Helminth parasitism of Galaxias maculatus (Jenyns 1842) in southwestern Australia

Abstract –  One cestode, Ligula sp. [possibly Ligula intestinalis (L.)], one trematode, Diplostomum sp., and two nematode parasitic worms, Eustrongylides sp. [possibly Eustrongylides gadopsis (Royal Society of South Australia, 64, 340)] and Contracaecum sp. are reported from Galaxias maculatus inhabiting a permanent freshwater lake and two intermittently flowing, saline rivers in southwestern Australia. Worms infecting fish are all larval; the definitive hosts are piscivorous waterfowl. Ligula sp. infected 12% of fish in the lake. Effects of infection include reduced lifespan, significant weight reduction of gonads of males and females and body weight of females. Infection reduces the proportion of males that attain spawning gonad stage more severely than it does in females. The prevalence and intensity of Ligula sp. infection were much less in the rivers. The infection of Pseudogobius olorum (Sauvage 1880) by this cestode is reported for the first time in Western Australia. Trematodes were much more benign in their effect on G. maculatus .     

Protozoan parasites of gilthead sea bream, Sparus aurata L., from different culture systems in Spain

Abstract. In a parasitic survey of gilthead sea bream, Sparus aurata L., cultured in different systems in Spain, eight protozoan species were found. Ectoparasites included two ciliates ( Trichodina sp. and a Cryptocaryon -like species), one dinoflagellate ( Amyloodinium sp.) and the zooflagellate Ichthyobodo sp. Endoparasites were represented by members of the Apicomplexa ( Eimeria sp.) and Myxosporea ( Polysporoplasma sparis. Ceratomyxa sp. and Leptotheca sp.). Ichthyobodo sp., Eimeria sp., Ceratomyxa sp. and Leptotheca sp. are reported for the first time in S. aurata. Amyloodinium sp. and Ichthyobodo sp. were associated with outbreaks of disease in larval and juvenile fish. Data on prevalence and intensity of infection and the location in the host are provided. The potential importance of these protozoan parasites for gilthead sea bream culture is discussed.     

Effect of marine Eubothrium sp. (Cestoda: Pseudophyllidea) on the growth of Atlantic salmon, Salmo salar L.

Atlantic Salmon, Salmo salar L., experimentally infected with marine Eubothrium sp. were kept together with uninfected salmon in the laboratory for 11 months in two tanks, 80 infected and 80 uninfected in each tank. The infected fish had a reduced growth rate compared with the uninfected fish. Significant differences in growth between infected and uninfected fish were not observed until several months post-infection. There was no correlation between the number of Eubothrium sp. and fish weight, indicating that even low intensity alters the growth rate of the salmon. The cestode had the same effect on both sexes of salmon. Haematocrit level was found to be significantly lower in infected compared with uninfected salmon in one of the samples during the experiment.     

Protozoan parasites of wild and cultured sea bass, Dicentrarchus labrax (L.), from the Mediterranean area

Abstract. In a parasitic survey of wild and cultured sea bass, Dicentrarchus labrax (L.), thirteen protozoan species were found. Ectoparasites included two ciliates ( Trichodina spp.), one dinoflagellate ( Amylodinium sp.) and one zooflagellate ( Cryptobia sp.). Endoparasites were represented by members of Apicomplexa ( Hemogregarina sp., Eimeria spp.). Microsporea (unidentified species) and Myxosporea ( Myxobilatus sp., Ceratomyxa spp., Sphaerospora dicentrarchi, Sphaerospora testicularis). Myxobilatus sp., Eimeria spp. and the microsporean were exclusively found in wild fish, whereas Amyloodinium sp. and Hemogregarina sp. were only detected in cultured fish. Data on prevalence and intensity of infections and on the location in the host are provided. The potential importance of protozoan parasites for sea bass culture is discussed.     

What are the consequences of infection by the introduced parasite Philometroides sanguineus for threatened crucian carp Carassius carassius populations in England?

