MEFISTO PREPARED APPLICATIONS MODELLING FISHERIES MANAGEMENT STRATEGIES IN THE MEDITERRANEAN

Transcription

1 MEFISTO PREPARED APPLICATIONS MODELLING FISHERIES MANAGEMENT STRATEGIES IN THE MEDITERRANEAN CASE STUDY 2: The sardine (Sardina pilchardus) and the anchovy (Engraulis encrasicholus) of Tarragona Sergi Tudela, Begoña Fernández The parameters of this case are tarrago.par & tarrago.sim

2 1. - General description The fishing of small pelagic -sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus)- and small pelagic horse mackerel (Trachurus spp.) and mackerel (Scomber scombrus y Pneumatophorus japonicus), accounts for the major percentage of disembarks done in Catalonia. The first two species stockpile the 56% of the total volume of the Catalonian catches. If we consider the four species, this percentage increases to 62%. The first objective species are the sardine and the anchovy because of their important economical weight compared with the other two species, horse mackerel and mackerel. The economical value of those four species, or more correctly groups of species, rise to 5511 million pesetas, the 30% of the total disembarks of Catalonia, and only the sardine and the anchovy represent the 90% of the total. Those populations of small pelagic have a great tendency to fluctuate in a natural way, and this has an enormous importance on the fishing. Everything is consequence of their short vital cycle and their dependency on the lowest levels of biological production (phytoplankton and zooplankton) very influenced by the environmental conditions. Those natural fluctuations make these species to be especially risky in overexploited stocks situations, because there are situations not predicted that can increase the overexploitation position of the resource. Table 1.- Catches and Value of Sardine and Anchovy at area (Catalonia) and at Tarragona s harbour CATALONIA, 1999 Catches (t) % Of the total Value (Euro) % Of the total Sardine 15, % M 11.6% Anchovy 5, % M 9.7% Total 21, % M 21.3% TARRAGONA, 1999 Catches (t) % Of the total Value (Euro) % Of the total Sardine 6, % 5.17 M 36.7% Anchovy % 0.89 M 6.3% Total 6, % 6.06 M 43.0% The anchovy is the second specie in importance of disembarks in Catalonia, while is the first if we talk from an economical point of view. The catches for this specie in 1995 (10135 t) meant the 16% of the total volume of disembarks. In economical terms represented a total of 2464 million pesetas, or what is the same the 13% of the value of the total catches. In summer is when this specie has its cycle of reproduction, so is the decisive point of catches. The data of 1993 corroborate that: During the months of May, June, July and August the catches arrived to the 63% of the annual total. The main harbours, with more than 1000t disembarked where, in order of importance: Roses, on the North of Catalonia, Vilanova, Barcelona, Tarragona and Arenys. On those

3 harbours carried out the 80.5% of the total disembarks. Nowadays, on the Catalonia area, it is used two fishing gears: the purse seine and the bottom trawl. The purse seine attracts their catches with artificial light, by this reason it only works during the night. The objective species of this gear are the small pelagic fishes, so the anchovy is one of the main objectives of this gear. Compared to the relatively sedentary behaviour of the Tarragona fleet, about thirty vessels, focused on the exploitation of the fishing spawning ground situated in the South of Catalonia, it is mentionable the high mobility of the rest of the purse seine fleet, specially the one in Barcelona and its surroundings. The latter, situated half way of the main fishing zones must cover long distances in accordance of the abundance of the resource. Figure 1- The purse seine gear The bottom trawl is normally not working over pelagics. The largest part of the pelagic catches in Catalonia was obtained by the purse seine. Only incidental catches of pelagic are landed by trawlers, but in some areas of the Tarragona coast (like St. Carles de la Ràpita) the trawlers adapt their nets in order to fish in the surface instead of the bottom. This new competence, between part of the trawl fleet and the purse seine fleet, is produced by the increase of the anchovy price and the overexploitation of the bottom fish resources. The Tarragona fleet has its fishing ground in the north of the river Ebro flow (St. Carles de la Ràpita is in the south). By this reason we only consider the purse seine fleet on this exercise. Table 2.- Fleet Structure by segments at Tarragona s harbour N (> 9 m) N (< 9 m) Total N GRT (t) GRT (%) Trawl 52 >12 m 21 <12 m Purse Seine* Bottom Long Lining Others Total

