Showing papers in "Journal of Applied Ichthyology in 1985"

Novel gene transfer into the fertilized eggs of gold fish (Carassius auratus L. 1758)

Abstract: Summary Novel gene which was microinjected into fertilized eggs of the goldfish replicated during the embryogenesis A proportion of the novel gene has been integrated into the host DNS of the 50-day-old transgenic goldfish

Piscivory and the development of bimodality in the size distribution of 0+ pikeperch (Stizostedion lucioperca L.)

Abstract: Summary During an eight years period the onset and development of piscivory of 0+ pikeperch was studied in the natural environment of a shallow, eutrophic Dutch lake. In some years the piscivory started as early as halfway June at a pikeperch size of circa 20 mm. The 0+ pikeperch predated mainly on the smaller 0+ smelt because these were the most slender preyfish available. The 0+ pikeperch is less and the 0+ perch is much less available because of their larger circumference. Small 0+ bream and roach became only available when their growth was retarded. The positively skewed size distribution of the 0+ pikeperch halfway June is precursory for the development of bimodality in the size distribution later in the season. A second modus of larger, piscivorous, 0+ pikeperch became relatively important in years when smelt was abundant. The survival rate of this category was appearantly higher than that of the smaller planktivorous individuals.

Feeding behaviour of major 0 + fish species in a shallow, eutrophic lake (Tjeukemeer, The Netherlands)

Abstract: Summary The forage base and the food selectivity of 0+ representatives of six abundant freshwater fish species were studied in a shallow, eutrophic Dutch lake. Most species relied on the zooplankton; the size-selective predation in early summer was directed to the smaller copepods and in late summer to larger cladocerans and copepods than concurrently present in the lake. Daphnia spp. and cyclopoid copepods were the main zooplankton taxa for smelt, perch and pikeperch. Energetically, the large cladoceran, Leptodora kindtii, was especially important for pikeperch. Bream and roach preyed upon smaller zooplankton than the other fish species. The influence of the zooplankton predation by abundant 0+ fish was clear from a small mean Daphnia size in September; this size is to be used as an indicator in fishery management. Neomysis integer, the most important macrofauna species, was consumed by perch, pikeperch and ruffe; pikeperch was most size-selective in this respect. The 0+ ruffe was a typically benthivorous fish. Only the 0+ pikeperch became piscivorous, especially in years when smelt was abundant.

The growth of juvenile flounders (Platichthys flesus L.) at salinities of 0, 5, 15 and 35%%

Abstract: Summary Growth and food intake of juvenile flounders from the Kiel Bight were measured experimentally at different salinities (0, 5, 15 and 35 %). The growth at the middle levels (5 and 15 %) was faster then at 0 and 35 %. The reason for lower rates of increase in the freshwater group is the lower food intake. In the 35 % group the slower growth is caused by the worse food conversion. The variance of the individual growth rates in the 15 % salinity group remains far below the values of all other groups.

Cod migration and transplantation experiments in the Baltic

Abstract: Summary In the first half of the paper a review is given of the occurrence and migratory habits of Baltic cod based on experience since the 1950s, results of extensive tagging experiments combined with information on changes in allele frequency for haemoglobin types, in meristic characters, and in otolith types. The latter pan of the paper is an account of about 15 transplantation experiments with tagged cod to study a potential homing ability of the fish. The very great importance of the threshold areas inside the Baltic and out to the Kattegat is stressed, and so are the hydrographic conditions in general for cod recruitment and migration. The waters west of Bornholm constitute an area of hydrographic instability with varying cod migrations and passive transport of fry with the currents. The migration east of Bornholm refers—except for local stocks and a varying contribution from the west-mainly to fish grown up in the central Baltic proper and northern areas. The latter fish migrate primarily southward for spawning, and as adults they usually stay in the southern waters east and north of Bornholm. The results of the transplantation experiments support a strong direct linkage of cod migration and hydrographic factors. Cod that were tagged and transplanted to a new area behaved and moved in the same way as the local stock. Indications of “homing” can be found in areas with suitable hydrographic gradients, such as changes in salinity, for example in the Oresund.

The influence of temperature on the growth of the European catfish (Silurus glanis L.)

Abstract: Summary The influence of temperature on growth, feed conversion, and protein and gross energy utilization was assessed in two experiments using the European catfish, Silurus glanis L. Animals of 55 g and 24 g were used in trials lasting 6 and 7 weeks, respectively. The optimum temperature for growth was within the range of 25 to 28°C, with the best results obtained at 27°C. Using a feed of low protein content (30.3%), a feed conversion of 1.67 was achieved at a specific growth rate of 1.78% of body weight/day.

The Representative Research Animal: Why Rainbow Trout (Salmo gairdneri Rich.)?

Abstract: Summary In laboratory research, the rainbow trout has become a counterpart to the white rat, because that fish is an adaptable species available in much of the developed world and stocks from egg through adult are available throughout the year. Moreover, many strains are recognized, and their propagation and laboratory maintenance are not particularly demanding. Also, knowledge of rainbow trout nutrition, husbandry, diseases, immune responses, toxicology, and carcinogenesis exceeds that of any other salmonid or coldwater teleost. The rainbow trout is the logical surrogate species in many studies of other salmonids.