Abstract – Nonnative parasites have the potential to detrimentally affect naïve hosts, resulting in negative consequences for their growth, condition and energetics. Here, the effect of the introduced parasitic nematode Philometroides sanguineus on crucian carp Carassius carassius populations in England was investigated. Populations of C. carassius populations are increasingly spatially restricted in England and under increasing threat from habitat loss and hybridisation. Parasite prevalence across 6 infected populations was <27% and, generally, there was no significant relationship between levels of infection and fish length and age. Parasite abundance ranged between 1 and 8 nematodes and was not significantly related to fish length and age. Comparison of the growth, body weight and condition, and energy reserves between infected and noninfected C. carassius revealed infection did not incur significant detrimental impacts on these parameters. Whilst this suggests that infection had only minimal impacts on the examined host fish, this may have been a consequence of a low proportion of fish <100 mm in samples (i.e., size‐selective effects) and some tests did suffer from low statistical power because of, for example, unbalanced sample sizes. It does, however, suggest that P. sanguineus may not be a major threat to the status of these C. carassius populations and infection by introduced parasites may not always incur significant impacts in naïve fishes.     

Perkinsus sp. infestation in carpet-shell clams, Ruditapes decussatus (L), along the Portuguese coast. Results from a 2-year survey

This study characterises Perkinsus atlanticus disease prevalence and intensity within the economically important beds of the clam Ruditapes decussatus along the Iberian Atlantic coast. Samples were collected from five different sites along the Portuguese coast (Ria Formosa, Ria do Alvor, V.N. Milfontes, Aveiro, Lagoa de Obidos) and in Galicia (Ria de Arosa) between winter 2000/2001 and 2002/2003. The infection level was evaluated by the Ray Fluid Thioglycollate medium (RFTM) method using the body burden assay. In addition, the measure of the condition index (CI) (percentage between the edible part and the total weight of the clams) was conducted to investigate a possible correlation between this parameter and the intensity of the infection. However, no clear relationship between infection intensity and condition index (CI) could be determined although a significant decline in CI was found for heavily infected clams. Results of a 2-year survey demonstrate the presence of Perkinsus sp. in all sampling sites albeit with different intensities. Sites where human interference was minimal showed the lowest levels of infection. There were no significant differences in Perkinsus sp. infection intensity between samples collected in winter and summer, in contrast with several studies describing higher intensities at the end of the summer. Nevertheless, major differences were observed from year to year and site to site, indicating that factors other than those responsible for seasonal climatic variations might affect the prevalence and the intensity of Perkinsus sp. infection.     

Quantitative investigation of Enteromyxum leei (Myxozoa: Myxosporea) infection and relative condition factor in cultured olive flounder Paralichthys olivaceus (Temminck and Schlegel)

Enteromyxum leei has been reported to cause emaciation disease in various fish species. To determine the effect of parasite intensity on cultured olive flounder Paralichthys olivaceus, we investigated the relationship between the relative condition factor (rCF = CF/standard CF × 100) and parasite load with quantitative polymerase chain reaction (qPCR) and the challenge test. A total of 57 cultured olive flounders were obtained from 11 fish farms and divided into five groups based on their rCF. We investigated the parasite intensity in the posterior intestine of the fish. The parasite load was closely matched to severe loss of body weight. In addition, olive flounders were inoculated either orally or anally with intestinal scrapings of infected fish or phosphate‐buffered saline. The fish were reared at natural water temperature and transferred to different tanks, and the water temperature was adjusted to 20°C after 6 weeks of inoculation. When the water temperature was increased to 20°C, the rCF decreased in the experimentally infected group. The results demonstrated that qPCR can be utilized to determine the relative abundance of E. leei in olive flounders and water temperature is an important factor to track the progress of the emaciation disease.     

