The Department of Fisheries on Friday reported that the populations of sardines and mackerel in the Gulf of Thailand have increased thanks to its conservation methods.
Bancha Sukkaew, the department's deputy director-general, said the boom in the population increased the yield of economically important fish by 1.6 times year-on-year.
The increased yield is due to the department's conservation policy imposing seasonal closures in the Gulf of Thailand.
Sustainable fishery practices are exempted from the ban because they are light and non-destructive, Mr Bancha said.
"The measures are found to be effective in rehabilitating and restoring marine species stocks," he said. "The upper Gulf is known to be filled with juvenile fish during the seasonal closure."
"They must be protected from being caught prematurely," Mr Bancha added.
The upper Gulf of Thailand is known as the "Kor-shaped gulf", an area where sought-after fish spawn. The closure takes place three times per year.
The first period is from June 15 to Aug 15 and the closure applies in the northwestern part of the Gulf from Prachuap Khiri Khan province's Hua Hin district to Samut Sakhon province's Muang district.
The second period is from Aug 1 to Sept 30 in the northeastern part of the gulf from Muang district to Si Racha district in Chon Buri. The closure area spans 1,650 square kilometres covering the inner gulf area off the coasts of Bangkok, Samut Prakan and Chachoengsao.
The southwestern part of the gulf is usually closed off for three months from Feb 15 to May 15. It is located in the lower section of Prachuap Khiri Khan, Chumphon and Surat Thani. The closure allows fish to breed and nurture their young.
This is the first time the initiative is showing results. The department first imposed closures to reduce overfishing in the Gulf some 50 years ago but achieved little success.
Conservationists have blamed the state for not being tough enough with commercial fishing trawlers which have used destructive fishing methods.
Last year the kingdom passed a tough law against the vessels after the European Union issued a so-called "yellow card" warning.