Sampling mobile macroinvertebrates: a role for light-traps?

Abstract

Light-traps have been routinely used to sample terrestrial insects for decades. They may provide a similar low cost standard method for sampling and monitoring mobile marine invertebrates. We deployed transparent plastic bottles, with their top inverted to form a funnel, and a chemical light-stick and weight inside, for at least 1 hour on the seabed (< 5 m depth) around Auckland, New Zealand. Traps collected 35 taxa of zooplanktonic and benthic taxa of 6 phyla, 11 classes, 12 orders. Most were Crustacea (26 taxa). Zooplankton included crustacean nauplii, cypris, zoea and megalopa larvae, gelatinous zooplankton, and calanoid Copepoda. In order of abundance, benthos included Amphipoda, Cumacea, Isopoda, Mysidacea, Ostracoda, Harpacticoida, Decapoda, Tanaidacea, Branchiopoda, Siphonostomatoida (caligid fish lice), Stomatopoda, Pycnogonida, and Collembola. Other taxa included Polychaeta, Clitellata (oligochaetes), Turbellaria, Nematoda, Chaetognatha, Gastropoda and Polyplacophora. These taxa are important prey of fish and thus a key link between primary producers and predators but collecting and sorting them from the benthos and plankton nets is time consuming. The light-traps have been efficient for introducing university students to the diversity of mobile macro-fauna and zooplankton. They show promise for surveillance of this component of marine biodiversity as they do for aerial arthropods.