Document(s) 4 de 11

Jaime Alberto Diaz-Sarmiento
Centro de Investigaciones Científicas
Universidad de Bogotá
Bogotá, Colombia

Ricardo Alvarez-León
Departamento de Ciencias de la Vida
Instituto de Humanidades y Ciencias Básicas
Universidad de La Sabana
Bogotá, Colombia

CHARACTERISTICS OF THE BASIN

Geography, Geology, Climate and Habitat

The Colombian Amazon includes 5.6% of the total area of the Amazon Basin (Figures 1 and 2), and represents 420,000 km² or 31% of Colombian territory (Figure 2). Although the Amazon (Solimões) River mainstem borders Colombian territory for only 120 km, six major tributaries to the north (Table 1), including the Caquetá River (Japura in Brazil) and the Putumayo River (Iza in Brazil) are important Colombian rivers in which migratory fish species are believed to spawn.

FIGURE 1. Map of Colombian Amazon basin

FIGURE 2. Distribution of Amazon basin territory, by country⁸²¹

TABLE 1. Main river systems in the Colombian Amazon Basin⁸²²

The present-day river systems have resulted from the processes associated with the uplift of the Andes during the Miocene (23 to 5 million years ago). Amazonian rivers began to run from west to east with this uplifting, and resulting large Neogene lakes and the erosion of long torturous waterways are believed to have created the rivers and drainage patterns of today.⁸²³

The northern Colombian Amazon now drains out of a western prolongation of the Guyana Shield, which divides the Amazon and Orinoco basins. The shield here consists of a Precambrian rocky base and outcrops, covered by thin sandy soil. The outcrops are vegetated with a distinctive caatinga community, while the remainder is covered by a

⁸²¹ TCA, 1995

⁸²² TCA, 1995; IGAC,1999

⁸²³ Frailey et al., 1988

mature rain forest ecosystem.⁸²⁴ The water draining from this area is variably acidic and poor in nutrients.

To the east and northeast, on the other hand, the Amazon drains out of the Andean highlands of over 4,000 m in elevation, with large amounts of water captured in fragile and unique ecosystems, such as the Paramos (misty mountains). On their way down, torrents erode soils rich in nutrients that are deposited on the large sedimentary floodplains, giving rise to the productive varzeas (flooded forests) of the Central Amazon valley of Brazil and some parts of the Putamayo and Solimões rivers in Colombia.

Productivity of the river and its floodplains is thus highly influenced by which drainage system is providing the water. In general, the mineral content of the waters and productivity in Columbia increases from north to south.⁸²⁵

The climate of the region is greatly influenced by the Inter-tropical Convergence Zone. Rainfall averages 2,500 mm/year in the lowlands and 4,500 mm/y in the Andean foothills (Table 2). These high levels of precipitation fall in a long and continuous rainy period between March and September in the north and a bimodal rain pattern to the south of the equator, with peaks in March and October.⁸²⁶

Average temperature in the Colombian Amazon ranges from 24–29°C and varies little with latitude. Diurnal fluctuation can, however, exceed 10°C. Relative humidity always exceeds 75%, solar brightness is less than 5 h/day, potential evapo-transpiration is 1,447 mm/y and the rainfall exceeds drainage capacity throughout the year, resulting in a constant excess of water in the soil. The wind intensity is low and diminishes through the day.⁸²⁷

TABLE 2. Climatic characteristics in different parts of the Colombian Amazon⁸²⁸

⁸²⁴ IGAC, 1999

⁸²⁵ Duque, 1995

⁸²⁶ PRORADAM, 1979

⁸²⁷ PRORADAM, 1979

⁸²⁸ PRORADAM, 1979

MIGRATORY SPECIES AND MIGRATION PATTERNS

Most of the South American fish fauna seems to have had a common ancestral origin in the Amazon Basin.⁸²⁹ Estimates of fish diversity for the entire basin range between 2,000 and 3,000 species.⁸³⁰ However, only 241⁸³¹ of the 500 expected to be present in Colombia⁸³² have been reported so far; of these, 69 can be considered migratory species in this region.⁸³³

Order Clupeiformes

Pellona spp.

This genus of freshwater herring is widely distributed in South American rivers, including the sardina and lacha in Spanish, the sardinha, apapa, and apapa-branca in Portuguese, and pellona or shad in English. In the Caquetá River, these fish migrate upriver for several hundred kilometers to spawn; traditional knowledge indicates fish also migrate into the river from Brazil. The fish can be as large as 73 cm (Pellona flavipinis),⁸³⁴ though most are smaller. They are pelagic and omnivorous, feeding on plankton and other items in the water column and surface. They are of relatively minor importance to fisheries, but are captured in artisanal and subsistence fisheries for local consumption. No fisheries data for this group are available. Species found in the Caquetá River are Rhinosardinia amazonica, Pellona castelnaeana, and P. flavipinis.

Order Characiformes

Brycon spp.

