1.4. Justificación del Estudio
2.2.6. Concepto de emociones
The purpose of this section is to see whether marine fisheries in Bangladesh have reached the sustainable level of exploitation. The sustainability for marine fisheries is examined using a bio- economic model. There are a number of biological models on fishery. Here the Schaefer model (Schaefer, 1954, 1957) is used since it can be applied in a fishery with limited data. The analytical framework and the adopted model for deriving the sustainable yield curve are discussed in sections 4.4.1 and 4.4.2 respectively.
4.4.1 Analvtical Framework
Fish are renewable resources which, like other resources can yield a harvestable surplus indefinitely when exploited on a sustainable yield basis. But they will be dissipated if they are overexploited. Fish are open-access resource or common property. This feature gives rise to a number of economic problems, such as over fishing, even extinction of fish species, inefficient use of factor inputs, low returns to fishing industries. Therefore, some sort of regulation of fishing industries is necessary.
In the exploitation of an open-access fishery, the relationship between fishing effort and the harvest or yield can be expressed in the form of a sustainable yield curve (Figure 4.5). Sustainable yield for any given stock size is the yield that can be harvested each year without affecting the fish stock, as the yield is equal to the rate of growth of the fish stock.
Schaefer model assumes a linear relationship between effort and yield. Total yield will increase with increases in effort until the point at which sustainable yield is highest. This is the maximum sustainable yield (MSY) which can be obtained from a fishery without impairing the capacity to renew itself. MSY is the maximum potential productivity of a stock in terms of catch. Any fishing effort beyond MSY leads to a decline in total yield because the fish stock declines due to overfishing. In Figure 4.5 it can be observed that two different levels of fishing effort can produce the same yield Y,. Fishing effort at level E, is the situation where there is underfishing.
Net growth of Y, can be obtained with a small population. But fishing effort represents overfishing as this level is beyond MSY. Here the growth can be obtained with a large population. At E, births greatly outnumber deaths because the population is small and food is ample. But at E^ births slightly outnumber deaths and the average size of the population is large.
Best possible allocation of resources is achieved when the marginal productivity of effort is equal to the marginal cost of effort. That is when the value of fish that a marginal unit of effort produce is equal to the value that a marginal unit of effort would produce in its best alternative use. The total revenue curve is the same shape as the sustainable yield curve in Figure 4.6. If it is assumed that the total cost for the fishery increases in proportion to effort, then the total cost curve for the fishery will be a straight line as shown in Figure 4.6. There is a linear relationship between fishing effort and income earned and as effort increases total income will also increase. The point of maximum profit to the industry per unit of effort is the point of maximum equilibrium yield (MEY). Because at ME Y the difference between total cost and total revenue is the highest. It can be seen that MEY occurs at a significantly lower level of effort than MSY, but this is the preferred goal of fishery economists since economic rent is maximized at this point. If the fishery is owned by sole owner it would be rational for him not to put in additional fishing effort once MEY is attained. Resources are properly allocated at this level since the value of the lost fish caught (marginal revenue) just balances the cost of producing it (marginal cost).
But fishery is an open-access resource. Fishermen will continue to enter it as long as they can make a profit from it, i.e. as long as the average revenue (AR) of the individual fisherman is higher than the average cost (AC). As fishing effort continues, total revenue (TR) will increase up to MSY. Beyond MSY the average yield per unit of effort will fall as there are now more fishermen exploiting a smaller fish stock. Total cost (TC) will also increase. Individual fisherman in an unregulated fishery will continue to enter it until the point is reached where they fail to earn any surplus over their variable costs. This point is usually called the open-access equilibrium yield (OAEY). At this point TC = TR. Here rents to the fishery equal zero and economically rational firms will not expand any effort beyond this point.
OAEY represents a misallocation of natural resources as increases in fishing effort beyond MEY bring in diminishing returns and declining profit margins as costs will increase more than revenue. Increases in fishing effort beyond MEY mean that inputs are being diverted from producing other goods of higher value to society, assuming that capital and labour are freely mobile between alternative employments. Unregulated fishing effort in a free access fishery will not only generate less rent than it could but its aggregate yield and gross income would also be lower than it should be. It is clear that well before OAEY is reached, the fish stock will be overexploited both economically and biologically.
At the equilibrium OAEY, fishermen can earn no pure profit after covering the opportunity costs of all inputs. Thus society earns no rent from the fish resource. Given that fish resources are scarce and need to be conserved, society should charge fishermen a rental for the use of the resource. The rental added to existing input costs would increase the total cost per effort and thus force the fishermen to reduce effort. This will result in conservation of the resource and maintaining it at a level which maximizes net economic benefits to society. It should be noted that the assumptions of the above discussion are (i) future value of resources are not discounted (ii) industry is perfectly competitive and each firm in the industry takes all prices, including factor prices, as given and constant over time.
