Gill Histology Research Articles

The effect of hydraulic flowback and produced water on gill morphology, oxidative stress and antioxidant response in rainbow trout (Oncorhynchus mykiss)

Hydraulic fracturing fluid are complex mixtures containing high concentrations of salts (up to 330,000 ppm), organic, and metal contaminants. However, little data exist on the potential mechanisms of toxicity of these flowback and produced wastewaters (FPW) on aquatic biota. Juvenile rainbow trout were exposed to either control, FPW (2.5 or 7.5%), FPW that had been treated with activated charcoal (AC), or a custom salt-matched control (SW; replicating only the salt content of FPW) for 48 hours. Gill histology revealed decreases in interlamellar cell mass (ILCM) and mean lamellar length in all treatments (FPW, AC and SW) compared to control, indicative of hyperosmotic stress. Liver CYP1A1 activity was significantly elevated by 7.5-fold in the FPW 7.5% treatment only, indicative of Phase I metabolism. Superoxide dismutase activity significantly decreased in the gills to all treatments with the lowest activity occurring in the 7.5% FPW group. Catalase activity increased in liver with the highest values noted in fish exposed to 7.5% FPW. No changes were observed with respect to glutathione-S-transferase, while increased lipid peroxidation was only observed in both FPW treatments (2.5, 7.5%). These data suggest a characteristic signature of FPW impact which may help in risk assessment and biomonitoring of FPW spills.

Parasitological Analysis and Gill Histopathology of Pearl Dace (Semotilus Margarita) and Brook Stickleback (Culaea Inconstans) Collected from the Athabasca Oil Sands Area (Canada)

Pearl dace (Semotilus margarita) and brook stickleback (Culaea inconstans) were collected from tributaries of the Athabasca River (Alberta, Canada), upstream (reference site) and downstream of oil sands deposits where fish were expected to be exposed to naturally occurring oil sands constituents. The objective was to determine if fish collected from these sites exhibited differences in the prevalence or intensity of infection by parasites or in gill histology. Dace did not display significant differences in these parameters. Alternately, upstream stickleback were predominantly infected by complex life history parasites, while downstream fish were primarily infected by parasites with simpler life histories. Moreover, downstream stickleback exhibited significantly more clubbing and aneurysms in secondary gill lamellae relative to upstream fish. This suggested a difference in habitat quality between upstream and downstream sites. However, based on basic body condition parameters of the fish, it would appear that any impacts upon the health of the fish due to the presence of naturally occurring oil sands associated chemical constituents would have been minor.

Análise histológica das brí­¢nquias e do fí­­gado de Bryconops caudomaculatus em diferentes concentrações de amônia

O objetivo foi avaliar os efeitos de diferentes concentrações de amônia não ionizada (zero; 0,15; 0,30; 0,50; 1,00 mg L-1 NH3) na histologia e morfologia das brí­¢nquias e fí­­gado de juvenis de Bryconops caudomaculatus. Após 96 horas de exposição, os peixes foram anestesiados e submetidos í­Â necropsia para coleta de brí­¢nquias e fí­­gado, que foram incluí­­dos em parafina. Alterações morfológicas nas lamelas secundárias das brí­¢nquias foram observadas em concentrações a partir de 0,15 mg L-1, como hiperplasia, hipertrofia, deslocamento epitelial, fusão lamelar, edema, aneurisma lamelar com ruptura do epitélio e aumento na largura das lamelas. O fí­­gado apresentou alterações histológicas (congestão nos capilares, processos inflamatórios e pigmentação endógena) na presença de 0,30 mg L-1 de NH3, que comprometeram as funções vitais, o metabolismo, processos de respiração, desintoxicação do organismo, hematopoese e provavelmente a osmorregulação. Os resultados sugerem que as alterações nas brí­¢nquias e fí­­gado podem ser usadas para monitorar o desempenho de peixes em cultivo intensivo.

Physiological and morphological investigation of Arctic grayling (Thymallus arcticus) gill filaments with high salinity exposure and recovery.

