Repeat Homing of Brown Trout (Salmo trutta) in Lake Eucumbene, New South Wales, Australia

1977 ◽  
Vol 34 (8) ◽  
pp. 1085-1094 ◽  
Author(s):  
R. D. J. Tilzey
Keyword(s):  
Rainbow Trout ◽  
Brown Trout ◽  
Salmo Trutta ◽  
New South ◽  
Tag Loss ◽  
Trout Population ◽  
South Wales ◽  
High Incidence ◽  
Brown Trout Salmo Trutta ◽  
External Form

Spawning runs of lentic-dwelling brown trout (Salmo trutta) and rainbow trout (S. gairdneri) in Swamp Creek, an inlet of Lake Eucumbene, were studied for 4 consecutive yr, and 3517 browns and 415 rainbows were tagged during 1968–70. A further 240 browns and 229 rainbows were marked in other inlets. Recaptures of marked browns in 1969 and 1970 showed a high incidence of repeat homing, up to 25.7 and 10.6% returning after 12 and 24 mo, respectively. Few rainbow trout homed. Tag loss and the mortality and maturation of marked browns were estimated and percentage homing and straying in 1969, 1970 and 1971 was calculated. High percentage homing [Formula: see text] in 1969–70 and the variance in external form in the lentic population suggested some genetic isolation within the brown trout population. Homing ability was not influenced by fish age. Percentage homing fell markedly in 1971 after the removal of nearly all resident brown trout from Swamp Creek and suggested racially distinct stream trout populations to be an important navigational cue to homing brown trout. Key words: repeat homing, Salmo trutta, homing frequency, navigation, racial cue, Australia

Bacterial Microflora of Wild Brown Trout (Salmo trutta), Wild Pike (Esox lucius), and Aquacultured Rainbow Trout (Oncorhynchus mykiss)

1999 ◽  
Vol 62 (11) ◽  
pp. 1270-1277 ◽  
Author(s):  
CÉSAR-JAVIER GONZÁLEZ ◽  
TERESA-MARÍA LÓPEZ-DÍAZ ◽  
MARÍA-LUISA GARCÍA-LÓPEZ ◽  
MIGUEL PRIETO ◽  
ANDRÉS OTERO
Keyword(s):  
Rainbow Trout ◽  
Brown Trout ◽  
Water Samples ◽  
Salmo Trutta ◽  
Pond Water ◽  
Intestinal Content ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
High Incidence ◽  
Brown Trout Salmo Trutta ◽  
Bacterial Groups

Initial numbers of bacteria associated with wild (brown trout and pike) and cultured (rainbow trout) freshwater fish as well as with the water in which they were caught were determined. Subsequently, a total of 979 randomly selected isolates were characterized and identified to the genus level. For all counts performed (aerobes, psychrotrophs, anaerobes, Enterobacteriaceae, and enterococci), no significant differences were observed in water samples, the highest level corresponding to psychrotrophs in pike environments (4.23 × 103 CFU/ml). Overall, the skin and intestinal content of brown trout were the most contaminated, while rainbow trout specimens (gills and gut) yielded the lowest numbers. For all bacterial groups, pike gills had the highest numbers. Counts for all of the sampling sites compare well with findings in other temperate geographical environments. Biological characteristics (feeding and skin properties) and the use of antimicrobials in aquaculture might have influenced these results. Motile and nonmotile aerobic gram-negative bacteria together with Enterobacteriaceae accounted for 50 to 70% of the psychrotrophs isolated from water. Micrococcaceae, lactic acid bacteria, Bacillus, and coryneforms were also found. The groups represented in psychrotrophic isolates from the outer surfaces do not reflected those detected in water, so it was common that those organisms recovered in significant numbers from fish were not detected in surrounding habitat of the fish. Motile aeromonads and Carnobacterium were the dominant psychrotrophs in the guts of pike and brown trout, respectively. The intestinal content of reared fish gave a high incidence of Bacillus and coryneforms, while Enterobacteriaceae was absent. Again, rearing practices could have influenced this finding. Listeria monocytogenes was not detected in any of the examined samples. Two strains of Salmonella, which belonged to the same serovar and lysotype, were recovered from pond-water samples taken from one facility on different sampling days. From the gut of a pike specimen and from the pike's environment, two Plesiomonas shigelloides strains of different serovars were recovered. These latter four strains were resistant to a considerable number of antimicrobial compounds (multiple antibiotic resistance indices > 0.2).

