For American fish, this is a good time to be alive. On May 14 the National Oceanic and Atmospheric Administration reported that a record six federal fisheries returned to health last year. After a decade of similar progress, 86 per cent of America’s roughly 250 federally monitored commercial fish stocks were not subject to overfishing, while 79 per cent were considered healthy.

This is also good for American fishermen. Commercial and recreational fishing generates an estimated $183 billion a year and supports more than 1.5 million full-time or part-time jobs. Rebuilding America’s 45 remaining overexploited fish stocks, NOAA estimates, could generate an extra $31 billion a year and half a million jobs.

That is a tribute to America’s having learned a simple truth that scientists, not fishermen nor politicians, should decide how many fish can be caught and enforced this insight with simple rules.

It has taken a while. America’s main fishery law established the importance of scientific quotas in 1976. They were routinely ignored, however, because of poor science and weak enforcement, abetted by influential fishermen notably in New England, which was built on once-rich Atlantic cod and haddock fisheries. The Massachusetts House of Representatives contains a conspicuous symbol of this: the Sacred Cod, a 200-year-old fish of solid pine that hangs from its ceiling.

Despite this totem, in the late 1980s cod fisheries in the Gulf of Maine and Georges Bank collapsed. This led to efforts to improve the fishery act, in 1996 and 2006, which forced the eight regional bodies that manage federal fisheries to introduce science-based quotas and 10-year recovery programs for depleted fisheries. The recent recovery of species, including New England scallops, mid-Atlantic bluefish and summer flounder and Pacific lingcod, is the result.

This signals another truth: Given a break, the marine environment often can replenish itself spectacularly.

America’s fisheries are probably now managed almost as well as the world’s best, in Australia, Iceland, New Zealand and Norway. Yet there is plenty of room for improvement. State-run fisheries, which tend to be close to shore and dominated by small-scale and inefficient fishermen, are less well funded, less well managed and much poorer for it.

New England groundfish stocks, including cod, also have not recovered: They account for 13 of the remaining depleted populations. This appears to be partly the result of environmental change, climatic or cyclical.

Furthermore, the politicians are still interfering. On May 9 the House of Representatives passed legislation forbidding NOAA from developing an innovative means of apportioning fishing quotas known as catch shares. These are long-term, aiming to give fishermen a stake in the future of their fisheries, and market-based, since they can be traded. They are also, in practice, good for fish.

Sadly, the two Republican congressmen behind the ban consider them to have been designed “to destroy every aspect of American freedom under the guise of conservation.