Freshwater environments are at risk of increasing salinity due to multiple anthropogenic forces including current oil and gas extraction practices that result in large volumes of hypersaline water. Unintentional releases of hypersaline water into freshwater environments act as an osmoregulatory stressor to many aquatic organisms including native salmonids like the Arctic grayling (Thymallus arcticus). Compared to more euryhaline salmonids, Arctic grayling have a reduced salinity tolerance and develop an elevated interlamellar cell mass (ILCM) in response to salinity exposure (17 ppt). In this study, we described the gill morphology and cell types characterizing the ICLM. Further, we investigated whether Arctic grayling could recover in freshwater following a short-term (<48 h) salinity exposure. Arctic grayling were exposed to 17 ppt saline water for 12, 24 and 48 h. Following the 24 and 48 h salinity exposure, Arctic grayling were returned to freshwater for 24 h to assess their ability to recover from, and reverse, the osmotic disturbances. Physiological serum [Na+], [Cl-] and total osmolality were significantly elevated and progressively increased at 12, 24 and 48 h salinity exposures. The 24 h post-exposure recovery period resulted in Arctic grayling serum ion concentrations and total osmolality returning to near normal levels. Similar recovery patterns were observed in the salinity-induced ILCM, which developed as early as 12 h of exposure to 17 ppt, and then reverted to control levels following 24 h in freshwater. Gill histology indicates an increased number of apically located mucous cells in the interlamellar space following salinity exposure of Arctic grayling. The scanning electron microscopy and transmission electron microscopy data show the presence of granule containing eosinophil-like cells infiltrating the ILCM suggesting a salinity-induced immune response by the Arctic grayling.

Effect of Mercury and Cadmium on the Oxygen Consumption and Gill Histology of Catla catla (Ham. 1822)

Mercury and cadmium are among the major heavy metal pollutants, contaminating aquatic ecosystems. These heavy metals were investigated in the present study for sub lethal toxicity on freshwater fish, Catla catla. The acute toxicity tests were conducted by static renewal bioassay method and 96 h LC50 value of mercury and cadmium to C. catla seed were found to be 0.0835 and 0.4225 mg L−1, respectively. For sub lethal studies 1, 3, 6, 12 and 24 % of the 96 h LC50 value were selected and significant decrease in oxygen consumption up to a maximum of 82.9 % for mercury and 79.8 % for cadmium as compared to control were observed. The gills of fish exposed to sub lethal concentration of the metals showed histological alterations including oedema, hemorrhage, hyperplasia, hypertrophy, necrosis, curling and fusion. Both, oxygen consumption and histopathological changes were observed to be dose and duration dependent. Present study also indicates higher toxicity of mercury as compared to cadmium on C. catla.

Plasma Stress Responses in Juvenile Red-Spotted Grouper (Epinephelus akaara) exposed to Abrupt Salinity Decrease.

The objective of the current study was to determine acute plasma stress responses in two size groups of juvenile Epinephelus akaara (average body weight: 8.4±2.1 and 3.3±0.6 g; 150 and 120 days after hatch, respectively) exposed to abrupt salinity drops (from 34 practical salinity unit, PSU seawater to 18, 10 PSU (experiment 1) or 26, 18, 10 PSU (experiment 2), respectively). Plasma glucose, glutamic oxalate transaminase, glutamic pyruvate transaminase, red blood cell counts, and gill histology were determined during 72 h exposure. Significantly increased plasma glucose, glutamic oxalate transaminase levels, and red blood cell counts were observed in fish exposed to 18 or 10 PSU. Histological changes, such as hyperplasia and lifting of epithelium in the gill secondary lamellae, were also observed in fish exposed to 18 or 10 PSU at 72 h post-drop. E. akaara exposed to sudden salinity drops to 18 or 10 PSU still seems to undergo the primary adjustment phase before fish reaches a new homeostasis, whereas fish exposed to 26 PSU seems to mount osmotic changes. Therefore, the no observed adverse effect levels for 72 h acute salinity challenge was 26 PSU in our study, and salinity drop to 18 PSU and below can possibly cause acute adverse effect, in which fish could be vulnerable to additional stresses such as a temperature changes or handling stress.

Histology of gills of Labeo rohita infected by crustacean parasite Argulus sps.

Histology of gills of Labeo rohita infected by crustacean parasite Argulus sps.

Histopathologic evaluation of postmortem autolytic changes in bluegill (Lepomis macrohirus) and crappie (Pomoxis anularis) at varied time intervals and storage temperatures.

