Concentrations of leucine aminoaphthylamidase (LAN) and soluble protein in tissues of rainbow trout, Salmo gairdneri
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Erythroid cells in chum salmon ( Oncorhynchus keta ) susceptible to infection with erythrocytic necrosis virus (ENV) were examined by light and electron microscopy. Cells of stages II, III, IV, V, and VI contained complete eyrthrocytic necrosis virions in the cytoplasm. Viruses closely resembling ENV were also detected in the nuclei of some erythroblasts. Some secondary consequences of ENV infection were a threefold greater mortality rate from vibriosis, a significantly decreased tolerance to oxygen depletion, and a decreased ability to regulate serum sodium and potassium in saltwater.
Larvicides are used to control sea lamprey ( Petromyzon marinus ) in the Great Lakes. These larvicides are useful because they are more toxic to sea lamprey than fish species found in the same habitat. The lampricides come from two classes of chemical compounds: (1) halonitrophenols, and (2) halonitrosalicylanilides. Selectivity of the larvicides appears to be based on the differences in the ability of sea lamprey larvae and fishes to detoxify and/or excrete the chemicals. Glucuronide conjugation is an important mechanism for detoxification of these larvicides by fish, and selectivity of larvicides may be due to differences in glucuronyl transferase activity between lamprey and fishes. If more detailed information were available on uptake, metabolism, excretion, and the biochemistry and physiology of lamprey as compared to fishes, it might be possible to design chemicals that would be more selective than those now in use.
The sterility method of pest control could be an effective tool in the sea lamprey ( Petromyzon marinus ) control program in the Great Lakes. Some of the requirements for its successful application have been met. A field study demonstrated that the release of male sea lampreys, sterilized by the injection of 100 mg/kg of P , P -bis(1-aziridinyl)- N -methylphosphinothioic amide (bisazir), will reduce the number of viable larvae produced. The actual reduction in reproductive success that occurred was directly related to the ratio of sterile to normal males in the population. The technique can be used in many ways in an integrated control program and has considerable potential for the more effective control of the sea lamprey. Eradication is a distinct possibility. Key words : sea lamprey, Petromyzon marinus ; pest control, fish control, sterile-male technique, sterilization, chemosterilants, bisazir, Great Lakes
Laboratory-produced progeny of Coregonus alpenae , C . zenithicus , C . hoyi , and C . kiyi and their wild parents were used to examine the contributions of genotype and environment to morphology. Morphological differences between parents and offspring were generally greater than those between species, indicating strong environmental effects. The phenotypic effects on most characters can probably be attributed to different developmental temperatures and perhaps to stresses in the hatchery not encountered in the Great Lakes. Genetic differences were inferred from morphological differences between offspring of different species raised under identical conditions. Genetic differences were demonstrated between C . hoyi and C . kiyi but not between C . alpenae and C . zenithicus which suggested that our samples of C . alpenae and C . zenithicus represented only a single species. The presence of unique stocks of coregonines in the Great Lakes, as well as of several species, suggests that management strategies should focus on both levels of diversity. Key words : Salmonidae, Coregoninae, Coregonus , morphology, Great Lakes, development, stocks
The relationship between body size and concentrations of Cu and Ag varied from strongly positive to strongly negative in four populations of the bivalve Macoma balthica in San Francisco Bay. The correlations appeared to be influenced by the degree of enrichment in tissues, size-dependent differences and seasonal variations in growth rate, and size-dependent differences in uptake rates. The use of benthic indicator organisms to assess metal contamination requires understanding the relationship between metal concentration and body size at least within each population, and in some cases within each sample from each population.
