The Empty Seas

De Lege Zee (The Empty Seas)
VPRO Noorderlicht / 25 min / 1997
Are fishery models suitable tools to manage fisheries? Up to the crisis at the Grand Banks at the Canadian eastcoast, people generally thought they were. But after the collapse of the worlds largest cod stock, there is solid reason for doubt. Uncertainties in the estimates, variability in nature and the short term perspective of managers make it necessary te develop another way of fisheries management. So claim fisherybiologists Robin Cook (Schotland), Sidney Holt (ex IWC) and Willem Dekker (rivo).

VPRO NOORDERLICHT
UITZENDING 28 SEPT 97
TITEL: DE LEGE ZEE

DR ROBIN COOK
FISHERY SCIENTIST
MARINE LABORATORY ABERDEEN
If you re a young cod, one year old and alive, your chances in making it to the age of four, when you d be old enough to spawn, is only 4%.

WILLEM DEKKER
VISSERIJBIOLOOG
RIVO IJMUIDEN
Ga je terugkijken, dan zie je dat we al jaren geleden gezegd hebben: we hebben ergens een rooie grens getrokken, daar willen we niet overheen. En we zijn er overheen.

DR SIDNEY HOLT
FISHERY SCIENTIST
We have to look for another way of managing fisheries. Playing with the models is interesting science but it is not necessarily the practical way of safely managing fisheries for the future.

POLYGOON ARCHIEF, 1947
IJmuiden leeft weer op. De trawlervloot telt nog slechts half zoveel boten als voor de oorlog, maar de opbrengst is enorm. Per schip worden soms 100.000 kilo vis aangevoerd en alleen aan haring komt in het hoogseizoen anderhalf miljoen kilo per week binnen.
De haring gaat onmiddelijk naar de afslag. De vangstrijkdom is mede het gevolg van het feit dat in de vijf oorlogsjaren vrijwel niet gevist werd.

DR SIDNEY HOLT
The first job I was given when I started in 1947 was to try to see if the fish in the North sea had increased as much as had been predicted when there was no fishing.

I was a new boy from the city seeing fishing for the first time. One of the images I had in Lowestoft was of a herring boats come in. And particularly one day, they were racing for the market, the early morning market, I was watching one of the herring boats come in through the opening of the port. It was coming in like a submarine. It was so loaded with fish, up to the gunners, completely overloaded, just went down. That was what herring fishing used to be like.

And we found that, as predicted, the fish had increased by being left for five years. The second part of my job was to try to see how we could calculate how much fishing there should be so that there in the future could always be steady catches without any collapse of the stocks.
To do that, we build on work that had been done before the war. The problem was to turn that into a way of actually calculating what we could do to advice the countries around the North sea what they should catch. And with my colleague Ray Beverton, we produced equations, algebraic equations.
How we did that is perhaps best illustrated by a graph. First graph is catch against stock, the amount of fish in the sea. It gives you a curve like that. This is the stock when there is no fishing. But here is where the catch has taken so much that there is no stock left. And in between there is a maximum.
The second graph is again of the stock, we call it parents. They ve given birth to young. So here s the number of young coming from the parents. And we think we have a curve like this. Now we can draw another graph. Here is the parent stock, the mature animals and here the young coming from the parents and we have a curve that s something like that.
We decided that for the plaice and haddock in the Northsea, we were in a real situation somewhere around here and what we wanted to do was to move towards this way to get bigger stock and bigger catch but with less boats and we wouldn t have much change in the number of young.
Instead with failures of management, most stocks have gone down this way towards the left. So you have smaller catches, smaller population and smaller number of young. You can see because here it becomes steep. It is potentially a catastrophic situation. You can have a collapse of the sort.

WILLEM DEKKER
VISSERIJBIOLOOG RIVO, IJMUIDEN
Wij bepalen hoeveelheid vis in Noordzee om te kunnen adviseren aan de regering, aan Brussel, over het viserijbeleid dat er gevoerd wordt.
Wij bepalen de dichtheid van visbestanden, de omvang van de visbestanden in wezen op twee manieren. En die twee manieren vullen elkaar aan. De eerste methodes zelf met een schip de zee op te gaan met een ons bekend net en jaar in jaar uit daarmee op vaste plaatsen te vissen. En de vangsten door te meten.
Hoe saai het ook is, hoe weinig vis je ook vangt of hoeveel vis je ook vangt. Je gaat door standaard. Dat levert ons met name veel informatie over de jonge vis. Oudere vis ook wel, maar veel minder.
De tweede methode die we gebruiken is dat we in feite zeggen de belangrijkste doodsoorzaak voor vis is de visserij. Visserij weten we vrij goed. Dat zijn mensen en die brengen vis op de wal.
Dus als wij ook op de wal staan en de vis waarnemen weten hoeveel ze aanlanden, welke soorten ze aanlanden, weten hoe groot die vissen zijn, welke geslachten ze hebben enz. Dan kunnen dus gaan terugrekenen wat er daarvoor in zee gezeten heeft.
Je kunt het vergelijken met de visserij als overlijdensregister. Als je het complete overlijdensregister in handen hebt kun je terugrekenen wat er eigenlijk zat. Die twee geCOMbineerd, aan de ene kant de visserijafslag en de aanlanding van vissers levert het meest eenduidige en exacte antwoord op. Aan de andere kant onze eigen bemonsteringstochten op zee leveren alleen maar een relatief getal. Nou heb ik twee dingen bij elkaar. Ik heb een relatieve maat en ik heb uit die visserij terugrekenend een absolute maat en dan kan ik die twee koppelen.
En dan kun je de vervolgstap maken en zeggen: Œik vang nou heel weinig jonge kabeljauw, dus hoef ik de volgende jaren ook niet te rekenen dat er in de markt, in de commerciële visserij noemenswaardig kabeljauw gevangen gaat worden. Er is gewoon heel weinig.

