The drop puts Ventspils behind Russia's new Primorsk terminal.
Latvia's other ports have fared less badly so far this year and all except Ventspils showed increases in the volume of liquid products handled.
A total of 28.37 million tons of cargo were handled in Latvia's ports in the first six months, which is 4.8 percent less than a year earlier. Ventspils handled 17.18 million tons in the same period, which is 2.7 million tons less than last year.
Reduced throughput of oil and petroleum products is the main cause of the slow down at Ventspils. The port handled a total of 12.6 million tons of liquid cargo, an 18.6 percent reduction on last year. The sharpest decrease was in the handling of crude oil, which was down by 1.84 million tons to 5.53 million tons. Petroleum product shipments declined by 719,000 tons in the same period and ammonia shipments by 275, 000 tons.
Riga Port, however, showed a sharp rise, handling 8.84 million tons, or 16.2 percent more than in the first half of last year. Liepaja's cargo handling also rose by 8.7 percent to 1.86 million tons.
The main reason for Ventpils' weaker performance was competition from Russia's Primorsk and Lithuania's Butinge terminals, as well as the Russian company Transneft's complete dominance of the market, said representatives of Ventspils Free Port.
They noted that Ventspils Nafta and Ventbunkers were the only liquid cargo terminals on the Baltic Sea which suffered reductions in throughput and resolved to examine the problem carefully.
Improving arrangements with Transneft is the port's No. 1 priority, said the representatives.
They pointed out, however, that the volume of cargo handled exceeded expectations by 183,000 tons.
The decline in ammonia handling is linked to lower world market prices for the chemical and a resulting reluctance to sell by exporters using the port.
Riga Port saw a 43.4 percent increase in throughput of its main commodity, dry bulk goods, to 3.3 million tons. Liquid cargo, mainly comprising petroleum products, increased by 2.73 percent to 2.59 million tons.
Liepaja Port's fortunes also improved as it experienced a 52.6 percent rise in handling of liquid cargo - mainly vacuum gasoil cargo, according to Ivo Kolins, a marketing specialist.
Also cargoes delivered to ports by rail increased, according to port analysts.
Ventspils expects to handle 34 million tons during the year as a whole.