Dynamic in-lake spawning migrations by female sockeye salmon

Abstract –  Precise homing by salmon to natal habitats is considered the primary mechanism in the evolution of population-specific traits, yet few studies have focused on this final phase of their spawning migration. We radio tagged 157 female sockeye salmon ( Oncorhynchus nerka ) as they entered Lake Clark, Alaska, and tracked them every 1–10 days to their spawning locations. Contrary to past research, no specific shoreline migration pattern was observed (e.g., clockwise) nor did fish enter a tributary unless they spawned in that tributary. Tributary spawning fish migrated faster (mean = 4.7 km·day⁻¹, SD = 2.7, vs. 1.6 km·day⁻¹, SD = 2.1) and more directly (mean linearity = 0.8, SD = 0.2, vs. 0.4, SD = 0.2) than Lake Clark beach spawning fish. Although radio-tagged salmon migrated to within 5 km of their final spawning location in an average of 21.2 days (SD = 13.2), some fish migrated five times the distance necessary and over 50 days to reach their spawning destination. These results demonstrate the dynamic nature of this final phase of migration and support studies indicating a higher degree of homing precision by tributary spawning fish.     

Effects of radio-transmitter antenna length on swimming performance of juvenile rainbow trout

Abstract –  Technological advances have lead to the production of micro radio-transmitters capable of being implanted in fish as small as c . 5 g. Although the actual tags are small, transmitters are equipped with long antennas that can increase drag and tangle in debris. We examined the effects of radio-transmitter antenna length on the swimming performance of juvenile rainbow trout, Oncorhynchus mykiss , ( N  = 156, mean mass = 34 g, mean fork length = 148 mm). Although we tested a variety of different antenna lengths up to a maximum of 300 mm, only the longest antenna significantly impaired swimming performance relative to control fish ( P  < 0.001). There was no difference in swimming performance between the sham (surgery, but no transmitter) and the control fish (handled, but no surgery), suggesting that the surgical procedure itself did not negatively affect the fish. Regression analysis, however, indicated that there was a significant decrease in swimming performance associated with increased antenna length ( R ² = 0.11, P  < 0.001). In addition, when held in laboratory tanks, fish with the three longest antennas (150, 225 and 300 mm) frequently became entangled with the standpipe. We suggest that researchers, under the guidance of the tag manufacturer, trim antennas to the shortest possible length required to detect fish in their specific study area. Antenna length is clearly an important issue for small fish, especially for species that inhabit complex habitats where antennas may become entangled, and where fish must attain speeds near limits of their swimming capacity.     

Measurement of casual blood pressure by implantable telemetry

AIM:To establish a method of casual blood pressure measurement by implantable telemetry and to improve the efficiency of telemeter. METHODS:The spontaneously hypertensive rats (SHR) were used as the experimental animal model, and the mean blood pressure (MBP) of 24 h and other physiological parameters were recorded for consecutive days by implantable telemetry. The data of MBP at different intervals of 30 min, 1 h and 3 h were calculated, and the dynamic change of the MBP was observed. The similarity of the MBP at different time intervals with the MBP of 24 h was compared by a similarity factor comparison method. RESULTS:The basic blood pressure of 24 h changed and fluctuated according to some rhythm. Interestingly, in the time period of 20:00~23:00, the MBP showed a high stability, and had a similarity to the MBP of 24 h. In further pharmacodynamic experiments, it was displayed that the MBP curve at this period was highly similar to the MBP curve of 24 h, and the similarity factor reached up to 77.8. CONCLUSION: Based on the time period of 20:00~23:00, the method of casual blood pressuremeasurement by implantable telemetry demonstrates high accuracy, repeatability and typicality, suggesting that it could be a new alternative blood pressure measurement method for improving the battery life and efficiency of telemeter to carry out long-term pharmacodynamic study.     

The effect of furosemide on left atrial pressure in dogs with mitral valve regurgitation

Background: The effects of furosemide on left atrial pressure (LAP) in dogs with mitral regurgitation (MR) have not been documented in a quantitative manner and between different routes of administration. Objective: To document LAP and echocardiographic parameters in MR dogs administered furosemide IV or PO, in order to document changes in LAP after furosemide treatment. Animals: Five healthy Beagle dogs (3 males and 2 females; aged 2 years) were used. Methods: Experimental, cross‐over, and interventional study. LAP was measured before the administration of furosemide, and 30 minutes, 1, 1.5, 2, 3, 4, 5, 6, 8, 12, and 24 hours after administration. Furosemide 1, 2, or 4 mg/kg IV, PO or placebo was administered. Results: LAP was significantly decreased with all administrations of furosemide but not after placebo (P < .05, respectively). The max reduction was observed 1 hour (1 mg/kg IV, 15.04 ± 7.02 mmHg), 3 hours (2, 4 mg/kg IV, 13.28 ± 8.01, 9.23 ± 4.92 mmHg), 4 hours (1 mg/kg PO, 14.68 ± 11.51 mmHg), and 5 hours (2, 4 mg/kg PO, 13.19 ± 10.52, 10.70 ± 7.69 mmHg). E wave and E/Ea were significantly decreased corresponding to the reduction of LAP after administration of 2 and 4 mg/kg (P < .05, respectively). Conclusions and Clinical Importance: LAP was decreased in proportion to the dosage of furosemide, which did not significantly differ between IV and PO of the same dosages. E wave and E/Ea might be useful for the treatment evaluation of furosemide.     