MICK EASEY
SCIENTIFIC OFFICER
MARINE LABORATORY LOWESTOFT
These are the otoliths of the fish I m taking out. They re part of the ear system. They help with balancing and detect movement in the water. This is how we tell the age of the fish.
They have rings in the same way as the rings of a tree. There s summer growth and winter growth and counting each pair of rings would be one years growth. This will be just over two years old.
Most of the fish are caught between two and three years old.
Cod matures round about two to three or four years old, so quite a large proportion of fish this size wouldn t have spawned.

WILLEM DEKKER
En dat is niet alleen bij kabeljauw, maar dat is bij vele vissoorten. Dat is de kern van wat wij groei-overbevissing noemen: de dieren pakken op een lengte op een leeftijd dat ze gewoon nog niet zo groot zijn als eigenlijk voordelig zou zijn.

DR SIDNEY HOLT
Too much fishing means the catches are going down catastrophically and the number of parents are going down catastrophically. And the number of young coming from the parents are going down catastrophically. So you have a situation for a complete collapse of the fishery such has happened with the herring a few years ago, such as is now happening with the cod in the North Atlantic.

COMMENTAAR
In 1992 voltrok zich voor de Canadese oostkust het grootste drama uit de visserijgeschiedenis. De legendarische visserijgronden voor Newfoundland bleken leeggevist. Œs Werelds grootste kabeljauwpopulatie was verdwenen, met als gevolg een volledig vangstverbod.

VISSERIJMINISTER CANADA
(ARCHIEF NATIONAL FILMBOARD OF CANADA)
I ve decided that effective at midnight tonight, there will be a moratorium on harvesting of northern cod until the spring of 1994.

COMMENTAAR
Maar de crisis duurt voort tot op de huidige dag en heeft veertigduizend mensen van hun baan beroofd. De crisis was het definitieve faillissement van visserijbeleid gebaseerd op populatiemodellen.

WILLEM DEKKER
Als je voor de Newfounland kabeljauwcrisis gezegd had: Œzijn de visserijmodellen zo goed dat we beheer kunnen plegen dan had iedereen geroepen: JAHA, kan. En dan blijkt op gegeven moment dat de marges toch niet zo smal zijn als dat je hoopte.

DR SIDNEY HOLT
One thing is that managers didn t take much note of the scientists. But knowing this, scientists often gave advice that they thought the managers would accept. So they were not so conservative as their scientists said they should be. So they would go towards. But you can t compromise with nature. So there was a failure of science there.

COMMENTAAR
De wetenschap mag dan haar lesje geleerd hebben van de Canadese kabeljauwcrisis, maar aan visserijbeleid is er nog niets veranderd. In een poging duidelijk te maken dat de kabeljauw ook hier gevaar loopt, publiceerde de Schotse visserijbioloog Robin Cook een artikel in NATURE. Hierin betoogt hij dat de Noordzee kabeljauw op instorten staat.

DR ROBIN COOK
FISHERY SCIENTIST
MARINE LABORATORY ABERDEEN
Perhaps I can explain the problem with this little diagram here. Normally we would expect for example the number of fish in the sea to be related to the number of young they can produce.
But as you can see, these are what we would actually observe when and counted the number of fish in the sea. And although they might follow this line, the actual observed points are scattered to a large degree around the line. So the line tells us what we may expect but the reality is something rather different. And that variability is due to things we cannot predict. It s due to things like how well the eggs survive in the sea and that may be due to currents and temperature and so on.
Clearly there is a lot of uncertainty but if I go back to this picture here, one thing that we can be certain about is in this corner here. If there s no stock, there s no recruitment. And although we cannot predict these exact points in advance, this line does describe what we would expect on average. And basically what this says is down in this corner we ll get less recruitment than up here. If we have a lot of stocksize, on average we ll get a lot more recruits.
Now in the last ten years or so, the cod stock has been at a low level and we ve had low recruitment combined with a high exploitation rate, which means we re going to stay down in this corner and we risk going down to where there s no stock size.

