DESCRIPTION OF THE FISHING ACTIVITY

Exploitation at all biological stages in various ecosystems

As mentioned above, eels colonize various ecosystems spreading from Mauritania up to the Arctic Circle. They are found in shallow coastal waters and are able to thrive in salt water for all or most of their development phase. Eels are also found in continental freshwater lakes and ponds of various depths. They colonize the estuarine part of rivers, freshwater swamps and the salt marshes in the Atlantic coast or the coastal lagoons of the Mediterranean. In these different ecosystems, the different biological stages are exploited using a large variety of fishing gear. Glass eels or elvers are caught off the coast or in the lower sections of rivers.

Nearly all the juveniles for Europe come from fishing activities along the Atlantic coast and the English Channel. In the Mediterranean, the catch of glass eel is not allowed on the French coast, but does occur in the estuaries of some Italian rivers such as the Arno and the Ombrone in Tuscany, the Tiber and the Garigliano in Lazio and the Volturno and Sele in Campania (Ciccotti, 2005). Harvest also occurs in Spain, e.g. in the delta of the Ebro River (Diaz and Castellanos, 2005). In Scandinavia, capture of glass eel is prohibited (Pedersen, 2005).

 

Fishing gear used

 

FIGURE 5
An anchored tidal net known as “tela” used on the Minho River, Portugal

A variety of gear has been used to catch eel juveniles (e.g. dip net, scoop net, fyke net with a fine mesh – 1 mm2), but these can be grouped in gear used by hand and gear pushed by a boat. There is an important difference in the efficiency between the two fishing techniques. In fact the catch amount is generally linked to the water volume filtered by the gear which tends to be much larger with a push sieve than with a hand sieve (also known as scoop net). Both techniques are used in France and Spain. In Portugal, on the Minho River, a special gear is used called the “tela” (Figure 5) (Coimbra et al., 2005).
The sieves used are generally circular with a diameter around 1.20 m often fixed pole ranging between 3–10 m in length. In France non-commercial fishers are permitted to collect glass eels as long as the catch per day is 500 g. The width of the sieve is restricted to 0.5 m, corresponding to a filtration surface of around 0.19 m?. However, in some French estuaries such as Gironde, Charente or Seudre different gear and respective dimensions are allowed as indicated in Table 2 (Figure 6). A comprehensive review on the characteristics of the fishing gear used to catch glass eels is given by Dekker (2002).
The gear describe above is usually used in the small-scale professional fisheries, which mainly occur in southern Europe (France, Spain, Portugal and Italy). An eel fishery also exists in Morocco, but it is prohibited in Algeria and Tunisia and along the Mediterranean coast of France. In the 1990s the fishery was authorized in Ireland, England and Wales (Knights, 2002; Poole and McCarthy, 2005). The boats used are generally less than 7 m in length. The investment in one such boat and the necessary fishing gear usually ranges between €20 000–30 000 (approximately US$31 500–47 300). The investment is higher for fishing boats operating in large estuaries and in coastal waters. In France, the sale of eel fishery products by non-commercial fishers is forbidden while in the Spanish Basque region this fishery is considered non-commercial and the sale of eel by non-commercial fishers is allowed (Diaz and Castellanos, 2005).
Table 2
Size and dimensions of the fishing gears used in France

Type of fishing gear Shape Surface of water filtration Pushed net Circular 2.26 m? Large Pushed net “Pibalour” Rectangular 8–14 m? Pushed net Squared 2.88 m? Pushed net Rectangular 3.60–4.32 m? Handled scoop net Oval ?0.8 m?
Source: Modified from Castelnaud et al., 2005.

