According to the commission, the bacterial infection, which weakened the immune system of the fish, and environmental factors such as high temperature and salinity of the water could have led to the death of the fish.

The Head of the Fish Health Unit of the Fisheries Commission, Dr Peter Akpe Ziddah, who disclosed this to the Daily Graphic, said the fish with weak immune system could have easily been stressed by the environmental factors.

Background

In October last year, there was a scare among fish consumers when news broke that more than six tonnes of dead fish (tilapia) had been discovered on the Fujian Fish Farm, owned by a Chinese firm.

Another incident was noticed at the end of the year along the Volta Lake.

The Fisheries Commission and the Veterinary Services initiated an investigation process to find the cause of the kills.

The findings

Following the incident and preliminary observation, Dr Ziddah said there was an initial suspicion that the emerging new viral disease, Tilapia Lake Virus (TiLV), was the probable cause of those deaths or a toxin introduced in the water body.

Therefore, he said, samples of the water and the fish were taken to various specialised laboratories in Ghana, the United Kingdom, Singapore and Norway to confirm the fears of a viral infection.

However, results from the samples sent to the Ghana Standards Authority and the various laboratories outside Ghana proved that there was neither toxin in the water nor the flesh of fish.

The investigation also indicated that the fish was negative for the viral infection (TiLV).

“We knew of the presence of some bacterial infections that were causing  heavy mortalities since 2014 and prominent was the strain streptococcus agalactiae 1b.

“This bacteria was contained by the use of an autogenous vaccine that was developed with the strain from the Volta Lake,” he explained.

Most of the results from laboratories abroad, he said, proved that there was a new bacterial introduction of the streptococcus agalactiae 1a.

He said the streptococcus agalactiae 1a was a very virulent (harmful) bacteria to fish.

Recommendations

Furthermore, he said, the investigations showed that the DNA of the bacteria found in the fish was of Asian origin.

He said the streptococcus agalactiae Ia might have been introduced into Ghana after someone brought in a new fish, saying “someone might have smuggled it into the country”.

“Most of the fish farmers believe that the local fish did not grow fast and so some of them smuggle some fish into the country through which some of these diseases appear,” he explained.

Additionally, he mentioned that the use of agro-chemicals along the banks of the Volta Lake was dangerous to the health of the fish and urged the public to desist from doing so.

Going forward, Dr Ziddah recommended that the biosecurity measures on fish farms and at the country’s entry points should be improved.

He further recommended the use of autogenous (local) vaccine from the strain found in Ghana to avoid recurrences.