WILLEM DEKKER
Het was geen verrassing. Voor mensen in wetenschappelijke kringen, voor zelfs mensen in beleidsadviseringen was het geen verrassing. Het is een beeld dat we al jaren kennen, wat al jaren lang via de geëigende kanalen doorgeven is maar wat op de een of andere manier in het politieke krachtenspel niet tot actie leidde. In feite wat begin dit jaar gebeurd is, is dat ietwat te doorbreken en te zeggen: Jongens, horen jullie nu wel wat we met z n allen zeggen. Maar het was geen verrassing.

DR SIDNEY HOLT
I don t think we have to stop this kind of modelling but we do have to do more than just model the fish-population or even the biological situation. We have to model the actual process of management. We have to be more like engineers than scientists and talk about the human side of this. The way the fisheries work and the way you manage the fishery and that doesn t depend just on the biology of the fish. It doesn t even depend mainly on the biology of the fish.

It was in the IWC that regulates international whaling that it became clear that the old methods were not working. We were so uncertain about everything: death rate of whales, reproductive rates, catch statistics were not good. Many things. So we had to find a way of dealing with these enormous uncertainty.
And a group of scientist came forward with an idea which was not to concentrate on trying to make better models of the population of whales or better estimates of the variables but to model the whole process of managing, setting catch quota, watching what happened and so on. And that s the model.
The way of doing this, is to invent a method of calculating catch quota for next year which will meet the objectives in some sort of compromised way and testing that out with a computer with all different values of every variable in the model.
But there s a price to be paid for this. That is that the managers have to commit themselves to apply the procedure and staying with it. It s like someone gambling. He s got to gain play and stay with it whatever happens next year you know.

COMMENTAAR
Zou de brede aanpak die door de International Whaling Commission ontwikkeld werd een oplossing kunnen bieden voor de crisis in het visserijbeleid?
In het Engelse vissersplaatsje Lowestoft werkt men er aan. In dit laboratorium ontwikkelden Sidney Holt en Ray Beverton vijftig jaar geleden het eerste visserijmodel. Nu wordt er gewerkt aan een nieuw visserijbeheerssysteem naar het voorbeeld van de International Whaling Commission. Aan het hoofd van de zogenaamde Fisheries Systems Modelling Group staat Dr Kevin Stokes.

DR KEVIN STOKES
FISHERY SYSTEMS MODELLER
MARINE LABORATORY LOWESTOFT
In our models we try to model the system that produces the data production. We model the assessment data itself and we also model the decision masking based on what comes out of the assessments. We also model the feedback that occurs when the decision is implemented it affects fishermen s behaviour and that of course affects the underlying system.
So we get a range of outcomes for every one simulation, it s not a single set of numbers. Because we collect many numbers for each simulation.
We re trying to determine what are the best decision rules to meet our objectives, given the understanding of the system. And understanding is what we get through our science.
It s not, if you like, hard physics or hard biology, but we re dealing with a system which includes human beings as that catch fish, human beings as they make decisions and who have goals in life, who want to achieve certain ends.
If there s a willingness internationally to put the effort in, on certain fisheries, then, in a matter of the next few years, we could have good management procedures up and running. Implementing them of course and keeping to the implementation is quite another matter. Not necessarily a scientific one.

DR ROBIN COOK
In dealing with the IWC-type procedure you explicitly take into account all the uncertainties that you think exist and you can make the kind of forecast which may not be a prediction of precisely how big the stock will be, but you can predict the kind of catch which will be safe in terms of the exploitation rate of the stock. So that s where the IWC procedure can be helpful.

WILLEM DEKKER
We weten nu dat onze getalsmatige aanpak van hoeveel vis zit er en welke risico s loop je, toch tot een eindsituatie leidt die we niet willen met z n allen. Die de maatschappij niet wil. Nou dan gaan we een stap verder. Ik kan niet overzien of wat Kevin nu aan het doen is voldoende is, maar het is wel een van de noodzakelijke stappen om verder te komen.

SIDNEY HOLT
You just need to have a management authority that stays with the rules for at least several decades. That s politically the most difficult thing to see, to imagine that we can deal with. That we have a management of a natural system which is a long term and not constantly distracted along the way from its long term goals.

CAMERA Piotr Kukla
GELUID Bert van den Dungen
MONTAGE Andries Udink
REGIE Jos Wassink

EINDREDACTIE Rob van Hattum
PRODUKTIE Karin Spiegel
Madelein Somer

© Het Inzicht / Jos Wassink, 1998

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