Chapter 12 - Fisheries

The aquatic ecosystem
The Peruvian Amazon fishery
Significant relationships between fishing and other development activities
Bibliography

Fish resources in Peruvian Amazonia are valuable economically, socially and culturally. The fishing industry did approximately US$56 million worth of business in 1981, with fish, an important nutritional component of the Peruvian's diet - and the Peruvian's imagination (Piazza and Vildoso, 1967). Abundant myths refer to aquatic resources and a surprising variety of names are given to the same fish in different indigenous languages. Fish have crucial roles in trophic structure, energy flow, nutrient cycling, and seed distribution, and some species show good potential for aquaculture.

The aquatic ecosystem

The Amazonian aquatic ecosystem is characterized by water with low mineral content and scarce nutrients (although with great local variation). It also exhibits profuse and complex relationships with the broad flood-plains and has a rich biota, particularly fish (around 2,000 species), that show a high species diversity at higher trophic levels. But this ecosystem, so stable in its natural state, is easily threatened when confronted with external disturbances, especially those caused by man (Bonetto, 1979).

The Amazon river basin drains more than 6.5 million square kilometers and has no rival in area drained and volume of water transported to the ocean (an average of 220,000 square m³/s). Approximately 2.5 million square kilometers lie less than 200 meters above sea level, with the majority of this territory being covered by a dense forest (Lowe-McConnell, 1975). This area is influenced by annual inundations that are very important to Amazon life cycles. The basin is drained by innumerable rivers of variable magnitude that flood extensive wooded areas and form marshes, lagoons, bays, and floating meadows. Often, these water bodies are interconnected (Bayley, 1981).

According to their origin and composition, waters in the larger rivers have been catalogued as "white," "clear," and "black," illustrating that the rivers and environments are different (Sioli, 1968).

White Waters, considered the richest in salts and nutrients, originate on the Andean slopes. They are turbid, with neutral pH, and their actual color is a light grey. The sediments causing the turbidity impede primary production in the river and settle along principal channels, flooded areas, and, especially, lagoons. As these sediments settle, they contribute nutrients that are important to natural productivity.

Clear Waters are poorly to moderately productive and originate from the archaic rocky zones of the Brazilian Shield and from areas of red and yellow tropical soils that do not have large wetland areas. They are more or less transparent in color, with yellow or green tones, and with a lightly acid pH. They play an important role in fish production in rivers with bays. Where the current diminishes, a type of highly productive river-lake forms, which sustains downstream fish populations.

Black Waters are of low biological productivity. These waters lack inorganic ions, have almost no nutrients, and are strongly acid. Originating in the lowest Amazonian terrain and wetlands that generally are dominated by podzol soils, they are loaded with organic material in colloidal suspension that give them their dark color.

As can be seen, the chemical and physical composition of the rivers depends upon their origins, sediments, and bottom types. They are secondarily influenced by human activity, chiefly mining, agriculture, and deforestation in the highlands. Thus, excessive sediments resulting from erosion cloud the water, modify the composition of river and lagoon bottoms, cause digestive problems in microphage fishes, and clog fish gills. Furthermore, the decomposition of large amounts of organic sediments can cause a decrease in the dissolved oxygen content of water, and dramatic phyto-plankton blooms, both of which are lethal for many fishes. Many sediments are toxic, especially those mixed with mine wastes, which are abundant in the Andes.

As the rivers descend from the highlands into the Amazonian plain, their temperature, volume, sediments, and nutrient loads all increase, while their current velocity decreases as does their grade. Meanwhile, the variety and abundance of fish species increase.

Throughout the Amazon region, particularly on the low plain, significant floods are produced during the period of high water (December-May) which recede during the period of low water (July-September). Because of this cycle, the height and volume of the rivers vary enormously (at Iquitos, the water level varies 12 meters), influencing trophic and reproductive cycles. During flooding, the amount of territory available to fish dispersion can increase more than 10 times. The majority of fish species begin reproducing when flooding begins and find places with abundant food and refuge in the flooded areas. The ecosystems of highest biological productivity are ox-bow lakes along large and medium-sized rivers, river bays, floating pastures, and seasonally-flooded forests (Torax, 1967).

