from a global
This article is a slightly edited version of the original in:FAO. 1999. Review of the state of world fishery resources: inland fisheries.FAO Fish. Circ. No. 942. Rome, FAO. 54pp.
Most inland capture fisheries that depend only
stocking natural waters to improve recruit-ment, bias fish assemblage structure to favoured species or maintain productive species that would not breed naturally in the system; fertilization to raise the general level of productivity and hence growth of the fish;
modification of water bodies to cut off bays and arms to serve for extensive and intensive fish ponds to increase control and nutrient flows;
Inland fishery enhancements are becoming a central theme in inland
waters and are widely applied nowadays. The exact contribution of enhancements to the
total inland capture fisheries production is difficult to estimate, but it is believed
that many inland fisheries are supported by various forms of enhancement, often combined
with conventional fisheries management practices.
water bodies has been generally more successful because these are easier to manage, do not require large amounts of stocking material and are often more productive. In contrast, introductions of new species with the aim to establish self-reproducing populations (auto-stocking) have been more effective to enhance fisheries in the larger water bodies.
Most enhancements are carried out to produce food and generate income (fisheries production), but also for the benefit of recreational fisheries, to restore collapsed fisheries and to control pests (aquatic weeds, mosquitoes).
Table 1. Available information on enhancements in Aquatic Sciences and Fisheries Abstracts 1
1 ASFA was searched as follows: 1/1978 _ 8/1996 for stocking; 1/1978 - 12/96 for introductions; 1/1978 _ 6/97 for engineering and fertilization
Perspective on Established
The most widespread introduced species that have established self-reproducing populations in open waters and globally contribute significantly to food production are Mozambique tilapia, common carp, rainbow trout, Nile tilapia and brook trout (Table 2). Mosquito fish and guppy have been widely introduced for mosquito control and grass carp for the control of aquatic weeds. The goldfish has been mainly introduced for ornamental reasons. The distribution of introduced species that established in the wild is given in Figure 1.
World Perspective on Stocking
With regard to stocking, common carp, rainbow trout, Atlantic salmon and brook/sea trout are relatively widespread as can be seen in Table 3. Most of the species in the table are stocked for food production, income generation and for recreational fisheries. Common carp and rainbow trout are also important introduced species that successfully established, but these species are also supported by hatchery production. The geographic distribution of stocked freshwater species is given in Figure 2. This figure is primary based on hatchery production data provided to FAO by its member countries, but for some countries with incomplete hatchery production data (e.g. China, Canada), species have been added on the basis of scientific literature.
|Table 2. Introduced/translocated
species that have established self-reproducing populations in the wild (Source: FAO
Database on Introductions of Aquatic Species (DIAS))
Figure 1. Geographic distribution of the number of introduced freshwater species that are established in the wild (Source: FAO Database on Introductions of Aquatic Species (DIAS))
Figure 2. Number of freshwater species reported to FAO as produced in hatcheries and released into the wild (Source: FAO Hatchery Production Database)
Table 3. Most commonly stocked freshwater species (Source: FAO hatchery production Database)
Figure 3. Number of ASFA references on introductions, translocations and stocking of inland waters (Source: FAO Inland Fishery Enhancements Database)
The United States, Poland, Australia, Finland, France, Iran and
Mexico report the highest number of species.
Asia and Oceania
A variety of species have been introduced to this region, mainly for the purpose of aquaculture. Many of these have established populations in open waters. Mozambique tilapia, common carp, rainbow trout and Chinese carps are important for commercial capture fisheries. For example, Mozambique tilapia established itself successfully in the larger reservoirs in Sri Lanka where it is now the main landed species (de Silva, 1988). This species also established itself successfully in many Indian reservoirs (Sugunan, 1995). Translocations of species within the country have created new fisheries in China. Most recently, icefish (Neosalax taihuensis and Protosanlax hyalocranius) was very successfully transplanted to various provinces of China. By 1997, the production reached 10 000 tonnes, of which transplanted icefish contributed as much as 8 000 tonnes (Miao, pers. comm.). Translocations of indiginous species have also been one of the major measures for enhancement of inland water bodies in Australia, mainly for the purpose of recreational fisheries (Petr, 1998). Introduction of Nile tilapia and common carp into larger reservoirs of the lower Mekong countries (Laos, Cambodia, Vietnam and Thailand) were generally successful whereas non-indigenous Indian and Chinese carps generally failed to establish themselves (Bernascek, 1997). Introduction of common carp in Indian reservoirs was not successful (Sugunan, 1997).
