5.1 Sea/Ocean Ranching
5.2 Coastal Lagoon Farming
5.3 Stocking of Inland Waters
5.4 Floodplain Fisheries Management
In contrast to aquaculture which involves the cultivation of aquatic life within controlled environments or the commercial production of certain aquatic species by managing the major part of their life history under strict control, culture-based fisheries increase production in natural environments by controlling a part of the life history of certain species and transplanting or releasing their seed or fry into the open waters (Honma, 1980). The juvenile fish, which are produced in hatcheries and are released into fresh-, brackish-, or marine waters, are allowed to propagate or grow on natural foods until they reach harvestable size (Thorpe, 1980).
Unlike aquaculture, culture-based fisheries are not limited by land or population pressures and do not have to modify or manage the culture system to approximate the natural environment since it uses the natural environment itself (Liao, 1988). Also, unlike aquaculture, harvests are uncertain and returns are more difficult to predict as the "release of fish to sea involves the number harvestable ultimately being reduced to 1-15% of the number released, depending on species and locality" (Thorpe, 1980).
Nonetheless, culture-based fisheries have been increasingly resorted to as means of enhancing the fishery resources, replenishing natural stocks whose populations have declined through over-exploitation or environmental degradation, or simply maximizing the productivity of a water body, be it an open bay, a coastal lagoon, or a freshwater reservoir. Their adoption or application on an expanded scale has in fact been identified as a high-priority item in the agenda for development in a number of regions in the world in the coming years (Table 6) (ADCP, 1989a).
The major types of culture-based fisheries include: (i) sea/ocean ranching as practised in Japan with various marine finfishes and the Kuruma prawn, and in the Pacific Ocean and Baltic Sea with salmon; (ii) coastal lagoon farming, as exemplified by valliculture in the Mediterranean; (iii) stocking and restocking in freshwater lakes and reservoirs; and (iv) floodplain fisheries management.
Sea ranching, in which juvenile fish are released to grow unprotected on natural foods in marine waters where they are harvested at marketable size (Thorpe, 1989), takes advantage of the sea as a large aquatic pasture (Liao, 1988). While it is practised in slightly differing forms around the world, in its distinctive form, young fish are released to the sea through ponds, enclosures or channels, and allowed to grow until they are ready for the market.
Sea ranching of salmon is widely practised in countries such as the United States (mainly Alaska, Washington and Oregon), Canada, Japan, USSR, New Zealand, Iceland, and the Baltic countries (Thorpe, 1980).
The most widely used species for ocean ranching is the Pacific salmon (Oncorhynchus sp.) because of the success of its artificial spawning coupled with the rapid growth and the high degree of its homing precision that makes it amenable to harvesting at maturity (McNeil, 1975 and 1980; Thorpe, 1980).
The practice of salmon ranching was initially carried out more than 100 years ago in the Nordic countries where salmon smolts were released into the Baltic Sea area (Ackefors, 1986).
Hatchery production of salmon in the United States dates back to 1872 when the US Fish Commission established its first hatchery on the McCloud River in California. This was followed by the first private salmon hatchery on the Rogue River, Oregon in 1877. The technology for artificial propagation of salmon was introduced to Japan in 1877 and to western Canada in 1884 (Thorpe, 1980).
In Japan, while salmon hatching and release have been carried out for nearly 100 years, the results were not considered very successful. It was only with the new method of intermediate feeding and timely release of salmon fry, starting in 1961, that significant advances in salmon production have been achieved (Honma, 1980). Most Japanese hatcheries use gravel-lined raceways to incubate larval salmon (alevins) and practise short-term feeding of newly-emerged chum fry on artificial diets (McNeil, 1980).
Pink and chum salmon are raised in equal numbers in Soviet hatcheries using technology similar to that of Japan. In the Pacific Northwest, chinook and coho salmon are the predominant species used in hatcheries where raceways and ponds for feeding juvenile fish are prominently featured.
In Alaska, floating raceways in protected saltwater bays had to be innovated to suit Alaskan conditions.
Canada's salmon farming industry has grown tremendously in the last five years as a result of its successful hatchery operations (Annett, 1989). Canadian hatchery workers have pioneered development and application of spawning and egg incubation channels which provide favourable environmental conditions for eggs and alevins. These techniques have been applied most successfully to sockeye, pink, and chum salmon (McNeil, 1980).
