Fish Health Assessment Research Articles

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.

Genomic and phenotypic response of hornyhead turbot exposed to municipal wastewater effluents

Laboratory tests with marine flatfish were conducted to investigate associations among gene expression, higher biological responses and wastewater effluent exposure. In the present study, male hornyhead turbot (Pleuronichthys verticalis) were exposed to environmentally realistic (0.5%) and higher (5%) concentrations of chemically enhanced advanced-primary (PL) and full-secondary treated (HTP) effluents from two southern California wastewater treatment plants (WWTP). Hepatic gene expression was examined using a custom low-density microarray. Alterations in gene expression (vs. controls) were observed in fish exposed to both effluent types. Fish exposed to 0.5% PL effluent showed changes in genes involved in the metabolism of xenobiotics, steroids, and lipids, among other processes. Fish exposed to 5% PL effluent showed expression changes in genes involved in carbohydrate metabolism, stress responses, xenobiotic metabolism, and steroid synthesis, among others. Exposure to 5% HTP effluent changed the expression of genes involved in lipid, glutathione and xenobiotic metabolism, as well as immune responses. Although no concentration-dependent patterns of response to effluent exposure were found, significant Spearman correlations were observed between the expression of 22 genes and molecular and/or higher biological responses. These results indicate that microarray gene expression data correspond to higher biological responses and should be incorporated in studies assessing fish health after exposure to complex environmental mixtures.

Selected haematological changes in <i>Clarias gariepinus</i> (Burchell, 1822) infected with a <i>Trypansosoma</i> sp. from the Vaal Dam, South Africa

The use of haematological techniques to assess fish health is generally accepted. The aim of the current study was to determine selected haematological changes that occur in Clarias gariepinus (Burchell, 1822). infected with trypanosomes. Blood films were prepared according to standard techniques to confirm trypanosome infections and whole blood was collected, the serum and plasma separated, and prepared for albumin and total protein concentration analysis. Plasma albumin levels were significantly higher in infected wild caught fish than in uninfected wild caught fish and uninfected breeding stock. Serum albumin levels were significantly lower in infected wild caught fish when compared to uninfected breeding stock. The total plasma and serum protein levels were within the normal range for C. gariepinus, that is, 3 g-6 g/100 mL. The total plasma protein levels varied significantly between the three groups. However, the total serum protein levels were only significantly different between uninfected breeding stock and uninfected wild caught fish, as well as uninfected breeding stock and infected wild caught fish. The total protein levels were significantly higher in infected wild caught fish than in the other groups, a possible indication of an infection or inflammatory host response.

A combined measurement of metal bioaccumulation and condition indices in juvenile European flounder, Platichthys flesus, from European estuaries

Condition indices and metal bioaccumulation of early life stages of juvenile flounder (5–10cm) were determined in three anthropogenic estuaries (the Scheldt, Seine and Loire) and compared to a reference site (the Canche). Significant correlations were found between metal concentrations in sediment and (i) fish liver for Cd, Cu, Ni, Pb, V and Zn and (ii) fish gills for Cd and Mn. Metal accumulation in juvenile flounder from the three anthropogenic estuaries coincided with significantly lower Fulton’s K indices (from 0.99±0.03 to 1.06±0.01mgmm−3) compared to those from the Canche estuary (from 1.02±0.01 to 1.13±0.01mgmm−3). This discrepancy in fish condition index increased with fish size and therefore, strongly depends on the time juvenile spend in estuary. Muscle lipid contents and Triacylglycerol to Sterol ratios were significantly lower in fish collected in the Scheldt (lipid content: 21.3±3.6%), Seine (17.9±19.8%) and Loire (19.5±2.4%) estuaries compared to those originating from the Canche (38.3±4.6%). This study highlights that combined measures of both fish metal contents and condition indices gives a relevant assessment of juvenile fish health growing in anthropogenic estuaries.