Ox-bow Lakes or Cochas

In low areas the rivers form innumerable meanders with branches more or less filled with water that, when cut-off from the rivers, form lagoons (cochas). Each cocha displays different characteristics according to the river water from which it originated, and that flow into it during floods, as well as according to its own shape, size and benthic composition. Generally, primary productivity of the cochas seems to increase with frequent blooms of cyanophytes. Cochas filled with white water are usually the most productive and provide sediments and stored nutrients to rivers during floods. Afterwards, the sediments settle and permit light penetration which, combined with the high temperature, yield rapid plant growth that is exploited directly and indirectly by fish populations.

River Bays (Mouth-bays)

Certain clear water and black water rivers contain stretches that behave limnologically more like lagoons than rivers. They form a continuation of the sedimentation zone (a type of restricted floodplain formed by river alluvium), constituting a strip of open, clear, and very slow water, that often has plankton blooms. The phyto-plankton produced is generally consumed downstream in areas where fish are abundant, particularly at the mouths of major tributaries. This formation is typical of tributaries of the middle and lower Amazon (Soili, 1968).

Floating Pastures

During periods of rising water, aquatic vegetation proliferates and forms dense mats that cover the water's surface, giving the appearance of islands (camalones). Floating pastures are common in rivers and cochas with white water (such as the Amazon), and in areas of sedimentation in clear water rivers. Their constituent plants exploit the nutrients carried by the water, development generally being limited by a pH of less than 5 (Sioli, 1968). Most of the plants which make up these islands belong to the genera Paspalum, Panicum, Echinochloa, Cyperus, Pistia, Eichornia, Marsilea, Salvinia, and Lemna. Camalones can completely cover some bodies of water, and obstruct navigation in rivers and major channels. They are perhaps the most productive bio-topes in Amazonia. Among their roots an abundant and varied fauna uses them for support, refuge, and food. A major limiting factor of camalones is that their oxygen content is often too low for certain species of fish.

Flooded Forest

The Amazon region's vast flat areas, gentle gradients of its rivers, and annual water level fluctuation contribute to widespread flooding of the lowland forest. Numerous populations of aquatic organisms invade these flooded areas to find food and refuge in both the surface humus and vegetation now covered with water and periphyton. Because of the low nutrient content of the waters and the low light penetration, indigeneous food productivity is low - principal sources of food, in fact, are forest flowers, pollen, fruits, and invertebrates that fall into the water. This food is critically important to the reproduction and development of many species, so some fish biomass is sustained in these areas. When the water recedes, the fish become confined to rivers and lagoons and are more susceptible to capture. Some authors believe that the fishing potential of entire Amazon regions can be evaluated by investigating flooded forest areas.

Fish and Fishing Productivity

Most Amazonian fish species are disbursed throughout river environments. In general, fish shoals are small in the principal rivers, becoming larger along beaches and in lagoons and channels with slow current, although fish frequently move between distinct environments during floods. More varieties of fish live in the Amazon basin than anywhere else in the world because of several factors: the size and age of the basin, the many kinds of habitats offered by the winding rivers, the diversity of niches in the low jungle rivers and adjacent lakes, and the high proportion of the river basin lying in the lowlands, offering comparatively stable conditions capable of supporting large numbers of fish (Lowe-McConnell, 1975). Maintaining this rich and diverse fish population depends on species that feed on organisms and organic material in ingested mud, for example, the clearly dominant genus Prochilodus, a typical forage fish. The largest fish species to be found in tropical freshwater environments - individuals of the genera Arapaima, Zungaro, and Pseudoplatystoma - can exceed two meters in length and 200 kilograms in weight.

