Pre-emergent movements and survival of F-0 larvae of Ophiogomphus rupinsulensis (Odonata: Gomphidae) in a northern Wisconsin river

Abstract

We marked and released 276 F-0 larvae of Ophiogomphus rupinsulensis in the fall of 2008 in a 99-m riffle (marking riffle) of a small, serially discontinuous, northern Wisconsin river (USA). We then recovered marked exuviae via exhaustive collecting on the banks of a 272-m sampling reach in which the marking riffle was located during spring of 2009. We collected 6054 exuviae of O. rupinsulensis along the sampling reach, including 3829 exuviae along the marking riffle (19.3 exuviae m^–1). Mark retention was complete and our ability to recover marked exuviae in the field was high (92%). We recovered 38 marked exuviae which provided a minimum estimate of survival (14%) for F-0 larvae from late September to the following June. The density of F-0 larvae in the marking riffle in late September was estimated at 22.6 larvae m^–2. Nearly all F-0 larvae made small downstream movements (97% moved < 60 m) at some time during the 36 weeks before emergence, but they did not make substantial longitudinal movements. These results affirmed the premise that locations of found exuviae of O. rupinsulensis along a small river are in close proximity to the habitats where the larvae developed.

Keywords: Odonata, dragonfly, Anisoptera, Ophiogomphus, larval movements, drift, emergence, exuviae

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