Energetic factors influencing foraging tactics of juvenile steelhead trout, Salmo gairdneri

1983 ◽  
pp. 173-180 ◽  
Author(s):  
Jerry J. Smith ◽  
Hiram W. Li
Keyword(s):  
Salmo Gairdneri ◽  
Steelhead Trout ◽  
Factors Influencing ◽  
Foraging Tactics

FACTORS INFLUENCING SEASONAL CHANGES IN THYROID ACTIVITY IN JUVENILE STEELHEAD TROUT, SALMO GAIRDNERI

1965 ◽  
Vol 43 (5) ◽  
pp. 719-729 ◽  
Author(s):  
J. G. Eales
Keyword(s):  
Body Weight ◽  
Seasonal Changes ◽  
Late Summer ◽  
Salmo Gairdneri ◽  
Thyroid Cell ◽  
Steelhead Trout ◽  
Thyroid Activity ◽  
Cell Height ◽  
Factors Influencing ◽  
Tall Cell

Seasonal changes in thyroid cell height and radioiodide indices of thyroid activity (CR and T/S) were measured in yearling and 2-year-old steelhead trout held in freshwater. Cell height was high in yearlings in mid-June and in 2-year-olds in late April and May at parr–smolt transformation; in both it was low in late summer and moderately high in winter. CR and T/S were high both at parr–smolt transformation and in late summer, but were low in winter. Only at parr–smolt transformation did cell height and radioiodide indices agree.Two-year-old potential smolts were held from January to May under four controlled temperature and photoperiod regimes. These experiments revealed that at parr–smolt transformation, both rising temperature and lengthening photoperiod induced the characteristically high CR and T/S values, but that the tall cell height depended on the lengthening photoperiod. Cell height and T/S were measured in yearlings (non-migrants) subjected to similar regimes at the same season. T/S was uninfluenced by photoperiod but responded to rising temperature. Cell height responses were more complex and indicated involvement of other variables.In September, small yearlings possessed significantly higher T/S and CR values than did large yearlings. A relationship between thyroid function and body weight could explain seasonal changes not attributable to temperature or photoperiod.

The regulation of day–night changes in hydroxyindole-O-methyltransferase activity in the pineal gland of steelhead trout (Salmo gairdneri)

1976 ◽  
Vol 54 (9) ◽  
pp. 1530-1534 ◽  
Author(s):  
John R. Smith ◽  
Lavern J. Weber
Keyword(s):  
Pineal Gland ◽  
Sharp Increase ◽  
Pineal Region ◽  
Salmo Gairdneri ◽  
Steelhead Trout ◽  
Methyltransferase Activity ◽  
Surgical Exposure

Elevation in pineal hydroxyindole-O-methyltransferase (HIOMT; EC 2.1.1.4) activity in juvenile steelhead trout was associated with the dark portions of three different photoperiods with a sharp increase in pineal HIOMT activity occurring in the first 4 h of darkness. This pattern of activity could be abolished by bilateral enucleation but not by surgical capping of the pineal region. Surgical exposure of the pineal region in blinded fish did not restore HIOMT responses to changes in lighting.

Movements of Rainbow Steelhead Trout (Salmo Gairdneri) in Lake Ontario and a Hypothesis for the Influence of Spring Thermal Structure

1986 ◽  
Vol 12 (4) ◽  
pp. 304-313 ◽  
Author(s):  
James M. Haynes ◽  
David C. Nettles ◽  
Kevin M. Parnell ◽  
Michael P. Voiland ◽  
Robert A. Olson ◽  
...  
Keyword(s):  
Thermal Structure ◽  
Lake Ontario ◽  
Salmo Gairdneri ◽  
Steelhead Trout

Time study of coronary myointimal hyperplasia in precocious male steelhead trout, Salmo gairdneri

1979 ◽  
Vol 34 (4) ◽  
pp. 375-381 ◽  
Author(s):  
Steven P. Schmidt ◽  
Edwin W. House
Keyword(s):  
Salmo Gairdneri ◽  
Time Study ◽  
Steelhead Trout

Fine structure of the external egg membrane of five species of Pacific salmon and steelhead trout

1985 ◽  
Vol 63 (3) ◽  
pp. 552-566 ◽  
Author(s):  
E. P. Groot ◽  
D. F. Alderdice
Keyword(s):  
Fine Structure ◽  
Chum Salmon ◽  
Pacific Salmon ◽  
Salmo Gairdneri ◽  
Membrane Thickness ◽  
Steelhead Trout ◽  
Outermost Layer ◽  
Additional Layer ◽  
Egg Membrane ◽  
Pore Canals

