Biocide Treatment of Ponds in Scotland to Eradicate Signal Crayfish

Abstract

This trial aimed to eradicate illegally introduced signal crayfish Pacifastacus leniusculus in the North Esk catchment, Scotland. Sites treated were (1) an isolated gravel-pit (c. 9,000 m 3 ), with crayfish present for 6 years; (2) three dammed ponds, (c. 5,000 m 3 ) and (3) a leaking, offline pond (c. 6,000 m 3 ), with crayfish for two years. Preliminary toxicity tests with substrate present indicated doses. Treatment at sites (1) and (2) (in October 2004, water temperature 13°C) comprised deoxygenation with sodium sulphite to stimulate emergence, then application of natural pyrethrum (Pyblast). Exposed margins were sprayed with Pyblast to prevent escapes. Crayfish mortality was high, but one survivor was seen after 5 days. Pyblast was applied from a tank with Na 2 SO 3 residue, which subsequent investigation indicated reduced Pyblast below the target 0.1 mg l -1 . Site (1) was re-treated (end October, target 0.15 mg l -1 Pyblast, no Na 2 SO 3 , 9°C). Mortality was confirmed using caged crayfish. Prior to treatment at site (2), throughflow was stopped and fish removed. Biomonitoring was carried out with freshwater shrimps Gammarus in the adjacent watercourse. Treatment of site (3) (December, target 0.2 mg l -1 , 4°C) necessitated continuous back-pumping of leakage for a 2-week recovery period to avoid contamination of the river downstream. Caged crayfish took up to 5 days for 100% mortality. No crayfish were found in a summer survey after the treatments with Pyblast alone, but were caught in the ponds with Na 2 SO 3 pre-treatment. Monitoring is required for 2-5 years. Key-words:Pacifastacus leniusculus, eradication, biocide, ponds, natural pyrethrum. ÉRADICATION DE L'ÉCREVISSE SIGNAL DANS LES ÉTANGS ÉCOSSAIS PAR TRAITEMENTS BIOCIDIQUES RÉSUMÉCet essai avait pour but d'éliminer l'écrevisse signal (Pacifastacus leniusculus) introduites illégalement dans le nord du bassin de l'Esk, en Ecosse. Les sites d'expérimentation furent une sablière isolée (ca. 9 000 m 3 ), trois étangs de retenue (ca. 5 000 m 3 ) et un étang perméable (ca. 7 000 m 3 ), avec des écrevisses depuis moins de deux ans, à l'exception de celles présentes dans la sablière depuis 6 ans. Des tests l'eau 13 °C) a compris la désoxygénation avec du sulfate de sodium pour stimuler l'émergence, et ensuite l'application du pyrèthre naturel (Pyblast). Les berges exposées furent vaporisées à l'avance avec Pyblast pour empêcher la fuite des écrevisses. La mortalité des écrevisses fut élevée, mais un survivant a été vu 5 jours plus tard. Le Pyblast avait été pompé à partir d'un réservoir contenant encore des résidus de sulfate de sodium, ce qui a probablement réduit la concentration de Pyblast en dessous de 0,1 mg.l -1 . Un nouveau traitement a été conduit fin Octobre avec 0,15 mg.l -1 de concentration en Pyblast et 0 en Na 2 SO 3 (température de l'eau 9 °C). La mortalité fut confirmée par l'utilisation d'écrevisses en cage. Aux trois étangs, l'écoulement a été arrêté avant le traitement, les poissons ont été retirés, la végétation des berges a été tr...

Managing invasive crayfish: is there a hope?

“…Yet attempts to manage invading populations often fall short of accomplishing their objective: none of the attempts made to contain the spread of NICS in the last decade has provided a definitive methodology (e.g., Blake and Hart 1995;Frutiger and Müller 2002;Stebbing et al 2003;Peay et al 2006). On the contrary, invasive crayfish's management should be a priority for most governments.…”

Studies on the White-Clawed Crayfish (Austropotamobius Pallipes) Associated With Muddy Habitats

“…Although short project reports are written, such work is rarely prepared for publication and any findings may go largely ignored. Post-project monitoring is not mandatory and is not often done (PEAY, 2003), although there are exceptions (PEAY et al, 2006).…”

The impact of signal crayfish (Pacifastacus leniusculus) on the recruitment of salmonid fish in a headwater stream in Yorkshire, England

“…These species are important elements of the overall aquatic biodiversity, but are not of interest for angling. Although the negative impact of signal crayfish on white-clawed crayfish is widely known, there appears to have been little published on the impact of signal crayfish on angling, apart from the nuisance of crayfish taking angling bait in some cyprinid fisheries (Peay and Hiley, 2004). Anglers on the River Wharfe have reported catching brown trout which have eaten juvenile crayfish (Birdsall, 2007, pers.…”