Stocking has yielded better results in the smaller water bodies,
though relatively large lakes and reservoirs have been stocked successfully in China. Bighead carp and silver carp are the main species stocked in China (60-80% of the stocked species). Chinese carps, Indian carps, tilapias, common carp and rainbow trout are the most common species used for stocking in this region. Stocking of the indigenous species (silver perch, golden perch and Australian bass) are important for recreational fisheries in Australia. Environmental engineering practices are not described frequently, but they do exist. Cage and pen culture are widespread, notably in China, Indonesia and the Philippines. Other measures include screening of inlets and outlets, protection and construction of spawning habitats, re-establishment of floodplain-river connections and the construction of brush parks.
The majority of countries in Africa report introductions. The
introduction of the Nile perch (Lates niloticus) has created a major commercial
fishery with substantial economic and nutritional benefits (Reynolds and Greboval, 1988)
but at the same time it is held responsible for disruption of the Lake Victoria ecosystem.
It has been a controversial introduction. The successfull introduction of the Lake
Tanganyika Sardine (Limnothrissa miodon) into Lake Kariba, Cahora Bassa and Lake
Kivu (Marshall, 1991; Lévêque, 1998; Spliethof, 1983) has contributed signi-ficantly to
Tilapias have been widely introduced in this region and in many
cases contributed significantly to fishery production (Juarez-Palacios and
Olmos-Tomassini, 1991). Self-reproducing populations of tilapias were formed in lakes and
reservoirs in Colombia and contribute significantly to the total fish production in the
country (Castillo Campo, 1996). T. rendalli and O. niloticus form an
important component of the fish catch in the reservoirs of northeast Brazil (Gurgel and
Fernando, 1994) and in Cuba they are the main species in culture-based fisheries (see
section on stocking). Common carp is also relatively wide spread in this region though
they did not successfully establish in Northeast Brazil (Gurgel and Fernando, 1994).
Salmonids (pacific salmon, brook trout) have been introduced to Chile and Argentina.
Numerous species were introduced to this continent and a considerable amount of literature is available (697 references in ASFA). These mainly deal with invasions and the related environmental effects of various accidentally introduced species such as Zebra mussel (Dreissena polymorpha), ruffe (Gymnocephalus cernuus) and sea lamprey (Petromyzon marinus) into the Great Lakes area. Information on intentional introductions involve those of various species to enhance recreational fisheries in small impoundments. For example, in California, 30 exotic species were introduced to enhance recreational fisheries of which black bass, catfish (Ictalurus spp.), sunfishes (Lepomis spp.) and striped bass (Morone saxatilis) contributed 42 to 77 percent to the angling catch in this State (Lee, 1995). In Florida, butterfly peacock bass (Cichla occelaris) was introduced into 11 coastal canals, where it has established self-reproducing populations and contributes significantly to the sports fisheries in the area, without significant negative impacts (Schafland, 1995).
In Ontario, Michigan and New York States, introductions of Atlantic salmon (S. salar) into Lake Ontario were done to restore the population (Jones and Stanfield, 1993). Pacific salmon (Oncorhyncus spp.) was introduced in the tributary streams of Lake Ontario (Rand et al., 1992) and the introduction of white perch (Morone americana) was successful in that it has become a major commercial species (Haynes et al., 1982). Small numbers of pink salmon (O. gorbusha) were released into Lake Superior in 1956 and have established significant populations (Bagdovitz et al., 1986). In Florida, blue tilapia (Oreochromis aureus) was accidentally released into public waters where it established itself successfully, resulting in a commercial fishery for this species (Hale et al., 1995).
