30 May 2010

Conservation spotlight: Three Aquarium species that are under threat

Ingrid Sinclair
Photograph by Dagny Warmerdam

Galjoen – Conservation status: Conservation Dependent

According to A Guide to the Common Sea Fishes of Southern Africa by Rudy van der Elst (Struik), “the galjoen was one of the first species recognised as being endemic to southern African waters.”

Despite being our national fish it is disappearing quickly, more than likely as a result of overfishing by net and line. That’s why it has been declared a protected species and recreational anglers may only catch two galjoen, at a minimum size of 35cm, per day between 1 March and 14 October each year. And they are not allowed to sell their catch.

The galjoen is now listed as a Red (no sale) species by SASSI, the Southern African Sustainable Seafood Initiative.

According to Fishbase.org, the galjoen “changes from black to silver almost instantly to blend with environment.” These fish reach sexual maturity at a length of roughly 34cm (which explains the catching restriction of 35cm) and spawning occurs during the summer.

You can meet our school of galjoen in the Kelp Forest Exhibit.

Photograph by Marius Burger

Western leopard toad – Conservation status: Endangered

The Western Cape is the only place in the world (east or west) where you will find the Western leopard toad. You can hear them calling out to each other when they’re about to start moving toward water to mate and lay eggs. How will you know? The male’s call sounds a lot like loud snoring.

Despite its singularity, the Western leopard toad is threatened by habitat loss. According to Arkive.org, although “it may tolerate a degree of habitat alteration, often being found in urban and suburban areas, the Western leopard toad is under threat from increased urbanisation, housing development and agricultural expansion within its already limited range.”

So keep your eyes open for these toads on the roads, particularly in August (the start of breeding season) and in November, when the young toads are making their way from the water to land. Please brake for the toads! And if you see one when driving, stop, pick it up, and put it on the other side of the road (in the same direction in which it was going).

You can meet Teddy, our tongueless toad, at the Frogs: Beyond the Pond exhibit.

Photograph by Michael Farquhar

Cape sea urchin – Conservation status: Near Threatened

Cape sea urchins typically live in vast numbers on shallow reefs. Once upon a time, the density of urchins was so great along the southwest Cape coast that you couldn’t walk comfortably to the water’s edge at low tide without feeling like you were treading on sharp needles.

Then, in 1994, the urchins did a mysterious disappearing act. In just two years they were virtually extinct in certain areas. 

The disappearance of the urchins had marine scientists baffled. What could have caused this strange phenomenon? They discovered that, prior to the disappearance of the urchins, the number of rock lobsters had increased considerably. It turned out that the lobsters were responsible, having simply devoured them!

Although Cape sea urchins alone are of little commercial value to humans, they provide important nurseries for abalone (perlemoen), which in turn have significant value. The spines of the urchins protect juvenile abalone from predators such as the octopus, klipvis and rock lobster. The dramatic disappearance of urchins left juvenile abalone vulnerable and in the open, making them an easy target for hungry predators.

You can see Cape sea urchins at Oceans of Contrast: Atlantic Ocean Gallery.

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