FIGURE 6
Examples of fishing gear and equipment used in France to catch and sort eels

Fishing statistics and stocking effort

The most accurate series of fishery statistics for the glass eel catch comes from the joint Working Group of the International Council for the Exploration of the Sea and the European Inland Fishery Advisory Committee (ICES/EIFAC) on eel (Anonymous, 2006). The data provided by the Working Group indicates that in 2004 five countries (i.e. France, Ireland, Spain, Portugal and the United Kingdom) declared a total production of glass eels of 198 tonnes. Whereas the total production in 1994 for the same countries plus the Netherlands was around 494 tonnes. The largest difference between the 2 periods comes from Spain where 150 and 4 tonnes were reported for 1994 and 2004, respectively. This difference may be due to an overestimation of the production in 19942.
The relative abundance index, the variation of which is shown in Figure 7, is estimated between the maximum of the data series and the value of the catch in a given year. This illustrates the start of the downward trend, showing that the decrease in eel abundance began during the 1960s in the Baltic or Scandinavian area, followed by a reduction in recruitment in the south of the North Sea during the 1970s. This was followed by a rapid decrease of the arrivals of glass eels in the central area from the south of British Islands down to the Iberian Peninsula during the 1980s.
The trends of the relative abundance indices defined from official statistics and from scientific series of catch abundance show that the decrease of the intensity of the glass eel recruitment began sooner in the North of the colonization area than in the South (Figure 7).
2 The series of statistics concerning glass eels landings provided by the Asturias Region in the framework of the INDICANG program give a figure of 8 metric tonnes for the fishing season 1995–1996 that confirms the level given for the Nalon River by the ICES group in 2006 (9 900 kg). So, it seems unrealistic to think that more than 100 tonnes of glass eel are caught off the Basque country and the Galician rivers, even if the small production from the Ebro River in the Mediterranean is added.

FIGURE 7
Trends of different series of glass eel catches for different zones of the colonization area, with moving average of 5 years have been used to smooth the information of high frequency

The decrease presently common to the whole area, and for the Mediterranean, has consequences for the purchase of the wild seed necessary for aquaculture and stocking. For European aquaculture, 2.5 kg of glass eels generally produce 1 ton of eel (7 pieces per kg). As European production is close to 10 000 tonnes of fish, around 30 tonnes of glass eels are necessary to support eel aquaculture each year, and the price has to stay below approximately 700 Euros per kilogram.
For restocking, the amount of glass eel purchased is roughly known, but the statistics provided by the ICES/EIFAC Working Group on eel don’t take into account all national restocking programmes. Figure 8 (from ICES/EIFAC WG on eel, 2006)

FIGURE 8
Restocking of glass eel and yellow eel juveniles in Europe

Source: Anonymous, 2006.
presents the series of glass eels or elvers introduced in the European waters from the mid-1940s to the present. Figures are lacking from France, Spain, Italy, Ireland, and Germany where some restocking programmes exist.
There are some major efforts among the countries involved in restocking. For example:
• In Belarus, from 1956–2002, more than 56 million eels were released into 44 water bodies covering a surface area of 48 500 hectares (Petukhov, 2002). Since 1988 no regular introductions have been made.
• In Poland, from 1951 to 1980, an average of 18.2 million eels was released annually into 559 lakes. These introductions, according to Leopold and Bninska (1983), had an important impact on eel harvests.
• In Lithuania, the first stocking operations took place between 1928 and 1939 when 3.2 million elvers were released into lakes of the Vilnius region (Shiao et al., 2006). Since the mid-1960s, Lithuanian lakes have been stocked with 50 million yellow eel juveniles representing an annual average rate of 1.1 million eels (Lozys, 2002).
• In Sweden, the stocking of lakes is an old tradition, beginning as early as the eighteenth century. From 1976–1980 about 1.5 tonnes of elvers were imported from France and stocked along the coast and in lakes. Starting from 1979, the Swedish Board of Fisheries allocated SKR425 000 (approximately US$63 500) for annual restocking activities (Wickstrom, 1983).
• In Ireland, Moriarty (1983) detailed the release of 13.8 million elvers from 1960 to 1974 into Lough Neagh to increase production. The results suggest that at least a tenfold increase in catch elsewhere in Ireland could be achieved by expanding the existing restocking programme.
• In Denmark, a national stocking programme has been in place since 1987, financed through sport fishing licence fees. The seed are imported from southern Europe, pre-grown in local farms and released in brackish (75 percent) and fresh (25 percent) water bodies. In 2004, the programme was scaled down due to the poor harvests and the high price of glass eel (Pedersen, 2005).

