Morten Kraabøl

Efforts to aid downstream migrating brown trout (Salmo trutta L.) kelts and smolts passing a hydroelectric dam and a spillway

The autumn and spring descent of 41 brown trout kelts (spent trout) (average total length Lt 75.9 cm) and the spring descent of 27 hatchery-reared smolts (average Lt 26.2 cm) were studied by radiotelemetry in 1993/1994 (kelts) and 1997/1998 (kelts and smolts) at the Hunderfossen dam and power plant, south-east Norway. In 1999 we studied spring descent of 48 untagged kelts by visual observations and video-monitoring at one spillway. In autumn 1993 and 1997, 62.4% and 44.0% of the tagged kelts migrated downstream to the dam at water temperatures between 0.1 and 0.8°C. During release of spillwater, the kelts gathered along the dam with limited movements. Neither smolts nor kelts used the 2 m submerged turbine shafts as a pathway to migrate downstream Hunderfossen dam. Nor did release of large amounts of deep water through spillways provide downstream migration possibilities for kelts and possibly for smolts. The majority of both smolts and kelts migrated downstream at short periods of surface water release through the spillways, indicating high importance of surface water release. The threshold value of descend of kelts at surface release was between 1 and 4 m3 s−1 which correspond to a water column between 12 and 36 cm. These findings are highly relevant regarding hydroelectric development in river systems containing iteroparous salmonid species.

A comparison of external and internal attachments of radio transmitters on adult crested newts Triturus cristatus

Telemetry studies of newt species demand small transmitters. Two types of external attachments (sutured to epidermis and backpack) and traditional implanting in the peritoneal cavity were tested between groups of 5 adult individuals of the crested newt Triturus cristatus (mass 6-15 g) held in terrariums under controlled environmental conditions. The newts were anaesthetized with 1.5 g l −1 MS222, delivered in water and buffered to pH 6.9 by Na2CO2. Surgical plane of anaesthesia was achieved after 5-12 minutes and lasted for 30-60 minutes. External tagging proved unsuitable because transmitters became entangled in vegetation, and all animals shed their transmitters shortly after tagging, except for one that died. Transmitters that were surgically implanted in the peritoneal cavity were more successful. By the fourth day following surgery, the animals that had undergone surgery behaved similarly to control animals with respect to the use of cover. Two of the newts died, however, without showing any signs of illness in advance, and the cause of death could not be established. Based on the present experiments and published studies, implantable transmitters appear to be the best method for radiotagging small and medium sized urodele species such as T. cristatus, to gain crucial information on spatio-temporal terrestrial activity patterns, habitat utilization and hibernation sites. Additional research is needed to evaluate both short and long term effects on activity, behaviour and survival.