THE imposition of fines totalling £720,000 on 17 fishing boat skippers yesterday marks the end of a fraudulent scheme that netted £45.7 million from illegal landings of fish.

Debate will continue, however, about the controversial quotas imposed by the EU which the fraud was designed to overcome.

During the trial it was claimed that the fraud was set up because the fishermen believed the quotas were out of kilter with the stocks of fish in the sea and the practice of landing "black" or undeclared fish was industry-wide. The operation, Scotland's largest-ever fishery scam, was far removed from the notion of struggling fishermen falsifying catches to make a living. As the judge, Lord Turnbull, made clear, the three-year operation was cynical, sophisticated and involved the connivance of a number of different interested parties. These included the fish processing factory Shetland Catch where a weigh belt and scales had been manipulated to allow false wastage figures to appear on a computer monitored by inspectors from the then Scottish Fisheries Protection Agency, now Marine Scotland. The company was fined £240,000.

Three more fishermen yesterday pleaded guilty to landing undeclared fish in a separate case which formed part of the same investigation. It has resulted in prosecutions for more than half the 26-strong pelagic fleet. Fraudulent returns from three unconnected processing plants were uncovered, indicating a deep discontent with the quotas. The success of the prosecutions underlines the vital importance of a rigorous inspection and regulatory regime in Scotland.

With bigger boats and improved technology for detecting shoals, the pace of decline in fish stocks is accelerating, making effective conservation measures essential. All those involved in the illegal landings wilfully ignored the public good in pursuit of personal wealth. Reduced fishing by the Scottish and other EU fleets has increased the sustainability of the mackerel fishery but when Iceland and the Faroe Islands, who set their own quotas, raise the limits beyond international agreements, the temptation is to flout the quotas.

Quotas, or shares of the total allowable catch for British boats, were originally allocated to vessels according to previous catch records but the majority are now given to fish producer organisations and traded as commodities. These cases confirm that quotas should be returned to the fishermen. Not only would this make the distribution of quotas more transparent, it would also give the skippers a sense of ownership of the stocks and a greater incentive to conserve them. Greater consideration should also be given to securing international agreement on no-fish zones, which have proved effective in many parts of the world.

Those who argue even bigger fines would be appropriate for a multi-million pound fraud should remember that those involved have already been required to hand over nearly £3million in confiscation orders. It is perhaps understandable when skippers have limited patience with the slow pace of international negotiations and become even more frustrated when they believe other countries ignore agreements. Nevertheless, when seas are overfished stocks collapse and fishing fleets and the communities that depend on them for livelihoods are the first to suffer.

The warning by Maria Damanaki, the European fisheries minister, that, unless urgent action is taken to preserve fragile stocks the children of Europe will see fish only in pictures, must be taken seriously. However unpalatable quotas, reduced days at sea or no-fishing zones may be in the short term, fishermen and producers must recognise that, although they might think have potentially most to gain by flouting the law, they ultimately have all to lose when caught doing so.