GARDEN ROUTE NEWS - A number of pufferfish washed up on seashores from Cape Town to Port Elizabeth at the weekend.
There were many dead pufferfish spotted on Mossel Bay beaches.
A scientist in Fisheries Research at the Department of the Environment, Forestry and Fisheries has provided a few reasons as to what might be the cause of the mortalities and strandings.
Puffer fish take in water and puff up when they are under stress. Sometimes they take in too much and their organs rupture.
Scientist Dr Stephen J Lamberth listed the following as possible causes of the deaths:
- "Harmful algal blooms. There is published work on instances where only pufferfish are poisoned by harmful algal bloom toxins." Dr Lamberth noted: "It's intriguing that a toxic fish is susceptible to another toxin.
- "Wind and waves. Big seas and strong winds can startle puffers, causing them to inflate, mostly with water but sometimes air, and the puffer fish balloons are washed ashore. This also sometimes happens during courtship, during which the inflated amorous males end up on the beach.
- "Spawning aggregations in the shallows during high sea conditions can result in mass stranding and mortalities. There have been some strong blows in the past month."
- "Inshore trawl discards."
Inshore fishing takes place in water up to thirty metres deep. It might be that trawlers are discarding the poisonous puffers from their nets. Although two environmentalists listed this as a cause when speaking to the Mossel Bay Advertiser, this seems an unlikely cause because the strandings were over a large stretch of coastline. There was even mention made to the Advertiser that puffers had washed up on the West Coast, although another report mentioned the area was Infanta - near Cape Town - to Port Elizabeth.
- Another possible cause listed by Dr Lamberth was: "Seismic activity. Puffers are bio-balloons and highly susceptible to physical damage from pressure changes and seismic waves," he noted. Seismic activity relates to the vibration of the earth or earthquakes. The seismic survey schedule for the past month needed to be checked, he said.
Dr Lamberth said the fish "could have been startled and inflated with the first pulses and popped with the rest".
He did not mention a change in water temperature as a cause, which is what many had thought was the cause of the deaths.
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