Modelización de la pesca. Propuesta para una regulación de las pesquerías de cerco andaluzas

Abstract

Despite the fact that there is a prolific and extensive literature on formulating fishery management policies under socio-economic criteria, its actual application to specific fisheries in the European Union has been and is almost non existent. Until now, it seems that the mangement agencies of the Fishery Administration, whether they are European, national or regional, are not using any different instruments than those used in biology, which, as we will see throughout this paper, can restrict the full application of the policies drawn up to manage the fisheries. The fisherman, like every businessman, tries to make as much profit as is possible or at worst not to make any loss. A policy which ignores this reality will have, as a consequence, limited chances of success, given that it will be difficult for the fisherman to comply with the rules set out. The factors which force the fishermen to overexploit a fishing ground are basically socio-economic. As H. Scott Gordon pointed out in 1953, overfishing is the result of the competitive race between each individual fisherman to get hold of resources to maximise his profits. Therefore, whenever they expect to make any additional profits from the resources they bring in new vessels to the fishery, up to the point that all the income that could be generated by the fishery is disippated. Just by putting the resources under some form of centralised management, the fleet could be prevented from operating on mere subsistence levels and, as a consequence, enable the fishermen to make some profit or income from their daily activity. However, this basic principle is forgotten by even some of the most common management measures which is why they are not only unable to reach the end of the competitive race but they can take exploitation to the extreme or even worsen the economic situation of the fisherman. In order to illustrate this we are going to analyse it through drawing up a bioeconomic model for a specific fishery: the anchovy fishery in the Spanish South Atlantic Region, included in the IXa statistical area of the International Council for the Exploration of the Sea(ICES). The anchovy (Engraulis encrasicholus) is a small pelagic fish with stocks distributed throughout the Mediterranean and the EuropeanAtlantic coast which have been exploited ever since one can remember. It has a gregarious character, which forms shoals of millions of fish which, in certain periods of the year, are found near the coast and even enter the mouths of large rivers. The exploited stock is usually formed by more than 80% of the fish from the captures of the previous year, which are caught when they reach an average size of 12 cm and weigh approximately 13 grs. However, it is quite common to find 3 year old fish in yield carried out in waters far from the coast. Its high relation of the temperature leads to good and bad periods where the catch varies from being exceptional, normal or minimal, depending on the climatic parameters which affect the annual harvest. In the South Atlantic Region, the exploitation of anchovies is carried out by the coastal purse seine fleet, mainly located in Barbate (Cádiz) and in other ports such as Punta Umbría and Isla Cristina in the province of Huelva. However, the Barbate fleet often alternates the anchovy catch from the Gulf of Cádiz with the exploitation in Moroccan waters, and, because the vessels are used for both expeditions, one cannot distinguish the origin of the boats. This is the reason why we are to concentrate on the analysis of the harvest and the effort series of the fleet based in the Province of Huelva. In the past, the anchovy catch, which the fleet alternatedwithsardines (Sardina pilchardus), yellow jack (Trachurus trachurus) and spanish mackerel (Scomber japonicus), continued well into the seventies, when it was used as fish flour. Although a sizeable amount was directed towards salted fish, canned fish or fresh fish consumption, anchovies were not considered to be an important catch for the seine fleet until the end of the seventies. However, after 1971, the "chirla" fishery (Chamelea gallina) experienced a sharp decline, it fell from 20,000 Tm in 1969 to just 3 Tm in 1973, in such a way that a sizeable amount of the towed rake vessels were used for trammel net, seine and rake fishing, so that they could be used in the fishery. Between 1971 and 1975, anchovy yield in the Moroccan fishing grounds (place used for casting fish nets)were drastically reduced, falling from 20,000 Tm to less than 2,000 Tm, causing a 200% increase in the price during this period, forcing the fishermen to increase production, thus the intensity of fishing is increased to such an extent that for a year and a half (until Jan 1976) there were extremely large catches. This brought about overexploitation of stock and the authorities having to limit the size of the caught fish and establish maximum tares. Little by little, the anchovy has become the fish with the greatest demand in fresh fish consumption, which has increased pressure on stock. However, the regulation of seine fishing in 1985 and, more specifically, the extremely high mackerel demand by the local canning industry between 1984 and 1987, made it possible for there to be a reduction in the intensity of fishing and further yield recovery, which increased from 324 Tm in 1986 to 1,035 Tm in 1995, in the fishing ports in the province of Huelva. In 1991, the "Secretaría General de Pesca Marítima" (SGPM) set out a plan for anchovy fishing. It authorised seasonal shipping, which was prohibited from the seine census of 1985 because it did not reach 20 GRT, for anchovy fishing, for three months a year (from February to May), excluding the rest of the fleet (single purpose) between the months of November and January. At present, temporary licenses for anchovy fishing are granted to 15 vessels (multipurpose), with a total of 158 GTR, a power of 1,501 horsepower and 67 crew size, whereas in the seine census (single purpose), there are 23 vessels with a total of 490 GTR, 3,580 HP and 169 crew members. The fleet as a whole is composed of 38 vessels with an average capacity of 17 GTR, an average power of 134 HP and an average of 6.2 crew members. The landing price set by the yield varies according to the average price of the network of central markets. This price is very much determined by imports from other countries (mainly Italy, France and Morocco), for this reason between 1990 and 1995 it has fluctuated around 350 PTA/Kg, making it impossible for there to be a relation between the landing and the price. This is very clear evidence of the control of the market by exporters who are usually agents' suppliers in the Mercasa network (Madrid and Seville). Therefore, it is the national price which determines the landing price, which is why we will allow a infinitely elastic demand for wholesale. The anchovy fishery of the South Atlantic Region showed at the beginning of the eighties serious signs of overexploitation. However, the reduction of effort during the mid-eighties made it possible for a significant recuperation of stock, but we still need a decrease in developed effort so that this fishery can be considered to operate on optimal levels. We have analysed the situation of the stock and determined the optimal effort and catch levels to reach the maximisation of today's value of the net social profit of the fishery. Likewise, we have evaluated the different forms of regulation which will permit the fishery to work on the desired level and we have determined the approximation development of the maintained equilibrium. Nevertheless, we are aware that all the results come from estimates we have made, therefore, from the statistical information we had available. Unfortunately, today's fishery statistics have considerable errors, both in the way the aforementioned information is collected and its reliability. For which perhaps, this paper must be taken as a sample of what could be possible if we were to have the correct information at our disposal. The methodology used throughout this paper can be an applicable alternative in cases where there is little or no biological information on the stock which we want to analyse, as happens with many fisheries in the Mediterranean and in the South Atlantic Region. Furthermore, the method of estimating the biological parameters and biomass can be easily generalised to multicohort models and with superimposedgenerations, and incorporate any other information available on direct evaluation simply by modifying the a priori distributions of the corresponding period. Likewise, the determining of the optimal stock levels, efficient regulation measures and approximation paths just as it has been presented in this paper, allow us to manage small fisheries that, on some occasions, are diluted in the statistic classification by large management areas used in the Atlantic