Amazonian fish can be categorized by origin and salt tolerance. Fresh water species are the most abundant in the basin and belong to the Caracoid, Siluriform, Osteoglosid, Gimnotod, Simbranchid, and Lepidosirenid groups. Secondary fish, confined to fresh water but capable of tolerating some salinity, are represented by Cichlids and Poecilids. Some 50 species of fresh water fish are derived from marine families, including the commercially-exploited fish Plagioscion, Sciaenidae, Pellona, and Clupeidae. Finally, some groups of marine origin, such as certain sharks, move into fresh water. Caracoids predominate in species abundance (43%), followed by the Siluriformes (39%) (Smith, 1979).

The importance of each fish species as a food source in the Peruvian Amazon can only be imprecisely determined. Capture data are available only from the large fishing enterprises, and do not include the great amounts of fish brought in by individual fishermen (Chapman, 1979). "Species" described in this data pertain to the common names of fish, which frequently encompass several species, genera, or even families. For example, the data from Iquitos describe only 20-25 species captured, when in reality, the number of species caught is much greater. Nevertheless, it is possible to realize the importance of the boquichico (Prochilodus nigricans), which makes up 48 percent of the registered catch. The paiche (Arapaima gigas) is also valuable and in great demand, constituting 10 percent of the catch, although it does not form schools or exist in large numbers. The Siluriformes, not counting the carachama (Loricarudae), make up 11 percent of the catch (Hanek, 1982).

The Peruvian Amazon fishery

Fish are the traditional food for people living along rivers, providing them with at least 60 percent of their animal protein. It is estimated that small-scale and commercial fishing in the Peruvian Amazon yields between 60 to 80 thousand metric tons per year. Fifty percent of this catch is consumed directly by humans, with a value of US$60 million per year. Figure 12-1 shows catch size estimates of fisheries in the Peruvian Amazon and their value. Figure 12-2 illustrates the commerce of fresh, dried and salted fish.

Figure 12-1 - PERUVIAN AMAZON FISHERIES: SIZE AND VALUE OF THE FISHERY INDUSTRY

Figure 12-2 - FLOW OF SALES OF FRESH (___) AND SALTED-DRY FISH (- - -) IN THE PERUVIAN AMAZON

Three types of fisheries can be distinguished in the Peruvian Amazon: artisan, commercial, and ornamental. Individual fisheries are widely dispersed, and the small boats used in this type of fishery restrict the fishermen to areas near their villages. Simple fishing gear is generally used, and the catches are consumed primarily by people living in villages along the riverbanks. Commercial fishing, based in the larger towns such as Iquitos, Pucallpa, and Yurimaguas, use gear designed to snare large numbers of fish at a time. The relatively large boats permit trips that last up to 30 days. Ornamental fishing is a specialized endeavor and varies according to the changing demands of the market.

Minimal Peruvian legislation regulates Amazon fisheries and is limited principally to the following areas: controlling harvesting techniques, (dynamite and other explosives, barbasco - Lonchocarpus nicou - and venomous substances); protecting aquatic turtles; creating protected areas in the Pacaya, Samiria, Pastaza, and Mazan rivers; and protecting the paiche, Arapaima gigas, while it breeds from October to February and limiting its capture to specimens at least 1.40 meters long. In the near future it will be necessary to develop regulations controlling fishing in bodies of water adjacent to settlements that, claiming exclusive rights to exploit these waters, come into conflict with native populations and commercial fishermen (Hanek, 1982).

Artisan Fishing

Nearly every man, woman and child who lives in a riverbank settlement fishes at least part-time. They keep what they need for their families and sell the remaining fresh fish to local markets; or dry and salt it for sale to merchants from the large towns.

Artisan fishing methods are simple and inexpensive. Equipment includes poles, hook and five meters of nylon line; arrows with several types of arrowheads, usually steel, used either with or without bows, farpas or arrows with detachable points, harpoons and lances, throw-nets (the most commonly-used gear), hoop-nets or honderas used by three or more fishermen in lagoons and backwaters, drag-nets operated by four or more fishermen and two boats, explosives, and tapajes or hoops of sticks forming traps placed across cocha outflows.