Fisheries By-Catch and By-Product Meals as Protein Sources For Rainbow Trout Oncorhynchus mykiss

Abstract— Fisheries by-catch and by-product meals are portrayed as ingredients having a great potential as ingredients in aquaculture feeds. The present study was designed to evaluate the nutritional value of shrimp by-catch meal, shrimp processing waste meal, and two fish meals made from Pacific whiting (meal with and without solubles) for rainbow trout by determining apparent digestibilityof these ingredients and conducting a 12-wk feeding trial with juvenile fish (average initial weight 20 g/fish). Apparent digestibility coefficients (ADCs) for protein in diets containing by-catch and processing by-products were 76% for shrimp by-catch meal, 79% for shrimp processing waste meal, 88% for Pacific whiting meal without solubles, and 92% for Pacific whiting meal with solubles. ADCs for lipid were higher than 94% for all the diets. ADCs for energy were 57% for shrimp by-catch meal, 73% for shrimp processing waste meal, 70% for Pacific whiting meal without solubles, and 73% for Pacific whiting meal with solubles. Growth performance was significantly affected by dietary protein source. Fish fed the shrimp by-catch meal diet had weight gain and feed conversion ratios similar to that of fish fed the control diet with anchovy fish meal. Fish fed diets containing shrimp processing waste and Pacific whiting meal with solubles had significantly lower weight gain and higher feed conversion ratios than the control diet. Growth was significantly lower in fish fed the Pacific whiting meal diet compared to fish fed the anchovy fish meal. The lower growth of fish fed diets containing Pacific whiting meal appeared to be a result of lower feed intake, indicating perhaps a lower palatability of this ingredient. Additional research addressing processing methods, nutritional manipulations, and palatability enhancement is needed to improve potential of some fisheries byproduct meals as ingredients in the diets of rainbow trout.     

The nutritional properties of co-dried fish silage in rainbow trout (Salmo gairdneri) dry diets

Feed ingredients containing fish silage and liquefied fish made from ground, whole Pacific whiting and co-dried in a vacuum dryer with mixtures of soybean meal and feather meal to facilitate drying were prepared. An additional batch of fish silage was co-dried with the other dry ingredients in the diet formulation that was used, Abernathy diet S8-1. Fish meal, made by vacuum drying Pacific whiting, was used in the control diet. Co-dried fish meal was made by co-drying Pacific whiting with a soybean meal-feather meal mixture. Fish meal was entirely replaced by the co-dried products in the experimental diets, which were fed to rainbow trout (Salmo gairdneri) for 32 weeks. The best growth and food conversion values were obtained by feeding the fish meal control diet or the diet in which the fish meal was replaced with co-dried liquefied fish. No significant differences in final weights were found between trout fed diets containing co-dried fish meal or co-dried fish silage (fish products were 25% of the diet), but these fish were significantly smaller than fish fed the fish meal control or the co-dried liquefied fish diets. Reducing the fish silage to 12.5% or increasing it to 50% further reduced weight gains in the trout. Food conversion values, protein efficiency ratios, and net protein utilization values generally followed the same trends between diets as did the final weight values. Apparent digestibility coefficients for the co-dried products were lower than for the fish meal, possibly because they contained soybean meal-feather meal mixtures. Organoleptic properties of the fish were not affected by diet.     

First record of infection by Trypanosoma sp. of Colossoma macropomum (Serrasalmidae), a neotropical fish cultivated in the Brazilian Amazon

Fish farming has grown rapidly in Brazil over the last two decades, due in part to the availability of water and species with potential for cultivation, such as Colossoma macropomum. This farmed fish, however, can be affected by parasitic infections with high mortality rates (>35%). The main objective of the present study was to describe the first occurrence of the Trypanosoma species in Colossoma macropomum, which occurred in fish cultured in the Brazilian Amazon region, as well as to morphologically characterize the trypomastigotes and the impact of these hemoparasites on the body condition of the hosts. The trypanosomes found in the blood of Colossoma macropomum were morphologically characterized by the size of the trypomastigote form, indicating the presence of only one morphotype. Of the 39 hosts examined from one fish farming, 41.0% were infected by Trypanosoma sp., with low levels of infection (mean blood density of 3.7/μL). The condition factor of the asymptomatic hosts was not affected by hemoparasitism. There was no correlation between the abundance of Trypanosoma sp. and the condition factor and size of the hosts. Finally, our understanding of host-parasite interactions and the detection of emerging diseases are fundamental for aquaculture.     