S. fontinalis was successfully transplanted in four lakes in Ontario (Fraser, 1989) but it has not been translocated extensively in North America. Lake trout (S. namaycush) has been widely introduced also in response to declining populations due to the invasion of the sea lamprey. Evaluation of 183 introductions of this species in Ontario, showed that lake trout failed to establish in shallower lakes with large littoral zones and richer fish communities with potential predators (Evans and Olver, 1995). Rainbow trout has been introduced into Appalachian streams where it dominates native brook trout (Clark, 1997).
Stocking of largemouth bass, its prey species, bluegill and other sport fishes is widely practised in the United States for recreational fisheries. Steelhead (O. mykiss) is extensively released to enhance recreational fisheries in British Columbia. Furthermore, grass carp is stocked in the Southern states to control aquatic weeds and various salmonid species are stocked in the Western States to restore and enhance river stocks. Important stocked species with high reported hatchery production in North America are salmonids, pikeperch, striped bass, largemouth bass and bluegill.
Europe and the former USSR
Relatively complete information is available about introductions in the former USSR countries, Norway, Sweden, Finland, Germany, Italy and France. Introductions have been widespread in Europe. Important species are common carp, rainbow trout, pikeperch (Stizostedion lucioperca), peled (Coregonus peled), grass carp and lake trout (Salvelinus namaycush). European eel (Anguilla anguilla) is also widely released.
Chinese carps (grass, silver and bighead), bream (Abramis brama), common carp, pikeperch (Stizostedion lucioperca), wels catfish (Silurus glanis) and peled (Coregonus peled) have successfully adapted in former USSR lakes and reservoirs (Berka, 1990). Translocation of the sturgeon Acipenser stellatus from the Caspian Sea into the Azov Sea basin was ineffective as the introduced stock has an average body weight 13 percent less than the native Azov stocks (Tsvetnenko, 1993). Pikeperch was successfully introduced into Lake Vozhe (Bolotova et al., 1995) and rainbow trout has been introduced in Irkutsk Reservoir (Angara R.) in 1992 and has become widely distributed in the reservoir. There is however a concern for the ecological conse-quences of this invasion and the probable diffusion of this species in Lake Baikal, where it has been recorded already (Shirobokov, 1993).
Vendace (Coregonus albula) was accidentally introduced to Lake Inari, a large oligotrophic lake in northern Finland in the 1950-1960s, and a significant fishery developed for this species (Mutenia and Salonen, 1992). In Norway, common carp has been widely introduced and is established in 30 lakes and ponds in southern Norway (Kaalaas and Johansen, 1995). Pikeperch was introduced in Norwegian Lake Gjersjoeen and changed the fish community from one dominated
by roach (Rutilus rutilus) to one dominated by pikeperch (Brabrand and Faafeng, 1993). North American crayfish (Pacifastacus leniusculus) invaded the fresh waters of Sweden and Finland and is considered responsible for the decline in native noble crayfish (Astcus astacus) through competition and disease transfer (Soederbaeck, 1995).
Information on introductions in Germany mainly relates to introduced crayfish, ruffe and grass carp for recreational fisheries. Seventeen species have established in open waters in Germany, among them rainbow trout, white fish (Coregonid spp.), Lepomis spp., Salvelinus spp. and pikeperch. White fish species have also been introduced to Northern Italian lakes. Salmonids have been introduced to the high-elevation streams and lakes in the Pyrenees, France. Brown trout, rainbow trout, brook trout, lake trout and Arctic charr (Salvelinus alpinus) did acclimatize but only lake trout and Arctic charr reproduced in their new environment (Delacoste et al., 1997). These species contributed to the development of recreational fisheries in this region. Though Arctic charr is native to France, the introduced exotic species is more important, colonizing 136 lakes (Machino, 1996).
Introductions of tilapias have been relatively successful in large water bodies due to the fact that this species establishes self-reproducing populations. Although regular stocking of this species is practised world wide, it is not clear in many cases if stocking programmes significantly enhanced fishery yields.
Translocations and stocking of indigenous species have been an effective measure to enhance recreational fisheries in Australia.
Stocking practices are least widespread in Africa, introductions are however relatively important in this continent.
The number of references on stocking and introductions in North America and Europe, including the former USSR, as noted from the ASFA literature, is significantly higher compared to the other continents.
Introduction and stocking of grass carp for aquatic weed control has been generally successful.
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