Can Copper-Based Substrates Be Used to Protect Hatcheries from Invasion by the New Zealand Mudsnail

Copper sheet (abbreviated SC), copper mesh (MC), copper-based ablative antifouling paint (AP), and copper-based nonablative antifouling paint (NP) were tested to determine each material's ability to serve as contact deterrents to the invasive New Zealand mudsnail Potamopyrgus antipodarum. Mudsnail responses to each surface treatment was measured across a range of water temperatures (8, 12, 18, and 24 degrees C), hardness levels (75, 125, 175, and 300 mg/L as CaCO3), pH values (6, 7, and 8.5), water velocities (0, 9, and 33 cm/s), and levels of surface fouling (0, 6, and 10 weeks of exposure). Mean crawling distances (MCD) by the mudsnails in the temperature, hardness, and pH experiments were significantly lower on the SC and MC surface treatment than the NP treatment. In the velocity experiment, static, nonflowing conditions produced the lowest MCD, whereas increasing water velocity from 9 cm/s to 33 cm/s did not produce a significant change in MCD on either the SC or MC surfaces. Finally, MCD did increase significantly on the AP surface treatment after exposure to surface fouling; fouling had no significant effect on MCD on the MC or SC surface. Overall, MC and SC were determined to be the most effective surfaces in limiting the locomotor activity of the mudsnail. By lining the inside surface of effluent pipes with either material, hatcheries may be able to eliminate a potential invasion pathway for this organism. Based on the maximum observed crawling distance observed throughout these experiments, we recommend that barriers constructed of MC or SC be a minimum length of 250 cm to provide a satisfactory level of protection against mudsnail invasion. Additional considerations include design and integration with other types of barriers.