4 Fishing during the night is done under the form of purse seine with light. The maximum authorized longitude of the gear is 330 meters. While the minimum deep of the fishing ground must be at least 30 meters. In winter-autumn is followed a twomonth close season, with the objective to prevent the capture of juveniles. Although there are daily fishing campaigns (with a weekly rest of 2 days), the vessels are not enforced to disembark the captures in a particular port, differently that what happens with the trawler fleet. In the particular case of Tarragona and its neighbouring ports, the ship-owners are organized in an "Asociación de Armadores de Cerco de la Provincia de Tarragona". The fleet exploits the rich fishing grounds on the South of Catalonia, assuring a constant supply for what they obtain the best prices in Catalonia Biological data Two species suppose the purse seine s largest catches: sardine and anchovy. The characteristics of this species in the Catalonian area, can be summarised as the next points: Anchovy There is a single biological stock in the North occidental Mediterranean. The anchovy is a daytime consumer of zooplankton (basically copepodods). In the area of Tarragona (south of Catalonia) in their trophic and reproductive activity, is registered an important space and temporal segregation. In this area spawning goes from April to October, with its maximum in July. Females arrive to sexual maturity between 11 to 13 cm. of size, in their second year of life. But the minimal legal size is established at 9 cm. In autumn and winter, there is an important amount of juveniles catch in the fishery. A single cohort (the one at level of critical age) represents the 50% of the total population biomass. The currently exploitation model, supposes the risk of recruitment overfishing. Sardine Sardine eats phytoplankton and zooplankton. Their reproduction is different than the anchovy; it is produced between Novembers to March. The areas of reproduction are far from the coast. But in spring and summer, the sardine feeds near the coastline. During that time it is possible to find important concentrations of fish near of the coast, especially in gulfs and near the rivers flows. The most important commercial catches are produced during the summer. The minimal legal size is 11 cm. The biological data of this fishery are obtained from samples at the Tarragona harbour and processed by the VPA program. This allows obtaining the information provided in tables 3, 4, and 5. To run this exercise, open the file tarrago.sim from MEFISTO. Then in the field stock of the model, we can find the parameter information placed in the right box.

5 Table 3. Growth and units of sardine and anchovy. SARDINE ANCHOVY a b L. Inf K TO Table 4. - Natural mortality, reproduction and recruitment. ASYMPTOTE 5,000,000,000 SARDINE RECRUITMENT CONSTANT S AT 50% 14,666,072,533 O BEVERTON & HOLT ASYMPTOTE 1,000,000,000 ANCHOVY S AT 50% 848,179,176 NATURAL MORTALITY SARDINE 0.60 FOR BOTH SPECIES ANCHOVY 0.81 Table 5. - Number of individuals per sort of age, Maturity index and F (mortality from fishing) Sardine Anchovy Age Initial Maturity Fg Initial Maturity Fg Population. index Population. index 0 2,402,844, ,600, ,305,587, ,750, ,457, ,955, ,331, ,823, ,289, ,336, ,184, ,827, ,251, , Economic data The study of the Tarragona's harbour is focused on the purse seine gear and their most important objective species, which are the sardine and the anchovy. We can see the economic data, obtained from samples when we open the field fisherman-market. In this field, there are different screens: country, fleet, fishing mortality and catch, vessel, accessory species and market. On the first screen we find the Country inputs. These data are the same for an economic area. There is no need to be a political country, as it can be a region, a country or a group of countries where the economic parameters of the box are the same. These data are the same in Spain (as an economic area), for this reason is presented the same data as in the other cases (Malaga or Gulf of Lion). The largest part of this information