Chemical and Organoleptic Comparison of Fish Sauce Made from Cold Water Species and Typical Thai Fish Sauce

ABSTRACT

Organoleptic and chemical properties of fish sauce made experimentally from the four cold water fish species–Arctic capelin, Atlantic herring, Atlantic cod and blue whiting–were compared with three first grade commercial fish sauces made from tropical anchovies. Although the flavor of the fish sauces made from cold water species were judged as inferior to the flavor of the tropical fish sauces, the blue whiting and Atlantic herring sauces obtained fair ranking. Chemical analyses revealed that sugar had been added in all the three commercial sauces. Although sugar is added during blending just before bottling, flavor enhancing chemical reactions, between amino groups and reducing sugars, probably occur during storage of the final product. Accordingly, this procedure should be adapted also in preparation of fish sauce from cold water species.     

Eimeria spp. from cyprinid fish of the Duero basin (north-west Spain)

Abstract. We describe three Eimeria spp. from extraintestinal sites of cyprinid fish of the Esla River; Eimeria leucisci from Barbus barbus bocagei, E. rutili from Leuciscus cephalus cabeda and Chondrostoma polylepis polyiepis and E. baueri sp. nov. from Carassius carassius . Data on the prevalence and intensity are given. Histopathological changes of the barbel kidney affected by E. leucisci are described. In the analysis of the population dynamics, a clear pattern of seasonality cannot be deduced. Influence of host age was clear only for E. leucisci in which the prevalence decreased significantly with the age of the barbel. We did not observe a clear influence of host sex on the infections.     

Atlantic salmon, Salmo salar L., previously infected with Neoparamoeba sp. are not resistant to re-infection and have suppressed phagocyte function

Previous studies have indicated that Atlantic salmon, Salmo salar L., affected by amoebic gill disease (AGD) are resistant to re‐infection. These observations were based upon a comparison of gross gill lesion abundance between previously infected and naïve control fish. Anecdotal evidence from Atlantic salmon farms in southern Tasmania suggests that previous infection does not protect against AGD as indicated by a lack of temporal change in freshwater bathing intervals. Experiments were conducted to determine if previous infection of Atlantic salmon with Neoparamoeba sp. would provide protection against challenge and elucidate the immunological basis of any protection. Atlantic salmon were infected with Neoparamoeba sp. for 12 days then treated with a 4‐h freshwater bath. Fish were separated into two groups and maintained in either sea water or fresh water for 6 weeks. Fish were then transferred to one tank with a naïve control group and challenged with Neoparamoeba sp. Fish kept in sea water had lower mortality rates compared with first time exposed and freshwater maintained fish, however, these data are believed to be biased by ongoing mortalities during the seawater maintenance phase. Phagocyte function decreased over exposure time and freshwater maintained fish demonstrated an increased ability to mount a specific immune response. These results suggest that under the challenge conditions herein described, antigen exposure via infection does not induce protection to subsequent AGD.     