The Brycon genus is quite diverse in South America, with several species in all areas contributing to sport and artisanal fisheries, as well as being

⁸²⁹ MinAmbiente, 1997

⁸³⁰ TCA, 1995; Goulding et al, 1988

⁸³¹ Alvarez-León et al., in preparation

⁸³² MinAmbiente,1997

⁸³³ primarily based on information from the Coqueta River: Baptiste-Ballera, 1998; Rodríguez-Fernández, 1991, 1999; traditional knowledge of Trujillo (2000, pers. comm.) as well as information in: Novoa et al., 1982; Taphorn, 1992; Froese & Pauly, 2001.

⁸³⁴ Froese & Pauly, 2001

aquaculture candidates.⁸³⁵ Colouration is striking, and several of the smaller species contribute to the aquarium trade as various kinds of tetras.⁸³⁶ The larger species are voracious piscivores as larvae,⁸³⁷ but omnivores with a preference for fruits and seeds as adults. Most are strong swimmers, and species important in the Colombian fishery carry out reproductive migrations of several hundred kilometers in large schools. Fishing is most pronounced during these migrations, contributing to fisheries for both local consumption and export, though catches appear to be decreasing (see discussion of fisheries). Species encountered in the Caquetá River are Brycon cephalus, Brycon brevicauda, Brycon melanopterus, and Brycon pesu, known primarily as sábalo in Spanish. B. cephalus is widespread in the Amazon⁸³⁸ and is the principal species in commercial fisheries. The other species are more restricted in range, with B. melanopterus possibly being non-migratory in parts of its range.⁸³⁹ B. pesu is of interest to the aquarium trade.⁸⁴⁰

Curimatella and Curimata spp.

These fish, known as branquinha in Brazil, are detritivorous species that are about half the size of Prochilodus and Semaprochilodus (max. ~20 cm). These species migrate upriver to spawn, probably in the order of 100–200 km. Fisheries on these species is for local consumption, and no specific catch statistics for Colombia are available. Species encountered in the Caquetá River include Curimatella alburna, Curimata cyprinoides, Curimata amazonica, Curimata planirostris, Curimata rutiloides, Curimata simulata, and Curimata vittata. Of these, C. vittata is also of interest to the aquarium trade.⁸⁴¹

Colossoma and Piaractus spp.

The gamitana (Colossoma macropomum), known as tambaqui in Portuguese, is of particular importance to the sport and commercial fishery in many parts of the Amazon, both for local consumption and for

⁸³⁵ see Chapters 2, 3, 4 & 5

⁸³⁶ Froese & Pauly, 2001; CEMIG, 2000

⁸³⁷ see Chapter 4

⁸³⁸ see Chapter 6

⁸³⁹ see Chapter 6

⁸⁴⁰ Froese & Pauly, 2001

⁸⁴¹ Froese & Pauly, 2001

export. This is a large omnivorous fish (up to 20 kg or more), with a preference for seeds and nuts. Beyond its regional importance as a food and sport fish, it is particularly known for its role in maintaining flooded forest ecosystems,⁸⁴² resistance to low oxygen conditions,⁸⁴³ and aquaculture.⁸⁴⁴ Reproductive migrations in Colombia extend for several hundred kilometers. Contribution to the Colombian fishery is significant, but relatively low.

The related gamitana rosa (Piaractus brachypomus), known as pirapitinga in Portuguese (synonymous with Colossoma brachypomum, Colossoma bidens and Piaractus bidens), is of less importance to export fisheries in Colombia, but is caught for local consumption. It is similar to C. macropomum, including in migratory habit, but is smaller and less well studied.

Leporinus spp.

The Leporinus species are known as boga and omima in Spanish, piau, piapara and variations in Portuguese. These are omnivorous species of the distinctive Anastomidae, or headstander, family. A variety is present in the Amazon Basin, with several of the larger species also present and important to fisheries in other basins of South America,⁸⁴⁵ including several of importance to the aquarium industry.⁸⁴⁶ In Colombian rivers, they appear to migrate several hundreds of kilometers to spawn, generally followed by a variety of catfish. The fish are generally omnivorous, limited in their diet by a characteristically small mouth. Size of the species that contribute to the fishery varies from 20 to 40 cm. The species are of importance to fisheries for local consumption, but specific catch statistics in Colombia are not available. Of the Leporinus spp. L. agassizi, L. brunneus, L. fasciatus, L. friederici, L. trifasciatus, L. granti, L. moralesi, L. niceforoi, L. obtusidens, and L. subniger have been reported for the Caquetá River fishery; of these L. subniger is distinctive to Colombia⁸⁴⁷ and L. fasciatus and L. granti are of interest to the aquarium trade.⁸⁴⁸

⁸⁴² Araujo-Lima & Goulding, 1998; Goulding, 1980

⁸⁴³ Saint-Paul, 1984

⁸⁴⁴ Lovshin, 1995

⁸⁴⁵ see Chapters 2, 3, 4 & 5

⁸⁴⁶ CEMIG, 2000

⁸⁴⁷ Froese & Pauly, 2001

⁸⁴⁸ Froese & Pauly, 2001

Mylossoma and Myleus spp.