Evaluation of the fish health assessment index in the Olifants River system, South Africa

The fish health assessment index (HAI) biomonitoring technique, developed in the USA and subsequently tested in South Africa, was re-evaluated in the Olifants River system using Clarias gariepinus, Oreochromis mossambicus and Labeobarbus marequensis during drought and flood conditions in 1994–1997 at the same sample sites in the Kruger National Park as used previously, as well as at Loskop Dam and Bronkhorstspruit Dam in the upper catchment. Parasite numbers recorded from Clarias gariepinus supported the HAI hypothesis that higher endoparasite and lower ectoparasite numbers occur at highly impacted areas. The apparent effects of pollution type on the ratio between ectoparasites and endoparasites are discussed. Environmental stressors such as flood conditions resulted in immunological responses, reflected statistically as changes in white blood cell percentage (WBC%). It is suggested that endoparasite and WBC% data provide the best overall assessment of fish condition in the Olifants River system. Modifications made to the HAI included further development of the original parasite presence/absence component into a more extensive parasite index component. The modified HAI index shows promise as a long-term biological monitoring tool in South Africa.

Histopathological changes in two potential indicator fish species from a hyper-eutrophic freshwater ecosystem in South Africa: a baseline study

Histopathological changes were identified in selected target organs from two freshwater fish species, Clarias gariepinus and Oreochromis mossambicus, inhabiting the hyper-eutrophic Roodeplaat Dam near Pretoria. A histology-based fish health assessment protocol was used, including a semiquantitative histopathological assessment of the gills, liver, ovaries, testes, kidney and heart. Water quality analyses showed selected variables to be above the recommended levels, including pH, ammonia, nitrogen, chloride and phosphorus. A number of histopathological alterations were identified in the target organs of both species, with the highest number being in the liver. Species differences were identified in terms of the severity of the alterations within all the organs, with most alterations being regressive in nature. This study provided valuable baseline data that could be useful for future biomonitoring studies.

A comparative assessment of the health status of feral populations of Clarias gariepinus from three dams in the Limpopo and Olifants river systems, Limpopo province, South Africa, using the fish health assessment index protocol

An evaluation of the health status of feral populations of the freshwater catfish Clarias gariepinus was carried out between 2009 and 2010 at three dams in the Limpopo and Olifants river systems with varying levels of human impact. Fish health was assessed using a modified health assessment index (HAI) protocol, with the inclusion of the inverted parasite index (IPI) and condition factor (K). These biomonitoring tools provide relatively simple and rapid indications of how well fish are coping in their environment. To verify the biomonitoring results, water quality analyses were included in the study. The nutrients and mining-related pollutants in the three dams differed to a great extent and showed an increasing trend in the order: Luphephe–Nwanedi Dams < Flag Boshielo Dam < Return Water Dam. The HAI score varied across the three sampling sites, with individual mean values of 93.3, 84 and 42.7 at the Return Water Dam, Flag Boshielo Dam and Luphephe–Nwanedi Dams, respectively. The top six metrics that correlated best with fish health scores were the levels of ectoparasites, haematocrit values and the condition of the gills, liver, skin and fins. Although the HAI successfully differentiated among the three localities, which differed in water quality, it was non-specific in response to contaminants. Notably, the premise set forth by the IPI that endoparasites increase with a decrease in water quality was not supported.

Health Assessment of fish communities exposed to pig slurry in the Vaal River, South Africa

This study evaluated the effects of untreated pig slurry on the general health of thefish communities in the lower Vaal area by using the Fish Health Assessment Index (FHAI)together with morphological biomarkers such as Gonad Mass Index (GMI), Hepato-SomaticIndex (HSI), the Condition factor (Cf) and microbial activity.

