Timothy J. Thom

Migration of freshwater fishes

Migration And Spatial Behaviour: Introduction. The Stimulus And Capacity For Migration: Stimuli For Migration, The Capacity For Migration, Piloting, Orientation And Navigation. Types Of Migration: Migrations At The Seasonal And Ontogenetic Scale, Diel Horizontal And Vertical Migrations. Patterns Of Migratory Behaviour In Freshwater Fishes: Arctic And Subarctic Regions, Temperate Regions, Tropical Regions. Taxonomic Analysis Of Migration In Freshwater Fishes, Lampreys Through To Freshwater--Dwelling Flatfishes (In 45 Sections). Methods For Studying The Spatial Behaviour Of Fishes In Fresh--And Brackish Water: Capture Dependent Methods, Capture Independent Methods, Choice Of Methods In Fish Migration Studies. Applied Aspects Of Freshwater Fish Migration: The Impact Of Mana s Activities On Freshwater Fish Migration. Mitigation Of Hazards And Obstacles To Fish Migration, Installation, Monitoring And Efficiency Of Fish Passes. Conclusions. Indexes

The potential use of PIT telemetry for identifying and tracking crayfish in their natural environment

A method for tracking crayfish and other benthic animals in rivers and streams, based on passive integrated transponder (PIT) technology, using a portable detector was investigated. The effect of implanting crayfish with PIT tags and the efficiency of the PIT tag detector system at locating tags is described. In a laboratory study 30 signal crayfish Pacifastacus leniusculus (>33.7 mm carapace length) were internally implanted with PIT tags (12-mm long×2.1-mm diameter) and 30 crayfish matched for size and sex were kept as controls and maintained for 6 months. Tagging had no significant effect on survival, moulting or growth of crayfish, and tag retention was 100%. The reader unit consists of an antenna coil mounted on a pole and designed to be moved over the streambed to search for tagged crayfish. Efficiency testing indicated that more than 80% of tags were identified and located when hidden within different stream microhabitats.

Winter movements and activity of signal crayfish Pacifastacus leniusculus in an upland river, determined by radio telemetry

Radio-telemetry was used to study the late autumn and winter movements of twenty adult signal crayfish Pacifastacus leniusculus (32.9–63.8 mm carapace length) an introduced exotic crayfish species, in the upland River Wharfe, northern England. The distances moved during the study varied greatly between individuals (0–328 m). Movements were generally sporadic; crayfish would remain in one position for several weeks and make occasional movements to new locations. Total distances travelled, linear range and ranging area did not differ significantly between males and females. The distance travelled in upstream and downstream directions did not differ significantly and there was no correlation between distance travelled and crayfish size. Several high flow events occurred during the study, but these did not cause any mortality or apparent displacement of crayfish downstream, suggesting that this is not a significant factor in downstream dispersal or mortality of adults of this invasive crayfish species in winter. A marked reduction in large-scale movements occurred in mid-December which coincided with a decline in water temperature. There was a less distinct pattern in local activity which was strongly correlated with water temperature and varied before and after mid-December.