Viral infection cycles in pike (Esox lucius L.).

Abstract: Summary Pike fry weighing 0.2 g were infected with five pathogenic viruses via the water and then fed to one-year-old, 60 g pike. A transer of the viruses from the prey to the predator was demonstrated. The VHS virus produced typical hermorrhages in the muscle of the second nost. Zusammenfassung Zyklische Virusinfektion beim Hecht (Esox lucius L.) Auf dem Wasserweg mit funf fischpathogenen Viren infizierte Hechtbrut (0,2 g) diente einjahrigen Hechten (60 g) als Nahrungsquelle und gewahrleistete hierdurch den Virustransfer. Das VHS-Virus induzierte im 2. Wirt typische Hamorrhagien in der Muskulatur. Resume Cycles d'infection viraie chez le brocket (Esox lucius L.) Des embryons du brochet (0,2 g) infices par l'eau servaient comme nourriture pour des brochets ages un an (60 g). Par cela le transfer du virus etait verifie. Le virus VHS causait dans l'hote seconde des hemorrhages typiques dans les muscles.

Review on the effects of pollution on marine fish life and fisheries in the North Sea

Abstract: Summary Information on possible effects of pollution on fish life is reviewed with special emphasis to the North Sea. Concentrations of heavy metals are high in onshore waters, sediments and organisms. Offshore regions are considered to be not endangered. In estuaries concentrations of certain heavy metals are often surpassing thresholds, which have been experimentally demonstrated to produce sublethal effects on marine organisms. Also mussel culture areas had to be closed due to excess of cadmium contamination. Mercury in fillets of cod in the southern North Sea sometimes reaches 0.3 ppm representing 1/3 of the legal limit. Reductions of inputs are necessary due to the bioaccumulative and toxic potential of heavy metals. Organochlorine contamination of water, sediments and organisms is higher in the southern than in the northern North Sea. In offshore areas clearly elevated levels of PCB's, which are the dominating organochlorine compound in marine organisms, have been analyzed. At present only a minor fraction of total organochlorine residues accumulated in marine biota is analyzed. Margins between experimentally derived lethal levels and those occurring in marine biota are narrow suggesting that sublethal effects might occur. One of the special concerns in the context of organochlorine contamination has to be seen in the potential of these substances affecting the reproductive capacity of marine organisms. Reduction measures are urgently necessary and should include substances with bioaccumulative and toxicological potential, which are not presently included in Marine Monitoring Programmes. Impact of oil pollution is considered to be a regional problem, although especially in estuaries concentrations in the water column might be high. Input through oil platforms has led to local reductions in benthic communities. Measures have to be taken, to further reduce these inputs also in view to avoid contamination of fish in the vicinity of oil fields. Oxygen depletion in German and Danish coastal waters has been shown to be a severe degradation in coastal water quality resulting in significant impact on fish populations. Indications for large-scale avoidance reactions of low DO-areas and mortalities of fish and benthos organisms have been demonstrated. It is suspected that the low DO-situations are related to increased nutrients input and high phytoplankton production. Improvement of the situation can only be expected, if input of nutrients is reduced. Reasons for the occurrence of toxic plankton blooms are not understood. An intensified research is necessary, to avoid damage to fisheries and mariculture. Although activity of radionucleids in North Sea waters is increased due to input of radioactive material from La Hague and Sellafield reprocessing units, the present levels of activity are not considered to be a threat for marine life. The same holds for thermal pollution, which is, depending on the recipient area, expected to have only local effects. Sewage sludge dumping and discharge of untreated sewage introduce significant amounts of accompanying heavy metals, which can be expected to have a negative influence on the total metal budget of recipient waters. Nutrient input through sewage will exhibit only local effects. Dumping of wastes from titanium dioxide industry are suspected to be causally linked to the occurrence of increased prevalences of certain diseases of dab in the German Bight. Present management strategies should take account of the fact that through dumping of waste from titanium dioxide production significant quantities of heavy metal are introduced into the southern North Sea. Also the incineration of chemical wastes at sea should be reduced due to uncertainties concerning quantities and toxicity of incineration products and their potential impact on marine life. It is concluded that clear evidence exists for pollution impact in estuarine regions. Most of the major estuaries at the North Sea coast show benthos reductions, which can be related to water quality and it has to be assumed that areas of a sublethal effect are located in the vicinity of those areas of well demonstrated effects. They are of unknown size and attempts have to be undertaken to quantify areas of sublethal impact. The occurrence of fish diseases is interpreted as an expression of degraded water quality. Some of the diseases detected can produce mortality, thereby having an as yet unquantified impact on fish populations. The presence of fish diseases also reduces the marketability of catches. It cannot be excluded that changes in species composition of fish populations in German Wadden Sea areas are related to pollution. Concentrations of organochlorine substances in fishes of the southern North Sea give rise to the concern that their reproductive capability might be impaired. Future work has to be directed to this problem. Impact of pollution on populations of marine organisms has so far not been demonstrated.

