On a trypanosome from the Atlantic cod, Gadus morhua L.

1972 ◽  
Vol 50 (7) ◽  
pp. 1051-1054 ◽  
Author(s):  
R. A. Khan
Keyword(s):  
New Zealand ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Infected Fish ◽  
Tautogolabrus Adspersus ◽  
Pseudopleuronectes Americanus ◽  
Blood Samples ◽  
Limanda Ferruginea

Trypanosomes were found in 145 (24%) of 610 Atlantic cod, Gadus morhua L., following examination of centrifuged blood samples. The smallest infected fish measured 26 cm. Generally, parasitemias were higher in cod 26–35 cm long than in larger fish, but were more prevalent among fish 56–70 cm. The parasite could not be transmitted experimentally to Pseudopleuronectes americanus, Myoxocephalus octodecemspinosus, M. scorpius, Tautogolabrus adspersus, or Limanda ferruginea, but uninfected cod were susceptible. The trypanosome appears distinct from Trypanosoma coelorhynchi Laird, 1951 from gadiform fishes in New Zealand waters. It is tentatively identified as T. murmanensis Nikitin, 1927 reported from the same host, G. morhua, captured at Murmansk, U.S.S.R.

Pathogenesis of Trypanosoma murmanensis in marine fish of the northwestern Atlantic following experimental transmission

1985 ◽  
Vol 63 (9) ◽  
pp. 2141-2144 ◽  
Author(s):  
R. A. Khan
Keyword(s):  
Marine Fish ◽  
Gadus Morhua ◽  
Condition Factor ◽  
Atlantic Cod ◽  
Infected Fish ◽  
Pathological Feature ◽  
Pseudopleuronectes Americanus ◽  
Potential Pathogen ◽  
Myoxocephalus Scorpius ◽  
Hemopoietic System

The susceptibility of four species of marine fish (Gadus morhua, Pseudopleuronectes americanus, Myoxocephalus scorpius, and Myoxocephalus octodecemspinosus) to leech-transmitted Trypanosoma murmanensis was assessed 49–60 days after infection by comparing condition factor, organ somatic indices, parasitological, hematological, and histological findings with corresponding uninfected animals. The fish were maintained at temperatures (0–1 °C) to simulate the environment where transmission occurs naturally. High mortality occurred in juvenile Atlantic cod and winter flounder, but deaths decreased with increasing fish size. No adult fish died except flounder when fin rot was present. Anemia was the most common pathological feature observed in young fish at necropsy, but its severity was not always correlated with the level of parasitemia. The persistent anemia was probably associated with an inactive rather than an impaired hemopoietic system. Condition factor and somatic indices of liver, spleen, and heart were altered in some infected fish groups. It is concluded that T. murmanensis is a potential pathogen, especially to juvenile American plaice, Hippoglossoides platessoides, in which high prevalences of natural infections have been observed in some areas of the northwestern Atlantic Ocean.

Experimental Infection and Pathogenesis of Viral Erythrocytic Necrosis (VEN) in Atlantic Cod, Gadus morhua

1986 ◽  
Vol 43 (5) ◽  
pp. 945-951 ◽  
Author(s):  
Paul W. Reno ◽  
Katherine Kleftis ◽  
Stuart W. Sherburne ◽  
Bruce L. Nicholson
Keyword(s):  
Infection Rate ◽  
Experimental Infection ◽  
Temporal Pattern ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Infected Fish

Mature Atlantic cod (Gadus morhua) were experimentally infected with viral erythrocytic necrosis (VEN) by inoculation with washed erythrocytes or ceil-free homogenates of erythrocytes from naturally infected fish. Approximately one third of the animals exposed exhibited active infections. The temporal pattern of infection was similar between naturally infected and experimentally infected fish. One to two months after infection, immature erythrocytes began to show clear evidence of VEN followed by a rapid increase in the proportion of infected immature erythrocytes, frequently reaching 100%. A subsequent dramatic drop in infection of immature erythrocytes occurred, coinciding with an increase of infection in mature erythrocytes. Significant erythroblastosis occurred when the overall erythrocyte infection rate reached approximately 10%, but none of the newly generated erythrocytes appeared infected. The peak infection rate (40–60% of erythrocytes infected) declined slowly and the infection, in most instances, was completely resolved.