Responses of juvenile sea bass, Dicentrarchus labrax, exposed to acute concentrations of crude oil, as assessed by molecular and physiological biomarkers

In the present study, juvenile sea bass were exposed for 48 and 96h to an Arabian light crude oil and their responses were assessed at the molecular and physiological levels. The aim of the study was therefore to assess (i) the short term effects of crude oil exposure by the measurement of several molecular biomarkers, (ii) the consequences of this short term exposure on fish health by using growth and condition indices measured after a decontamination period of 28 and 26d in seawater. Hydrocarbon petroleum concentrations was monitored during the 96h experiments and an increase of PAH concentrations were found in fish following both exposure times. An 7-ethoxyresorufin-O-deethylase (EROD) induction was observed after 48h of exposure, while a significant decrease in the sea bass specific growth rate in length and for the RNA:DNA ratio was observed 28d after that exposure ceased. The EROD induction doubled after the 96h exposure, and a significant increase in GST activities was observed. A significant decrease in the specific growth rates, the otolith recent growth, the RNA:DNA ratio and the Fulton’s K condition index were then observed in sea bass 26d after the 96h exposure to mechanically dispersed crude oil compared to the control. The present study shows that growth and condition indices can prove useful in assessing fish health status following an oil spill. Their complementary analysis with sensitive molecular biomarkers as EROD could improve the determination of oil spill impact on fish populations.

Fish and ecosystem health as determined by parasite communities of lake whitefish (Coregonus clupeaformis) from Saskatchewan boreal lakes

In northern Canada, there is increasing concern about the potential negative impacts of industrial activities on wildlife and ecosystems. Therefore, a study was conducted on lake whitefish (Coregonus clupeaformis) from Montreal and Reindeer lakes, Saskatchewan, to assess fish health and condition, and ecosystem integrity of these northern lakes. In Montreal Lake, all fish were infected by ≥2 parasite species. The most prevalent parasite at this site was the larval trematode Ichthyocotylurus erraticus, which was detected in all fish examined. All Reindeer Lake whitefish were shown to harbour ≥1 parasite species. The most prevalent parasite (found in 87.9% of fish) at this locality was the larval trematode Diplostomum sp. Macroscopically visible pathogenic changes were not noted. Gross energy values of whitefish were 4.40 ± 0.88 MJ/kg and 5.14 ± 1.14 MJ/kg for Montreal Lake and Reindeer Lake, respectively, indicating that fish have sufficient energy stores to withstand stressful conditions. The parasite communities were species-rich and diverse, with Shannon diversity indices of 2.12 (Montreal Lake) and 2.02 (Reindeer Lake). The ratios of allogenic/autogenic as well as planktonic/benthic parasite species did not indicate atypical environmental conditions. Together the findings suggest that in both lakes there is currently no significant anthropogenic impact on the whitefish populations and ecosystem health.

Temporal variations in haematological and biochemical indices of the Caspian kutum, Rutilus frisii kutum

The pattern of haematology and blood biochemistry variations of healthy adult female kutum Rutilus frisii kutum (Cyprinidae) was investigated in the three reproductive states: maturing (autumn), pre-spawning (winter), and spawning (spring). Red blood cells, haemoglobin, and haematocrit were highest in autumn, whereas the highest values for white blood cells, mean corpuscular volume (MCV), and mean corpuscular haemoglobin (MCH) were observed in winter. With the exception of MCV and mean corpuscular haemoglobin concentration (MCHC), fish size had no effect on haematological and biochemical parameters. MCV was higher in larger fish, whereas the reverse trend was found for MCHC. Decreased levels of plasma glucose, cholesterol, and triglyceride in the pre-spawning period, when female ovaries were developing, may have been due to the combination of reproductive effects and food shortage in winter. Total protein levels were lower during the maturing period than during the pre-spawning period. The results of this study suggest that temporal variations in haematological and biochemical parameters of blood are significant and should be considered when these parameters are used to assess fish health status.