Since the fishermen are also farmers, they easily combine fishing and agriculture. The flooding cycle, fish behavior, and the seasonal requirements of agriculture all impose a sequence of activities on riverbank communities (Figure 12-3). During high. water, there is little activity, but as the water recedes, fishing increases. Later, as flooded areas dry, crops are sown in muddy areas and during low water, fishing increases.

Figure 12-3 - ARTISAN FISHING ACTIVITIES IN RELATION TO THE FLOOD CYCLE

Commercial Fishing

The commercial fishing fleet of the Peruvian Selva has an estimated 476 boats and is based in the larger towns of the region (Hanek, 1982). Some of the same methods and equipment are used in commercial fishing as are used in artisan fishing (throw-nets, honderas, and drag-nets) although they are of greater size and number. In addition, commercial fishing uses agallera nets, which are constructed according to the characteristics of the fish being sought and the places where the fishing will take place. Among the best known nets are the menudera for small fish, the gamitanera for the genus Colossoma and the paichetera for the paiche.

Commercial fishing catches, and to some extent small-scale fishing catches, are processed simply, with 74 percent of the fish being eaten fresh or frozen, 12 percent dried and salted, 11 percent salted, and 3 percent smoked.

Ornamental Fishing

Ornamental fish have been captured and exported from the Peruvian Amazon since 1951. Since 1977, however, the catch has declined somewhat because of over-fishing, competition from other producer countries and regulations. Domestic use of ornamental species is almost negligible (0.5%), although it is increasing. During the 1970s, more than 155 million fish worth US$6.5 million were exported.

The fisherman, the aquarist who receives and stores the captured fish, and the exporter all share the profits of this industry which generates work for more than 3,000 people. Various fishing methods are used: the malla which is a net of very small openings operated from shore by two individuals, the pusahua a type of hand net with a circular mouth and a fine mesh; and, the tarrafa a casting net made of minute mesh. The capture and sale of these species are economically important around Iquitos.

Table 12-1
COMMONLY USED GROUPS OF ORNAMENTAL FISH

Nearly 125 species of ornamental fish are captured (Table 12-1) but these are classified commercially into four groups:

- the "neon tetra" or "piaba" group, represented by one species, Hyphessobrycon innesi. This was the primary commercial species until 1977 and constituted an average 45 percent of the total fish exported during the 1960s;

- the shirues, carachamas, and doras group that includes approximately 30 species in the family Callichthydae;

- a miscellaneous group consisting of approximately 70 species of the family Characidae; and

- the rare fish group, which includes fish of high commercial value on the international market, such as the discus (Synphysodon discus), the angelfish (Pterophyllum sealare), the pacu (Metynnis sp. and Myloplus sp.), the arowhana (Osteoglossum bicirrhosum), and the pirarara (Phractocephalus hemiliopterus).

Ornamental fish are captured in ravines, cochas, and springs in Amazonian rivers and tributaries. Some species are caught only in certain localities. For example, Osteoglossum bicirrhosum is found in the Tapiche river (a Ucayali tributary); Symphysodon discus is found in the Putumayo and Nanay rivers; and, Pimeloduspictus, Pimelodella cristata, and Pimelodus maculatus are caught in the lower Ucayali river (Pucallpa region). Most ornamental fish are captured when waters are retreating (Hanek.1982).

Aquaculture Development

While fish populations can still sustain current fishing levels, possibilities for increased exploitation do not appear promising - especially in certain regions. For example, Bayley (1982) estimates that the Palcazu river fishing region, which extends to the river's confluence with the Pachitea river, allows a catch of 590 tons annually. However, these stocks cannot sustain a population significantly larger than the current 12,000 people at the present level of individual consumption of 122 grams of fish per day.

Prospects of increasing fish production through aquaculture, appear favorable. Two methods are most promising: managing lagoons in the low jungle region; and extensive and semi-intensive aquaculture in the Selva Alta and the Central Selva. Management of lagoons and cochas in the low jungle involve creation of feeding and refuge areas similar to the acadja system of Africa, accompanied by monitoring of fish populations and perhaps introduction of important species. This method, discussed in more detail later, is a possible solution to certain conflicts between small-scale and commercial fishermen. In the highlands extensive aquaculture is, at the moment, limited by the scarcity of appropriately modified bodies of water.