The leech as a vector of a fish piroplasm

1980 ◽  
Vol 58 (9) ◽  
pp. 1631-1637 ◽  
Author(s):  
R. A. Khan
Keyword(s):  
Marine Fish ◽  
Blood Meal ◽  
Gadus Morhua ◽  
Infected Fish ◽  
Binary Fission ◽  
Gut Contents ◽  
Pseudopleuronectes Americanus ◽  
Infected Blood ◽  
Fish Blood ◽  
Anarhichas Lupus

A piroplasm, Haemohormidium beckeri, is redescribed from two marine fish, Lycodes lavalaei and Lycodes vahlii (Zoarcidae). The parasite divided by both binary fission and schizogony. In the latter process, up to eight merozoites were produced and these developed within mature erythrocytes. Infections were prevalent among fish from areas off the Labrador coast. Parasitemias, which varied from light infections to estimates of 60 parasites/1000 erythrocytes, were recorded in 15 fish for about 6 months. Subinoculation of infected blood initiated infections in two perciform fish, Myoxocephalus octodecemspinosus and Anarhichas lupus, but not in a pleuronectiform, Pseudopleuronectes americanus, or a gadiform, Gadus morhua. Natural infections were present in three leeches, Platybdella olriki, that had fed on an infected L. lavalaei. Piroplasms were also observed in the gastrointestinal content of all 94 laboratory-reared leeches, Johanssonia arctica, dissected 7 through 109 days after engorgement on infected fish blood. Inoculations of gut contents from leeches after digestion of a blood meal produced infections in uninfected fish. Natural transmission occurred when leeches were fed again on susceptible fish, whereas pipetting entire leeches into the stomach of fish did not initiate infections. This is the first evidence that leeches transmit piroplasms in nature to fish.

Marine Fish Tissue Culture

1963 ◽  
Vol 20 (3) ◽  
pp. 679-684 ◽  
Author(s):  
P. M. Townsley ◽  
H. G. Wight ◽  
M. A. Scott
Keyword(s):  
Tissue Culture ◽  
Marine Fish ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
White Perch ◽  
Kidney Tissue ◽  
Fish Tissue ◽  
Pseudopleuronectes Americanus ◽  
Myoxocephalus Scorpius ◽  
Raja Radiata

Cell proliferation of tissue explants of different organs from marine fish has been achieved in a nutrient solution composed of Medium 199 plus 10% human serum. Fin, spleen, heart, kidney, liver, gonad, brain, uterus, and thymus tissues have been cultured. The tissues were obtained from sexually mature Atlantic cod (Gadus morhua), white perch (Roccus americanus) winter flounder (Pseudopleuronectes americanus), thorny skate (Raja radiata), American goosefish (Lophius americanus), pollock (Pollachius virens), and shorthorn sculpin (Myoxocephalus scorpius). An actively dividing cell culture of flounder kidney cells prepared by mechanical disruption of the kidney tissue was maintained through serial transfers over several months. Heart explants from the cod vigorously pulsated in tissue culture.

Infectivity of Trypanosoma murmanensis to leeches (Johanssonia sp.)

1977 ◽  
Vol 55 (10) ◽  
pp. 1698-1700 ◽  
Author(s):  
R. A. Khan
Keyword(s):  
Marine Fish ◽  
Gadus Morhua ◽  
Developmental Stages ◽  
Infected Fish ◽  
Winter Flounder ◽  
Pseudopleuronectes Americanus

Experiments were designed to test the infectivity of trypomastigotes of Trypanosoma murmanensis to leeches at intervals after metatrypomastigotes had initiated infections in marine fish. Infectivity was determined by the presence of developmental stages in recently emerged leeches (Johanssonia sp.) that had fed on experimentally infected fish. A total of 1235 leeches were used in this study. The results indicate that the three morphotypes can initiate infections in leeches. Moreover, some trypanosomes are infective at least 24 h after transmission (16 (67%) leeches became infected). Few leeches acquired infections after feeding on infected winter flounder (Pseudopleuronectes americanus) between 2 and 12 days and on a cod (Gadus morhua) 4–5 days, but all those which fed 7 through 93 day s on five species of marine teleosts became infected. Some of the leeches transmitted infections to uninfected cod. It is believed that the leeches which harboured no developmental stages might not have ingested trypanosomes.