The spawning channels produce fry with a capacity for rapid growth and high survival because they simulate high-quality natural spawning beds. Incubation channels, shallow raceways with a silt-free gravel bed, enable the alevins from artificially fertilized and hatched eggs to complete their development in a natural substrate (McNeil, 1975).
Salmon fry that need to be raised in low-salinity or fresh water before release into marine waters (e.g., sockeye, coho, and chinook) have to be transferred from the incubation system to feed-lot systems consisting of tanks, raceways, ponds, floating pens, or a combination or modification of these. The newly emerged fry are given frequent feedings of high-protein diets containing vitamin supplements and certain fats (McNeil, 1975).
Aside from the widely popular Pacific salmon, other marine species have been used for ocean ranching in Japan. The Japanese National Culture-Based Fishery Project, which was started in 1953, has succeeded in developing techniques for mass seed production and subsequent release of juveniles of commercially valuable fish/shellfish, such as the Kuruma prawn, red sea bream, blue crabs, sole, flounder, and yellowtail, into the Seto Inland Sea (Table 15). The Project has now reached the stage where the fishermen themselves carry out the release of fry and manage the propagation work. The Project, based on its earlier successes, has been expanded on a national scale with the construction of a large number of Prefectural Centers for Culture-Based Fisheries all over Japan (Table 16) (Honma, 1980).
The Ezo abalone, Haliotis discus Hanai, is one of the most important species for ocean ranching in Japan, with about 1.15 million hatchery-produced juveniles released in 1980 in rocky areas of the Sea of Japan around Hokkaido. Likewise, the giant Ezo scallop, Patinopecten yessoensis, is propagated in the Okhotsk Sea, the Nemuro Channel, and in other areas of the Hokkaido coast (Saito, 1984).
Table 15. National fish farming centres for culture-based fisheries and species being used
|
Warm water areas |
Tamano Centre |
Blue crab, grouper |
|
Yashima Centre |
Yellowtail, butter fish |
|
|
Hakatajima Centre |
Red sea bream, sole |
|
|
Kamiura Centre |
Red sea bream, hardtail, horse mackerel |
|
|
Komame Centre |
Red sea bream, hardtail, yellowtail |
|
|
Shibushi Centre |
Kuruma prawn |
|
|
Goto Centre |
Yellowtail, Spanish mackerel, cuttlefish |
|
|
Okinawa Centre |
Amber jack, siganus spp, tuna |
|
|
Mid-Pacific Centre |
Bass, striped pigfish, parrot bass, lobster |
|
|
Cold water areas |
Miyako Centre |
Flounder, stone flounder, rock fish, crab, prawn |
|
Akkeshi Centre |
Horsehair crab, rock-trout, king crab, flat fish |
|
|
North Japan sea Centre |
Cod, prawn, flounder |
|
|
Western Japan sea Centre |
Snow crab, sea bream, octopus, squid |
Source: Honma, 1980
Table 16. Prefectural fish farming centres for culture-based fisheries
|
Prefecture |
Construction cost (1 000 yen) |
Area (a2) |
Capacity of ponds and tanks (t) |
Species dealt with |
|
Niigata |
542 964 |
35 093 |
1 739 |
Kuruma prawn, abalone, red sea bream, flounder |
|
Ishikawa |
268 048 |
53 383 |
2 095 |
Red sea bream |
|
Fukui |
928 358 |
40 000 |
4 867 |
Kuruma prawn, abalone, red sea bream, blue crab |
|
Shimane |
591 656 |
22 000 |
3 503 |
Abalone, red sea bream |
|
Yamaguchi |
365 717 |
20 000 |
1 493 |
Red sea bream, scorpion fish |
|
Miyagi |
