His sentiments are shared by state-employed caviar fisherman all along Iran's Caspian coastline, who fear the days of their expeditions on board tiny motorised fishing boats for their livelihoods are numbered amid rising concerns over dwindling fish stocks.

The number of caviar fishermen in the Iranian Caspian provinces has already declined by half in the past 15 years under government job-shedding schemes designed to tackle what is recognised as an environmental crisis.

In the down-at-heel port of Bandar-e Turkman, where Mr Makhdoom lives, the prospect of further job losses is regarded with foreboding among the mainly Sunni Muslim population, many of whom feel economically neglected by Iran's Shi'ite-dominated leadership.

The possibility is growing after the US Fish and Wildlife Service announced a ban on imports of beluga caviar, the most prestigious Caspian Sea variety. The embargo has provoked cries of anguish from Iran's fishing bodies, which say their fishermen are being unjustly penalised for illegal practices more common in the other Caspian states of the former Soviet Union.

The ban was prompted by environmental fears - expressed by the United Nations' Convention on International Trade in Endangered Species (Cites), which sets fishing quotas for the Caspian - that the 150-million-year-old beluga species is facing extinction due to overfishing and illegal poaching.

The European Union, the second-biggest importer after the US, has so far resisted pressure to impose a similar ban. But with the US representing 80 per cent of the caviar export market, its embargo has potentially devastating consequences for Iran's already hard-pressed Caspian fishermen.

Existing US trade sanctions, imposed since the 1979 Islamic revolution, have been circumvented in recent years by routing large stocks of caviar through third countries to the United States, where beluga caviar sells at more than $67,000 a kilogram.

The blockade also applies to exports from the other four Caspian littoral countries, Russia, Azerbaijan, Kazakhstan and Turkmenistan, all former Soviet republics, where illegally caught caviar fish are believed to outnumber those caught legally by 12 to one.

Legal catches in the Caspian - which holds more than 90 per cent of the world's caviar, produced from the tiny black eggs of sturgeon - fell from about 30,000 tonnes in the late 1970s to less than one-tenth of that by the year 2000.

Experts say the decline has been exacerbated by a proliferation of new dams and other development projects, blocking rivers that were once ideal reproductive habitats for the Caspian sturgeon.

The downward trend is unlikely to be reversed, according to the Iranian Fisheries Ministry, by an embargo that it says will merely force its fishermen out of business and further strengthen mafia-backed poaching and smuggling rings.

'We are being punished for the sins of other countries,' said Mostafa Aghilinezhad, head of the caviar division in the Fisheries Department of Golestan province, the heart of Iran's caviar trade. 'Illegal fishing takes place in all the Caspian countries, but it's on a lower level here.

'Banning the sale of caviar isn't the right way. Instead, the Americans and Europeans should take practical steps to help the Caspian Sea states by strengthening organisations like Cites. When the Soviet Union broke up, all the steps it took to protect caviar stocks collapsed. But in Iran, nothing has changed. We are still doing what we always did, and certainly more than the other Caspian states.'

Iranian officials point to a network of fish farms carrying out carefully designed breeding programmes and a 1,000-strong coastal police force to combat poachers.

Out at sea, the prospects of salvation seemed remote for Mr Makhdoom.

'Every year the number of fish we catch declines,' he said. 'In previous years there would be times when we caught 20 or 30 fish per day. But those days are gone.'