In what direction should the fishing mortality target change when natural mortality increases within an assessment?

2016 ◽  
Vol 73 (3) ◽  
pp. 349-357 ◽  
Author(s):  
Christopher M. Legault ◽  
Michael C. Palmer
Keyword(s):  
Mortality Rate ◽  
Empirical Evidence ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Stock Assessment ◽  
Total Mortality ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Limanda Ferruginea ◽  
Trade Offs

Traditionally, the natural mortality rate (M) in a stock assessment is assumed to be constant. When M increases within an assessment, the question arises how to change the fishing mortality rate target (FTarget). Per recruit considerations lead to an increase in FTarget, while limiting total mortality leads to a decrease in FTarget. Application of either approach can result in nonsensical results. Short-term gains in yield associated with high FTarget values should be considered in light of potential losses in future yield if the high total mortality rate leads to a decrease in recruitment. Examples using yellowtail flounder (Limanda ferruginea) and Atlantic cod (Gadus morhua) are used to demonstrate that FTarget can change when M increases within an assessment and to illustrate the consequences of different FTarget values. When a change in M within an assessment is contemplated, first consider the amount and strength of empirical evidence to support the change. When the empirical evidence is not strong, we recommend using a constant M. If strong empirical evidence exists, we recommend estimating FTarget for a range of stock–recruitment relationships and evaluating the trade-offs between risk of overfishing and forgone yield.

Swimming Endurance of Some Northwest Atlantic Fishes

1966 ◽  
Vol 23 (3) ◽  
pp. 341-347 ◽  
Author(s):  
F. W. H. Beamish
Keyword(s):  
Swimming Speed ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Winter Flounder ◽  
Pseudopleuronectes Americanus ◽  
Northwest Atlantic ◽  
Sea Raven ◽  
Longhorn Sculpin ◽  
Hemitripterus Americanus ◽  
Swimming Endurance

Endurance was determined in relation to swimming speed and temperature for Atlantic cod, Gadus morhua Linnaeus, redfish, Sebastes marinus (Linnaeus), winter flounder, Pseudopleuronectes americanus (Walbaum), and to swimming speed at 8 C for longhorn sculpin, Myoxocephalus octodecimspinosus (Mitchill), sea raven, Hemitripterus americanus (Gmelin), and ocean pout, Macrozoarces americanus (Block and Schneider).In an activity chamber at a swimming speed of 4 body lengths per second (BL/sec) Atlantic cod swam for about equally long periods at 5 and 8 C, and redfish and winter flounder each about equally long at 5, 8, and 11 C. The pattern was similar for higher speeds. At 14 C winter flounder swam longer at 6 BL/sec than at the lower temperatures. For swimming speeds less than 4 BL/sec all species swam longer at the higher temperatures. At 8 C, the only temperature at which all species were tested, endurance at comparable swimming speeds was greatest for winter flounder, followed by cod, redfish, longhorn sculpin, ocean pout, and sea raven.