Role of the crayfish Cherax destructor clark as food for trout in Lake Eucumbene, New South Wales

1983 ◽  
Vol 34 (3) ◽  
pp. 407 ◽  
Author(s):  
RA Faragher
Keyword(s):  
Rainbow Trout ◽  
Brown Trout ◽  
Salmo Trutta ◽  
New South ◽  
New South Wales ◽  
Water Levels ◽  
Size Analysis ◽  
Fish Length ◽  
Freshwater Crayfish ◽  
South Wales

The freshwater crayfish C. destructor was a major dietary item for brown trout, Salmo trutta L., and rainbow trout, S. gairdneri Richardson, in Lake Eucumbene, New South Wales. The incidence of crayfish in the diet increased, particularly in brown trout, over the period 1972-1977. The proportion of the trout's diet comprising C. destructor increased with length of brown trout but not with length of rainbow trout. The size of crayfish ingested was postively correlated with fish length for both species of trout, although rainbow trout tended to ingest smaller crayfish than brown trout of equivalent size. Analysis of the crayfish's diet revealed predominantly plant material. Spawning by the crayfish was apparently confined to the period December-April. The abundance of C. destructor in Lake Eucumbene was apparently low until about 1970 but increased between 1972-1977. A decline in the average size of brown and rainbow trout in the angler catch occurred from 1959-1960 until 1977-1978. Hypotheses are suggested for the increase of the crayfish population since impoundment of the lake (1957). Factors considered include predation by trout and the biology of the crayfish, particularly related to its occurrence in this lake, which has fluctuating water levels and a short season suitable for growth and spawning.

Comparative exploitation exploitation by recreational anglers of brown trout, Salmo trutta L., and rainbow trout, Oncorhynchus mykiss (Walbaum), in Lake Eucumbene, New South Wales

1992 ◽  
Vol 43 (4) ◽  
pp. 835 ◽  
Author(s):  
RA Faragher ◽  
GNG Gordon
Keyword(s):  
Rainbow Trout ◽  
Confidence Interval ◽  
Brown Trout ◽  
New South ◽  
New South Wales ◽  
Likelihood Method ◽  
Linear Regression Method ◽  
Tag Loss ◽  
South Wales ◽  
Significant Difference

Exploitation rates of syrnpatric brown trout and rainbow trout in Lake Eucumbene, New South Wales, were estimated from a tagging study. Tag returns were analysed by applying a non-linear regression method. Tag loss was estimated from a concurrent double tagging study using a maximum likelihood method. No significant difference at the 5% level was found between the rates of tag loss of the two species. The annual exploitation rate for rainbow trout was 26.7% (95% confidence interval 24.2- 29.2%) and was significantly less for brown trout, 8.8% (95% confidence interval 4.2-13.5%).

Effects of pH on Sodium Uptake in Norwegian Brown Trout (Salmo Trutta) from an Acid River

1980 ◽  
Vol 88 (1) ◽  
pp. 259-268
Author(s):  
PHILIP G. McWILLIAMS
Keyword(s):  
Brown Trout ◽  
Salmo Trutta ◽  
Population Decline ◽  
Acid Media ◽  
Sodium Uptake ◽  
Trout Population ◽  
Uptake Rates ◽  
Effects Of Ph ◽  
Brown Trout Salmo Trutta ◽  
External Ph

Sodium uptake rates were measured in wild and hatchery reared Norwegian brown trout (Salmo trutta) exposed to media of a range of pH. Sodium uptake was strongly dependent on external acidity, being reduced in media of low pH. Wild fish from the naturally acid R. Tovdal (S. Norway) were more tolerant of acid media than hatchery reared fish. The effects of increasing external sodium concentrations were strongly influenced by low external pH. The results are discussed with respect to brown trout population decline in certain areas of S. Norway.

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