Semi-intensive aquaculture can be carried out in harmony with agriculture, as described in Figure 12-4. Generally, in tropical countries this method is considered a likely possibility for providing employment and low-cost food while, at the same time, requiring little investment of money and other resources. In Peru, particularly in the last 10 years, experimental stations at Pucallpa, Tarapoto, Satipo, Iquitos, and Moyobamba have initiated research into developing this type of aquaculture, while the private sector has also shown increasing interest. Although results have not yet been published concerning species introduced into the zone, it is estimated that semi-intensive production and production associated with other rural activity would not be less than four tons per hectare per year, with two annual harvests and with fish averaging 300 grams in weight (Schuster et al, 1955). Additionally, efforts to breed large numbers of fish fry and to improve techniques for their cultivation are increasing, especially with the genera Colossoma and Brycon. Yields of these fish in experimental ponds, using natural breeding and requiring only the investment of animal manure and some agricultural wastes, have exceeded 3.5 tons per hectare per year, with some operations producing over 5 tons per hectare per year (Guevara et al, 1981; Pedini, 1981; da Silva, 1981).

Significant relationships between fishing and other development activities

Fish harvesting methods, particularly those used in artisan and commercial fishing, have begun to have a negative impact on the fish supply. Most detrimental have been habitat destruction and indiscriminate fish harvest, which not only take large fish and adults appropriate for consumption, but also innumerable young. While various Amazonian species show excellent potential for cultivation in ponds, the natural environment must still be the source of these fish; they are difficult to breed in captivity, and fall pray to caiman, fish eating birds and otter which can invade ponds and prey on the cultivated fish or complete with them for space and food.

Forestry, agriculture and cattle breeding all interact negatively and positively with fish, fishing and aquaculture. Because fish and flooded forests interact symbiotically, with the forest providing food and refuge and certain fish species distributing seeds, deforestation for agriculture can negatively affect fish in several ways: modifying habitat through deforestation and erosion; polluting water with pesticides and excessive amounts of fertilizer; and impeding the migration of certain fish species by dam construction. Harvesting the forest for wood can modify the aquatic environment as well. Sawmill wastes are toxic; when they cover the bottoms of lagoons, they decrease the amount of dissolved oxygen.

Agriculture that causes flooding can provide food and refuge to fish while fertilizer in less than toxic amounts can provide nutrients to increase fish production. On the other hand, some fish can invade and damage poorly-managed rice farms.

Generally, livestock grazing negatively affects fish in the same way as agriculture. Some fish, in turn, are dangerous threats to livestock. On the positive side, many fish species control livestock disease vectors when they are in their aquatic stages, and livestock feces, washed by the rains, contribute to the fertilization of natural water bodies.

Figure 12-4 - INTEGRATION OF TROPICAL FISHERY AND AGRICULTURE - LIVESTOCK ACTIVITIES

Water weeds originating from cleaning of the pond that could be used to feed livestock.

Water weeds originating from cleaning of the pond that could be used to feed livestock.

Fish interact with land animals through predation and competition for food. Examples are also known in which the excessive hunting of caiman, capybara, and zambu-Ilidora has caused a decrease in fish populations, because of the loss of fertilizing excrement and loss of control of more efficient fish predators, such as piranha.

Among the most important disturbances of fish and fish habitat produced by human activities are the destruction of seasonally-flooded forests, sedimentation, urban and industrial pollution, dam construction and the construction of other barriers. Further, in some areas population increase requires more food fish, especially when supply of wild animals diminishes (Berger, et at., 1979). In addition, incorporation of western customs into the lives of native populations leads to the elimination of myths and customs that hold certain areas to be dangerous to fishermen and thus create fish refuges. By reducing religious holidays this process also increases the number of fishing days (Smith, 1979).

