Fish stocks hard to keep them healthy!

(Fishing News 11 April 2003)

Iceland scientist Jon Kristjansson argues that stocks are healthiest when their density is kept down and that EU fisheries policy is misguided. He sites the success of management in the Faeroes to back his case.

The recent EU fisheries management measures, to shut down the cod fishery and reduce the fishing of other demersal species by half, have been implemented to conserve the cod. It is said that the reason for the bad shape of the cod stock is overfishing over a long period of time, and that the remedy is to shut down the fisheries. "Overfishing" is the key"buzzword" in modern fisheries management and the solution is to reduce or stop fishing.

Density dependant growth

It was proven at the beginning of the last century that growth of trout in Norwegian lakes was density dependant. By reducing the number of trout in a small lake, growth rate and overall condition of the fish could be improved. In experiments, where fishing effort was decreased, the growth rate went down and it increased again when fishing effort was increased.

Since then, this has been applied in fresh water fisheries management. I feel tempted to to quote J.A. Gulland 1968 (International Biological Program Handbook No 3): "At least until recently, probably more damage to the fishery ( in the sense of the catch being less than it might have been without regulation) has been caused through regulation being introduced before they are needed, than through regulations being introduced to late. This is particularly true in fresh water, where any one fish stock is likely to be entirely within the jurisdiction of a single government, so that the regulation can be more easily introduced and enforced than in international high-seas fisheries."

This "old" view is interesting in todays situation: Easily introduced and enforced reduction of fleets and fisheries!

Accepted in freshwater and widely used, density effects on growth have provoked little attention in sea-water fisheries. In official ICES reports reports concerning fishery management growth rate in fish stocks, or the the condition of individual fish, is rarely an issue. Fish are measured by length and this later converted to weight by tables based on a long term mean length/weight relationship. This is used to convert fish numbers to stock biomass. Growth, or length/weight relationship (condition of the fish) is not used to as a measure of the well being or the state of the individual fish.

If individual fish are slender, the fish are hungry. Reduced fishing does not help the fish, on the contrary, it will make the situation worse.

In the North Sea, thin slow growing haddock is abundant. This is mainly the 1999 year class, now four years old, spawning at a size of approximately 30 cm. This is a clear sign of hunger, not stemming from general lack of food but high abundance of haddock, leaving very little food for the individual fish. If this is the case, then reducing the fishery in order to conserve the cod stock is wrong management.

In this context it is interesting to look at the situation in the Faeroe Islands, where similar suggestions , fish less now in order to fish more later, were rejected by the authorities.


Today, the fisheries around Faeroes is managed by a days at sea system, but this has not always been so. As elsewhere, 200 nautical mile exclusive economic zone (EEZ) was introduced in 1977. Until then, demersal fishery by foreign nations was uncontrolled outside the four mile limit but now Faroese vessels take most of the catches.

Fig 1. Catches of cod in Faeroe waters 1960-1992.
The catch is swinging between 22000 and 42000 tons fairly regularly in a period of 8-11 years. The fishing pressure is more or less similar through this period, the catch reflecting the size of the stock. The downturn is not caused by "overfishing" as the stock recovers under the same fishing pressure. It is also known that individual growth is slow when catches are high, growth is fast when catches (stock) are low. There are other factors than just fishing that control the stock size.


In the period the fishery was regulated by area closures, mesh size regulation, the same trend as elsewhere - increase mesh size to protect small fish. At the beginning of the 1999s more than 50% of waters shallower than 200 fathoms were closed for trawling. The catches went down, perhaps as a result of these restrictions, and a catch quota management system was introduced 1994.

But it was met with considerable criticism as it resulted in discarding and in misreportings of the catches and was discontinued from 31 May 1996. In cooperation with the fishing industry and the fishery biologists, the Faroese government developed a new system based on individual transferable effort quotas in days within fleet categories. The new system entered into force on 1 June 1996.

The outlines of the system is that the fishing area is divided into zones around the islands. Small boats, jiggers and long- liners are allocated fishing days in the innermost zone. Small trawlers are allowed to fish inside the 12 mile limit part of the year. Large trawlers and pair trawlers have to fish further out. There are also mesh size regulations and areas closed for fishing all the year or part of the year.

There are no catch limits - the catch reflects the state of the fish stocks. Discards are considered to be minimal and fishermen and the fishing industry are satisfied with the system.

In the last few years there has been a considerable pressure from the ICES to reduce the number of fishing days. as they considered the demersal stocks were being harvested outside safe biological limits. ICES have set limits for minimum biomass and minimum spawning biomass for each stock and the management target is to have the stocks within these "safe" limits.

The number of fishing days has already been reduced by 15% since the system was introduced in 1996 and the fishing industry and the Faeroish government is against a further reduction. Their argument is that since the stocks have been able to sustain similar fishing pressure for centuries, there is no reason for that they should not continue to do so.

In May 2001 the advice from ICES was to ban the haddock fishery:

"ICES recommends that there be no fishing in 2002 on this stock. ICES recommends that a rebuilding plan is developed, aiming at preventing a further decline in SSB below B lim. The rebuilding plan should take into account technical interactions with other gadoids and ensure that fisheries do not expand when good year classes do occur, until SSB has increased above B pa."

The Faeroise government did not follow this advice. They argued that it would would be impossible to stop fishing haddock in a mixed fishery. Also, landings showed good catches of small haddock and cod, indicating good recruitment. ICES based the management on the assumption that in order to "secure" good recruitment the spawning stock should be increased. But interestingly, rexamination of the data on spawning stock size and recruitment showed quite different relationship - when the spawning stock was increasing, recruitment was decreasing and vice versa. This is explained in Figs 2-4.

Fig 2. Stock/recruitment for Faeroe haddock.
The conventional way to show a spawning/recruitment relationship is to plot the size of the spawning stock (ssb) in a particular year against the number of recruits resulting from that spawning. From this figure it is difficult to tell whether large, medium or small spawning stock gives the best recruitment. There is no obvious relationship.

Fig 3. Another way of looking at the problem is to plot spawning stock and recruitment by time. It can be seen that the recruitment is highly variable, and increase in spawning stock follows a strong year class. Also, when spawning stock is relatively high, recruitment seems to be low and vice versa.

Fig 4. After filtering the data by using three year running average to remove high frequency noise and making that to swing around a medium term average by subtracting nine year average, we see a very interesting relationship: Recruitment and spawning stock oscillate in anti-phase around the medium term mean with a frequency of 6-10 years, approximately two life spans of a haddock. When the spawning stock is increasing, the recruitment is decreasing and vice versa.

The conventional argument that to spare the fish in order to increase the spawning stock and thereby secure good recruitment in the future is wrong. On the contrary, increasing harvest by hard fishing and thus keeping the stock size moderate, is more likely to increase recruitment in the long run, giving a sustainable good harvest. The Faeroese fisheries minister therefore decided not to decrease the number of fishing days.

In 2002 similar advice came from ICES - reduce the fishing effort by 35% (haddock) and 50% (cod). This advice was also ignored and the haddock catch increased from 14000 to 22000 tons and the cod catch from 26000 to 36000 tons.

Furthermore, stock assessment show that not only are catches increasing but stocks as well. The question arises: If the stocks are increasing, how then can the fishing pressure be to high?