Evaluation of a number of treatments to be used as biosecurity measures in controlling the spread of the invasive killer shrimp (Dikerogammarus villosus)

Published source details Stebbing P.D., Sebire M. & Lyons B. (2011) Evaluation of a number of treatments to be used as biosecurity measures in controlling the spread of the invasive killer shrimp (Dikerogammarus villosus). CEFAS report, Final contract report C5256, 40pp.
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This study is summarised as evidence for the following.

	Action	Category
	Ponto-Caspian gammarids: Change water temperature Action Link
	Ponto-Caspian gammarids: Change water pH Action Link
	Ponto-Caspian gammarids: Add chemicals to the water Action Link
	Ponto-Caspian gammarids: Control movement of gammarids Action Link
	Ponto-Caspian gammarids: Change salinity of the water Action Link

Ponto-Caspian gammarids: Change water temperature

A controlled laboratory study in 2011, England, UK (Stebbing et al. 2011) found that heating water killed the invasive killer shrimp Dikerogammarus villosus. All shrimp died within a 15 minute exposure period when immersed into water at temperatures >36°C. All shrimps died immediately when immersed into water at temperatures >43°C. For each temperature tested, a container holding five shrimp was filled with water with measured temperatures of 28.4, 31.1, 36.3, 38.9, 43.2°C. A control set of five shrimps was held at ambient temperature (14-15°C). Shrimps were observed over a 15 minute period and then moved to freshwater at ambient conditions (14-15°C) to check for mortality over an 80 minute period.
Ponto-Caspian gammarids: Change water pH

A controlled laboratory study in 2011 in England, UK¹ (Stebbing et al. 2011) found that lowering the pH of water did not kill the killer shrimp Dikerogammarus villosus. None of the shrimp died during the test period. Tests were conducted on 5 captive shrimp immersed for 15 minutes in de-chlorinated water of different pH values. Values ranged from pH 7.2-3.1. Hydrochloric acid was used to adjust the pH of the test solutions. Dead and live shrimp were counted.
Ponto-Caspian gammarids: Add chemicals to the water

A controlled laboratory study in 2011 in England, UK (Stebbing et al. 2011), found that when added to freshwater, iodine solution, acetic acid, Virkon S and sodium hypochlorite killed the killer shrimp Dikerogammarus villosus, but methanol, citric acid, urea, hydrogen peroxide and sucrose did not. For iodine solution (FAM30) there was 100% mortality within 15 minutes when the shrimp were placed in solutions of 4-6 ml per litre. However, FAM30 is an irritant and so was not considered a practical control method. For acetic acid, a 10% solution was required to kill all the shrimp in 15 minutes. At lower concentrations, no shrimps died during the test period. However, fifteen minutes was considered too long for acetic acid to be a practical control method. For Virkon S, all shrimp exposed to a 1% solution died within 15 minutes, with half dying within eight minutes. However, Virkon S has a relatively short shelf life and a capacity to bleach and can damage equipment and so was not considered a practical control method. For sodium hypochlorite, at 50,000 parts/million, half of the shrimp were killed within 4.5 minutes. However, at that concentration it is lethal to humans and so is not practical. Equipment containing shrimp could be soaked in sodium hypochlorite at 200 parts/million for over an hour, but is considered impractical. None of the shrimps died when exposed for 15 minutes to methanol (1 or 10 %), urea (1 or 10 g/litre), citric acid (15 or 150 mg/litre), hydrogen peroxide (100 mg/litre), or sucrose (10 or 100 g/litre. All tests were conducted on 5 captive shrimp. Dead and live shrimp were counted.
Ponto-Caspian gammarids: Control movement of gammarids

A controlled laboratory study conducted in 2011 in England, UK (Stebbing et al. 2011) found that carbonating water did not kill the invasive killer shrimp Dikerogammarus villosus but 100% of the shrimps were stunned (stopped moving). A test group of five captive shrimp was immersed in carbonated water for 15 minutes. Dead and live shrimp were counted.
Ponto-Caspian gammarids: Change salinity of the water

A controlled laboratory study conducted in 2011 in England, UK (Stebbing et al. 2011) found that adding salt to freshwater did not kill the killer shrimp Dikerogammarus villosus. None of the shrimp died during the test period. This included shrimp exposed to salinity levels 3.5 times more saline than normal seawater. Tests were conducted on 5 captive shrimp immersed for 15 minutes in de-chlorinated water of different salinities ranging from 5 to 160 grams of salt/litre. Artificial marine salt was used to adjust the salinity in the test solutions. Dead and live shrimp were counted.