On the other hand, fish can cause problems for human beings; some fish are dangerous, while others transmit or are intermediate hosts for diseases. Poorly-managed ponds can encourage the spread of vectors of such diseases as malaria, encephalitis, and, in some neotropical areas, bilharzia (Eyzaguirre, 1979).

Dam construction is one of the activities that obviously can threaten fish populations, especially by interrupting water flow retaining sediments that contain nutrients; release of water that contains toxic substances and high oxygen demand; and forming barriers that impede fish migrating for reproduction. Measures to resolve such problems include evaluation of minimum water requirements in dammed watersheds and provision of minimum flow when dam reservoirs are being filled, the periodic discharge of retained sediments, and the avoidance of releasing toxic waters that generally accumulate at the bottom of reservoirs.

On the other hand, new reservoirs created by dams present new fish habitats that can be used in extensive aquaculture. Certain fish species also eat the plants that are damaging to turbines as well as control disease vectors that can multiply because of dams. Below the dam, ponds that use dam-regulated water can be constructed to provide fish fry for extensive cultivation in reservoirs. Road construction can negatively affect fish by filling channels, by limiting fish migration, and by causing erosion due to the destruction of riparian vegetation and by increasing the number of areas accessible to commercial fishing. The principal problem with mining, especially in Andean headwaters, causes downstream pollution by mine tailings - the severity of which depends on the type of tailing. This is a serious conflict, since mining in Peru is economically important and actively pursued. Storage and purification of tailings is difficult and such regulations are seldom complied with.

Petroleum extraction has two negative aspects: on site petroleum pollution where it is being extracted or transported (especially by pipeline); and formation of chemical barriers, especially saline water, formed by dumping oil wastes and formation water into Amazonian rivers. Snedaker (1977) has shown that the Corrientes river's dilution capacity in Peru is less than one third that required to accommodate the salt water being discharged into it. The result is that a salty stretch exists in its channel between Trompeteros and the Tigre River that acts as a chemical barrier for fish during the spawning season. Larval and juvenile fish are especially affected, particularly those belonging to strictly freshwater species, including the very important Caracids and Silurids. This is a difficult problem to solve, because petroleum is so economically important to the country. Nevertheless, it will soon damage an important food source for riverbank populations in parts of Peruvian Amazonia.

Conflicts of interest exist regarding the use of fish resources in floodplain lagoons and cochas during the dry season. On one side are riverside populations; on the other are industrial fishermen that enter these areas to fish for export to cities. Riverside populations use simple fishing methods and claim, not without reason, that industrial fishermen reduce the fish available to them. Conflicts also arise over the use of those species where the adult stage is used for food and the juvenile stage is exploited for ornamental purposes.

In both natural and artificially-created bodies of water, extensive aquaculture can produce significant fish populations that can sustain both small-scale and commercial fishing. These techniques can include the introduction of native and introduced species into reservoirs. Many native species that breed in still water environments can sustain fisheries or serve as forage fish, including the paiche or the tucunare (Cichia oceltaris). Equally, when introduced from artificial enclosures or natural sources, certain species become very productive in reservoirs (Colossoma, Brycon, and Prochilodus). Cultivated exotic species, however, can escape and destroy habitat (as has occurred with the common carp, Cyprinus carpio) and prey on and compete with native species. Some local species can also become nuisances when placed in ecosystems that encourage their proliferation where they are resistant to controls. Such is the case with the piranha, Serrasalmus, and the "jaraco," Hoplias.

Although semi-intensive aquaculture using naturally-produced wild fish species can reduce the availability of these fishes, little such activity is carried out, because of the costs and difficulties involved with transporting fry from spawning areas to areas where semi-intensive aquaculture is most profitable. Experimental techniques for the controlled cultivation of native species is applicable to the conservation and repopulation of these species in the low jungle as well as in producing ornamental species. Aquaculture will probably never compete significantly with fishing interests, because of its low production levels and because demand for fish still exceeds supply.

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