A comparative study of the effects of high pressure on proteolytic degradation of sardine and blue whiting muscle

ABSTRACT:   High-pressure technology is used as an alternative to heat processing because of its inactivating effect on microorganisms and enzymes. However, it can also alter the structure of other muscle proteins. The present study compares the effects of high pressure (300 MPa, 7°C, 20 min) on the proteolytic degradation and alterations in the myofibrillar proteins of sardine and blue whiting muscle. Also, muscle homogenates and enzyme extracts were pressurized in order to evaluate the high-pressure effects on unprotected proteolytic enzymes outside the whole muscle structure. Peak proteolytic activity was found to occur at 55°C in both species. The peak activity pH was pH 3 for the sardine and pH 8 for the blue whiting; the main enzyme families being aspartic proteases in the former and alkaline serine proteases in the latter. Pressurization lowered activity levels at the peak activity pH and temperature in the fish muscle (by 30.8% in the sardine and by 9.5% in the blue whiting) and also slightly in the enzyme extracts (by 16.8% in the sardine and by 19.4% in the blue whiting). The electrophoretic profiles disclosed higher protein degradation in the pressurized muscle. Overall, the observed changes in proteolytic activity can be attributed not only to the effect of high pressure on the enzymes, but also and mainly, to the effect on other muscle proteins.     

Diet of demersal fish species in relation to aquaculture development in Scottish sea lochs

The diets of demersal fish, principally haddock (Melanogrammus aeglefinus), whiting (Merlangius merlangus) and several flatfish species, sampled from four Scottish sea lochs (Hourn, Kishorn, Duich and Nevis) which support aquaculture sites, were examined in order to determine whether the impact of aquaculture on benthic biodiversity would affect the diets of demersal fish. Loch Kishorn had the highest maximum planned aquaculture production, loch Nevis follows and lochs Hourn and Duich have the lowest planned production. Samples were collected from locations less than and more than 2000 m from fish farm cages. Fish close to the fish farm cages were on average of greater individual weight than those further away from fish farms. Haddock ate predominantly Malacostracan crustacea, Ophiurid echinoderms and Polychaete annelids; whiting ate predominantly Malacostracan crustacea and teleost fish and flatfish ate Malacostracan crustacea, Polychaete annelids and Ophiurid echinoderms. A small number of saithe sampled had eaten mainly fish farm pellets. Dietary variation in each species was analysed in relation to loch, proximity to aquaculture facilities and fish size. Diet of whiting varied with body size. Dietary differences were observed between the lochs and between sites close to and far from farms in two lochs although these differences cannot be specifically attributed to aquaculture development. Controlling for differences between individual lochs, proximity to aquaculture facilities did not consistently affect diet composition.     

Liver of the fish Gymnotus inaequilabiatus and nematode larvae infection: Histochemical features and expression of proliferative cell nuclear antigen

Histopathological lesions due to third‐larval stage of nematode Brevimulticaecum sp. within the liver of a subpopulation of 31 Gymnotus inaequilabiatus from the Pantanal Region (Brazil) were studied with histochemical and immunohistochemical methods. In 93.5% of fish, livers harboured nematode larvae and the intensity of infection ranged from 8 to 293. In livers with highest number of larvae, the hepatic tissue was occupied primarily by the nematodes. Each larva was encircled by focal inflammatory granulomatous reaction. Within the thickness of the granuloma, three concentric layers were recognized: an inner layer of densely packed epithelioid cells, a middle layer of mast cells (MCs) entrapped in a thin fibroblast‐connective mesh and an outer layer of fibrous connective tissue with fibroblasts. Epithelioid cells and fibroblasts within the thickness of the granuloma wall were positive for proliferative cell nuclear antigen (PCNA). Moreover, several hepatocytes in infected liver were immunoreactive to PCNA. Occurrence of rodlet cells and MCs in parenchyma, in close proximity to the encysted nematode larvae and near the blood vessel of infected liver, was observed. Macrophage aggregates (MAs) were numerous within the granulomas and scattered in parenchyma of the infected liver. High quantity of haemosiderin was encountered in MAs and hepatocytes of infected liver.     