Species of these genera include the palometa, garopita, and garopa in Spanish, and pacu in Portuguese. They are relatively small discoid fish (12–25 cm), omnivorous in nature, that migrate a few hundred kilometers for reproduction. Three species are recorded in the fishery of the Caquetá River: Mylossoma aureum, Mylossoma duriventre (= duriventris), and Myleus schomburgki. These fish are of importance to the fishery for local consumption; the latter two are also of interest to the aquarium trade.

Rhaphiodon vulpinus and Hydrolicus spp.

These fish, known as machete and payara in Spanish and peixe-cachorro in Portuguese, are distinctive carnivorous schooling fish in the Cynodontidae family, characterized by an elongated body and pronounced, protruding canine teeth. In Colombia, Raphiodon migrates several hundred kilometers for reproduction. The Hydrolicus spp. (H. pectoralis and H. scomberoides in the Caquetá River) probably migrate shorter distance. The species contribute to the fisheries for local consumption, but no catch statistics are available. H. scomberoides is also of interest to the aquarium trade.⁸⁴⁹

Salminus spp.

The Salminus species, dorado or salmón in Spanish and dourado in Portuguese, are medium-sized carnivorous migratory fish particularly appreciated by sport fishermen throughout their range in South America, as well as by commercial fisheries where numbers are adequate. Salminus affinis, Salminus hilarii and Salminus maxillosus are present in the Caquetá River and contribute to fisheries for local consumption, but no catch statistics are available. Reproductive migrations appear to extend several hundred kilometers, though the extent of migration by S. affinis is not known.

Schizodon fasciatum

Schizodon spp. occur widely in South American rivers, often under the name of piava or ximboré. These are herbivorous relatives of the Leporinus spp., long-distance migrators, quite numerous, and important

⁸⁴⁹ Froese & Pauly, 2001

components of the food chain. In general, they do not constitute a significant fishery, but Schizodon fasciatum (lisa in Spanish and acurupintado in Portuguese) is fished in Colombia for local consumption. No catch statistics on this fish are available.

Semaprochilodus and Prochilodus spp.

Semaprochilodus spp. and Prochilodus spp., know in Spanish as yaraquí and bocachico respectively (jaraqui and curimatã in Portuguese), migrate upriver several hundred kilometers during high water to spawn. These fish form part of the important detritivorous fish group of South American rivers discussed more fully in the previous chapters. They grow up to about 40 cm and contribute to fisheries for local consumption in Colombia. No specific data on their capture in Colombia are available. Species reported for the Caquetá River are Semaprochilodus amazonensis (=insignis), Sema-prochilodus brama, Semaprochilodus theraponura (=insignis), Prochilodus nigricans, and Prochilodus rubrotaeniatus. P. nigricans, and S. insignis are considered widespread in the Amazon, and are reported to migrate long distances, while S. brama and P. rubrotaeniatus are more restricted in distribution.⁸⁵⁰ P. rubrotaeniatus is possibly restricted to headwater regions of only a few rivers,⁸⁵¹ living in pairs,⁸⁵² and may have more restricted migratory behaviour.

Serrasalmus spp.

The piranhas, including piraña in Spanish and pirambeba, palometa or piranha in Portuguese (piranha are considered as Pygocentrus spp., a subset of the Serrasalmus-like species, by some authors⁸⁵³). These fish contribute to fisheries for local consumption in Colombia, though catch statistics are not available. Although some countries restrict trade for fear of introductions into local waterways, several species have entered the aquarium market.⁸⁵⁴ The piranhas are carnivorous and omnivorous fish, fairly small in size. Serrasalmus (Pygocentrus) nattereri, Serrasalmus rhombeus, Serrasalmus spilopleura, and Serrasalmus striolatus have been

⁸⁵⁰ see Chapter 6

⁸⁵¹ see Chapter 6

⁸⁵² Froese & Pauly, 2001

⁸⁵³ Britski et al., 1999

⁸⁵⁴ Froese & Pauly, 2001

reported from the Caquetá River. Seasonal movements of less than 100 km by these fish have been reported for this region, but these are probably not strictly for reproduction.

Triportheus spp.

Triportheus albus, Triportheus angulatus, and Triportheus elongatus have been found in the Caquetá River. These fish are small pelagic fish (11–22 cm), primarily insectivorous in nature.⁸⁵⁵ Like the Pellona spp., these are known as sardinha in Spanish and sardina in Portuguese, but are of the same genus as the hatchetfish in English. Migrations of 100 km or less have been reported, but it is not clear if these are for reproductive purposes. They contribute in a minor way to the Colombian fisheries for bait, subsistence and local consumption.

Order Siluriformes: Pimelodidae

Brachyplatystoma spp.

The Brachyplatystoma catfish, including, in Spanish, the various zúngaros, and the pirabutón, are the mainstay of the commercial export fishery in Colombia. Brachyplatystoma filamentosum, Brachyplatystoma flavicans, Brachyplatystoma vaillanti, Brachyplatystoma juruensis, and Brachyplatystoma rouseauxi are present in the region, with the first three the best known and the most important to the fishery. B. juruensis is also of interest to the aquarium trade.⁸⁵⁶ Reproductive migrations of these species may extend to over 1,000 km.⁸⁵⁷ These fish are more extensively described in the following section and in Chapter 6.