Influence of water‐borne iron on the liver of Poecilia reticulata (Peters 1859)

Abstract: Summary The influence of water-borne iron (500 μg × 1-1 and 2 mg × 1-1) on the liver of Poecilia reticulata is studied by means of electron microscopy. The uptake and effect of iron is affected by a. the chemical speciation of the metal: Iron complexed with tri-polyphosphates is more deleterious than inorganic Fe3+; b. the nutritional status of the fish: In food-deprived Poecilia reticulata iron is absorbed and enhances starvation-induced liver damage. In fed animals, there is no uptake at all. Mild alterations of hepatocyte ultrastructure are attributed to an unspecific stress response.

Resistance of the European catfish (Silurus glanis) to channel catfish virus

Abstract: Summary European catfish (Silurus glanis) fingerlings (2 to 4 g each) were tested for susceptibility to channel catfish virus (CCV). They had supported CCV replication at 2 days after intraperitoneal injection with 0.1 ml of saline containing 105 TCID50. Homogenized visceral organs (liver, kidney and spleen) contained 104 TCID50/0.1 ml at 2 days post inoculation (PI) but at 4 days the titer decreased to 101 TCID50. Bathing European catfish in CCV yielded only one positive sample with a titer of 100.83 TCID50 per 0.1 ml of tissue. No clinical signs of CCV developed and no virus related deaths occurred.

The cultivation of marine amphipods and their use as food for young Salmonids

Abstract: Summary Populations of the amphipod, Anisogammarus pugettensis (Dana) 1853, can be raised for several generations under laboratory conditions. Compared with the growth of another amphipod, Eogammarus confervicolus Stimpson 1856, A. pugettensis grew more rapidly to maximum biomass and reached a new generation earlier when both were grown under their optimal growth conditions. A. pugettensis grew faster in upwelled impoundments containing epiphytic diatoms than under laboratory conditions. In fish feeding studies, the amphipod E. confervicolus is an adequate diet for salmonid growth when compared with Oregon moist pellets.

Enzym‐elektrophoretische Untersuchung zur Artunterscheidung von Blaufelchen (Coregonus lavaretus wartmanni Bloch): und Gangfischen (Coregonus lavaretus macrophthalmus Nüsslin) aus dem Bodensee‐Obersee, Bundesrepublik Deutschland

Abstract: Summary Enzym-electrophoretic examination for species identification of wbitefish (Coregonus lavaretus wartmanni Bloch and C.l. macrophthalmus Nusslin) of the upper pan of Lake Constance, Federal Republic of Germany

Histopathological changes due to infections with Cryptobia iubilans Nohýnková 1984, in two cichlid fishes

Abstract: Summary Histopathological study of infections with Cryptobia iubilans Nohýnkova 1984 in two species of freshwater aquarium cichlids (Herichthys cyanoguttatum and Cichlasoma meeki) revealed severe tissue changes which were not limited to the digestive tract but also affected other principal body organs. The lesions were extensive enough to cause mortalities C. iubilans is thus far the only clearly pathogenic species among cryptobias infecting fish.

The distribution of connective tissue content in swimming muscle of cod (Gadus morbua)

Abstract: Summary The amount and distribution of connective tissue in the swimming muscle of cod (Gadus morhua) have been determined. By biochemical analysis, the collagen was found to make up 1,5 % of the total protein content. Measured by light microscopical morphometric analysis, the areal fraction of the connective tissue elements was found to be 3,0 % of the total muscle area. The areal fraction of myocommatal connective tissue mentioned above was found to be 2.3 %. The thickness of the endomysial sheath was calculated by morphometry based on electron microscopy, and was found to be 0.30 and 0.16 μ for red and white fibres, respectively. The areal fraction of the endomysial sheaths was 2.3 % in red muscle and 0.5% in white muscle. The endomysial sheaths make up 25% of the total connective tissue in the swimming muscles. These sheaths influence the binding properties of fish muscle products.

Murine monoklonale Antikörper gegen Vibrio anguillarum vom Serotyp I und II

Abstract: Summary Murine monoclonal antibodies against Vibrio anguillarum serotype I und II Four stabil hybridoma cell lines against the Vibrio anguillarum strain 820/15/8 Kopenhagen—a typical serotype I strain—were raised. Three hybridoma cell lines producing monoclonal antibodies against the Vibrio anguillarum strain 134/82/1 Kiel (Serotype II) were established. The specifity of the antibodies was screened by ELISA. Monoclonal antibodies reacted with the characteristic determinant of the respective serotype only.

Differential Mortality Rates of Fin-Clipped and Carlin-Tagged Roach (Rutilus rutilus L.)

Abstract: Summary Roach were marked by fin-clipping (N= 15888) or tagged with Carlin-tags (N= 1476) during their spawning migration in two tributaries to Lake Arungen, Norway, in 1980. A total of 1746 of these roach were recaptured during spawning in 1981. The recapture rate of fin-clipped roach was significantly higher than the recapture rate of Carlin-tagged roach, probably due to differential mortality rates.