A fishing boat sails on Lake Kariba

…as overfishing hits Lake Kariba

LAKE Kariba has become a victim of overfishing with over 1 100 commercial fishing rigs exploiting various types of fish in the world’s second largest man made water body, the Financial Gazette’s Companies & Markets can report.
The lake has a maximum carrying capacity of 500 commercial fishing rigs but somehow the authorities in Zimbabwe and Zambia — the two countries that share the dam — have allowed the number of rigs to more than double, resulting in overfishing in Lake Kariba.
There were 725 kapenta rigs on the Zimbabwean side of the lake in 2014, against a carrying capacity of 406.
What it means is that the Zambian side now has about 375 fishing rigs.
To sustainably exploit fish in the lake, both countries must trim the rig population to a combined 500.
Obviously, this will result in serious job losses.
Of the recommended 500 rigs, Zimbabwe should operate 275 while Zambia must have 225.
These ratios are based on the surface area of the lake occupied by each country.
The Parks and Wildlife Management Authority of Zimbabwe (PWMAZ) says that kapenta output in the lake declined to 8 746 tonnes in 2013, from 19 957 tonnes in 1993.
Output was expected to drop further to 8 500 tonnes last year.
“The resource is being harvested at unsustainable levels,” says the PWMAZ. “Both countries have committed to a phased reduction over (a period of) 10 years starting 2014. Zimbabwe will reduce at a rate of 13 rigs per year and Zambia will reduce at a rate of 50 rigs per year,” added the parks authority.
At least 2 000 jobs have been lost on the Zimbabwean side of Lake Kariba, where a predator called crayfish has also been devouring kapenta, the biggest source of jobs and incomes on the transnational water body.
There were about 4 000 workers in the industry a decade ago, according to the General Agricultural and Plantation Workers’ Union of Zimbabwe, which says about 2 000 employees were still gainfully employed in the kapenta fishing industry as of last year.
More jobs are likely to be indirectly affected by the emergence of crayfish whose scientific name is cherax quadricarinatus, which has spread in Lake Kariba’s waters.
The ruthless predator which produces clusters of eggs that hatch prolifically could be multiplying at a faster rate than previously thought, in essence affecting the breeding of all fish species.
A report by the University of Zimbabwe titled Invasive Australian crayfish cherax quadricarinatus in the Sanyati Basin of Lake Kariba: a preliminary survey, indicates that the invasive predator is now also in the Bumi Basin, about 80 kilometres west of the resort town.
The report was done in 2012.
There is a high possibility that the crayfish scourge might have spread to other basins in the past 24 months.
The report confirms fears of a potential devastation of the industry, whose annual turnover plunged to about US$10 million last year, from about US$20 million in 1993.
While authorities are looking for desperate measures to correct the effects of overfishing in Lake Kariba, other hurdles have also emerged.
Receding water levels have become more pronounced in the lake in recent months because of the effects of climate change.
Ecologists say the influence of climatic variables, such as rainfall, temperature and evaporation rates, are also exerting pressure on kapenta populations.
Results from a research done to determine trends showed that rainfall has been decreasing at the rate of 0,63 millilitres per annum in the region that the lake occupies.
Evaporation rates have also rose by an estimated 31 percent during the period, which partly explains the declining water levels in the lake.
A study by the Royal Society of South Africa said in addition, temperatures around Lake Kariba have been rising in the past 50 years.
The World Bank  in a report released in November last year said “fishing dependent” countries were at risk because “fishing activities are poorly regulated” and “are very vulnerable to the combined impact of climate change and over-exploitation”.
“Fish catch has not been good for two years in a row. Research has even raised the possibility of fish supply significantly declining over the next decades, because of the combination of climate change and the hydropower network,” said the bank, referring to a global problem affecting all fishing regions.
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