Information is lacking on preserving fish carcasses to minimize postmortem autolysis artifacts when a necropsy cannot be performed immediately. The purpose of this study was to qualitatively identify and score histologic postmortem changes in two species of freshwater fish (bluegill—Lepomis macrochirus; crappie—Pomoxis annularis), at varied time intervals and storage temperatures, to assess the histologic quality of collected samples. A pooled sample of 36 mix sex individuals of healthy bluegill and crappie were euthanized, stored either at room temperature, refrigerated at 4 °C, or frozen at −20 °C, and then necropsied at 0, 4, 24, and 48 h intervals. Histologic specimens were evaluated by light microscopy. Data showed that immediate harvesting of fresh samples provides the best quality and refrigeration would be the preferred method of storage if sample collection had to be delayed for up to 24 h. When sample collection must be delayed more than 24 h, the preferred method of storage to minimize autolysis artifacts is freezing if evaluation of the gastrointestinal tract is most important, or refrigeration if gill histology is most important. The gill arch, intestinal tract, followed by the liver and kidney were the most sensitive organs to autolysis.

Gill histopathology and micronucleus test of Astyanax jacuhiensis (Cope, 1894) (Teleostei, Characidae) to evaluate effects caused by acute exposure to aluminum

http://dx.doi.org/10.5007/2175-7925.2016v29n1p75A contaminação de ecossistemas aquáticos por alumínio (Al) é geralmente ocasionada por várias atividades antropogênicas. Diversas alterações morfológicas, fisiológicas e bioquímicas observadas em organismos aquáticos podem ser atribuídas à exposição ao Al. Neste contexto, o objetivo desse estudo foi investigar os efeitos da exposição aguda de peixes da espécie Astyanax jacuhiensis a diferentes concentrações de Al através da histologia de brânquias e frequência de micronúcleos (MN) e anormalidades nucleares (AN) em eritrócitos. Os animais foram expostos às concentrações subletais de 0.3 mg/L e 30 mg/L de alumínio em pH neutro por 72 h. Um grupo controle foi mantido em água filtrada. As alterações branquiais foram caracterizadas por hiperplasia e hipertrofia de células epiteliais, fusão lamelar, edema, descolamento epitelial, aneurisma e necrose. Um aumento significativo (p&lt;0.05) foi observado na frequência de lamelas alteradas nos grupos expostos às duas concentrações de Al em comparação aos animais controle. No entanto, não foram observadas diferenças significativas nas frequências de MN e AN. Embora não tenham sido encontradas evidências de genotoxicidade, os resultados encontrados na análise morfológica sugerem que o Al foi tóxico para os peixes nas duas concentrações testadas em pH neutro.

Improving aeration for efficient oxygenation in sea bass sea cages. Blood, brain and gill histology

AbstractAn air diffusion based system (Airx) was developed to control the dissolved oxygen levels in aquaculture sea cages. The system was introduced and then tested for 37 days in a sea bass sea cage (aerated cage). A second sea bass sea cage, without the AirX, was used as a control. Oxygen levels were measured in both cages at the start of the trial, before the AirX system was introduced, and during the working period of the AirX system. Fish samples were collected 15 days after the AirX system was introduced and at the end of the experiment. Blood smears were prepared and examined microscopically. Erythrocyte major axis, minor axis and area of fish erythrocytes were measured. Leucocyte differentiation was also examined. In the control cage, the fish had significantly larger red blood cells when compared with the red blood cells of the fish in the aerated cage. Histological examination of the gills and brain revealed no morphological differences or alterations between the two groups of fish. This study demonstrated that an air diffuser system could improve the water quality of fish farmed in sea cages and enhance sea bass physiological performance, especially if DO levels fall below 60% oxygen saturation.

Impact of sublethal di-n-butyl phthalate on the aquaculture fish species Nile tilapia (Oreochromis niloticus ): histopathology and oxidative stress assessment