The theoretical framework discussed here provides the basis of computing costs and returns in the fishery sector. Costs per unit of catch, total effort, returns per unit of effort, catch per unit of effort and economic rent over time in each type of fishery can be calculated. Zero economic rent in a fishery would indicate that the fishery is overexploited and negative rent would imply that the resource is fully exploited. Therefore, some means of regulation of fishing effort is required if fish resources are to be protected from dissipation.
4.4.2 The Model
The analytical framework presented in the previous section shows that in the Schaefer model catch per unit of effort is a linear function of effort i.e.
Y/f = a - bf (4.8)
where,
Y = sustainable yield
f = effort
a and b are constants
Equation (4.8) can be written as:
Y = a f - b f (4.9)
Differentiating equation (4.8) with respect to f and setting dY/df = 0 the level of effort (f^y) giving maximum sustainable yield can be derived:
dY/df = a - 2bf = 0
a = 2bf
fm sy = a/2b (4.10)
Putting the value of f in equation (4.9) the maximum sustainable yield (Y ) is obtained:
T fm ay = a(a/2b) - bfafAlb:)
= aV2b - aV4b
aV2b(l - 1/2)
The parameters a and b can be estimated by a linear regression of equation (4.8) from the fishing effort and yield data. In order to estimate equation (4.8) time series data for the period 1972 to 1988 are used in this study.
4.4.3 Calculation of Effort
Since various types of fishing effort are used to catch fish it is difficult to aggregate these inputs into a single index. The problem could be solved by converting the inputs into time, for example, hours, days or months of fishing. Different types of fishing efforts are complementary to each other. That is, a larger number fishermen also reflects the fact that a larger number of nets and boats are used and vice versa. So any one of these inputs expressed in units of time could be a proxy of fishing effort. The number of fishing boats could be another estimate of effort. In this study the effort is measured in terms of fishing crafts.
The calculation of effort in terms of boats is complex. In the marine fishery there are three types of fishing crafts with different efficiency which need to be converted into one unit. Three types of fishing crafts are used for marine fisheries - trawlers, mechanised boats (MB) and non mechanised boats (NMB). The number of non-mechanised boats is not available except for the period 1985 to 1988. Assuming that there is an annual increase of 200 NMBs the number of NMBs for the remaining years is obtained.
Trawlers fish about 200-250 metres away from the shore and 100-110 metres deep in the sea. The length of the vessels varies between 25-45 metres. Most of the vessels used in Bangladesh for fishing were imported in 1981. The average longevity of these vessels is 30 years. The engine capacity of these trawlers varies between 400 to 1250 horse power (HP). On the other hand, MBs fish upto 40 metres depth into the sea. The size of MBs is between 9-14 metres long. The engine capacity of MBs is around 15 to 45 HP. These boats operate mainly three types of nets: (i) small mesh drift (gill) net with 100 mm mesh size, (ii) large mesh drift nets with 200 mm mesh size, and (iii) seine nets (encircled nets) with 100 mm mesh size. NMBs are traditional sail boats. Fishing gears used by these are set bag net, long line fishing, beach seine and cast
net. The average horse power (HP) of fishing trawlers in Bangladesh is 577 and of mechanised boats 40 HP (BMFA, 1995). The annual catch data show that the fishing efficiency of a non mechanised boat is only 10 percent of a mechanised boat. So a power of 4 HP is assigned to a non-mechanised boat.
Table 4.13 Unadjusted fishing efforts in marine fisheries
Year Fishing Crafts U sed in Marine Fisheries Horse Power o f Fishing Boats
Trawler Mechanised Boats Non- M echanised Boats* THP = Number o f Trawlers x 577 M B HP = Number o f MB X 40 N M BH P = Number of N M B X 4 1972 10 200 3800 5,770 8,000 15,200 1873 21 276 4000 12,117 11,040 16,000 1974 21 1000 4200 1,2117 40,000 16,800 1975 26 1000 4400 15,002 40,000 17,600 1976 26 1050 4 6 0 0 15,002 42,000 18,400 1977 26 1100 4 8 0 0 15,002 44,000 19,200 1978 26 1200 5000 15,002 48,000 20,000 1979 26 1300 5200 15,002 52,000 20,800 1980 24 2000 5400 13,848 80,000 21,600 1981 35 2050 5600 20,195 82,000 22,400 1982 53 2100 5800 30,581 84,000 23,200 1983 73 3347 6000 42,121 133.880 24,000 1984 67 3300 6200 38,659 132,000 24,800 1985 45 3137 6559 25,965 125,480 26,236 1986 49 3132 6461 28,273 125,280 25,844 1987 52 3317 14014 30,004 132,680 56,056 1988 52 3317 14014 30,004 132,680 56,056
* Figures from 1972 to 1984 are assumed.
THP Trawler horse power
MB HP M echanised boat horse power
N M BH P Non-m echanised boat horse power