A histology-based fish health assessment of the tigerfish, Hydrocynus vittatus from a DDT-affected area

The Pongolapoort Dam (PPD) in the Phongola River, Kwa-Zulu Natal, South Africa and the surrounding area are classified as intermediate to low risk malaria areas and are continually being treated with DDT for malaria vector control. DDT is known as an endocrine disrupting chemical posing estrogenic and anti-androgenic properties and therefore might impact on the health of the 18 freshwater fish species found within this system. Of these species the tigerfish, Hydrocynus vittatus, is targeted by both recreational and local subsistence fishermen and was recently included in the South African threatened or protected species list. Their protected status and importance as a food source therefore emphasises the need for their health status elucidation. Previous research on H. vittatus in the Phongola floodplain highlighted DDT biomagnification in this species. Recent data show that the sum of the DDT levels in February 2009 (5403.9ng/g lipid) and July 2009 (5537.4ng/g lipid) is still comparable to the high levels found 30years earlier. The aim of the current study was thus to determine the health status of H. vittatus in relation to DDT exposure by means of a histology-based fish health assessment protocol. Tigerfish were collected in February 2009 (n=30) and July 2009 (n=15) and gill, kidney and liver tissue were subjected to histological analyses. Mean Index values showed that the Kidney Index (IK), Gill Index (IG) and Fish Index (IFISH) were higher in fish from the February survey while the Liver Index was higher in those collected during July. Liver alterations identified included intercellular oedema, granular degeneration, vacuolation, nuclear pleomorphism and lymphocyte infiltration. Kidney alterations included dilation of the glomerulus capillaries, vacuolation and hyaline droplet degeneration. Gill alterations identified included telangiectasia and hyperplasia of the secondary lamella, congestion, and rupture of pillar cells. Although histological alterations were observed, the histology based fish health assessment protocol indicated that the H. vittatus population in PPD were in a healthy state. The histological assessment did not reflect the DDT exposure induced effects that were anticipated. However, the biomagnification effects in other tertiary consumers in the PPD such as crocodiles and fish eagles cannot be ruled out.

Effects of pulp and paper mill effluent on fish: A temporal assessment of fish health across sampling cycles

The Canadian environmental effects monitoring (EEM) program is a regulated, cyclical, industry-funded program designed to determine whether receiving water impacts exist when a mill is in compliance with its discharge limits. The results from three cycles of the fish monitoring program (1992 to 2004) are available from over 200 surveys of fish compared between sites located upstream and downstream of pulp and paper mill effluent outfalls. Previous meta-analyses have shown a national average response pattern across cycles characterized by an increase in endpoints measuring energy storage and growth and a decrease in a reproductive endpoint, consistent with a response of nutrient enrichment in combination with some form of metabolic disruption. Although the national average pattern of effects was temporally consistent, there was some variability in the magnitude of effects among cycles. Questions were raised as to whether the intercycle variability was due to changes in effluent quality or due, at least in part, to other factors. The present study compares responses over the first three cycles, and shows that the choice of sentinel species is likely to be a major contributing factor to the variability in observed effects. Subset analyses using studies from mills that used the same sentinel species across cycles reveal fairly uniform responses and little evidence of significant improvements in overall fish health from cycles one to three. However, a meta-analysis using 1991 data collected from 10 mills before the implementation of the EEM program and data from the same mills collected during cycles one to three of the program reveal significantly reduced effects on relative liver weight and potential improvements in other endpoints.

Application of a fish health assessment index and associated parasite index to Clarias gariepinus (Teleostei: Clariidae) in the Vaal River system, South Africa

The aim of this study was to determine if the fish health assessment index (HAI) developed in the USA and associated parasite index (PI), when applied to Clarias gariepinus at two localities in the upper and middle Vaal River system, could distinguish between localities on the grounds of water quality. Elevated HAI values, correlating with poorer chemical and physical water quality, were recorded from the Vaal River Barrage site. Parasite data were congruent with the main PI premise that prevalence and intensity of endoparasite infection would be higher at the more polluted locality, with the converse being recorded for ectoparasites. It was therefore possible to distinguish between localities with different water quality, based on parasites present on the hosts.