Pseudoplatystoma spp.

The pintadillo rayado and pintadillo tigre, Pseudoplatystoma fasciatum and Pseudoplatystoma tigrinum respectively, described in previous chapters, are large carnivorous catfish. P. fasciatum is of principal importance to the Colombian export fishery. These fish migrate between 300–500 km in Colombian rivers, but it is not clear if these are purely for reproductive purposes.

⁸⁵⁵ Britski et al., 1999

⁸⁵⁶ Froese & Pauly, 2001

⁸⁵⁷ Barthem & Goulding, 1997

Other migratory Pimelodids

Other migratory catfish of the Pimelodidae family also contribute significantly to the fishery in Colombia. They are carnivorous and appear to migrate several hundreds of kilometers to spawn; most are also described in the previous chapters and in the following sections. The species reported for the Caquetá River that are the most important to fisheries are Leiarius marmoratus, Sorubim lima, Sorubimichtys planiceps, Brachyplatystoma platynema, Paulicea luetkeni, and Phractocephalus hemiliopterus. Pimelodus blochii, Pimelodus pictus, Pinirampus pirinampu, Platynematichthys notatus and Calophysus macropterus are also present, but are of less significance to the commercial fishery. P. pictus, P. pirinampu, C. macropterus, and P. hemiliopterus are also of interest to aquarists.

Order Siluriformes: other families

Hypophthalmus and Ageneiosus spp.

Hypophthalmus edentatus and Ageneiosus brevifilis are medium-sized catfish of the Caquetá River (50–60 cm in length) that belong to the Pimelodidae⁸⁵⁸ and Auchenipteridae families, respectively. Both are found in various South American rivers, but reproductive migration does not appear to occur in all locations. H. edentatus, known as the mapará in Spanish and Portuguese and the highwaterman catfish in English, refers to at least three species: H. edentatus, H. marginatus and H. fimbriatus. They are distinctive in that they are filter-feeding planktivorous catfish and appear to be migratory in the Colombia and Tocantins rivers,⁸⁵⁹ travelling relatively short distances, but not migratory in the Itaipu Reservoir, where it has been introduced.⁸⁶⁰

A. brevifilis, known in Spanish as the bagre paisano or bocon and in Portuguese as the mandubo or bocudo, are distinctive in that they lack the barbels so common in catfish. The fish are nevertheless carnivorous, as are most other catfish, feeding on other fish and crustaceans.⁸⁶¹ Short migrations for reproductive purposes appear to occur in Colombia, but are not described for other basins.

⁸⁵⁸ Britski et al., 1999

⁸⁵⁹ see Chapter 6

⁸⁶⁰ A. Agostinho, pers. com.

⁸⁶¹ Froese & Pauly, 2001

Order Perciformes

Plagioscion squamosissimus

The pescada, known in Portuguese as the pescada do piau, in Spanish as the curvina or curvinata and in English as silver croaker or South American silver croaker, is an euryhaline fish⁸⁶² that has invaded many reservoirs of Brazil, contributing significantly to commercial and sport fisheries.⁸⁶³ The fish is an aggressive carnivore, with a preference for eating other fish, and makes more use of open water than many other native migratory species. It thus does very well in the reservoirs where it has been introduced, often to the detriment of other species. It is a member of the drum family (Sciaenidae) and one of the few representatives of the perches in South American freshwater.

The pescada is native to the Colombian Amazon Basin, and contributes to commercial fisheries for local markets. While not considered migratory in most other parts of its range, including other parts of the Amazon,⁸⁶⁴ it appears to carry out migrations of several hundred kilometers in Colombian rivers twice a year.

Principal Fishery Species

Of all the migratory species, large catfish of the Pimelodidae family such as dorado (B. flavicans), lechero (B. filamentosum), pirabutón (B. vaillanti), and pintadillo (P. fasciatum) dominate studies and data collections. B. vaillanti and B. flavicans are two of the most important migratory catfish species in commercial fisheries of the Amazon Basin, representing (together with B. filamentosum P. fasciatum, and S. lima) more than 90% of the total fish landings.⁸⁶⁵ Barthem and Goulding (1997) reviewed their migratory patterns and the geographical distribution of life stages and size classes. These authors hypothesize that spawning occurs only in the Upper Amazon, including the Colombian portions of the Caquetá, Putumayo and Amazon rivers, while larval and juvenile rearing occurs only 1,800 km downstream near the estuary (see also Chapter 6).

