“Alien” Invasion in the MPAs

Mediterranean Mussels | Western Cape | South Africa

Dazzled by several animals washed ashore, I could not help but wonder how pristine the MPAs (Marine Protected Areas) really were.

Spot the intruders...

I was definitely not the only perplexed one after all. A few weeks ago, I had the chance to assist Ben Brooker, a Masters student from the University of Cape Town, who was doing field work in the Tsitsikamma MPAs. South Africa has 23 MPAs along its coastline that aim at protecting marine coastal habitats by prohibiting or restricting anthopogenic disturbance. Conservation efforts in the MPAs have so far held up direct habitat degradation. Nevertheless, while no-take areas have been established to maintain biodiversity and ecosystems functions, little was known and done about the introduction and control of dangerous alien species populations.

Strolling on the rocky shores, few are aware of inconspicuous alien species blending in subtly with native populations. But, one should not be fooled by the “shell” and belittle the threats some non-indigenous, more specifically invasive species, can pose. For instance, the Mediterranean mussel (Mytilus galloprovincialis) was first recorded on the coastline of Tsitsikamma in 1993 and in a decade has already started displacing the competitively inferior native brown mussel (Perna perna) and limpet Scutellastra granularis from prime rock space. Now that the Mediterranean mussels’ offshore larval pool is too vast to be

contained, control of the invasive mussel populations is thought to be impossible.

“M. galloprovincialis has out-competed the limpet S. granularis on semi-exposed and exposed rocky shores on the West Coast. It is likely that this has had a negative impact on the traditional harvest of this limpet species by artisanal fishers for use as lobster bait. This appears to be the only known negative socio-economic impact for this species. On the other hand, higher growth rates for this species relative to the local mussel species, has almost certainly contributed significantly to the success of the local mussel culture operations.” – National Dept. of Agriculture, 2012.

It cannot be denied that some alien species can have valuable socio-economic benefits. In 2010, South African mussel aquaculture was valued at ZAR9.1 million (DAFF 2012). However, biological impacts of invasive species can be irreversibly detrimental to native biota. In the long run, invasive species may hinder sustainable development through the pressures they exert on the ecosystem.

Whether in or outside the MPAs, South African marine ecosystems remain vulnerable to anthropogenic impacts (E.g. subsistence, recreational or commercial use, habitat modification, accidental or deliberate introduction of invasive species, climate change and pollution). While management authorities develop critical policies, taking into consideration both ecological and socio-economic factors, each and one of us can further contribute to the safeguard of the oceans by making the right choices.

“Each one of us can make a difference. Together we make change”- Barbara Mikulski

How can you help?

For one, if you are in South Africa, choose to eat fish only from sustainable fisheries such as snoek, hake, gurnard and calamari. You can even check the status of a fish before you order or buy it. SMS the kind of fish or seafood, e.g. squid, to 079-499-8795 and a return message will tell you about the fish.

-Tried it... it actually works!!!

For more information you can visit the SASSI  website.

Green- fine to eat

Orange-uncertain, so eat less often

Red- it is illegal to sell these fish. The fishery is either over-exploited, damages the ocean, or is illegal.

Also on the help list;

• Obey marine regulations and refrain from destructing marine habitats 
• Help protect the coast taking part in conservation programs like Coastcare and the Adopt-a-beach initiative. 
• Educate others about the importance of a healthy ocean 
• Report problems when you see one 

For more information you can refer to: 

DAFF. 2012. Department of Agriculture, Forestry and Fisheries Aquaculture Annual Report 2011 South Africa. ISBN: 973-1-868-71-355-4.