6 can be obtained from general statistical publications. Here, as well as in the other boxes the economic unit used is the Euro ( ). To introduce changes in the fuel price, firstly, we introduce in this box the initial price (the average of the first year) and afterwards, in the field events is possible to change it at different moments. At the second screen fleet we find the common data of all the vessels of the fleet considered. Here we are only considering one fleet: purse seine. These data are obtained from the statistical publications or from the enquiries. The summary of this data is presented in the tables 6, 7 and 8. Some of the parameters included are hypothetical, as the annual increase of the Catchability and the modifier Capital / Catchability. The third screen is fishing mortality and catch ; we fill this information from the biological information obtained from the VPA application. At the screen vessel we find the individual data obtained from the enquiries. When in the box boat, we specify one of the vessels (here the name is changed to a code), appears all data related to that vessel in the left boxes. All of these data was obtained by enquiries; the summary of this information is presented in tables 6 to 8, where we can find the most distinguishing traits of the fleet. All the figures are in euro ( ).

7 Table 6.- Cost structure and technical structure of Purse seine fleet Capital ( ) average by vessel 277, Insurance ( ) x year, average by vessel 414, Annual costs ( ), average by vessel 13, Commercial cost % Owner s share % 45 Daily ice s expenses ( x day), average 33 GRT, average Crew, average Fuel consumption (liters x day), average Fishing hours per day of fishing 11 Fishing days 190 Number of vessels 26 Table 7.- Market Sardine price ( x kg) 0.77 Anchovy price ( x kg 2.01 Table 8. - Other economic factors Opportunity cost 2% Financial cost 5% Fuel price 0.27 per liter At the vessel box all the information given by enquiries is introduced vessel by vessel. It is possible to see the parameters of each vessel, when a specific vessel is selected in the vessel box (C-13 in the picture).

8 The screen accessory species is empty, because for this case we are considering that the sardine and anchovy suppose the practical totality of the landings value (like happened in the Malaga's case). The last screen is market. The base price is calculated in per Kg and is a figured obtained from the average of all the sardine prices of the last year. The behaviour of the prices is not directly related with the local production. As shown in figures 2 and 3, large productions put the local market prices down but a shorter production not always raises prices. Figure 2- evolution of the sardine price y = 772,02x -0,1512 R 2 = 0,

9 Figure 3- evolution of the anchovy price y = x R 2 = With all the Tarragona data we do not achieve a price equation enough significant. R 2 is less than 0,2 in both cases. Also there are problems to estimate the total amount of fish introduced in the local market, not only from local catches, but also from the regional production of other harbours or from other countries. By these reasons we cannot consider in the box the modifier of price in relation to the supply, and we consider this equal to zero. Another question concerned with prices is that it does not exist data linking sizes with prices and if we reach to know them, of course, in that case the study will be more concrete. By the reasons in the market box we consider the modifier price related to weight and supply equal to cero. Finally the only figure introduced is the base price that represents in this case the shadow price of this market (average price). 4. Application With the data shown above it is possible to run the model and obtain the deterministic or stochastic outcomes. In this case, we obtain predictions over the behaviour of the fishery, in the case that all the conditions established remain constant. In order to do this you must press the icon go. You must remember to save the program before clicking on the simulation. The simulation is projected to run on a 25 years scenario but this is also easy to modify.

