A mark and recapture study of water beetles (Coleoptera: Dytiscidae) in a group of semi-permanent and temporary ponds

A year mark and recapture study of aquatic Dytiscidae (Coleoptera) in a group of seven semi-permanent and temporary ponds in Cheshire (UK) is described. Pond water levels showed strong seasonal fluctuations with most ponds drying and refilling on several occasions over the study period. Sampling and labelling of aquatic Dytiscidae was carried out at monthly intervals. Beetles were labelled by fixing numbered waterproof paper labels to the elytra with cyanoacrylate `Superglue'. A total of 780 beetles were marked and released of which 11.5% were subsequently recaptured over varying time intervals of one month to eighteen months. The six species marked (Agabus bipustulatus (Linnaeus, 1767), Acilius sulcatus (Linnaeus, 1758), Colymbetes fuscus (Linnaeus, 1758), Dytiscus marginalis (Linnaeus, 1758), Ilybius ater (De Geer, 1774) and Ilybius fuliginosus (Fabricius, 1792)) are all known to be highly flight mobile. Colymbetes fuscus did not move between ponds as a result of ponds drying up in the summer. The behaviour of Dytiscus marginalis and Acilius sulcatus was found to be in broad agreement with previous accounts of dispersal from over-wintering ponds into temporary ponds in the spring with movement back to permanent ponds in the summer as the temporary ponds dry up. In contrast, Agabus bipustulatus did not migrate when ponds dried up in the summer but remained in terrestrial vegetation in damp pond basins for several months after open water had disappeared, only migrating if the basin dried out completely. Both species of Ilybius were captured and marked in very low numbers and no recaptures were made. As more ponds became temporary over the years of the study Agabus bipustulatus persisted while the other five species declined or were lost altogether.