Fine structure of the external egg membrane of five species of Pacific salmon (sockeye, Oncorhynchus nerka; pink, O. gorbuscha; chum, O. keta; coho, O. kisutch; and chinook, O. tshawytscha) and the anadromous steelhead trout (Salmo gairdneri), is examined and compared using the scanning electron microscope. Membrane thickness in fixed material varies for the six species as follows (micrometres, [Formula: see text]): sockeye, 34.15 ± 0.15; pink, 61.64 ± 1.53; chum, 53.05 ± 0.33; coho, 27.96 ± 0.48; chinook, 50.82 ± 0.74; steelhead, 30.74 ± 0.11. The membrane consists of a thin outermost layer, the externus, 0.2–0.3 μm thick, and the internus, 24–55 μm thick, which constitutes the remainder of the membrane. In sockeye, pink, and chum salmon and steelhead trout, an additional layer 3–8 μm thick, the "subinternus," occurs beneath the internus. The entire membrane appears fibrous except for the thin and apparently solid externus. Pores in both the inner and outer surfaces are arranged in a hexagonal pattern and are connected by pore canals traversing the membrane. Except in the sockeye, plugs commonly were seen blocking the external openings of the pore canals. Significance of the egg membrane fine structure is considered in relation to several of its roles in the water-activated egg: semipermeability, retention of internal pressure, and mechanical protection. A structural and functional analogy is drawn between the fine structure of the salmonid egg membrane and the mammalian aorta.

Swimming Stamina Differences Between Genotypically Distinct Forms of Rainbow (Salmo gairdneri) and Steelhead Trout

1977 ◽  
Vol 34 (7) ◽  
pp. 996-1003 ◽  
Author(s):  
H. Tsuyuki ◽  
S. N. Williscroft
Keyword(s):  
Rainbow Trout ◽  
Lactate Dehydrogenase ◽  
Key Words ◽  
Low Frequency ◽  
Water Velocity ◽  
Salmo Gairdneri ◽  
Steelhead Trout ◽  
Very Low Frequency ◽  
Time Required

Rainbow trout (Salmo gairdneri) homozygous for liver lactate dehydrogenase alleles ldhHαA and ldhHαB were artificially propagated and their swimming stamina compared. The time required to fatigue 50% of the HαAHαA phenotypes in fixed water velocity tests was 2.3 times greater on the average than that of HαAHαB phenotypes.Likewise, LDH phenotypes HαAHαA, HαAHαB, and HαAHαB of steelhead trout from the Thompson River were artifically propagated and their swimming stamina compared. In contrast to the rainbow trout, significant differences in stamina among the three phenotypes of steelhead were not evident in the stocks from this river nor between phenotypes HαAHαB and HαBHαB from another stream, the Vedder River, which has a very low frequency of the ldhHαA allele. The stamina of young steelhead from the Thompson River was, however, 3.8 times greater than that of those from the Vedder River. Key words: stamina, LDH, rainbow trout, steelhead, phenotype, swimming, fatigue

Life History and Smolt-to-Adult Survival of Keogh River Steelhead Trout (Salmo gairdneri) and the Relationship to Smolt Size

1988 ◽  
Vol 45 (7) ◽  
pp. 1110-1122 ◽  
Author(s):  
B. R. Ward ◽  
P. A. Slaney
Keyword(s):  
Age Structure ◽  
Predictive Models ◽  
Adult Survival ◽  
Salmo Gairdneri ◽  
Adult Size ◽  
Steelhead Trout ◽  
Adult Age ◽  
Large Fluctuations ◽  
The Relationship ◽  
Size Estimates

A decade of data on wild steelhead trout (Salmo gairdneri) from a coastal stream in British Columbia demonstrated large fluctuations in smolt number, age structure, size, estimates of adult run sizes, smolt-to-adult survival, and adult age. Adult runs averaged 922 (range 209–2730) with approximately 10% repeat spawning incidence. Females repeat spawned more than males and were more abundant as kelts, but maiden run adults were equally male and female. The proportion of males returning after 1, 2, and 3 yr in the ocean averaged 3, 62, and 35%, respectively; 58 and 42% of females returned after 2 and 3 yr, respectively. Adult age structure, smolt number, and smolt size varied biennially. Adult size decreased with freshwater age, but increased with ocean age of returns. Males were larger at each ocean age. Mean number of smolts (50:50 sex ratio) was 5543 and varied fivefold. Mean smolt length was 173 mm and mean weight was 49 g. Smolts were 2–5 yr old, and freshwater age 3 was most prevalent (average 56%). Mean survival from smolt to adult was 16% (7% from 1978 cohorts to 26% from 1982 cohorts). Survival was positively correlated with smolt length and weight. However, 1982 cohorts had twice the survival of other cohorts, possibly related to El Niño. No clear relationship was found between return age and mean smolt size, but on average, freshwater age was inversely related to ocean age. The relationships suggest that predictive models may be developed over the longer term from this type of study.

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