Phthalates such as di-n-butyl phthalate (DBP) and their esters are widely used plasticizers, their ubiquitous presence in daily life, inevitably leads to their restricted use due to important environmental pollution and health impacts and endocrine disruption potential. The aim of this study was to examine the effects of a sublethal concentration of 10 mg L−1 DBP on haematocrit (HCT) values, gills and liver histology, malondialdehyde (MDA, 2-thiobarbituric acid-TBA reactivity) and reduced glutathione (GSH) levels in gills and liver tissue as oxidative stress biomarkers in the aquaculture fish species Nile tilapia (Oreochromis niloticus) after 24 (DBP-24) and 96 (DBP-96) h exposure. No differences were found between per cent HCT values in the 24 h exposure groups (P > 0.05). Response of antioxidant defence systems in liver and gill tissues of the fish were dependent on exposure duration and changed to a higher extent during 96 h. MDA levels in liver tissue increased in DBP treated fish in comparison to the control fish. However, the differences between the exposure and control groups were not significant (P > 0.05). A statistically significant decrease (P > 0.05) was recorded in gill MDA levels in the DBP-96 group when compared to the control and DBP-24 groups. The liver GSH levels were unchanged in the DBP treated fish. However, GSH levels were significantly lower in the gill tissue of the DBP-96 group. Exposure to DBP caused several degenerative changes in the histology of gill and liver tissue. Gills displayed hyperaemia, epithelial lifting, oedema, talengiectasia, epithelial hyperplasia and fusion of secondary lamellae, whereas in liver several circulatory anomalies (hyperaemia, blood congestion and sinosoid dilatation) and vacuolization of hepatocytes were observed. Histopathological results demonstrated that the gills were more affected than the liver perhaps due to their direct contact with DBP.

Effects of Nano-particles on Histo-pathological changes of the fish.

Regarding fast development of the nanotechnology and the probably of it’s side effects on aquatic body organs, this study investigate the effects of nanosilver administration on histology of gill, kidney and biochemical parameters in common carp. The silver nanoparticles were synthesized in a one-step reduction process in an aqueous solution. 60 O. mykiss were obtained from a local commercial hatchery. Fish were divided randomly into four groups. Control group was kept in dechlorinated tap water without any add-on material. Experimental groups were exposed to concentration of 3, 300 and 1000 mg/L of nanosilver solution for eight weeks, respectively. Biochemical analyses of sera, histological alterations of the gill and kidney tissue were done. Aneurism in the secondary lamellae and hyperplasia of epithelium in gills, adhesion of the gill lamellae, inducing hyaline cast formation, significant decreasing in the glomerular diameter and formation of intra cytoplasmic vacuoles in the various urinary tubules were seen in experimental groups. The serum levels of total protein was decreased significantly (P < 0.05) by increasing nanosilver concentration but ALP, LDH, AST and ALT increased significantly (P < 0.05). It is concluded that nanosilver induces gill and kidney damages and changes the biochemical parameters of O. mykiss juveniles in different concentrations.

A histology-based study in apparently healthy wild freshwater stingrays Potamotrygon motoro

Histopathological studies are important as a reference in pathological process. There are a few of these studies in elasmobranchs. The aim of this study was to describe the histology of kidney, spleen, liver, and gills of wild apparently healthy Potamotrygon motoro. However, we observed some pathological findings in these animals. Nineteen P. motoro were collected from the Parana River, Brazil. Histology of kidney, spleen, liver, and gills were performed according to usual procedures. Briefly, the organs were immersed in 10 % formaldehyde solution for 48 h and routinely processed, embedded in paraffin (5–6 mm thick), and subsequent staining with hematoxylin–eosin (HE), Perls’, and Schmorl’s stains. Histological surface areas were measured using Image Pro Plus software 6.3. We observed that melanomacrophages around the portal vein were larger and more abundant than in the area without the bile duct. Moderate steatosis was observed in most fish, large amount of melanomacrophages and lymphocytes in the gills, liver, and spleen comparing with other studies in this species that could suggest that the immune system in these animals is constantly active. No clinical signs were observed in the fish. Studies are necessary to characterize the immune response against pathogens in elasmobranchs, especially in the Potamotrygon species.