Groups of sea lamprey ( Petromyzon marinus ) eggs fertilized by males previously immersed in an aqueous solution of p , p -bis(1-aziridinyl)- N -methylphosphinothioic amide (bisazir) at concentrations of 10–100 mg/L produced fewer normal, live prolarvae after 15–17 d of incubation than did groups of eggs fertilized by normal males. Mortality of embryos or prolarvae was nearly 100% in groups of eggs fertilized by males that had been immersed in a 50 mg/L solution of bisazir for 4 h or in a 100 mg/L solution for 2 h. The immersion technique appears to be an efficient method of sterilizing large numbers of male sea lampreys for use in a proposed sterile-male-release program. Key words : sea lamprey, Petromyzon marinus ; pest control, fish control, sterile-male technique, sterilization, chemosterilants, bisazir, Great Lakes
Starch gel electrophoresis was used as a means of recognizing species and stocks in Lake Superior Coregonus . Allelic variability at isocitrate dehydrogenase and glycerol-3-phosphate dehydrogenase loci was recorded for samples of lake herring ( Coregonus artedii ), bloater ( C. hoyi ), kiyi ( C. kiyi ), and shortjaw cisco ( C. zenithicus ) from five Lake Superior localities. The observed frequencies of genotypes within each subsample did not differ significantly from those expected on the basis of random mating, and suggested that each subsample represented either a random sample from a larger randomly mating population or an independent and isolated subpopulation within which mating was random. Significant contingency X 2 values for comparisons between both localities and species suggested that more than one randomly mating population occurred among the Lake Superior ciscoes, but did not reveal how many such populations there were. In contrast to the genetic results of this study, morphology seems to be a better descriptor of cisco stocks, and identification of cisco stocks and species will still have to be based on morphological criteria until more data are forthcoming. Where several species are sympatric, management should strive to preserve the least abundant. Failure to do so could result in the extinction or depletion of the rarer forms.
Annual harvests of lake herring ( Coregonus artedii ) in American waters of Lake Superior declined from an average of 2 million kg in 1936–62 to less than 25 000 kg in 1978. Analysis of commercial fishing records revealed that the sequential overexploitation of discrete unit stocks caused the collapse of the herring population in Wisconsin waters. In each of six major spawning areas, catch exceeded the productive capacity of the stock and the stock failed. Because stocks in the six areas were exploited sequentially, mostly in groups of two or three simultaneously, the demise of the stocks was not readily apparent until the last two failed in the early 1960s. After the collapse of the last major spawning stock, the fishery dwindled but may have continued to overexploit the remaining small stocks. The residual populations were apparently able only to replace themselves. Some form of density-independent mortality was apparently operating to prevent their recovery during the 1960s and 1970s. Key words : lake herring, overfishing, Lake Superior
The high-performance liquid-chromatography (HPLC) procedure requires only minutes per sample, is specific, and is relatively sensitive (limit of detection < 0.005 mg/L for both chemicals). A combined buffer (pH 4) and internal standard (3-chlorodiphenylamine) reagent is added to the water sample, which is injected through a Sep Pak C 18 disposable cartridge. The cartridge adsorbs and retains both the lampricides and the internal standard. The quantitative elution of the three chemicals from the cartridge with a small volume of methanol effectively concentrates the sample and provides sample cleanup. The methanol extract is then analyzed directly by HPLC on an MCH 10 reverse phase column by using a methanol:0.01 mol/L acetate buffer (87:13, v:v) as the mobile phase at 2 mL/min and detected by ultraviolet spectrophotometry at 330 (or 254) nm. A microprocessor data system further facilitates the procedure by quantifying off-scale peaks and yielding results directly in units of concentration (mg/L).
The concentration of infectious hematopoietic necrosis (IHN) virus was determined in eight organs and two body fluids from each of 60 adult sockeye salmon ( Oncorhynchus nerka ). Included in the sample were 4 males and 56 prespawning, spawning, or spent female fish. All fish were infected, and virus was present in nearly all organs. There was an overall tendency for the mean concentration to increase in many of the organs over time as the fish progressed in ripeness. In prespawning females, IHN virus could be detected in all organs and in ovarian fluid but not in serum; the incidences were highest in the gills, spleen, and pyloric ceca, and the titers were highest in the pyloric ceca and liver. Incidences of infection in the organs were higher in spawning than in prespawning females and higher still in spent females in which the incidence of virus was 100% in all organs except brains (78%) and sera (67%). Virus concentrations in organs or fluids ranged from 5 to 4.0 × 10 9 plaque-forming units per millilitre. In males, the highest incidences of virus were found in gills, pyloric ceca, and liver. The gills were the only organ in which the virus concentration in males exceeded that of females. Key words : infectious hematopoietic necrosis, IHN, fish virus, viral pathogenesis, sockeye salmon
Infectious hematopoietic necrosis virus caused mortality of sockeye salmon ( Oncorhynchus nerka ) in streamside egg incubation boxes. Virus was not detectable in eggs or alevins; its first isolation coincided with the appearance of dead fish in a trap on the outflow from the box. Mortality due to the virus did not occur in every egg box studied. However, when fry from the boxes were held in the laboratory, epizootics began as much as 3 wk later, with total mortality exceeding 90%. More than 96% of the dead fry had titers exceeding 10 5 plaque-forming units per gram. The peak incidence of virus in fry migrating in the river coincided with the arrival of hatchery-produced fry, although some fry believed to have been produced by natural spawning were also infected.Englis
Review of: Microbial Diseases of Fish. Edited by R.J. Roberts, Special Publication No. 9 of the Society for General Microbiology. Academic Press, London. 1982. 305 p. $40.50 (U.S.).