TABLE 3
Variation in glass eels price from 1993–2006

Source: Nielsen, T., personal communication, 2007.
In recent years the price of glass eel has increased significantly due to the growing Asian demand and due to a decrease in the glass eel production by half since 1995 (400–500 tonnes compared to the current 200 tonnes) (Tables 3 and 4). This situation allows the glass eel fishery to retain its profitability even at low harvest levels, but creates difficulties for eel growers and fishery managers in finding the seed for aquaculture and restocking activities. A rapid price increase during the 2004 season impacted the restocking programme in Europe (e.g. Denmark) and most probably the overall profitability of the aquaculture sector.

Fishing seasonality

In the main areas of glass eel distribution, i.e. the Atlantic coast from the south of the British Islands down to Morocco and in the Mediterranean, migration occurs during the whole year as observed by Charlon et Blanc (1982) in the Adour River in the south of France, by Antunes (2002) in the Minho River in the north of Portugal and Sobrino et al. (2005) in the Guadalquivir in the south of Spain. However, the main fishing season occurs during a more restricted period as defined by fishing regulations or by economical constraints, such as an insufficient density of juveniles in the estuary for fishing to be profitable.
Fishing periods differ according to the river basin district: November to March in Italy, with a peak in January (Ciccotti, 2002), and in the southern part of France (Prouzet et al., 2001). For the Adour River, the main fishing season shortened with the reduction in the eel resource (Prouzet, 2002). During the 1960s the length of the main fishing season was four months (from November to February). Currently the fishing season is no longer than two months, either November-December or December-January. On the Cantabrian coast of Spain, the main fishing season generally occurs between December and February (Garcia Flores, Herrero and de la Hoz Reguls, 2005).
152 Capture-based aquaculture: global overview
In the southern part of the European Atlantic coast, the fishing season takes place earlier. For example, in the Guadalquivir estuary of Spain, the fishing season is between October and March of the following year, with peak fish densities between November and January (Sobrino et al., 2005). The fishing season is generally later in the north of France. For example, in the Loire River, the main fishing season is between January and March, as in the Vilaine estuary (Feunteun et al., 2002). In the Channel (Baie de Somme), the fishing season takes place between February and April, with March the best month (Rostiaux and Delpech, 2006).
In England and Wales, most of the glass eels are caught in the spring, but some pigmented elvers may be caught later in the season (Knights, 2002). In Ireland, glass eels are known to arrive off the Irish coast beginning in mid-December, but significant catch takes place in the estuaries from February to mid-April (Poole, 2002).
Handling procedures and equipment used for transportation
There is not a single standard procedure for handling European glass eels. As the methods of capture vary greatly from country to country (e.g. traps, dip nets, trawls), even from region to region, so do the ways of handling and transporting the fish. The commercial boats operating in French rivers are among the most representative way of handling the fry. The fishermen typically trawl for 5–25 minutes and deposit the catch on a plastic grid (mesh size 5 mm) on top of a holding tank (see Figure 6). The most active glass eels will immediately find their way through the grid while wounded and exhausted specimens will have to be helped with the aid of a brush. A variety of other small organisms such as shrimps, worms, fish, etc., find their way through the grid as well. Larger items are discarded overboard. The young eels are kept in the tank and the water is renewed, depending on the equipment onboard. After fishing the tanks are emptied into a fine net and the eel catch placed into buckets with a little water or into flat boxes if there is a substantial catch.
The eel catch is taken to a local collecting station, which is either a building situated along the river bank or a mobile station, e.g. a van with a tank and scale for weighing the catch. The eels are carefully drained of water, checked for bycatch and dead fish, and placed into the holding tank. A receipt is issued to the fisher, and once a week a payment invoice is issued based on the tickets collected, which are added up and multiplied by the “riverbank price”, i.e. the price paid to the fisher. The price can vary from river to river, depending on the quality of the fish supplied, which often depends on the fishing method used.
After resting, the live eels are retrieved from the holding tank and transported to the wholesaler following the removal of dead fish and bycatch. The wholesaler may employ a team of riverbank collectors who receive a regular salary and a bonus for every kilogram of eels collected. Alternatively, the wholesaler may simply purchase the fish from autonomous collectors. Dead fish are usually sold separately.
After a further resting period of 24 hours, any dead and damaged fish or remaining bycatch (mainly shrimp, nereid worms, eel fingerlings and other species of small fish) are removed. Wounded glass eels, usually called “swimmers” or “whites” (as they turn milky in appearance) are removed by hand nets or skimmers as they are likely to die during transportation or when released into the farming tanks. The fish are kept in the wholesale facility for 2–4 days depending on their quality, market prices and transport availability. The temperature in such holding tanks can be controlled, which is important at the beginning and end of the fishing season when the water temperature may exceed 10 °C. The correct temperature limits weight loss and pigmentation, the market preferring transparent glass eels rather than dark ones. Once the eels have recovered from fishing stress they are ready to be delivered to buyers, who are European eel farmers or Asian importers. The latter are mainly in China, which imports over 90 percent of all glass eels shipped to Asia.