⁸⁶² Froese & Pauly, 2001

⁸⁶³ see Chapters 2 & 5

⁸⁶⁴ Ribeiro, 1983

⁸⁶⁵ INPA, 1993,1994,1995,1996,1998

Migratory Patterns in Colombia

The high costs and limited success of tagging experiments have hindered fish ecologists in answering many questions about temporal and spatial dynamics in the large geographical area of the Amazon Basin. In Colombia, most of the information on migratory species comes from the Caquetá River system, where experimental studies on biology and fisheries have been carried out over the last two decades (Table 3).⁸⁶⁶ Fisheries statistics have provided additional information, especially for large commercial catfish species, and the traditional knowledge of indigenous communities has proved helpful in understanding migration, behaviour and habitat use of fish communities.⁸⁶⁷

Migratory movements vary from small local displacements of a few kilometers to hundreds or even thousands of kilometers up or down main channels of large rivers.⁸⁶⁸ It is presently believed that migration patterns vary greatly among species groups and that migration can be for spawning, feeding or population dispersion.⁸⁶⁹ During these movements, which are not fully understood for most species, individuals migrate between lotic and lentic systems of white, clear and black waters, taking advantage of the different conditions created by the flood pulse that allows seasonal use of a variety of habitats.

Traditional knowledge of fishermen at the confluence of the Caquetá and Metá rivers,⁸⁷⁰ suggests the following sequence of migrations:

Migrations start as waters rise, with small fish species (< 5 cm, collectively known as sardina) the first to show concerted movement. These move upriver along the banks of the Caquetá and in the flooded vegetation along its margin (the varzea) for about two months, in visible schools. The Pellona spp. (freshwater herring: also known as sardina) and the Hydrolicus spp. (carnviorous characids) are the next to be seen, but only in the river channel and in the largest tributaries, and for a shorter period of time. The Pimelodus spp., Sorubim spp., and Pseudoplatystoma spp.

⁸⁶⁶ Arboleda-Ochoa, 1989; Baptiste-Ballera, 1988; Agudelo-Córdoba, 1994; Hernandez et al, 1994; Gómez-León, 1996; Muñoz-Sosa, 1996; Rodríguez-Fernandez, 1991, 1999

⁸⁶⁷ Rodríguez-Fernandez, 1991; Prada-Pedreros,1989; Hernández et al., 1994; Rodríguez-Fernandez, 1999

⁸⁶⁸ Barthem & Goulding, 1997; Junk et al., 1997

⁸⁶⁹ Junk et al., 1997

⁸⁷⁰ L. Trujillo, pers. comm.

catfish are seen next, followed by most of the remaining characids (Prochilodus, Semaprochilodus, Colossoma, Piaractus, and Brycon spp.). The longer-range migrating catfish appear to pursue this latter group, including the Brachyplatystoma spp. and P. luetkeni. The catfish L. marmoratus and the Tripotheus spp. sardina are then seen later, still within the high water period. Other catfish move upstream during the

TABLE 3. Seasonal movements of fish in the Middle Caquetá River Basin⁸⁷¹

⁸⁷¹ Arboleda-Ochoa, 1989. No observations were made July and August. Observations made near Araracuara.

low water period, including P. pirinampu, C. macropterus, H. edentatus, B. vaillanti, and Plathynematichthys notatus. No downstream migrating schools are observed, though mature fish of a variety of migratory characids and catfish are at times seen moving down tributary streams in a less concerted fashion.

Although there are differences in habitat use between species and size-classes, research generally supports this traditional knowledge and provides complementary information. Most Characids have been reported to leave floodplains and start upriver spawning migrations in the river as the water levels begin to rise. For the Caquetá, Rodríguez-Fernández (1991) reports that large groups of Prochilodus spp., Curimata spp., Brycon spp., Hydrolycus scomberoides, P. castelnaeana, C. macropomum and some species from the family Anastomidae move upstream in the main channel, and are easily detected by local fishermen, especially in rapids. These movements are referred to as subienda, occurring primarily during the high-water season from June-September. Fish in the Lower Caquetá River appear to come from Brazilian waters, though it is not clear if these migrate the whole distance along the river or if a number of populations are migrating coincidentally. Peak concentrations of migratory fish occur sequentially in the Lower Caquetá River at Puerto Cordoba (100 km from the Brazilian border), at the confluence with the Metá River (250 km upstream), the waterfalls of Araracuara (500 km from the border), and then the waterfalls of Angosturas (a further 50 km upstream) (Figure 1).⁸⁷² The fish arrive at Araracuara already at the end of the highwater season, and Baptiste-Ballera (1988), reported that during the subienda, individuals of Schizodon spp., Prochilodus spp., and Rhaphiodon spp. migrated through the large rapids while Brycon brevicauda spawned before ascending. Spawning of most fish occurs in the mainstem channel of the Caqueta River.

Spent fish appear to enter the floodplains after spawning, though some may also forage in the varzea during the subienda and return to the river mainstem to spawn in October. Baptiste-Ballera (1988) reported the seasonal entry of Brycon, Semaprochilodus, Prochilodus, Myleus, Colossoma, Leporinus and Pseudoplatystoma spp. into floodplains of the Caquetá and

⁸⁷² Arboleda-Ochoa, 1989, Rodriguez-Fernandez, 1999

Yari rivers to feed, and similar events have been proposed for other rivers such as the Amazon,⁸⁷³ Cahuinari,⁸⁷⁴ and Igara Parana.⁸⁷⁵

