What is going wrong in the North Sea?

In Shetland Seafood News, NO. 209, June 2003

Article by Jon Kristjansson

In the recent years cod stocks in the North Atlantic have been in crisis. The problem is claimed to be overfishing. Strangely, this "problem" only occurred after the introduction of 200 nm EEZ's in 1975-1976. Until that time, the fishing fleets moved from one place to another, i.e. where the fish was. They left fishing grounds that had been fished down and headed for grounds where the fishing was better. That strategy ensured that all grounds were harvested, and no nation was able to stop fishing in order to "build up" the fish stocks. In recent years, this build up policy has lead to unexpected results: Stocks have declined, overfishing is taking the blame, but, is that correct? Reduced fleets and reduced fishing power has only made the situation worse.- Could the contrary be the case? Has there in fact been underfishing?

Fig. 1. The fishing pressure of the English trawl and seine fleets 1978-1999. During the period the fishing pressure from the trawl fleet has been reduced by a factor of 4.5, and the seine fleet has almost disappeared (From ICES CM 2001/ACFM:07).
Still scientists maintain that the fishing mortality is increasing. Could their measurements be wrong?

Last year ICES recommended a closure of the cod fishery in the North Sea. They said the cod stock was near to a collapse, similar to the Northern cod at Newfoundland few years ago. That stock has for a decade been used as a terrifying example of overfishing, even if the biological data from the stock at the beginning of the ninetie suggested starvation. The term "overfishing"seems a kind of a waste basket for unexplained biological phenomena.


Little by little, Canadian scientists have opened the door for other explanations of the collapse of the stock. They have found that natural mortality is very high, the Northern cod up to 55% per year and the fish only reach the age of five, without any fishery!

Approximately 70 Fisheries and Oceans scientists and fisheries managers, participants from the fishing industry, and Canadian, American, British and Icelandic scientists, attended a meeting in Halifax on 17 to 26 February 2003. About half of the meeting was devoted to assessing why most Canadian East Coast cod stocks have not recovered despite more than a decade of strict conservation measures.

They looked at more than 40 possible reasons, settling on the following factors as the most likely explanations:

"The harsh environment in the 1990s affected survival and fish growth. When the moratoria were applied to cod stocks in the early 1990s, most of the fish were small for their age and many were in poor condition, having little energy reserves to survive over winter months or critical stages of their life cycle. The energetic condition of cod following spawning was particularly low in the early 1990s, and may have been low enough to cause high mortality in some of the cod stocks.

In addition to harsh environmental conditions, reduced cod stocks were facing predation by an increasing number of predators, in particular seals. Estimates of cod consumed or otherwise killed by seals are believed to be high enough to have affected recovery. In the Gulf, increasing abundance of mackerel and herring also resulted in high predation on cod eggs and larvae.

Taken together, environmental conditions and increased predation resulted in poor growth and poor survival for cod."

They do not mention fishing as a significant factor in the collapse. However, when the scientists try to explain why the stocks do not recover they regard fishing as one of the factors:

"While catches from commercial fisheries have been much reduced in comparison to the levels achieved in the 1970s and 1980s, they remain sufficiently high to contribute significantly to mortality. There is also evidence that poor fishing practices, such as under-reporting or not reporting cod catches, discarding small fish and outright poaching, occur in both the commercial and recreational cod fisheries.

In summary, the lack of recovery is the result of a number of factors that have worked simultaneously or in turn to affect fish growth, reproduction and fish survival. These stocks experienced high mortalities due to the combined effects of fishing, poor environmental conditions and increased predation. In addition, under their current low stock abundance and poor productivity, cod stocks are not generating young fish in sufficient numbers to secure a recovery to the levels previously experienced.

Taken together, these factors strongly suggest that there will not be a prompt recovery in any of these stocks in the near future."

Consequently, the Canadian fisheries Minister has just announced a total fishing ban. The ordinary people of Newfoundland are no longer allowed to catch 15 fish per year for private consumption.

Furthermore, fisheries Minister Robert Thibault now says he's looking for new technology to control the East Coast seal population and is willing to see the herd's numbers drop sharply in an effort to revive cod stocks. However, he also says that he's not going to change his mind about closing the cod fishery indefinitely.

It was clear already in the eighties that something was happening. The growth rate was falling, so was the condition (weight at given length) and the liver index, but codfish store energy in the liver. Age and size at maturity was also falling. These are all signs of shortage of food for the individual fish, the stock as a whole, that is to many fish sharing to little food and/ or, possibly, bad environmental condition.

