Distribution, substrate preference and habitat enhancement of the isopod Austridotea lacustris in Tomahawk Lagoon, Otago, New Zealand

Abstract

Aquatic isopods are cryptic, semibenthic components of food webs in coastal water bodies in southern New Zealand. The distribution and abundance of endemic Austridotea lacustris in a modified, urban coastal lagoon were related to selected environmental and habitat variables in field studies and laboratory experiments. Isopods were four times more abundant on lumps of roading conglomerate used in shoreline consolidation than on bricks and natural rocks. Isopod densities were unrelated to the size of the substrate units or their development of biofilm, a major food source for isopods. In experiments to test settlement behaviour with concrete and wood substrates of different structural complexity (with and without holes), isopods showed clear preferences for wood over concrete substrates, and for more complex (more holes per unit area) than less complex (few, or no holes) wood substrates. By increasing the habitat complexity in coastal water bodies, it might be possible to restore and increase populations of aquatic isopods.

Keywords:

• crustacean behaviour
• substrate complexity
• coastal lakes
• habitat restoration
• predator avoidance