Gill Histopathologies Following Exposure to Nanosilver or Silver Nitrate

Fish gill is the site for many crucial physiological functions. It is among the first sites of xenobiotic exposure, and gill histopathological alterations may be detected soon after toxicant exposure. Silver (Ag) is one of the most toxic metals to aquatic organisms mainly due to its ability to disrupt ionic regulation. The goal of this study was to determine the effect of ionic and nanoscale Ag on fathead minnow gills by examining gill histology and Na+/K+-ATPase immunoreactivity. Fathead minnows were exposed to two measured concentrations of silver nitrate (AgNO3: 1.3 or 3.7 μg/L as Ag+), citrate silver nanoparticles (citrate-AgNP: 15 or 39 μg/L), and polyvinylpyrrolidone-AgNP (PVP-AgNP) (AgNP: 11 or 50 μg/L). Circulatory disturbances were the most prevalent gill alterations detected and were significantly increased in all Ag treatment groups compared to control. AgNO3 (1.3 μg/L) was the only treatment that significantly elevated the number of total mucous goblet cells present. In all other Ag treatments, the percent of degenerated goblet cells was significantly increased compared to control. When the sum of all histopathological abnormalities (weighted index) was calculated, all Ag groups displayed a significantly higher index, with citrate-AgNP having the highest toxicity (index of 10 ± 0.32 versus 2.4 ± 0.6 in controls). Gill Na+/K+-ATPase immunoreactivity was decreased by Ag. These results indicated that both AgNO3 and AgNP created similar disruptions in gill structure and ionic regulation, possibly due to the ionic Ag portion of each treatment.

Gill histology of Nile tilapia Oreochromis niloticus following chronic and acute exposure to ammonia

Ammonia is a common aquatic pollutant and is toxic to fish. The main nitrogenous compound excreted by fish is also ammonia, which may reach toxic concentrations in high-density fish culture, reducing growth and productivity. In this study, changes in gill structure and mucus cell distribution were examined when juvenile Nile tilapia, Oreochromis niloticus, were exposed to chronic and acute concentrations of ammonia. For chronic exposure, the tilapia were exposed to daily increments in ammonia concentration rising from 0 mg L-1 ammonia on Day 0 to 5 mg L-1 by Day 8; the experiment was terminated on Day 9. There were obvious histopathological changes to the gills over this period including hypertrophy and fusion and of the secondary lamellae. The mucus cell number in gill histology sections were observed to increase until Day 6 then decrease thereafter until the termination of the trial. For the acute exposure, juvenile tilapia were exposed to 5 mg L-1 ammonia for 5 hours. Hourly changes to the gills were monitored, with notable changes to gill filaments and an observed increase in the mucus cell number over the duration of the experiment.

Histopathological and bacterial study of skin and gill of grass carp, Ceteopharyngodon idella, (Valenciennes 1844) exposed to copper sulfate and potassium permanganate.

The gill histology and bacterial load of skin of the grass carp juveniles were investigated in relation to various concentrations of copper sulfate and potassium permanganate. For this purpose, the sublethal doses were determined after a pre-test and then the experiment was done in five treatments (for copper sulfate: 1, 1.94, 3.71, 7.07 and 15mg/l and for potassium permanganate: 0.25, 0.52, 1.91, 2.27 and 5mg/l) with three replicates inside the glass aquaria. Also, one group without disinfecting product was considered as control for each experiment. The microbial and histopathological investigations were done after 96h exposure. According to results, the lowest bacterial load (CFU/g) of skin was observed in 15mg/l copper sulfate treatment and 0.25mg/l potassium permanganate treatment (P<0.05). Also, the histological investigation showed a range of histopathological alternations in gills tissue including lamellar necrosis, hyperplasia, lamellar adhesion, haemorrhage, clubbing of gill lamellae. The severity of these alternations increased with increasing of the doses of the copper sulfate and potassium permanganate. In this regard, the highest histological damages were observed in 15mg/l copper sulfate and 5mg/l potassium permanganate respectively. Our results showed that low dosage of potassium permanganate has best effect on reducing of bacterial load of skin with lowest adverse effects on gill tissue.

96 h LC50, behavioural alterations and histopathological effects due to wastewater toxicity in a freshwater fish Channa punctatus.

The aim of the study was to evaluate the toxic impact of wastewater from sites 1 and 2 of Tung Dhab drain in the state of Punjab, India, on fish behaviour, morphology and gill histopathological biomarkers in comparison to control group. Static non-renewal tests were conducted for 96 h to determine LC50 of the wastewater for both sites using five concentrations (6.25-100%). Fish were regularly noticed for any deviation in behaviour and external morphology. Physico-chemical analysis of wastewater was done using standard methods recommended by APHA/AWWA/WEF (2005). Chronic toxicity tests were conducted for 15 and 30 days with sublethal concentrations of wastewater (50-90% of LC50) and gill histopathology was assessed. Wastewater near a paper mill was more toxic as observed from LC50 values of 72.45%. There was evident deterioration of water quality as the recorded values of some parameters were higher than the standard discharge limits. The test fish exhibited increased air gulping and surfacing, erratic movements initially and decreased opercular movements as the exposure period increased. Morphological observations include increased body colouration, mucus secretion, scale loss and haemorrhages on the skin and lower lip. Alterations in the gill histology such as complete lamellar fusion, epithelial lifting and intraepithelial oedema, haemorrhages, lamellar necrosis and aneurysm were noted in the test fish. Results demonstrate that the fish exposed to wastewater from both sites showed significantly greater change in gill organ index (IG) as compared to control fish for 15 and 30 days.