As the water levels drop, movement from the flooded forest areas back to main channels of rivers and large streams commonly begins.⁸⁷⁶ The fish may then move upstream again, as suggested by the concentration of fish at the Araracuara Falls: peak fish concentrations at this location only occurs in December-January, whereas 100 km downstream this peak occurs before September.⁸⁷⁷ Baptiste-Ballera (1988) observed upriver migratory movements of this kind in the Caquetá River between October and March for Rhaphiodon spp., Schizodon spp., Prochilodus spp., Hypophthalmus spp., Platynematichthys spp., M. duriventre, Triportheus spp., and Pimelodid catfish and found evidence of a permanent presence of Brycon spp. and Leporinus spp. in the headwaters of some tributaries. There is little evidence of concerted downstream movements in the Caquetá during high water comparable to those reported as part of the dispersion migration in the Madeira.⁸⁷⁸

Migrations of some catfish species cover great distances. Barthem and Goulding (1997) described the migratory patterns of B. flavicans and B. vaillanti, the long distance migratory patterns most frequently observed. Based mainly on fisheries data and the biology of these species in the Middle Caquetá River Basin, these authors propose the existence of exclusive nursery habitats in the delta of the Amazon River and spawning grounds more than 3,000 km upriver in Colombia.⁸⁷⁹ B. filamentosum, the largest of the commercial species (max. known size 280 cm) in Colombia, provides most of the data on seasonal movements of this group of fish in Colombian waters. Rodríguez-Fernández (1999) has suggested that migration in the Middle Caquetá River Basin peaks in September-January, as water is receding and captures are the greatest.

Although less studied, some contrasting migratory trends along the main river channel have been proposed for catfish species such as

⁸⁷³ Jimenez-Segura, 1994

⁸⁷⁴ Walshburguer et al., 1990

⁸⁷⁵ Santamaria, 1995

⁸⁷⁶ Junk et al., 1997

⁸⁷⁷ L. Trujillo, pers. comm.

⁸⁷⁸ Barthem & Goulding, 1997

⁸⁷⁹ Arboleda-Ochoa, 1989; Rodriguez-Fernandez, 1991; Muñoz-Sosa, 1996

P. fasciatum and P. hemioliopterus.⁸⁸⁰ According to Rodríguez-Fernández (1991), few P. hemioliopterus are caught during the period of the lowest water levels in February and when high water levels stabilise after April, but many are caught when the water levels are rising in the intervening period of March to April. This suggests that the species migrates in the main river channel only as the water level is rising. P. fasciatum, on the other hand, is caught primarily between January and April, suggesting a more prolonged migratory and/or resident period in the river channel.

Relationship Between Habitat and Fish Distribution

The relationship between habitat and distribution of fish species is still poorly understood for the Colombian Amazon, as it is for most of the basin. Although migratory movements have been reported in several studies,⁸⁸¹ little attention is paid to the absence of fish species in places that appear to enjoy the same habitat and water quality as others that are densely occupied, or to the presence of large quantities of fish in habitats with little food and poor water quality. Descriptions of transient occupation of habitats, such as floodplains and lakes, are frequently reported.⁸⁸² In order to understand the distribution of organisms, Pulliam (1996) proposed several notions: (1) suitable habitats are often unoccupied, (2) density is a misleading indicator of habitat quality, (3) organisms are often found in unsuitable habitats, and (4) for some populations, the majority of individuals occur in “sink” habitats. Hanski et al. (1996) defines sink habitats as the continuous area of space within which a local population lives where the growth rate, at low density and in absence of inmigration, is negative. These challenging ideas will have implications for fish ecologists in the design of management and conservation strategies.

⁸⁸⁰ Rodriguez-Fernandez, 1991

⁸⁸¹ Baptiste-Ballera, 1988

⁸⁸² Goulding et al., 1988; Baptiste-Ballera, 1988; mesSaint-Paul et al., 2000; Silvano et al., 2000

IMPACTS ON MIGRATORY SPECIES

Fisheries Impacts

Commercial fisheries

While there are no detailed descriptions of the development of commercial fisheries in the Colombian Amazon, present-day fisheries appear to have evolved out of artisanal fisheries conducted by indigenous communities. Most of the fishing is still carried out by indigenous people, and continues to reflect traditional fisheries knowledge and subsistence economies. Along the Caquetá River Basin, members of at least 10 different ethnic groups carry out commercial fishing activities.⁸⁸³ From their relations with the colonists, indigenous people have been incorporating economic-dependent expectations into their life style; however, fishing activities are still managed with shamanistic and cosmological considerations, according to the spatial and temporal habitat symbolism.⁸⁸⁴

The growth and consolidation of these fisheries for export from the region has been closely linked to improved transport to major cities in the Colombian interior. Nevertheless, most fish were marketed as dried products until the introduction of freezer plants in the 1970s⁸⁸⁵. Currently, the fishermen sell their catch to large freezer plants, from where it is flown by charter aircraft to Bogotá (Figure 3). According to available statistics, all of this commercial catch is migratory species.

