Massive fish die off in Great Salt Pond

POSTED: 03/12/13 10:50 AM

St. Maarten – The Nature Foundation and its sister organizations St. Maarten Pride and Epic have been addressing the massive fish die off in the Great Salt Pond for the last few days. The majority of fish that died were of the genus Tilapia.

‘Oreochromis aureus’, which is commonly known as Blue Tilapia or Israeli Tilapia, is a species of fish in the ‘Cichlidae’ family. Native to Northern and Western Africa, and the Middle East, through introductions it is now also established elsewhere, including parts of the United States and the Caribbean, where it has been declared an invasive species and has caused significant environmental damage.

The Blue Tilapia is a freshwater fish with a high tolerance for brackish water. Adults are usually 5 to 8 inches (130 to 200 mm) in length and weigh 5 to 6 pounds (2.3 to 2.7 kg); the largest recorded specimen was more than 21 inches (530 mm) long and weighed more than 10 pounds (4.5 kg). The Blue Tilapia are mouth brooders, and broods range from 160 to 1600 eggs per female. O. aureus is primarily herbivorous, but will occasionally consume zooplankton; the young include small invertebrates in their diet.

Tilapias are an introduced species in St. Maarten, having established themselves over the last 10 to 15 years in the Great Salt and Fresh Ponds. The presence of the Tilapia has to be closely studied for the effects on the Native Fish population, however the die-offs of a tolerant species such as the Tilapia has to raise concerns about the water quality of St. Maarten ponds.

Since January the island has been experiencing very little rainfall, hot and on occasion calm weather. This, together with land reclamation activities in the Great Salt and Fresh Ponds has resulted in poor water circulation and a drop in dissolved oxygen (DO) levels in the ponds. The drop in these levels has resulted in oxygen depleted water (a DO level close to 1 part per million is essentially oxygen depleted compared to a normal level of 7 ppm) which in turn results in fish die offs. The worry is that the Tilapia will be the first species to die, followed by Tarpon, Mullets and other native fish species.

The Nature Foundation and the Pride and Epic have relocated approximately 600 Tilapia from the Great Salt Pond into the Fresh Pond were oxygen levels are greater, however with the continuous hot weather these fish are also in danger of becoming threatened.

The ROB department of Vromi, Clean St. Maarten and the Aeration pumps from Windward Roads all contributed in trying to get the situation stabilized, although by the time that equipment was mobilized a significant number of fish were already dead.

The Nature Foundation would like to echo governments’ advice not to eat the fish; doing so might have some significant health consequences.

The foundation would also like to urge the public to take the necessary precautions and prepare to deal with an unpleasant smell in the Great Bay area. Although the fish are being cleaned there is a risk of a bad smell and also an increase in flies.

The foundation recommends that the levels of the ponds be continuously managed in order to reflect meteorological conditions in order to avoid further die offs.


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