03%, 63.98 ± 6.75% and 0.22 ± 0.04%, respectively. The result also revealed a correlation between the OS and the SR; the higher the OS, the lower the SR. This correlation tended to be weak at the sequential nursing stages. Our study suggested that the EN crossbreed has high potential to improve offspring quality in the near future.

Fecundity studies of the African catfish Clarias gariepinus (Burchell, 1822) fed Coppens feed and Unical aqua feed in circular concrete tanks

Fecundity studies of the African catfish Clarias gariepinus (Burchell, 1822) fed Coppens feed and Unical aqua feed in circular concrete tanks

Biosynthesis of long-chain polyunsaturated fatty acids in the African catfish Clarias gariepinus: Molecular cloning and functional characterisation of fatty acyl desaturase (fads2) and elongase (elovl2) cDNAs7

Fish differ in their capacity for endogenous synthesis of long-chain (C20–24) polyunsaturated fatty acids (LC-PUFA) from dietary C18 precursors (α-linolenic and linoleic acids). Understanding this capacity is of benefit to fish feed formulation. This, together with the importance of fish as the primary source of omega-3 LC-PUFA in the human diet has necessitated the rigorous study of the biochemical and molecular mechanisms involved in the LC-PUFA biosynthesis pathway in fish species. Studies have shown the potential of a species for LC-PUFA biosynthesis is associated with the complement and function of fatty acyl desaturase (fads) and elongase of very long chain fatty acid (elovl) gene it possesses. The present study therefore aimed to investigate these genes in the African catfish (Clarias gariepinus), the most commercially important farmed fish species in Sub-Saharan Africa. A fads2 and an elovl2 cDNA were cloned containing open reading frames (ORF) of 1338 base pair (bp) and 864bp specifying proteins of 445 and 287 amino acids, respectively. Functional characterisation by heterologous expression in yeast showed that the Fads2 was bifunctional with Δ5Δ6 activities catalysing the desaturation of both 18:3n-3 and 20:4n-3 and their corresponding n-6 fatty acids, 18:2n-6 and 20:3n-6. The Elovl2 showed activity towards C18, C20 and C22 PUFA with highest activity towards C20 and C22 PUFA. Tissue expression analysis showed a typical freshwater species expression pattern; higher expression in the liver compared to brain and all other tissues with the exception of elovl5 which showed highest expression in the intestine. Consistent with feeding studies of typical freshwater fish species that show their essential fatty acid requirement can be satisfied by dietary C18 PUFA, the present study confirms that the LC-PUFA biosynthesis pathway is active in the African catfish C. gariepinus. Statement of relevanceClarias gariepinus has enzymes to use dietary vegetable oils.

14. PENGARUH LAMA PERENDAMAN LARVA DALAM HORMON METIL TESTOSTERON ALAMI TERHADAP PENJANTANAN IKAN LELE DUMBO (Clarias gariepinus) The Effect of Soaking Time of African Catfish Larvae (Clarias gariepinus) in Natural Methyl Testosterone Hormone on Masculinization

The purpose of this study was to determine the effect of immersion time on African catfish (Clarias gariepinus) larvae in natural methyl testosterone hormone on masculinization. This study was conducted in Center of Fish Culture Lamnyong, Banda Aceh. Experimental animals used in this study were 270 African catfish larvae aged 10 days. The study was designed using completely randomized design (CRD) with 3 treatments and 3 replications. African catfish larvae aged 10 days in group P1, P2, and P3 were immersed in natural methyl testosterone hormone for 10 hours, 20 hours, and 30 hours, respectively. Observations were carried out until fish reach 50 days old. Data were analyzed by analysis of variance (Anova) followed by least significant difference test (LSD). Percentage of male catfish observed in P1, P2, and P3 were 64.24 %, 93.11%, dan 59.94% respectively. As a conclusion, immersion with natural methyl testosterone hormone can change the sex of catfish to be male. ____________________________________________________________________________________________________________________ Key words: african catfish, methyl testosterone natural, masculinization

Effects of hydrothermal processing on nutritional value of Canavalia ensiformis and its utilization by Clarias gariepinus (Burchell, 1822) fingerlings

Jack bean (Canavalia ensiformis) is one of the underutilized legumes in animal feed production partly because of its high antinutritional factors. This study investigated the nutritional value of C. ensiformis seed subjected to hydrothermal processing in the diet of the African catfish Clarias gariepinus. Five batches of C. ensiformis seeds were hydrothermally processed in boiling water (100°C) for 0, 10, 20, 30 and 40min, respectively. Proximate composition of the seed showed no significant effect of hydrothermal processing on protein and fat content of C. ensiformis. However, all essential amino acids were significantly affected. The anti-nutritional factor canavanine was not markedly reduced even at 40min hydrothermal processing. Fifty fingerlings of C. gariepinus (1.07±0.01g) were stocked in 15 hapas measuring 1×1×1m3, labeled in triplicate according to five isonitrogenous diets (35% CP) formulated using the processed C. ensiformis seed at an inclusion level of 27%. The highest body weight gain (2.73g), specific growth rate (2.26gday−1), feed conversion efficiency (34.11%) and protein efficiency ratio (0.078) were observed at hydrothermal treatment of 30 and 40min. Hydrothermal processing of C. ensiformis up to 40min could be exploited in the commercial and on-farm production of catfish diet at 27% level of inclusion.