FIGURE 3. Fisheries marketing structure in the Caquetá River

⁸⁸³ Rodríguez-Fernandez, 1999

⁸⁸⁴ Rodríguez-Fernandez, 1991

Fishing is now the most important income-generating activity and the main source of protein in the Colombian Amazon Basin. It has become fundamental for local and regional economies that previously relied on extractive activities such as rubber-tapping, fur-trading, and gold mining. Fishing is also of great social significance, particularly at the local level, as it is one of the few legal income-generating activities that the largely indigenous populations can pursue in the area. However, income inequities are significant. For example, only only a few colonists, that control the fishing industry through paternal agreements with the indigenous fishermen, own all the freezer plants. Fishers’ income represents 15% or less of the overall profit in this system.

The demographic evolution of fishing communities in the Colombian Amazon Basin has been little studied, but studies on main rivers like the Caquetá⁸⁸⁶ and the Amazon⁸⁸⁷ show the existence of a highly dispersed rural population in small and medium-sized villages like Araracuara, Puerto Santander, La Pedrera, and Leticia, with freezing units and airport infrastructure.

Collection of fisheries data

The study of fisheries and the implementation of a data-collecting system in the Colombian Amazon is very recent. In 1979 the Institute of Natural Resources Renovation and Environment (INDERENA), began monitoring commercial catches in some of the main landing centres (Table 4), a task that was assumed in 1992 by the newly created National Institute for Fisheries and Aquaculture (INPA).

Several studies conducted by universities, NGOs and research institutions in the last decade have complemented the knowledge of several aspects of fisheries biology and ecological trends of commercially important migratory species like B. filamentosum, B. flavicans, P. fasciatum and P. tigrinum, P. luetkeni, P. hemiliopterus, Brachyplatystoma platynema, P. nigricans, and Brycon spp.⁸⁸⁸

⁸⁸⁵ Rodríguez-Fernandez, 1999

⁸⁸⁶ Arboleda-Ochoa, 1989; Rodríguez-Fernandez, 1991, 1999

⁸⁸⁷ Prada-Pedreros, 1989

⁸⁸⁸ Arboleda-Ochoa, 1989; Baptiste-Ballera,1988; Agudelo-Córdoba, 1994; Celis-Perdomo, 1994; Gómez-León, 1996; Muñoz-Sosa, 1996; Rodríguez-Fernandez, 1991, 1999

TABLE 4. Main fisheries landing centres in Colombia⁸⁸⁹

Summary of landings

Official information available for the Colombian Basin (subsistence catch not included) suggests irregular catch patterns ranging between 5,000 to 10,000 tons a year for the entire basin (Figure 4), with exceptional peak catches like those of 1993, which exceeded 13,500 tons.⁸⁹⁰ Most of the species included in the statistics are migratory catfish, dominated by large species like B. filamentosum, B. flavicans and P. fasciatum. Only a small proportion is migratory fish species of the Characidae family, like Brycon sp., C. macropomum and P. nigricans (Table 5). ⁸⁹¹

Fisheries of migratory species exhibit marked seasonal and annual variation. High catches are reported during the low water period, with a

FIGURE 4. Annual catch of migratory fish species in the Colombian Amazon basin⁸⁹²

⁸⁸⁹ Arboleda-Ochoa, 1989; Rodríguez-Fernández, 1991,1999; CAP, 1993; INPA, 1993, 1994, 1995, 1996, 1998; Anzola-Potes, 1995, TCA, 1995; Espitia, 1996, Agudelo-Cordoba, 1999; Fabre & Alonso, 1999

⁸⁹⁰ Anzola-Potes,1995

⁸⁹¹ INPA, 1993, 1994, 1997, 1998

⁸⁹² INPA, 1993, 1994, 1995, 1996, 1998

considerable decrease during the period of rising water and flooding of the forest.⁸⁹³ Seasonal movements are not simultaneous for main migratory species and some trends for sequential displacement in the main river channel have been detected for large catfish.⁸⁹⁴

The Amazon port of Leticia is, despite the tiny fraction of Colombian territory traversed by the mainstem of the river, the main marketing centre in the Colombian portion of the Amazon Basin (Table 4). This is due mainly to the contribution of Brazilian captures (more than 80% of the market). In 1992, 88% of the total volume of the Colombian freshwater fisheries was actually caught in Brazil.⁸⁹⁵ The fish market of Leticia handles 95% of the Colombian Basin total and has evolved from handling 2,500 kg in 1980 to nearly 9,000 for 1997, with an installed storage capacity of 800 tons and 50 to 60 fish merchants.⁸⁹⁶

TABLE 5. Catch of principal migratory fish species in the Colombian Amazon⁸⁹⁷

⁸⁹³ Muñoz-Sosa, 1996

⁸⁹⁴ Rodríguez-Fernandez, 1999

⁸⁹⁵ TCA, 1995

⁸⁹⁶ Agudelo-Córodoba, 1999

⁸⁹⁷ * = Information is not available

Second in importance to the Amazon River are the fisheries in the region of the Middle Caquetá River (Table 6), with catches sold through small fishing towns such as Araracuara, Puerto Santander and La Pedrera. Almost the whole catch reported in the statistics are of migratory species (Figure 5), and according to the study of Rodríguez-Fernández (1999), in the catch from 1992–1994 a few large catfish species predominate (Figure 6). Unlike Leticia, where better and cheaper transport possibilities exist, the marketing of characid fish species in the Caquetá Basin is negligible. However, these species may be very important to subsistence fishermen and, if comparable to Brazil and Peru, this catch may be substantial.⁸⁹⁸

