We all know the observer effect: Behaviour changes when someone is watching. Drivers suddenly become law-abiding near speed cameras or at the sight of a police car. Believe it or not, even electrons change their behaviour under observation, physicists recently found out.

The observer effect is present not only on our roads or in the physics lab. It also occurs onboard fishing vessels. Just put an observer on a vessel and see what happens.

Research in New Zealand and overseas shows that fishing vessels with observers report larger quantities of bycatch than vessels in the same area not carrying observers. Even so, there is increasing interest in the use of video cameras onboard vessels, since one observer cannot witness all behaviours round the clock.

Auckland University recently released a report that reconstructed New Zealand’s total catches from 1950 to 2010. It found that under-reporting of landed catches and discarding of unwanted bycatch at sea are widespread. Considering the estimated rates of under-reporting and discarding, the reconstructed total catch was estimated at 2.7 times more than officially reported.

When Prime Minister John Key was asked about such massive under-reporting, he effectively rejected the problem. Instead, he pointed to recent Niwa research that puts the discard rate at about 6 per cent. In other words, there was not a big problem.

The Ministry for Primary Industries (MPI) is responsible for placing observers onboard fishing vessels, and Niwa is responsible for analysing the observer data.

The official discard rate is 6.6 per cent. It is difficult to reconcile the gap between Auckland University’s findings and this official discard rate. Let’s try it anyway.

First, the official discard rate does not include any observer data from the inshore fisheries, where some fisheries are understood to have the greatest problems with discarding and misreporting catches. MPI has placed around one-quarter of its total observer coverage on inshore fisheries. So, we have to ask why this observer data was not included in calculating the discard rate.

Second, the official discard rate is based solely on data collected by observers onboard offshore fishing vessels from 1991 to 2013. We do not know what the data show post-2013 or what data might be available pre-1991 that might have influenced the decision to put a discard ban in place in 1990.

Third, the data supporting the official discard rate was from 20 to 25 per cent of the fishing effort in offshore fisheries. We do not know anything about the discard rate for the unobserved 75-80 per cent of the effort in those fisheries.

Finally, the discard rate does not consider the prevalence of discarding that may have been intentionally hidden from observers, or the influence that the observer effect can have on fishing behaviours.

It is fair to say that any attempt to go beyond observer data in calculating a discard rate inevitably delves into illegal, hardtofind unreported activities that would require consideration of multiple data sources.

Some sources will introduce uncertainty and biases; they will also provide a richer understanding of the context and evaluation of the potential extent of the problems.

Auckland University’s findings may have overstated the problems for now. However, recently leaked MPI investigation reports raise some serious questions about discard practices currently. If New Zealand has followed the trend worldwide in reduced bycatch and discards, we don’t really know.

We have only received an official discard rate based on a very small, selective portion of New Zealand’s fishing history, which is likely the most positive sample possible.

The New Zealand public would likely not tolerate this type of selectiveness in other official reporting, such as the rate of workplace accidents, the road toll, or suicide rates.

MPI could have provided a more complete estimate of the discard rate. As the government’s watchdog for fisheries, MPI should provide the public with a discard rate that represents all the observer data that it holds. The public would have more confidence in a new discard rate if its calculation was independently audited.

Since MPI is adamant that Auckland University report’s findings and methods are flawed, MPI should provide the public with its own estimate of illegal, under-reported catches and discards from 1950 to 2010.

Better yet, this estimate could be accompanied by an explanation of what will make the upcoming integrated electronic monitoring and reporting system operate most effectively.

The effectiveness of the integrated system will depend on whether it provides an observer effect onboard vessels that continually changes behaviours. The system’s effectiveness will also depend on the standards that MPI is held to when reporting on the discard data.

Or, to say it in the words of Lenin, ‘‘Trust is good; control is better.’’ He obviously knew a thing or two about the observer effect.