Assessing the toxicity of biocides on the North American signal crayfish Pacifastacus leniusculus (Dana) to aid eradication

O'Reilly, Sinead (2015) Assessing the toxicity of biocides on the North American signal crayfish Pacifastacus leniusculus (Dana) to aid eradication. MSc(R) thesis, University of Glasgow.

Abstract

North American signal crayfish Pacifastacus leniusculus (Dana) have been introduced into much of mainland Europe over the course of the last century, primarily to satisfy a demand for human consumption. Over the last three decades the invasive signal crayfish have become a major problem throughout the UK. Control or eradicate methods have proven challenging. Since the discovery of signal crayfish in Scotland in 1995, many methodologies have been attempted to eradicate them. One of the most promising methodologies has been a natural pyrethrum known as Pyblast, a commercially available pesticide which is generally used to treat household pests. However, when used in aquatic environments, Pyblast is non-specific to crayfish and has a negative impact on non-target organisms, ranging from other aquatic invertebrates to amphibians and fish. Achieving the concentrations needed to kill crayfish means that it is also prohibitively expensive to use. Pyrethroid insecticides are well known to be highly toxic to crustaceans and the synthetic pyrethroid Deltamethrin is considered to be the most toxic of those available. Formulated products of AlphaMax (deltamethrin) and Salmosan (azamethiphos) are used to treat sea lice on farmed salmon, however the use of these chemicals as a means to eradicate signal crayfish remains unknown. This present study tested the acute lethality of these formulations on various life stages (from hatchlings to adults) of signal crayfish under laboratory conditions.

Results from this current study show early life stages most sensitive to both Pyblast and Deltamethrin. Based on the acute toxicity tests, stage I hatchlings showed significant differences in sensitivity between family populations when exposed to Pyblast with lethal concentration (LC50) values ranging from 2.62 - 20.99 µg/lˉ¹ at 48h. Stage II crayfish were not significantly less sensitive than stage I, 5.23 µg/lˉ¹ and 6.43 µg/lˉ¹ respectively. Juveniles had a 48h LC50 of 57.95 µg/lˉ¹ and were significantly more sensitive than adults. Adult females had a 48h LC50 of 118.25 µg/lˉ¹ and adult males LC50 of 111.13 µg/lˉ¹. Adult females showed the higher tolerance than males to Pyblast at 24h exposure, however males were more affected than females after 48h exposure. Adults had an acute 48h LC50 of 26.49 ng/lˉ¹ value for formulated Deltamethrin. The 48h LC50 for adult crayfish exposed to Salmosan was 15.27 mg/lˉ¹. Adult crayfish were most sensitive to Deltamethrin and least sensitive to Salmosan. The LC50 values obtained during the current study were 52-69% less than that previously estimated 0.2 mg/lˉ¹ for field trials. Analyses of water samples taken during Pyblast toxicity trials on adult crayfish indicated that over 50% of the pyrethroid was removed from solution by rapid breakdown over 48h.

• Item Type: Thesis (MSc(R))
• Qualification Level: Masters
• Keywords: Signal crayfish, invasive, eradication, Pyblast, pyrethroids, LC50
• Subjects: Q Science > QL Zoology
• Colleges/Schools: College of Medical Veterinary and Life Sciences > Institute of Biodiversity Animal Health and Comparative Medicine
• Supervisor's Name: Bean, Professor Colin. W. and Adams, Professor Colin. E.
• Date of Award: 2015
• Depositing User: Ms Sinead O' Reilly
• Unique ID: glathesis:2015-6429
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 28 Aug 2015 15:38
• Last Modified: 03 Sep 2015 09:43
• URI: https://theses.gla.ac.uk/id/eprint/6429