A histology-based fish health assessment of four commercially and ecologically important species from the Okavango Delta panhandle, Botswana

The health status of four commercially and ecologically important fish species from the Okavango Delta was assessed, using a histology-based health assessment protocol, to establish baseline data for future toxicity studies. Following the calculation of a necropsy-based health assessment index (HAI), the histological responses of the liver, gills and gonads were assessed and compared between Clarias gariepinus, C. ngamensis, Oreochromis andersonii and Serranochromis angusticeps. Population HAI results showed that O. andersonii was most affected in terms of necropsy-related alterations, followed by S. angusticeps, whilst identical low values were calculated for C. ngamensis and C. gariepinus. Quantitative histological results corresponded with the HAI results. The liver and gills of O. andersonii were most affected in terms of the percentage prevalence of the histological alterations identified. These were mostly associated with inflammation, and progressive and regressive changes. The histology of the liver and gills was also more affected in terms of the type and severity of the histological alterations identified, compared to that in the gonads of all four species. The majority of alterations were most likely caused by the prevalence of parasitic infections.

The impact of water exchange rate on the health and performance of rainbow trout Oncorhynchus mykiss in water recirculation aquaculture systems

A controlled six-month study was conducted in six replicated water recirculation aquaculture systems (WRAS) to assess fish health indicators in relation to high feeding/low flushing conditions. Juvenile rainbow trout (Oncorhynchus mykiss) were stocked in six identical WRAS (1000 fish per system), and were maintained over the study period between 25 kg/m3 (minimum) and 80 kg/m3 (maximum) densities. Three WRAS received a relatively high makeup water exchange rate (2.6%), while three systems received only 0.26% exchange; mean feed loadings of 0.39 and 4.1 kg/day per m3/day of makeup water flow were maintained for the high and low exchange treatments, respectively. At the end of the study period, there were surprisingly no significant (p<0.05) differences in average fish weight between treatment groups. Percentage survival was excellent in both high and low makeup system populations (99.5%±0.1 and 98.9%±0.4, respectively). Histopathological evaluation revealed a significant increase in splenic and skin lesions in low makeup system fish relative to those sampled from the high makeup systems, while lesions in the posterior kidney were more prevalent in the high makeup system fish. Plasma chloride and blood urea nitrogen were also significantly different between fish from the two treatment groups, and caudal fin quality assessment showed significantly greater fin erosion in low makeup system fish. Despite these clinical and subclinical differences, there appeared to be no major treatment effect on overall fish performance.

Comparisons of swimming performance in rainbow trout using constant acceleration and critical swimming speed tests

Maximum swimming performance of seasonally acclimated rainbow trout Oncorhynchus mykiss was compared among short‐duration constant acceleration tests (Umax) and with the well established, but longer duration critical swimming speed (Ucrit) test. The present results show that Umax was insensitive to a range of acceleration rates that differed by more than three‐fold. Thus, test duration could be reduced from 58 to 18 min without affecting the estimate of Umax. The value of Umax, however, was up to 57% higher than Ucrit. Only the slowest acceleration rate tested (an increase of 1 cm s−1 every min) had a significantly lower Umax, and this was up to 19% higher than Ucrit. Even so, the potential saving in the test duration was small (70 v. 90 min) when compared with a ramp‐Ucrit test (a standard Ucrit test but with the water velocity initially ramped to c. 50% of the estimated Ucrit). Therefore, swim tests that are appreciably shorter in duration than a ramp‐Ucrit test result in Umax being appreciably greater than Ucrit. An additional discovery was that the ramp‐Ucrit performance of cold‐acclimated rainbow trout was independent of the recovery period between tests. These results may prove useful in making comparisons among different swim test protocols and in designing swim tests that assess fish health and toxicological impacts.