781 000 |
24 218 |
1 000 |
Kuruma prawn, abalone, Hokkai prawn |
|
Kanagawa |
445 000 |
5 948 |
1 225 |
Kuruma prawn, abalone, red sea bream |
|
Aichi |
1 500 000 |
137 400 |
1 382 |
Kuruma prawn, abalone, sweet fish |
|
Toyama |
302 500 |
16 000 |
2 050 |
Kuruma prawn, abalone, red sea bream, blue crab, plaice, sea urchin, top shell, sweet fish parrot bass |
|
Saga |
546 850 |
10 632 |
1 426 |
Kuruma prawn, abalone, red sea bream, bloody clam sea urchin |
|
Nagasaki |
580 000 |
35 000 |
2 309 |
Kuruma prawn, abalone, sea bream, parrot bass |
|
Kumamoto |
429 800 |
17 115 |
3 200 |
Abalone, red sea bream, parrot bass |
|
Shizuoka |
330 000 |
5 000 |
2 975 |
Kuruma prawn, abalone, sea bream, southern scallop |
|
Wakayama |
700 000 |
15 000 |
2 850 |
Kuruma prawn, abalone, red sea bream |
|
Okayama |
587 400 |
18 700 |
1 520 |
Blue crab, black sea bream, scorpion fish, shrimp |
|
Fukuoka |
519 588 |
29 849 |
3 450 |
Kuruma prawn, abalone, red sea bream |
|
Ehime |
694 521 |
33 600 |
5 514 |
Kuruma prawn, abalone, red sea bream |
|
Tokushima |
618 100 |
40 000 |
1 786 |
Kuruma prawn, abalone, red sea bream, blue crab |
|
Oita |
362 400 |
9 000 |
2 423 |
Abalone, red sea bream |
|
Kagoshima |
650 033 |
30 000 |
4 520 |
Kuruma prawn, abalone, red sea bream, southern scallop |
|
Akita |
635 000 |
35 000 |
- |
Kuruma prawn, abalone, red sea bream, blue crab, flounder, sweetfish |
|
Miyazaki |
621 000 |
19 735 |
2 966 |
Kuruma prawn, abalone, red sea bream, parrot bass, hard tail |
|
Tottori |
1 055 516 |
30 000 |
5 616 |
Abalone, flounder, sand borer, plaice, top shell, bay scallop, sea cucumber |
|
Aomori |
1 282 001 |
23 584 |
1 463 |
Abalone, flounder |
|
Mie |
526 550 |
13 000 |
1 133 |
Kuruma prawn, abalone, red sea bream, clam, sea cucumber, scorpion fish |
|
Iwate |
1 230 053 |
32 474 |
3 744 |
Abalone, flounder, sea urchin, hokkai prawn |
|
Hokkaido |
598 530 |
15 000 |
1 150 |
Abalone, Hokkai prawn |
|
Yamagata |
640 000 |
41 010 |
2 695 |
Kuruma prawn, abalone, flounder |
|
Fukushima |
885 089 |
50 000 |
2 460 |
Abalone, stone flounder, sea urchin |
|
Ibaragi |
385 729 |
8 000 |
- |
Abalone, clam, sea urchin, sea bass, ark shell, whelk |
|
Chiba |
1 482 000 |
16 830 |
4 471 |
Red sea bream, flounder, sea bass |
|
Kyoto |
350 000 |
10 000 |
874 |
Abalone, red sea bream, penaeid |
|
Hyogo |
616 369 |
18 440 |
2 294 |
Kuruma prawn, red sea bream, blue crab, flat fish, rock fish |
|
Hiroshima |
1 089 975 |
40 000 |
4 702 |
Red sea bream, blue crab, black sea bream |
|
Kagawa |
545 000 |
10 000 |
1 910 |
Kuruma prawn, black sea bream, sea bass, bloody clam |
|
Kochi |
- |
- |
- |
- |
|
Okinawa |
- |
- |
- |
- |
Source: Honma, 1980
Extensive lagoon farming is a traditional activity in various European and Mediterranean countries with a production of about 10 000 t/y (Girin, 1981). Among the Mediterranean countries, Italy has the largest areas of brackish water (called "valli") that are exploited for lagoon farming of commercially valuable species like Anguilla anguilla, Mugil cephalus, Liza aurata, Liza saliens, Liza ramada, Chelon labrosus, Dicentrarchus labrax, and Sparus aurata.
Restocking of the valli/coastal lagoons is carried out by anadromous, natural, and annual migration and by artificial restocking. Catches from the valli primarily depend on the quantity of fingerlings which entered the lagoons some years before and on the quantity of fingerlings stocked.
