Richard North, 13/11/2012  

Flume Tank 4 Separator_trawl2.jpg

The media whinges about "freedom of speech", telling us that we would be so much worse off without them. Then you see this sort of thing in the Telegraph and you wonder why they bother.

"Young inventor lands Dyson award with safety net for fish", trills the paper, telling us that "a fishing net with a built-in 'emergency exit', designed by a young British inventor to tackle overfishing, has won the annual James Dyson global award for inventors".

Dan Watson's SafetyNet, we are told, lets young "unmarketable" fish escape. "It has a series of rings which allow fish of the wrong size or type to swim free, tackling the almost 50 percent of catches which are thrown back. Many of these fish do not survive".

It then goes on to tell us: "SafetyNet exploits the way different fish try to escape when stressed. Since smaller fish swim up, while larger fish swim down, the net's design only catches mature species. The rest can escape through the net's illuminated rings" (illustrated below).


The report continues: "Mr Watson said: 'Water flowing through the wide open meshes guides the smaller fish to freedom while the larger ones are retained'" and so we hear that, "The 27-year-old Royal College of Art graduate beat finalists from 17 countries to win an overall prize of £10,000". 

Now, it is entirely up to the prize committee if it wants to make make fools of themselves, but it is entirely another thing for a newspaper uncritically to report such obvious stupidity, the points here being several and well known.

Firstly, for many decades, mesh sizes on fishing nets have been regulated, and mesh designs defined, which will allow undersize fish to escape. This is simply not an issue. The need to avoid discards in mixed fisheries requires separation of species.  In short, "discards" are a species issue, not a problem of undersized fish.

Secondly, any new type of net must be hydrodynamically stable and fuel efficient (not causing unnecessary drag on the fishing vessels, thereby increasing fuel costs). You test this using a flume tank (pictured top - showing a separator net, optimised for Haddock fishing), without which your design is worthless. Costs there are well in excess of £10,000 for a single design. Without such tests, the "SafetyNet" is worthless junk and just the sight of his "illuminated rings" suggests a massive increase in drag.

Third, escape strategies for different fish vary not by size and age but by species. Thus, when Mr Watson says: "... smaller fish swim up, while larger fish swim down …" he is simply wrong. Some species, like Haddock, swim upwards to clear a net … Cod tend to hug the bottom, where they mainly feed.

But what is remarkable is that there is absolutely nothing new about the idea of selective fishing. I was writing about it in 2007 and here are some examples of proven designs. The ideas are decades old.

The ultimate point though is that net design is only one part of a complex problem. To get these things to work properly, one is often exploiting marginal differences in behaviour between species, which also vary in different fisheries. What will work in clear, fast-flowing waters with sandy bottoms will not necessary work in turbid, slow-flowing esturine fisheries with muddy bottoms.

The trouble is then, to have effective selective fishing, you need hundreds of different, fisheries-specific designs, different towing rigs (just as important) and different fishing strategies. Such is the huge variety needed and the need for close supervision, that - in respect of the EU member states waters - the Commission admit they simply do not have the resources to write and promulgate the hundreds of different regulations needed, or implement them properly.

That is the killer point. The effective problem is a structural one, inherent in the CFP. No amount of net design will change that.

Going back to to point about the reporting, then, in days gone by the Telegraph had a specialist farming and fishing correspondent who knew about such things. Confronted with the sort of tosh we see today, he simply would have ignored the story, or written a critical appraisal.

What he would not have done is written this silly story which fails to educate, and simply cements in obvious errors, perpetuating a flawed understanding of the fishing policy which is blighting our industry.

But, as the man once said – and it is ever more true today - without a newspaper, you may be uninformed. But spend your hard earned money and you will simply end up misinformed. And the reason we should care if this stops happening is?


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