An endangered seahorse selectively chooses an artificial structure

Abstract

The development of a residential marina estate within the Knysna estuary, South Africa, introduced Reno mattresses (horizontal wire cages filled with rocks) as a novel habitat for the endangered Knysna seahorse Hippocampus capensis. Consistently high seahorse densities on these artificial structures, despite the availability of seagrass habitat, begged the question of whether this habitat was chosen by the seahorse in preference to natural vegetation. An in situ habitat choice experiment was conducted which focused on the choice made by adult H. capensis between natural vegetation (Zostera capensis) and artificial (Reno mattress) habitat within a choice chamber. Seahorses were significantly more likely to move away from Z. capensis onto a Reno mattress structure or remain on this structure. This study concludes that higher H. capensis densities on Reno mattresses within Thesen Islands Marina are owing to some positive feature of this habitat and the underlying processes responsible for the choice made by this species (additional food, holdfasts, protection) can now be investigated.

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Acknowledgements

This research project was approved by SANParks, and conducted in accordance with their scientific research regulations and requirements. We thank Thesen Islands Home Owners Association and the Rufford Foundation for financial support to Louw Claassens, the Knysna Estuary Monitoring Platform (KEMP) project for water quality data, Rondevlei Scientific Services Offices of SANParks for permission to undertake fieldwork in the Knysna Section of the Garden Route National Park, Mike Davies for assistance in data collection, David Harasti for his support and guidance, and Brian Allanson and Richard Barnes for their continued support and advice.

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Correspondence to Louw Claassens.

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Claassens, L., Booth, A.J. & Hodgson, A.N. An endangered seahorse selectively chooses an artificial structure. Environ Biol Fish 101, 723–733 (2018). https://doi.org/10.1007/s10641-018-0732-4

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Keywords

  • Zostera Capensis
  • Hippocampus capensis
  • Habitat choice
  • Estuary
  • Reno mattress