Fig. 2. Mean weights at ages 2-8 of cod in division 2J (Labrador), as determined from sampling during bottom-trawl surways in autumn. Note that in 1994 fish older than 5 have disappeared and the average maximum weight is less than one kg.

Abrupt changes in fishing or predation patterns can cause unpredicted changes in fish stocks. Reduced fishing pressure seems to lead to under nutrition and stunting. How long it takes for the stock to adapt to the "new" regime is at present unknown, reaserch is minimal as everything is explained by "overfishing". The declination of the fishery off Newfoundland was very harsh. The catch by offshore trawlers was 400,000 tons in 1972 and dropped to only 55,000 tons in 1978, when the foreign fleet had mostly left the grounds after the 200 mile fishing limit was imposed.

The North Sea

After visiting the fish markets in Aberdeen and Peterhead I was of the opinion that the haddock I saw showed clear symptoms of hunger. I concluded that if the haddock population was starving, it would neither help the cod, nor the haddock, to reduce the fishery. A cod taking to the bottom in its first year of life would have a hard time looking for food amongst large numbers of starving haddock. I considered the hunger symptoms to be the result of overcrowding, leaving little food for the individual fish. In fact I considered this might be the result of a long and continuous battle to reduce the fishing pressure.

The main advice from the scientists has been to reduce the fishing effort and it is interesting to examine how the recommendations have been adhered to. Below is a graph that shows the TAC set by the politicians and the landings in the period 1987-2001.

Fig. 3. ICES advice, TAC, solid line, and landings, broken line, 1987-2001

It can be seen that the politicians have followed the advice from ICES and the landings have in most instances been lower than the TACs. The question arises why stocks decline when scientific advice has been followed so closely? The scientists have given the following explanation:

"Fishing mortality has consistently been underestimated and stock size overestimated in previous assessments, and the current assessment suffers from the same problem. The quality of the assessment improved in 2000 and 2001 due to the exclusion of commercial CPUE data. This year the assessment again showed retrospective bias, possibly because of a decrease in the quality of the landings data in 2001." (ICES Cooperative Research Report no. 255).

By saying this they admit that they have based their advice on wrong measurements since 1987!

There is no biology in the explanation but in the scientific reports it says:

"In recent years the growth rate of North Sea cod has declined. The reasons for this are not known, but if growth remains slow, the rate of recovery of SSB will be delayed. Slower growth may also expose juveniles longer to discarding" (ICES Cooperative Research Report no. 255).

Slower growth is usually a sign of food shortage, and should tell the managers that the assumption of excess food allowing "build up" of the stock does not hold.

In my opinion the assumption of surplus food, allowing for an increase of the demersal stocks in the North Sea, was wrong. When fishing pressure deceased, number of fish increased and less food was left for the individual fish. Selective fishing, caused by increased mesh size, that targets the bigger fish, has compounded the problem by altering the community balance (inter- and intra- specific competition, - predation). There are more small individual in the population and they face a stiffer competition from other species as well.

The scientists even admit that the growth in all fish stocks in the North Sea has been slowing down in recent years, without being able to explain it. This strongly supports the explanation of overcrowding.

It is interesting that in every case that fishing pressure is decreased by reducing number of ships or fishing days, fishing mortality, measured or estimated by scientists seems to increase. This finally leads to closures. This calls for rethinking and reorganizing of the scientific research.

The question whether industrial fishing could be the cause of the food shortage has been put forward. There is not a simple answer to this. Now the haddock and small size cod are starving. They are generally benthic feeders, feeding on animals on the bottom. They are not fish eaters. Haddock feed on sand eels as opportunists, i.e. in certain periods of the year when sand eels are available or abundant, but they are mainly bottom feeders. More sand eels would not solve their hunger problem. Cod also feed on bottom animals when they are small. They become fish eaters as they become large. The large cod I saw from the North Sea were well fed, showing that for cod large enough to become a fish eater, food is abundant.

Removing industrial fish also means removing competitors, increasing the available food for small cod and haddock. Is also thins out the overabundant small haddock making life easier for the remaining ones.

Source of information:

ICES webside: www.ices.dk

DFO webside: www.dfo-mpo.gc.ca

Authors webside: www.fiski.com/english/eindex.html