ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb04196.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

A chemically specific analysis for plasma thyroid hormones has been used to disclose a seasonal bimodality in the concentrations of thyroxine (T4) and triiodothyronine (T3) in the plaice; maxima in both hormone levels occur in winter and in summer. The ratio of T4concentrations to T3varies seasonally being at a minimum in summer. A highly significant correlation of T4plasma levels with the landings per unit fishing effort for the same area has been observed.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb04197.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Pearl Danios(Brachydanio albolineatus–Blyth) were allowed four days for acclimation in river‐water filled aquaria maintained at a mean temperature of 27° C. A different concentration of DL‐thyroxine (T4) was added to each of two aquaria. A third aquarium served as a control and received no hormone. Photoperiod, feeding, aeration, and observer interference were controlled so as not to influence the results of the study. Mean swimming speeds for the fish in each aquarium were calculated. Data were subjected to analysis of variance and the Student‐Newman‐Keuls Test. Compared with the control, significant(P<0.05) increases in swimming speed were found with concentrations of thyroxine in water of 1:4x 106and 1:1 x 106. The difference in swimming speed between the two hormone‐treated groups was not significant. The fact that exogenous thyroxine will increase swimming speed may indicate that endogenous thyroid hormone plays a significant role in such fish behaviour

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb04198.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

The concentrations of thyroxine (T4) and triiodothyronine (T3) in the blood plasma of rainbow trout (Salmo gairdneriRichardson) at intervals throughout the year have been measured by a chemically specific gas‐liquid chromatographic (GLC) method. Mean hormone levels showed a seasonal variation, maximal levels of both hormones occurring in winter and minimal concentrations in mid summer. An apparent secondary maximum in mean T4and T3concentrations was observed in spring. (T4)/(T3) ratios have been found to be highest in winter and lowest in summer. A radioimmunoassay procedure, validated by GLC analyses, revealed the presence of a diurnal rhythm in serum T4levels of trout sampled in September and in Apri

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb04199.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Behavioural and physiological mechanisms postulated for the control of downstream migration of Atlantic salmon smolts are reviewed briefly, and some new evidence is presented for their refusal to undergo sustained swimming. Although these mechanisms imply passive displacement as the primary means of emigration, it is likely that active components must also exist as the rates of travel of smolts through loch systems are only slightly slower than those recorded for river systems. The timing of these movements within 24 h periods is reviewed and it is shown that the predominantly nocturnal emigration pattern is evident on occasions in alevin, fry and parr stages also. Thus at migration the diel periodicity probably represents a seasonal locomotor rhythm which, under changed behavioural and physiological circumstances, results in downstream displacement.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb04200.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

This paper describes and evaluates a 50 mHz radio telemetry system for studying river movements of adult Atlantic salmon (Salmo salar). In fresh water for most applications radio telemetry is preferable to ultrasonic telemetry, because the receiving element (antenna) can be above water, and radio signals are scarcely affected by turbulent, weedy or ice‐covered water. Within the range of 10–200 mHz higher frequencies are preferred, since the efficient antenna size is inversely proportional to frequency, and attenuation of signals is independent of frequency. Transmitters were cylindrical (6.5–9.6 cm long * 1.9 cm diam) with a 0.5 wavelength antenna trailing from one end. Each emitted pulsed signals on one of 20 crystal‐controlled channels between 49.100 and 49.385 mHz. Transmitters were placed in the stomachs of salmon and the antenna trailed out the last gill slit. Receivers were portable 20‐channel manual or automatic scan models, and antennas were 48 cm diam capacitor tuned loops. Some salmon regurgitated transmitters. Two salmon were recaptured and showed no ill effects from carrying transmitters for 32 and 42 days. Pulse rate had little effect on known transmitter life under natural conditions. Known tag life was variable, but averaged 70 days for transmitters with 1000 mah batteries. The range of transmission of transmitters to a receiving system in an airplane at 410 m altitude was about 10 km, and to a boat about 1 km. Range to a land vehicle was variable depending on obstructions. From the airplane transmitters can be located within a radius of a

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb04201.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Seasonal, diel and tidal rhythmic activity of hatchery‐reared Atlantic salmon (Salmo salar) smolts migrating through a large estuary was studied by ultrasonic tracking of 46 individuals during two seasons. Prior to 10 May each year most smolts were inactive and remained near shore in shallow water. After 10 May nearly all smolts moved away from the release point into swift water and made rapid seaward progress. Initiation of migration each year occurred when river and hatchery water temperatures rose above 9°C. Migration in the estuary was largely passive drift, and as a result there were distinct tidal rhythms of ground (‘swimming’) speed and net seaward travel. There were no diel rhythms in ground speed or net seaward travel; smolts drifted seaward on the tides during both day and night. Smolts may be slightly deeper during day than

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb04202.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Observations on smolt migration in a chalkstream over a period of four years indicate a relationship between number of fish migrating during the day and maximum afternoon water temperature. Few fish move below an apparent threshold temperature. This threshold appears to be different each year, varying with the general water temperature of the period proceeding the main run. Tests made with dummy telemetry tags indicate that their use to observe natural migratory behaviour may be justified.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb04203.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Ultrasonic telemetry was used to follow the movements of two groups of smolts in the estuaries of two small Scottish rivers. Hatchery reared smolts released into a typical wedge flow, partially mixed estuary had movements which were dominated by the influence of tide on the direction of water flow. The net movements of wild native smolts in a two layer flow estuary, in which freshwater flow dominated, was downstream but were intermittent consisting of short steps and numerous long pauses. The hatchery reared smolts escaped from the estuary within a tidal cycle, moving out on an ebb tide. The wild smolts remained in the estuary for periods up to 108 h, none escaping within one tidal cycle.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb04204.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

The swimming excursions of individual perch, measured automatically, within either cages in Windermere or in a trough on the shore, showed increases at dawn and dusk and in the summer. Similar measurements in troughs in the laboratory showed increased activity following a change from light to dark and vice versa, a pattern that was obliterated by either continuous light or continuous darkness. These results are discussed in relation to water temperature and catches of perch in traps.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb04205.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY