Theoretical Aspects

A “tragedy of the commons” (see Hardin 1968) is likely to occur when resources are owned collectively by society and open to any one who wishes to exploit them (open access). In such a situation, the physical and legal accessibility of the resource to any user will lead to users competing with one another for a greater share of the resource, since it is in each user's best interest to harvest as much of it as he can. Without restrictions there is a tendency to overexploit the resource, or to exploit it too rapidly for regeneration to take place, or to exploit it to destruction and extinction. The ills of such uncontrolled exploitation arise because a free-access resource is. by definition, nobody's property. As Bromley (1986) has stated, the phrase to describe the situation should not be the popular one “everybody's property is nobody's property”, but rather “everybody's access is nobody's property”.

A resource such as air may be ownerless (res nullius) and freely accessible, whilst another such as grazing land may be owned in common (res communes) by a well-defined group of people. Since others outside the group cannot use this resource, exploitation is confined and access is thus not completely free (see Ciriaey-Wantrup and Bishop 1975).

Fishery resources are renewable natural resources which, like other renew- able resources, can yield a harvestable surplus indefinitely when exploited on a sustainable yield basis, but may collapse if they are overexploited. Fishery resources have certain characteristics which collectively serve to differentiate them from other renewable resources. First, they belong to the group of resources such as wildlife and migratory waterfowl known as fugitive resources which, because they are mobile, must be captured (that is. reduced to possession) before they can be allocated (see Ciriacy-Wantrup 1952). This mobility, limited in the case of demersal fish, high in the case of pelagic fish, and very high in the case of migratory species such as the tuna and the whale, makes their capture an unpredictable affair.