Effects of acute stress on aggression and the cortisol response in the African sharptooth catfish Clarias gariepinus: differences between day and night.

African sharptooth catfish Clarias gariepinus were housed under continuous dim light (1 lx) or 12L:12D (350-0 lx) cycles. The number of skin lesions, as indicator of aggressive acts, and plasma cortisol levels, as indicator of stress-axis activity, were measured at baseline as well as following a stressor (given in the light or dark phase). Results showed that (1) baseline plasma cortisol levels were not different between photoperiods, (2) the number of baseline skin lesions was highest for C. gariepinus housed under continuous dim light, (3) stressor-induced peak levels of plasma cortisol were highest in the light phase and (4) the number of skin lesions following a stressor was highest in the dark phase. The higher number of stressor-related skin lesions in the dark (active) phase suggests increased stressor-induced aggression while in the active phase. In addition, the data suggest that housing under continuous dim light does not result in higher stress-axis activity, as measured by baseline levels of cortisol, but does result in more stressor-induced aggression, as measured by the higher number of skin lesions. The latter may be related to the fact that the continuous dim light photoperiod has twice the number of dark-phase (active) hours in which stressor-induced aggression is stronger compared to the 12L:12D photoperiod, which has a light phase in which stressor-induced aggression is lower.

A review of Clarias gariepinus invasions in Brazil and South Africa.

African sharptooth catfish Clarias gariepinus is native to most of Africa and small parts of Asia, but has been introduced to 37 countries mainly for aquaculture. This review of introductions, establishment, spread and impact of C. gariepinus in Brazil and outside of its native range in South Africa provides evidence that the species has been able to overcome all barriers to invasion in both countries. Following initial introductions across geographical barriers, containment seems to have been impossible and escape from aquaculture facilities and spread by illegal introductions is an invasion pathway in both countries. There is evidence of individuals dispersing rapidly following escape, and surviving and reproducing at multiple sites in a wide spectrum of habitats in both countries. There is a severe paucity of research on impacts, many of which are inferred from field and laboratory observations, but have not been demonstrated at population or community level. Such impact studies are urgently required to better understand the consequences of these invasions and to develop appropriate strategies to mitigate impacts and spread.

The effect of water renewal on growth of Clarias gariepinus fingerlings

Abstract The aim of this study was to determine the effect of different water change frequency on the growth of African catfish Clarias gariepinus. Fingerlings with initial mean weights of 7.02 ± 0.05g were stocked (50 fish each) in fifteen concrete tanks (2×2×2m) and were conditioned under five different treatments of water renewal, namely: TRT1 (no water change), TRT2 (water renewed daily), TRT3 (water renewed after four days), TRT4 (water renewed after eight days) and TRT5 (water renewed after fourteen days). After 56 days of feeding, results revealed best growth performance of fingerlings in tanks with water renewal frequency of TRT3 and TRT4. Similarly, survival was higher in these frequencies compared to the others; the control treatment, however, had the least performance for all parameters measured. It is therefore recommended that water renewal should be done once between four and eight days to enhance growth of African catfish fingerlings reared in a static system.

Early appearance of the retinal tapetum, cones, and rods in the larvae of the African catfish Clarias gariepinus

In the retina of the African catfish Clarias gariepinus, the pigment epithelium and the tapetum were formed in newly hatched larvae, the cones developed within 2 days, and the rods within 3 days after hatching. The retinal tapetum shone under surface light under a light microscope; the shine was located in the apical projections of the pigment epithelial cells. Early appearance of the retinal elements enables African catfish larvae to see and feed well even in dim light.

Risk screening of non‐native freshwater fishes in Croatia and Slovenia using the Fish Invasiveness Screening Kit

AbstractThe Fish Invasiveness Screening Kit (FISK) version 2 was used to assess the invasiveness potential of 40 introduced and translocated freshwater fish species to Croatia and Slovenia. Based on a priori classification of invasiveness, receiver operating characteristic analysis of FISK scores from two independent assessors resulted in a statistically significant calibration threshold of 11.75. This indicated that FISK was able to discriminate reliably between non‐native species likely to pose a high risk of being invasive and those likely to pose a medium or low risk of invasiveness. Seven species were categorised as ‘medium risk’ and the other 33 as ‘high risk’, whereas no species was categorised as ‘low risk’. The two highest scoring species were European catfish Silurus glanis and North African catfish Clarias gariepinus. Mean scores for all species classified a priori as invasive were ranked as ‘high risk’ sensu lato and fell into the ‘moderately high risk’ subcategory. FISK proved to be a valid tool for assessing the risks posed by non‐native fishes in Croatia and Slovenia. For this reason, it can be adopted as a reliable tool for the prevention of new translocations or introductions of potentially invasive species in the risk assessment area, as well as to assist in decisions regarding future management (i.e. monitoring, control and eradication) and conservation strategies.