Individual consistency between diel activity during rearing and behavior after release in red tilefish <Emphasis Type="Italic">Branchiostegus japonicus</Emphasis> revealed by laboratory observation and acoustic telemetry

ABSTRACT:   To determine characteristics which may reflect the behavioral quality of red tilefish Branchiostegus japonicus after release, five wild and four hatchery-reared fish were observed in a laboratory and in the sea. The diel activity of the fish was recorded on video tape for 2 days in a tank, where the light condition was regulated to vary periodically over 24 h. The individuals were then released in Maizuru Bay and tracked using acoustic telemetry. Four wild individuals became most active at dawn during a day in the tank, and settled near the release area to stay for 28–104 days after release in Maizuru Bay. In contrast, one wild and four hatchery-reared individuals were not active at dawn, and then did not settle in Maizuru Bay after release. Among the four settled wild individuals, the more active a fish had been in the tank, the more distant the individual moved from the release point until its settlement. The diel activity pattern should be a factor deciding whether red tilefish would settle nearby after release, and the relative amount of activity during rearing is probably related to the degree of dispersion within the release area.     

Habitat use and movement of river blackfish (Gadopsis marmoratus R.) in a highly modified Victorian stream, Australia

Abstract –  Movement and habitat use of river blackfish ( Gadopsis marmoratus R.) was studied in a highly modified central Victorian stream (Birch Creek), Australia, using radio telemetry ( N  = 10) and mark–recapture ( N  = 113) between October 2001 to May 2002, and November to December 2002 respectively. Blackfish had a small home range of 10–26 m with strong affinity to a pool. However, small movements within a pool were common which resulted in relatively large cumulative movements. At a diel scale there were no significant differences in blackfish movement between day and night (Kruskal–Wallis test, P  = 0.95). Six of seven blackfish translocated 40 m upstream or downstream of their original positions returned within 48 h, suggesting strong affinity not only to a pool, but also to a small region within a pool. Blackfish utilised slow flowing (0–20 cm s⁻¹) and deep waters (40–60 cm). Blackfish were strongly associated with the instream cover habitats of undercut banks and boulders. Significant differences were recorded in instream cover and water velocity used by blackfish between day and night (Kruskal–Wallis test, P  = <0.01). At night blackfish used open areas with high water velocities whereas during the day blackfish used complex undercut banks with low water velocities.     

Agonistic behaviour patterns of the slender mongoose,Herpestes sanguineus

Winter reproductive activity is exhibited by females of the viviparous lizard, Cordylus p.polyzonus. Vitellogenesis commences in May (autumn), continuing throughout the winter months with ovulation in October. Females are pregnant during summer and give birth in late summer (February). Clutch size is positively correlated to female body size. During embryonic development, ovarian follicles remain small and translucent and the corpora lutea progressively decrease in size until parturition occurs. Embryonic growth was characterized by a concomitant decline in embryonic yolk mass. Although considerable variation was observed in the fat body mass, maximal fat body mass peaked in winter (June) and in mid-summer (December). The onset of vitellogenesis corresponded to declining photoperiod and environmental temperatures.     

Atlantic salmon living on the edge: Smolt behaviour and survival during seaward migration in River Minho

The Atlantic salmon (Salmo salar) population of the River Minho represents the southern natural distribution edge of the species. In line with the general trend for Atlantic salmon, this population has been declining over the years and is now at a critically low level. With river connectivity compromised by a large dam just 80 km upstream the River Minho's outlet, and an expected deterioration of climatic conditions, it is urgent to increase our knowledge of this population and identify survival bottlenecks that can be addressed. In this study, we used radio and acoustic telemetry to track Atlantic salmon smolts during their migration towards the sea and record both survival rates and possible causes of mortality. The recorded survival for the tagged migrating Atlantic salmon remained below 55% in the three studied years, indicating that the in‐river loss of smolts is likely a strong constraint to this population. From the smolts to which a likely cause of mortality could be attributed (34%), most appear to have been removed from the river (25%), with two confirmed events of bird predation and one of mammal predation. Interestingly, eight tags were recorded moving back upstream, likely indicating predation by larger fish. Increasing predator populations (e.g. cormorants, Phalacrocorax carbo) and invasive predators (e.g. American mink, Neovison vison) lead to elevated predation pressure on this already strained Atlantic salmon population, and further studies quantifying their impact in more detail could prove crucial for future management considerations.     

Summer survival and activity patterns of estuary feeding anadromous Salmo trutta

There is generally a very poor understanding of how anadromous brown trout, Salmo trutta, use marine ecosystems. In this study, we use acoustic telemetry techniques to test four alternative hypotheses for estuarine coastal habitat use by this species on a population in the Clyde, west-central Scotland. Anadromous brown trout in their second (or more) summer feeding in the marine environment did not show patterns of estuarine use predicted from studies on other populations of this species. They did not (a) use the inner Clyde Estuary as a staging post for onward migration to open coastal waters, nor did they (b) pass through the estuary rapidly nor did they (c) make multiple incursions into freshwater. In contrast, fish utilised a very geographically constrained area of the inner estuary (<8 km in length), within which fish were highly mobile, exhibiting more activity during a flooding tide and exhibited high survivorship compared with reports from other studies. The reasons why estuarine use by anadromous brown trout in the Clyde may differ from that reported elsewhere is discussed.