Growth and performance of Atlantic salmon, Salmo salar L., following administration of a rhabdovirus DNA vaccine alone or concurrently with an oil-adjuvanted, polyvalent vaccine

This research demonstrates for the first time an absence of growth-related side effects in Atlantic salmon, Salmo salar L., following the injection of a DNA vaccine alone or concurrently with a commercially available, polyvalent, oil-adjuvanted vaccine. Using weight and specific growth rate measurements, individually tagged Atlantic salmon were monitored for 2028 degree days (dd) post-vaccination. During this time, DNA-vaccinated fish did not differ in weight, length, condition factor or specific growth rate compared to unvaccinated control fish. While differences in weight were observed between unvaccinated control and concurrently vaccinated fish, there were no significant differences in weight, length, condition factor or specific growth rate between concurrently vaccinated fish and adjuvant-vaccinated fish, suggesting that only adjuvant vaccination affected growth. To further determine if concurrent injection of a DNA vaccine and a polyvalent, oil-adjuvanted vaccine had a physiological impact on the Atlantic salmon, swimming performance tests were performed at 106 dd post-vaccination with U _crit,1, U _crit,2, the U _crit recovery ratio (RR) and the normalized RR being similar to values obtained from unvaccinated control fish. In summary, this study shows that concurrent injection of a DNA vaccine and a polyvalent, oil-adjuvanted vaccine does not negatively influence the growth or swimming performance of Atlantic salmon compared to adjuvant vaccination alone.     

Changes in the innate immune response of Atlantic salmon, Salmo salar L., exposed to experimental infection with Neoparamoeba sp

An experiment was conducted to determine the effect of Neoparamoeba sp. infection on the innate immune responses of Atlantic salmon. Atlantic salmon were experimentally infected with Neoparamoeba sp. and serially sampled 0, 1, 4, 6, 8 and 11 days post-exposure (dpe). Histological analysis of infected fish gill arches identified the presence of characteristic amoebic gill disease lesions as early as 1 dpe with a steady increase in the number of affected gill filaments over time. Immune parameters investigated were anterior kidney phagocyte function (respiratory burst, chemotaxis and phagocytosis) and total plasma protein and lysozyme. In comparison with non-exposed control fish basal respiratory burst responses were suppressed at 8 and 11 dpe, while phorbol myristate acetate-stimulated activity was significantly suppressed at 11 dpe. Variable differences in phagocytic activity and phagocytic rate following infection were identified. There was an increase in the chemotactic response of anterior kidney macrophages isolated from exposed fish relative to control fish at 8 dpe. Total protein and lysozyme levels were not affected by Neoparamoeba sp. exposure.     

Effect of Dietary Inclusion of Blue Mussel Extract on Growth and Body Composition of Japanese Flounder Paralichthys olivaceus

Dietary inclusion of a water-soluble fraction of blue mussel Mytilus galloprovincialis was examined as a feeding stimulant for juvenile Japanese flounder Paralichthys olivaceus . The control diet mainly consisted of fish meal, potato starch, and pollack liver oil. Five, 10, and 20% (weight/weight) of the control diet was exchanged with aqueous extracts of blue mussel meat in experimental groups. Fish of about 10 g in initial body weight were fed each diet to satiation, twice daily, 6 d per wk for 6 wk at 20 C. The final body weight, weight gain, and feed efficiency of fish fed the diets containing blue mussel extracts were significantly higher than those of fish fed the control diet. However, these parameters were not different among experimental groups containing blue mussel extract independent of the inclusion level of extract. A similar trend was shown in protein efficiency ratio as fish fed the control diet had a significantly lower protein efficiency ratio than the other dietary groups. Compared to the control diet, higher plasma protein and lower triglyceride were found in fish fed the diets with the extract, while other blood constituents were relatively similar for the dietary groups tested. On the other hand, whole-body crude lipid content and lipid retention of fish fed the diets with the extract were generally significantly higher than those of fish fed the control diet. Whole body crude protein was identical regardless of the dietary composition; however, protein retention of fish showed a similar trend to lipid retention.