The activity of the erythrocyte enzyme δ-aminolevulinic acid dehydratase (ALA-D) was measured in 35 catostomids (black redhorse, Moxostoma duquesnei ; golden redhorse, M . erythrurum ; northern hogsucker, Hypentelium nigricans ) collected from three sites on a stream contaminated with Pb-, Cd-, and Zn-rich mine tailings and from an uncontaminated site upstream. Enzyme activity was expressed in terms of hemoglobin (Hb), DNA, and protein concentrations; these variables can be determined in the laboratory on once-frozen blood samples. Concentrations of Pb and Zn in blood and of Pb in edible tissues were significantly higher, and ALA-D activity was significantly lower, at all three contaminated sites than upstream. At the most contaminated site, ALA-D activity was 62–67% lower than upstream. Lead concentrations in the edible tissues and in blood were positively correlated ( r = 0.80), whereas ALA-D activity was negatively correlated with Pb in blood ( r = −0.70) and in edible tissues ( r = −0.59). Five statistically significant relations between Pb and Zn in blood and ALA-D activity were determined. The two models that explained the highest percentage (> 74%) of the total variance also included factors related to Hb concentration. All five significant models included negative coefficients for variables that represented Pb in blood and positive coefficients for Zn in blood. The ALA-D assay with results standardized to Hb concentration represents an expedient alternative to the more traditional hematocrit standardization, and the measurement of ALA-D activity by this method can be used to document exposure of fish to environmental Pb.
We used a mass balance equation relating total mortality of age II and older alewives ( Alosa pseudoharengus ) to their removals by predatory fish and other sources of mortality as the basis for estimating that the forage base in Lake Michigan could support an additional 13 000 to 21 000  t of lake trout ( Salvelinus namaycush ) or a total lake trout biomass between 15 000 and 23 000  t . This biomass estimate is projected with biomasses of other trout and salmon held at 1979 levels. Major premises of this approach are that (1) the sustained availability of age II and older alewives to salmonines will ultimately limit the expansion of salmonine stocks, (2) the alewife population was oscillating without trend during 1973–80, and (3) additional limited predation on alewives would be compensated by a reduction in natural mortality caused by physiological stress and disease.
From 1979 to 1982,188 chinook salmon ( Oncorhynchus tshawytscha ) were tagged with radio transmitters to locate spawning areas in the glacial Kenai River, southcentral Alaska. Results confirmed that an early run entered the river in May and June and spawned in tributaries, and a late run entered the river from late June through August and spawned in the main stem. Spawning peaked during August in tributaries influenced by lakes, but during July in other tributaries. Lakes may have increased fall and winter temperatures of downstream waters, enabling successful reproduction for later spawning fish within these tributaries. This hypothesis assumes that hatching and emergence can be completed in a shorter time in lake-influenced waters. The time of upstream migration and spawning (mid- to late August) of the late run is unique among chinook stocks in Cook Inlet. This behavior may have developed only because two large lakes (Kenai and Skilak) directly influence the main-stem Kenai River. If run timing is genetically controlled, and if the various components of the two runs are isolated stocks that have adapted to predictable stream temperatures, there are implications for stock transplantation programs and for any activities of man that alter stream temperatures.
This volume is composed of 24 papers presented at an International Seminar on Fish Health Problems held 23–27 June 1981 at Szarvas, Hungary.