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Ecology

Are MPA’s the best way to conserve the seahorse population?

Article: Harasti D, Martin-Smith K, Gladstone W (2014) Does a No-Take Marine Protected Area Benefit Seahorses? PLoS ONE 9(8): e105462. doi:10.1371/journal. pone.0105462

Introduction

As human population grows, the amount of marine resources available declines. Over-fishing, pollution, climate change, and habitat loss are all factors that contribute to the decline of many marine organisms. Several species of seahorse are now considered threatened, according to the IUCN Red list, due to the unsustainable trade of seahorses for aquarium use as well as the harvest of seahorses for traditional Chinese medicines.

Marine Protected Areas (MPAs) have been implemented across the world to help conserve marine organisms, protect them from overfishing and allow them to live a stable life without human interference. Researchers from Australia and Tasmania set out to understand the benefits of MPAs on one specific species, the White Seahorse (Hippocampus whitei).

 

Methods

For four years, monthly surveys were conducted to determine the relative abundance of White Seahorse populations between four different sites in Australia (Fig.1). Two sites were positioned in a sanctuary zone, protected of all fishing since 1983, and the other two sites were located in a habitat zone, meaning commercial fishing was restricted, but local fishing and boating allowed.

As each seahorse was observed, the sex and age class (juvenile or adult) was noted, as well as any predator interactions. Predator species of the white seahorse were observed to either attack or feed on the seahorse.

Figure 1. Location of study sites in Australia

 

Results and significance

Between 2006 and 2009 a total of 2,104 white seahorses were observed. A significant difference in seahorse numbers was observed between the two different types of location; 1,802 seahorses were found in the non-sanctuary zones and 302 were found in the sanctuary zones (Fig. 2). As for the predation, five species of culprits were witnessed bullies: the dusky flathead fish, the eastern red scorpionfish, the striped anglerfish, and two species of octopus. The predators were observed either attacking or feeding on white seahorses a total of thirteen times during this study, 9 in the sanctuary zones and 4 in the non-sanctuary

Marine Protected Area’s are established the help preserve species from fishing pressure, but this study suggests that White Seahorses might not actually benefit from MPAs. With decreased seahorse abundance comes increased predator abundance, meaning MPAs may not be helping the seahorse population, but they are preserving a higher abundance of fish species that just so happen to be predators of the seahorse.

While MPAs are effective for the conservation of many species, seahorses may not be one of them. Other management strategies such as habitat restoration projects or artificial reefs might be more beneficial to seahorse conservation. The greater risk of predation in the no-take sanctuary zones most likely caused a decrease in seahorse population, therefore a small scale MPA could be more beneficial, reducing the amount of predators, but still protecting the area and habitat from fishing pressure.

Figure 2. Mean monthly abundance of the White Seahorse

 

Cover Photo Credit: Jones, Andrew. Image of Hippocampus whitei. Photograph. Ikelite Underwater Housing <http://andrewtrevor-jones.com/ikelited300.html>

Valeska Upham
For my fisheries and aquatic science PhD I am working on how to tank raise urchins and transplant them onto reefs across the Florida Keys in order to help reverse the phase shift from algae dominated back to coral dominated.

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