Valliculture, as the practice is called in view of its being fish culture-based, is one of the most ancient forms of aquaculture in the Mediterranean region. Its origins date back to the first rudimental fish pond and fattening systems used along the Adriatic and Tyrrhenian coasts. This technique was developed by the upper Adriatic populations to exploit the seasonal migrations of some fish species from the sea into the lagoon and delta areas which were more suitable for their growth. The fish returned to the sea because of altered environmental conditions (temperature) of the sea or for reproduction. To exploit these periodic movements, large brackish areas were enclosed to prevent the fish returning to the sea and complex permanent capture systems, fish barriers, were developed consisting of barriers in the channels communicating with the sea to catch the adults. Later, from the simple ponding of fry freely entering the lagoon from the sea, came a man-made seeding of fry fished elsewhere and introduced into the basins to be reared for a few years (Ardizzone et al., 1988).
The successful management of coastal lagoons using hatchery-bred fry of important species is thought to hold considerable promise world-wide for expansion in the future.
Brush-park fisheries are a traditional form of low-technology aquaculture which is practised in coastal lagoons and brackish waters in many areas of the world. The brush parks are constructed in a variety of forms and sizes, but basically a brush park consists of an inner core, or concentric circles, of densely packed tree branches or other material surrounded by an outer, more substantial wooden framework which is fished periodically, usually by encirclement.
In coastal lagoons the most sophisticated forms of brush-park fisheries occur in Benin. There are several basic types of brush-park fisheries in Benin where they are known collectively as "acadjas". They vary from each other in configuration, construction and fishing characteristics. The acadjas are constructed of tree branches with harder woods forming the peripheral structure and with soft wood branches with many ramifications forming the interior of the acadja. Acadjas are preferentially placed in shallow, quiet waters of no more than 1.5 m depth (Kapetsky, 1981).
Fishing is accomplished by surrounding the smaller types of acadjas with a net after which all of the branches are removed and the net is then pursed. For the larger brush parks the surrounding net is fished in a step-wise process by gradually moving the net inwards as branches are removed until the fish are concentrated in small areas and can thus be removed with traps, baskets, and hand-nets. After fishing, the used branches are replaced and new ones added as necessary (Welcomme, 1972).
Elsewhere in Africa, brush-park fisheries are found in coastal lagoons in Nigeria, Côte d'Ivoire, Ghana, Togo, and Madagascar. Elsewhere in the world, brush-park fisheries are found in Negombo lagoon in Sri Lanka and have been introduced in some Mexican lagoons.
Among the most advocated and widely used practices for the management of the fisheries resources of lakes and reservoirs throughout the world is the stocking and recapture technique (De Silva, 1988).
Species stocked are either indigenous or exotic and either herbivorous, carnivorous, or omnivorous. In the developing countries of the tropics, where the production of more fish for food is the goal of any fisheries activity, high-yielding herbivores, detritivores and plankton feeders (like tilapia and carp), are commonly stocked in lakes and reservoirs. This is in direct contrast with the developed countries in temperate zones where carnivores like trout and bass are stocked in lakes and reservoirs to support the recreational or sport fishery (Baluyut, 1983). The major lakes and reservoirs in ASEAN countries, for example, have been stocked with hatchery-produced fingerlings of a wide variety of species including tilapia, various Chinese and Indian carps, milkfish, mullet and catfish.
In China, around 65%, or 1.4 million ha, of reservoir area out of a total of two million ha are farmed and managed like fish ponds. They are stocked with fingerlings and following a period of growth, mature fish are harvested. The species used are the common carp, grass carp, silver carp, bighead carp, mud carp, and Wuchang bream (Megalobrama amblycephala) in varying densities and species ratios (Beveridge and Phillips, 1988). Reservoir fisheries in China are almost entirely dependent on the regular release of large quantities of fingerlings because the Chinese carp do not spawn outside their area of origin. In many instances, therefore, stocked fish make up over 90% of fish catches from reservoirs (Lu, 1986).