Estuarine fish health assessment: Evidence of wastewater impacts based on nitrogen isotopes and histopathology

Sewage effluent is a powerful agent of ecological change in estuaries. While the effects of sewage pollution on water quality are usually well documented, biological responses of exposed organisms are not. We quantified health impacts in the form of pathological tissue changes across multiple organs in estuarine fish exposed to elevated levels of treated wastewater. Structural pathologies were compared in wild populations of four fish species from two subtropical estuaries on the east coast of Australia that differ substantially in the amount of direct wastewater loadings. Uptake of sewage-derived nitrogen by fish was traced with stable nitrogen isotopes. Pathologies were common in the liver, spleen, gill, kidney and muscle tissues, and included granulomas, melanomacrophage aggregates, and multiple deformities of the gill epithelia. Tissue deformities were more frequent in fish exposed directly to wastewater discharges. Mullet ( Valamugil georgii) were most affected, with only a single specimen free of pathologies in the sewage-impacted estuary. Similarly, in those fish that had structural abnormalities, more deformities were generally found in individuals from sites receiving sewage. These spatial contrasts in impaired fish health correspond to significantly enriched δ 15N values in fish muscle as a consequence of fish assimilating sewage-N. Overall, the pattern of lower health and enriched δ 15N values in fish from sewage-impacted areas suggests that organism health is lowered by sewage inputs to estuaries. Measurements of organism health are required to understand the effects of sewage on estuarine ecosystems, and histopathology of fishes is a powerful tool to achieve this.

Immune response in the tilapia, Oreochromis mossambicus on exposure to tannery effluent

The objective of the study was to investigate the effect of chronic exposure to sublethal concentrations of tannery effluent (TE) on the specific immune response and nonspecific immunity in tilapia, Oreochromis mossambicus. The effluent from the tannery was collected directly from a chrome-tanning factory situated in Dindigul district, Tamil Nadu, India. Apart from chromium (88.2 ppm), the effluent contained appreciable amount of calcium carbonate and sodium sulphate. Groups of fish (45–50 g) were exposed to 0.0053, 0.053 or 0.53% [0.1%, 1% or 10% LC 50] of TE for 28 days. The specific immune response of fish was assessed by antibody response to heat-killed Aeromonas hydrophila by ELISA and bacterial agglutination assay. Nonspecific immune mechanisms were assessed in terms of serum lysozyme activity, production of intracellular reactive oxygen species (ROS) and reactive nitrogen intermediates (RNI) by peripheral blood leucocytes (PBL). The results indicate that chronic exposure of fish to 0.53% of TE, significantly suppressed antibody response, nonspecific serum lysozyme activity, and ROS and RNI production. Exposure to 0.053% (1% LC 50) of TE also caused a similar suppressive effect though at a lesser degree. In conclusion, the study shows, that exposure to sublethal concentrations of TE, can lead to adverse effects on selected immune reactions in tilapia. Further, these findings may be important in terms of monitoring fish health and risk assessment during periods of fluctuating levels of pollutants in the natural and farm environments.

Parasites of Winter Flounder (Pleuronectes americanus) as an Additional Bioindicator of Stress-Related Exposure to Untreated Pulp and Paper Mill Effluent: A 5-Year Field Study

A study was conducted in a marine inlet to assess the effects of untreated discharges from a pulp and paper mill, a municipality, and industries in western Newfoundland on winter flounder (Pleuronectes americanus), a fish species shown previously to be sensitive to environmental contaminants in sediment. The fish were captured by SCUBA divers about 2 km down-current from the mill discharging effluent containing resin acids, and at three reference sites 2 to 11 km away near the opposite shore, each spring in five consecutive years and the fish were necropsied on site. A total of 360 and 339 flounder were examined near the mill and references sites, respectively. Several bioindicators were used to assess fish health including parasites. More fish exhibiting external and microscopic lesions in several tissues, lower condition factors, elevated hepatosomatic index, and delayed reproductive development were observed in samples taken near the paper mill than at the reference sites. A higher prevalence of an ectoparasite, Cryptocotyle lingua, but a significantly lower mean abundance of three metazoans infecting the digestive tract was noted in fish near the mill than in the reference samples. These results, comprising abnormal fish size distribution, low body condition factor, external and internal lesions, enlarged liver, delayed gonadal development, and changes in parasitism, were stress-related, indicative of impaired health, and associated primarily with untreated discharges from the pulp and paper mill. This integrated and multidisciplinary study also provides further evidence on the use of fish parasites as a valid and an additional bioindicator in programs monitoring environmental contaminants.