10 In order to do graphs you must go to the icon graphs and then open the simulation that you are testing. The outcomes of the deterministic simulation has been shown at figure 4. Figure 4. -The situation of the sardine and anchovy fishing nowadays and a 25 years projection. The results showed that the stock, catches and investment, basically remain constant. But at long term they were taking a decreasing tendency, this is especially important in the benefits, which at the level of the individual vessel are in many cases negative from the beginning. We are going to propose a modification of the initial situation and study the characteristics of the new scene. In this case we suggest: Scenario 1: Modification of the selectivity factor. We leave the same parameters from the years 1 to 4. But from the years 5 to 10: we modify the selectivity on cohort 0 set at 0 and for the cohort 1 is reduced to 0.5. This supposes that the gears allow to leave the net the fish of minor age (0 and 1 cohort). The way to do this is to enlarge the size of the mesh. To introduce this modification in the model, we open in the icon events (calendar figure). Then we go to the tree, at the level species (Fisherman > Country > Tarragona > Fleets > Purse seine > Species) and select first sardine field. In this specie we select in the cohort 0 the parameter selectivity factor and the option point and the push insert. Then appears a new box, where we selected year 2005 and value 0. For the same cohort we repeat this operation for the years 2006 to After we repeat the same operation for the cohort 1, and from 2005 to 2010 we introduce the value 0.5. Then we move to anchovy species and repeat the operation for the cohort 0 (put 0 value) and 1 (put 0.5 value).

11 When these changes are completed, save the new parameters and running the simulation. Then is possible to see the outcomes in the graphic facilities of MEFISTO. The figure 5 shows in different graphs the effects of the modification of the selectivity factor, which is a management measures (change of the mesh size) that allows a new situation: the sardine is not exploited during the first year of life and the effort over the adults is reduced. Figure 5. - The result of the simulation presented at the scenario 1, which was a modification of the selectivity factor, introduced from the year 2005 to The consequences to maintain in the period 2005 to 2010 a high selectivity in the cohorts 0 and 1, is an increase of the biomass in sardine and anchovy in this period. In the case of anchovy this better situation remain from 2010 to In both cases the catch and the incomes remain higher after the second year (2006) to end of period (2025). Also the profits go from a small negative situation (before 2005), go down in 2006 but then go up to a close upper zero (a sustainable position from a socio-economic point of view) from 2007 to The two last graphics show the evolution of cohorts of sardine and anchovy. In both cases the biomass of cohorts 1 and 2 are the ones that obtain more benefits of the measures over cohorts 0 and 1. In general trends. the new situation remain sustainable, but after 2020 the cohort 2 beguine to decline at new. In long term to assure the sustainability is necessary to maintain a high selectivity over initial cohorts, all the time.

12 Scenario 2: Introducing a subsidy: We are trying now to introduce other kind of measures. In the initial situation many vessels obtain negative benefits. What happens if the administration tries to solve this situation with some subsidies to the fishermen? We suppose a little economic help to the purse seine. The administration gives subsidies of in 2005, 2006 and 2007 as a total incentive. Remember that the total income is near 9 millions by year. To introduce this modification in the model, we open in the icon events (calendar figure). Then we go in to the tree at level purse seine (Fisherman > Country > Tarragona > Fleets > Purse seine) and select it. In the field purse seine we select the parameter subsidies and the option point and the push insert. Then appears a new box, in this we selected year 2005 and value For the same field we repeat this operation for the years 2006 and When these changes are completed, save the new parameters and running the simulation. After is possible to see the outcomes in the graphic facilities of MEFISTO. The figure 6 shows in different graphs the effects of the introduction of these subsidies only in tree years of the total period ( ). Remember that these subsidies affect directly the income of the fishermen. The consequences to introduce the subsidy from 2005 to 2007 is more longer than these years. In fact this action produce a change in the tendency that remains for the rest of period to The catch remaining more or less constant, but the biomass decline severally, special in the sardine case. The profit from a small negative situation (before 2005), goes up in 2005 but after goes significantly down (in spite that in 2006 and 2007 exist a subside). The two last graphics show the evolution of cohorts of sardine and anchovy. In both cases the biomass of all cohorts is reduced after In the second scenario the most important is to show the change in the tendency, from a point near the equilibrium to a new situation that drives the fishery to the economic collapse. Against a simple perception of the problem, the help of the administration in this scenario, do not contribute to obtain a socio-economic stability. On the contrary, after a short recuperation, pushes the sector to collapse.

13 Figure 6. - The result of the simulation presented at the scenario 2, which was an introduction of a subsidy from 2005 to 2007.