Rates of Digestion of Different Prey in Atlantic Cod (Gadus morhua), Ocean Pout (Macrozoarces americanus), Winter Flounder (Pseudopleuronectes americanus), and American Plaice (Hippoglossoides platessoides)

1982 ◽  
Vol 39 (5) ◽  
pp. 651-659 ◽  
Author(s):  
J. Stevenson Macdonald ◽  
Kenneth G. Waiwood ◽  
Roger H. Green
Keyword(s):  
Goodness Of Fit ◽  
Gadus Morhua ◽  
Prey Species ◽  
Atlantic Cod ◽  
Graphical Analysis ◽  
Winter Flounder ◽  
Pseudopleuronectes Americanus ◽  
Evaluation Procedures ◽  
Visual Index ◽  
Hippoglossoides Platessoides

Stomachs of ocean pout (Macrozoarces americanus), Atlantic cod (Gadus morhua), winter flounder (Pseudopleuronectes americanus), and American plaice (Hippoglossoides platessoides) were removed and dissected 5, 12, 20, and 30 h after the fish had fed voluntarily to test the evacuation rates of three different prey species. Two evaluation procedures were used: a visual index of recognizabiiity, and a graphical analysis of percent of each prey recovered versus time since feeding. Three decay models were tested for goodness of fit to the evacuation data. The polychaete worms were the first to become unrecognizable, followed by amphipods. These species showed significantly different rates of evacuation when compared with the bivalves which were recognizable for the longest time. The exponential decay curve gave the best overall fit to the data. However, a linear model gave a good or better fit to the decay rate of the bivalve. The evacuation rates of different prey should be considered in estimating daily rations of fish in their environment.Key words: digestion, stomach content, food organism, Yoldia sapotilla, Tmetonyx cicada, Nephtys incisa

Enhancing the reproductive potential of local populations of coastal Atlantic cod (Gadus morhua)

2002 ◽  
Vol 59 (10) ◽  
pp. 1685-1695 ◽  
Author(s):  
J S Wroblewski ◽  
H W Hiscock
Keyword(s):  
Gadus Morhua ◽  
Egg Quality ◽  
Atlantic Cod ◽  
Local Population ◽  
Reproductive Potential ◽  
Pseudopleuronectes Americanus ◽  
Farmed Fish ◽  
Potential Fecundity ◽  
Spawning Period ◽  
Natural Diet

We investigate the feasibility of enhancing the reproductive potential of northern Atlantic cod (Gadus morhua L.) populations resident in Newfoundland and Labrador bays by "catch, grow out, and release". This entails trapping juvenile and young adult fish from the local population, increasing their growth, maturation rate, and potential fecundity by feeding them a natural diet in net pens, and then returning the fish to their natal bay habitat to spawn. To determine whether multiyear farming affects spawning success, we determined the spawning period and egg quality of cod held in captivity for three growth seasons. Farmed cod spawned in a net pen concurrently with wild cod in Trinity Bay during 1995 and produced fertilized eggs from which viable larvae hatched. Sonic tracking showed that cod farmed for 3 years and then released reintegrated with wild cod aggregations over known spawning grounds. Recaptures of tagged fish several years after release suggest that farmed fish remained in the bay as members of the resident population. Fishing mortality (bycatch in coastal fisheries for lumpfish (Cyclopterus lumpus) and winter flounder (Pseudopleuronectes americanus)) of released farmed cod was not negligible, emphasizing that any enhancement effort must be carried out under a complete fishing moratorium.

Two New Host Species for the Parasitic Fungus Ichthyophonus hoferi in the Northwest Atlantic

1972 ◽  
Vol 29 (12) ◽  
pp. 1776-1777 ◽  
Author(s):  
Jerry D. Hendricks
Keyword(s):  
Gadus Morhua ◽  
Gulf Of Maine ◽  
Atlantic Cod ◽  
Parasitic Fungus ◽  
New Host ◽  
Yellowtail Flounder ◽  
Limanda Ferruginea ◽  
New Hosts ◽  
Longhorn Sculpin ◽  
New Host Species

Microscopic examination of kidney tissues from eight Gulf of Maine fish species revealed cysts of the fungus Ichthyophonus hoferi, Plehn and Mulsow, in individuals from three species. Two of these species, the longhorn sculpin (Myoxocephalus octodecemspinosus) and the Atlantic cod (Gadus morhua), are new hosts for this parasite in Gulf of Maine waters. The other species, the yellowtail flounder (Limanda ferruginea), was previously reported as an Ichthyophonus host.

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