Europe

The eels are usually transported in trucks fitted with specialized holding tanks or packed dry in polystyrene boxes and delivered by air or road to the final destination. Transport can last up to 36 hours. As eel catches have decreased recently, small trucks are usually used, e.g. 3.5 to 12 tonnes, fitted with 1 to 4 insulated tanks to prevent temperature fluctuations. Eighty percent of the trucks use pure oxygen instead of compressed air in order to reduce transportation stress and water turbulence from aeration. The trucks are also equipped with oxygen and pressure monitoring alarm systems. The trucks transport from 150 to 900 kilogram of glass eels. Payment is issued once the fish are safely delivered to the farm.

China

European eels are sold to importers, who buy import licences from the relevant government authority. Once the eels arrive in China, they are sold to distributors who transport the fish to the provinces where the farms are located. Chinese farmers are not in a position to import the fish directly due to strict foreign exchange regulations and transportation and organizational constraints. Furthermore the import licences are mainly in the hands of few large companies. The eels are initially cooled, weighted and dry packed into specially designed boxes for shipping. Packing has reached a high degree of technical sophistication and a team of 3 persons can pack up to 500 kilograms/ hour (Figure 9).
The boxes are transported to the airport in refrigerated trucks, and transferred to the airline companies who are generally well informed on the delicate nature of the goods. The plane cargo hold is usually maintained at +5 °C during the flight. Customs clearance in Asia is carried out as quickly as possible in order to shorten the overall transport time. The maximum transport time to ensure good eel survival is around 38 hours, with an average time of 26 hours. When the fish arrive in Asia they are delivered to an unpacking facility usually located within an hour drive from the airport. During unpacking, the seller’s agent is usually present to report on quality. The typical guarantee in China is a maximum 3 percent loss and a maximum deviation of 5 percent in the number of glass eels/kg, as the Chinese importers sell the glass eels to the local farmers by piece. Following this inspection process the fish are repacked within 4–6 hours after reception and transported to the Chinese provinces that farm the eels, mainly Fujian, Jiangxi and Guandong. Fish shipped to China are paid in advance by the importers.
Reliable techniques have been developed for the transport of glass eels to the farms and only unpredictable accidents cause severe mortalities, e.g. truck accidents, flight problems. Over 95 percent of the shipped eels make it to their final destination alive. The weak link is the capture methods used

FIGURE 9
A box sample used for the transport of live glass eels to Asia (top) and a European eel delivery truck (bottom)

in some areas. Mortalities up to 45 percent can still be recorded in some rivers in the north of France compared to the 10 percent reported in the southwestern part of France or the 2–3 percent loss reported in England. The fishing sector needs to reduce mortalities throughout its capture operations.