Treatment of textile effluent in a developed phytoreactor with immobilized bacterial augmentation and subsequent toxicity studies on Etheostoma olmstedi fish

A static hydroponic bioreactor using nursery grown plants of Pogonatherum crinitum along with immobilized Bacillus pumilus cells was developed for the treatment of textile wastewater. Independent reactors with plants and immobilized cells were also kept for performance and efficacy evaluation. The effluent samples characterized before and after their treatment showed that the plant–bacterial consortium reactor was more efficient than those of individual plant and bacterium reactors. COD, BOD, ADMI, conductivity, turbidity, TDS and TSS of the textile effluent was found to be reduced by 78, 70, 93, 4, 90, 13 and 70% respectively within 12 d by the consortial set. HPTLC analysis revealed the transformation of the textile effluent to new products. The phytotoxicity study on Phaeseolus mungo and Sorghum vulgare seeds showed reduced toxicity of treated effluents. The animal toxicity study performed on Etheostoma olmstedi fishes showed the toxic nature of untreated effluent giving extreme stress to fishes leading to death. Histology of fish gills exposed to treated effluent was found to be less affected. The oxidative stress related enzymes like superoxide dismutase and catalase were found to show decreased activities and less lipid peroxidation in fishes exposed to treated effluent.

Effects of Acute and Chronic Nitrite Exposure on Rabbitfish Siganus rivulatus Growth, Hematological Parameters, and Gill Histology

Nitrite is toxic to fishes and is often encountered in recirculation aquaculture systems. Accordingly, the nitrite tolerance of potential aquaculture candidates needs to be assessed before the fish can be farmed in land-based recirculation systems. In the present work, we studied the susceptibility of the marbled rabbitfish Siganus rivulatus to nitrite. In the first experiment, we placed fish at 0, 40, 50, 60, 70, 80, 90, 100, 110, 120 and 130 mg l-1 NO2-N and evaluated 96 h LC50. In the second experiment we measured survival and growth of fish reared at 0, 10, 20, 30, 40, and 50 mg l-1 NO2-N for eight weeks. Blood parameters of fish in the various treatments were also measured and gill histology studied. Finally, methemoglobinemia in fish reared at various nitrite conditions was assessed. The NO2-N 96 h LC50 of S. rivulatus juveniles was 105 mg l-1. In the growth experiment, fish mortality was greater than in the control at NO2-N concentrations 30 mg l-1 and greater. Growth in all treatments was less than in the control but there were no significant differences among treatments. Aqueous nitrite affected various hematological parameters such as hematocrit and total hemoglobin. Compared to other aquacultured marine fishes, the marbled rabbitfish is considered tolerant to environmental nitrite.

Health of sharptooth catfish Clarias gariepinus in Pongolapoort Dam, South Africa: a comprehensive study

A histology-based fish health assessment protocol was used in 2009–2010 to assess the health status of Clarias gariepinus from Pongolapoort Dam, South Africa. Nineteen fish were collected by angling. The histology of liver, kidney, gills and testes or ovaries was semi-quantitatively assessed and compared to that of fish from a reference site in the Okavango Panhandle, Botswana. Necropsy observations indicated that C. gariepinus from Pongolapoort Dam were in poorer condition than those from the Okavango Panhandle. Microscopic analysis showed that the mean liver index (I L), gill index (I G), testis index (I T) and ovary index (I O) were higher, although not statistically significant, in fish from the Okavango Panhandle. The difference in the results between the necropsy-based observations and semi-quantitative histological results was due to the external abnormalities detected in the necropsy analysis, including parasites and skin lesions, not expressing as changes to cell and tissue structure. According to the parameters measured, C. gariepinus from Pongolapoort Dam were in a healthy state.