Seahorse friendly management of artificial nets

The White’s Seahorse is a protected species in New South Wales. This species of seahorse has experienced significant population declines due to degradation in its natural habitat.

University of Sydney’s Michael Simpson is working at SIMS as part of a larger Sydney Harbour study looking at the White’s Seahorse use of artificial structures, in particular swimming nets, as habitat.

This species of seahorse has been found to inhabit swimming nets in various locations around the harbour, and they are often found  in higher numbers on the nets than on surrounding natural habitat. In fact, an experiment conducted by Michael at  SIMS two years ago showed that this species chose swimming net material over other available natural habitats found in Sydney Harbour. Therefore, if maintained properly, these nets could potentially be a valuable conservation tool for this species, as natural habitat is in steep decline due to the increased urbanisation of coastline in recent years.

One council has installed a net at Parsley Bay created with copper free “seahorse friendly material”.  In order to explore any possible benefits such a material might have for seahorses in Sydney Harbour, the investigation is 1) Comparing the seahorse population on this net to seahorse populations on other nets around the harbour that are constructed of regular material, and 2) Installing net panels constructed with seahorse friendly material and regular copper braided material at multiple locations and comparing seahorse colonisation to both net types.

However, one confounding factor for the research is that the seahorse friendly net is only available in blue, whereas the regular copper braided material used to construct most nets around the harbour is white.

In order to attribute habitat choice to material type, we must account for the confounding factor of colour. To solve this problem, Michael is running another habitat choice experiment in the SIMS Ian Potter Research Aquarium  where seahorses will be placed in a tank, or “choice chamber”, in which they have the option to inhabit either white or blue netting that is otherwise identical. Their choice of habitat is recorded every half an hour over twelve hours, and if the time spent on either habitat is different to 50% then a choice has been made.

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