In Israel, many water storage reservoirs (10-40 ha area, 5-7 m depth) originally constructed for irrigation, are now stocked with a range of species including tilapia, mullet and carp, usually grown in intensively managed polyculture systems (Sarig, 1984, and Hepher, 1985, as cited in Beveridge and Phillips, 1988).
Sri Lanka's large perennial reservoirs and small seasonal tanks constitute the country's main freshwater resource. These are regularly stocked with fingerlings of the different carp species (Indian, Chinese, and common) which are produced at Government-run hatcheries spread all over the country. Since the Indian and Chinese carps do not spawn in the reservoirs/tanks, they have to be stocked regularly to sustain the fisheries. There is thus large pressure on the State to accelerate its seed production programme to keep up with the large demand for fingerlings. It is interesting to note that unlike the Philippines and Thailand, for example, where fish seed production is largely a private sector undertaking, the Sri Lankan Ministry of Fisheries is primarily responsible for the production of carp fingerlings for distribution among the various reservoirs and seasonal tanks.
In Cuba, most of the freshwater fish is produced from seeding of the country's small to medium size reservoirs; in Colombia, some dams are stocked and restocked with mullets (FAO, 1986).
African small reservoirs are stocked mainly with tilapias and Clarias. In Zambia the most important species for stocking reservoirs are Tilapia melanopleura, T. macrochir, T. andersonii, and Haplochromis spp. In Zimbabwe the fish most commonly used for dam stocking are Oreochromis mossambicus, O. macrochir, T. rendalli, and several exotics like black bass and rainbow trout (Balarin, 1984).
The floodplains of tropical rivers, with their extensive network of swamps, lagoons, lakes, and ponds, have great potential for increased fish yields through better and more efficient management using either capture or culture techniques, or a combination of both.
Floodplain fisheries is a seasonal activity depending on the duration and amount of flood filling the low areas. Management of the floodplains for aquaculture and/or culture-based fisheries therefore needs to be properly timed to coincide with the seasonality of the fisheries and the water level in the floodplain.
In its simplest form, floodplain management/intensification involves merely connecting the primary channel of the river with adjacent flood plains by cutting a channel through the levy. As water levels rise, water and fish are swept outward through the channel, being caught via various gears when they return to the main river as the flood waters recede.
Floodplain management is widely practised in Africa where there are large riverine systems and associated floodplains. The practice is believed to have started back in the 1940s in Sudan (Scudder and Conelly, 1985). In the Ubangi River in Zaire, natural levees were raised with channels left open to allow fish to enter adjacent pools, and then closed off with wickerwork to form an immense fish trap. The pools could be stocked so heavily, it would be necessary to feed the fish (Leynseele, 1979 as cited in Scudder and Conelly, 1985).
In Benin, rectangular fish ponds with the long axis often running perpendicular to the river, are actually dug to increase the habitat available to the fish and to ease their capture as flood waters fall. After the annual flood has filled the ponds, the entrances are fenced off from the main river, with the pools fished toward the end of the dry season at which time vegetation growing in the ponds is removed and fences are advanced inland to concentrate the fish before they are captured (Welcome, 1979 as cited in Scudder and Conelly, 1985).
Another form of floodplain management involves the installation of brush parks or acadjas, as has been practised in several countries in West Africa (Kapetsky, 1981), and in Kampuchea and Myanmar in Asia (Hickling, 1961 as cited in Scudder and Conelly, 1985).
Brush parks involve placing vegetation in shallow water areas of floodplains to attract fish. The "park" is subsequently surrounded with netting prior to the capture of the resident population. In simpler cases, floating vegetation may be placed in the water to attract fish in search of food and refuge, and are fished within a few days. In more sophisticated cases, the floating vegetation is surrounded by stakes or branches which are driven into the river or lake bottom. Construction occurs after the annual flood with the structures fished at intervals of several weeks to several months depending on conditions. Yields as high as 28 t/ha/y were reported by Welcomme (1979), for brush parks in the Ouémé River in Benin, without apparently affecting the catch by other fishing methods in the area.
It is believed that floodplain management, because of the low cost of establishment of brush parks and other installations to modify the floodplain, presents an interesting alternative for increased fish production from extensive, still largely under-utilized water bodies, especially in regions of the world where aquaculture per se may not be that acceptable on account of the prevailing customary tradition of fish capture.
