Back in the 80’s when I started to pretend to understand how fisheries were managed by studying Marine Biology and Fisheries, one of the 1st book you read is On the Dynamics of Exploited Fish Populations by Sidney Holt and Ray Beverton which was published in 1957. The book is a cornerstone of modern fisheries science and remains a reference even today.
Schaefer model of surplus production (biomass dynamic) as a function of stock size showing the major reference points. MSY = maximum sustainable yield; BMSY = the biomass at which MSY occurs; and B0 = the average unexploited biomass of the stock (the average ‘carrying capacity’). @FAO
The Beverton–Holt model sets up a classic discrete-time population model which gives the expected number (or density) of individuals in a generation as a function of the number of individuals in the previous generation. With time the model was modified and changed, as the original Beverton and Holt per-recruit models assumed knife-edge selectivity and constant fishing mortality and natural mortality for all ages. They assumed that stock is in equilibrium i.e. that the biomass and age -structure are constant from year to year. Also assumed that recruitment is constant from year to year, which is likely to be false at high fishing mortalities when low spawning biomass may reduce recruitment, plus the present variables and changes due to climate change. Yet with no doubt, the man was one of the founders of what we see today as fisheries biology.
So I was saddened to hear of the passing of Dr Holt a few days ago on the 22/12. My interest in his work was also more recent (I quoted him a couple of times) , as he was a hard critic of the concept of MSY (Maximum Sustainable Yield). This concept is at the basis of most worldwide fisheries management policies and MSY was adopted at the policy level in 1958.
Yet Carmel Finley in his article, “The Social Construction of Fisheries, 1949”, recognizes that world word two the United States of America (U.S.) were looking for open seas and skies, for military purposes but also for fishing purposes. These objectives were threatened by territorial claims made by some Latin American countries over their neighbour waters. In 1948, with this context of international disputes and tension, Wilber McLeod Chapman was announced as the U.S. State Department under-secretary advisor for the industry. Within months of being assigned to this position, Chapman crafted the U.S. Policy on High Seas Fisheries. The policy had two main goals: uphold the principle of the freedom of the seas and establish fish stocks could be conserved without claiming expanded territorial limits, this second objective scientific foundation was the MSY.
The Policy was published in the Secretary State Bulletin in 1949 (Finley notes that this was not a refereed scientific journal). After the publication of the Policy three fishery treaties and two commissions were signed with different countries: Mexico, Costa Rica, etc, establishing that stocks were to be managed to produce MSY.
In 1953, the International Law Commission recommended that new ocean law was needed to deal with the escalating fisheries conflicts. The United States suggested that a technical conference should be held to give guidance to the law commission. After this request, the International Technical Conference on the Conservations of Living Resources of the Seas was finally held at FAO headquarters in Rome between April and May 1955. The conference was held in the middle of growing tensions because of fishing disputes between different countries, and the U.S. did not want the conference to deal with territorial issues.
The International Law Commission accepted the “technical advice” of the Rome meeting and MSY was adopted at the policy level in 1958 and was included in other highly important international agreements. Namely international agreements promoted by the United Nations.
The first of these international agreements was UNCLOS, the result of the third United Nations Conference on the Law of the Sea that took place from 1973 to 1982. This agreement defines the rights and responsibilities of nations in their use of the world’s oceans, establishing guidelines for businesses, the environment, and the management of marine natural resources, including fisheries. In this agreement, the MSY principle is introduced when defining measures of conservation of the living resources in article 61 and 119.
Some years later, in 1995, the United Nations published the UNFSA which objective was to ensure the long-term conservation and sustainable use of the straddling fish stocks and highly migratory fish stocks trough the effective implementation of the relevant provision of UNCLOS. Under the Article 5, general principles, the concept of MSY is introduced again…. In fact, UNSFA complements UNCLOS, establishing MSY to manage shared and non-shared fish stocks all over the world.
Is criticism is even more remarkable as Holt served with FAO (as Director of the Fisheries Resources and Operations), as well as Secretary of the Intergovernmental Oceanographic Commission and Director of UNESCO’s Marine Sciences Division among others, from 1953 to 1980… exactly the times that the MSY concept became entrenched.
His opinion about it hardcore (read his article), I just quote some parts here:
”MSY both enthrones and institutionalizes greed. It is a perfect example of pseudo-science with little empirical or sound theoretical basis. As a target for management of fisheries, or even as the anchor for so-called ‘reference points’, it is inadequate and its pursuit increases the likely unprofitability, and even collapse, of fisheries.”. As we have seen, the first MSY notorious international appearance was done by Mr. Chapman who had introduced MSY in the Secretary State Bulletin in 1949, not a refereed scientific journal. Later on, the idea of conservative management by trying to hold exploited populations to provide MSY has become solidified in law and regulations “with no more science than there ever was to support it”.
Holt highlights, for example; the assumption that the biological productivity of the population (and hence the rate of sustainable yield) is determined solely by its size or density. He states that when two populations having the same initial number of individuals, with the same size and belonging to the same specie with the same growth rate may have different behaviours if they have different mortality rates due to both or either fishing and natural causes, this would lead to different productivities and hence sustainable yields.
Furthermore, he adds that “the sustainable catch in weight and value depends as much on the age and so the size composition of the population as it does on its biomass”. Following this idea determining how old are the animals in the catches and for how long they have been allowed to grow is as important as their numbers or even their combined weight. “MSY calculation depends critically on what ranges of fish size and age are being exploited”
To finalize with Holt reflections about MSY and its use in the world fisheries management it is necessary to say that he has recognized having offered his support for MSY twice in his life, but only because the adoption of MSY was an improve, progressive policy regarding the policy it was being used until that moment.
At the same time, he recognises that twice he enthusiastically offered support for MSY. How come? In both cases – regarding the extreme depletion of the populations of large whales, in 1974, and the EU Commission’s recent proposals to adopt it generally in EU waters – the question was how to get away from a policy of seeking merely current sustainability, instead of the recovery of stocks to more productive abundances and states. Shifting from ‘sustainability’ to notional MSY was in those cases an improved, progressive policy. It has, however, its dangers, as we saw with Japan’s pressure, in the 1970s, to reduce hitherto lightly exploited whale populations – such as the minke and Bryde’s whales in the Southern Hemisphere – down to their presumed MSY ‘levels’. I have since thought that maybe one should not support certain things for tactical reasons that one would not support if thinking strategically. My mother sometimes told me that in some ways a white lie was worse than a real one.
In any case, whatever you think about the man, he made me think and I always like that.
Rest In Peace