TABLE 6. Total commercial catch in the three main Colombian river systems⁸⁹⁹

FIGURE 5. Composition of migratory fish catch in the Middle Caquetá River⁹⁰⁰

⁸⁹⁸ Bayley & Petrere, 1989

⁸⁹⁹ Agudelo-Córdoba, 1999

⁹⁰⁰ Rodriguez-Fernandez, 1999

FIGURE 6. Changes in the catch of principal migratory fish species in the Middle Caquetá River basin 1992–1994⁹⁰¹

Fishing gear

Colombian fishermen, reflecting a combination of traditional and modern methods, use a variety of fishing gear (Table 7). The trend in fisheries in the last decade shows a decrease of the capture per unit effort for all of the main fishing gear types and especially for stationary and drift nets.⁹⁰² Timing and effort put into fishing varies over the year with changes in availability of migratory fish and with the fishing methods used. Drift nets are the most time-consuming and profitable gear in regions like the Lower Caquetá River where fishermen work average sessions of 12 hours during the night.⁹⁰³ Harpooners work exclusively in large rapids like Araracuara and La Pedrera on the Caquetá River (also at night), but since they have to share the few appropriate spaces, their sessions are limited to 6 hours a day.

Another commonly used technique is “hook-hanging” or “hanging-line” which is practised throughout the year, but more by occasional or part-time fishermen, and during the daytime. In this procedure, the fisherman uses a 60–80 m polyester rope tied to a strong tree branch and

⁹⁰¹ Rodriguez-Fernandez, 1999

⁹⁰² Rodríguez-Fernandez, 1999

⁹⁰³ Rodríguez-Fernandez, 1991

TABLE 7. Main fishing gear types used in the Colombian Amazon⁹⁰⁴

⁹⁰⁴ Adapted from Prada-Pedreros, 1989

TABLE 7. continued

TABLE 7. concluded

anchored to the bottom by a stone. A baited hook is hung from the rope at about 3 m from the bottom. This technique is not very time consuming and requires only the monitoring of hooks for bait replacement or collection of the catch.

Overexploitation

Barthem et al. (1991) describe several different forms of fish overexploitation related to growth, recruitment and ecological factors that are likely to occur in the Amazon Basin. However, analysis of the official statistics shows short-term decreases and instabilities in the volume of captures reported for the Caquetá and Amazon rivers.⁹⁰⁵ Data available from studies in the collecting centres of the 5 principal subsystems of the Colombian Amazon are insufficient to construct useful models for any of the migratory fish species.

An estimated total potential catch of 5,000–10,000 tons/y has been proposed for the Colombian Amazon,⁹⁰⁶ corresponding to 2.5–5% of the annual yield for the whole basin.⁹⁰⁷ The existing information and the limited data series are, however, insufficient for drawing conclusions about exploitation levels and maximum sustainable yields, especially when 80% of the catch in the Colombian market may be from Brazilian waters. Since most of the information used to infer migratory patterns comes from fisheries that are highly selective and that depend on seasonal effort, special emphasis should be placed on research designed to take account of these characteristics.

Overfishing of sexually mature individuals is the most direct threat to migratory species. Unfortunately, information on the proportion of individuals caught in relation to the total spawning population is not available. Data analysed by Muñoz-Sosa (1996) for the Caquetá River suggest that some populations are being over-harvested, based on the calculation of a negative instantaneous growth coefficient (r=0.2167).

A decade ago Barthem et al. (1991) noted that since populations of large catfish are not yet over-exploited in the Amazon and habitat health is still good, we may be experiencing our last chance to improve our knowledge of tropical species and to guarantee their management and

⁹⁰⁵ Agudelo-Córodoba, 1999

⁹⁰⁶ Min. Ambiente, 1997

⁹⁰⁷ Bayley & Petrere, 1989

the conservation of evolutionarily viable populations. This advice is likely still valid, though for how long we do not know.

Other Impacts

Development

Although there are no large infrastructure projects underway in the Colombian Amazon Basin, some proposals for construction of hydroelectric dams or navigation corridors have been put forward.⁹⁰⁸ Based on past experience and keeping in mind the precautionary approach, special attention will be needed to avoid threats like those facing migratory fish in other parts of the Amazon.⁹⁰⁹

Brachyplatystoma spp., with its high spatial and temporal dependence on environmental conditions, may be highly vulnerable to habitat loss or degradation. Since larval stages of most fish species are highly susceptible to sediment increase and chemical pollutants, and mature (reproductive) individuals are the targets of commercial fisheries, threats to either sexually mature or larval life stages will have important consequences on population demographics throughout the basin.

Habitat of the Colombian Amazon appears to be relatively healthy. However, several economic activities, including gold mining and illegal agriculture, should be monitored carefully. A rapidly growing fleet of Colombian and Brazilian balsas (dredging units) supported by antigovernment forces are exploiting gold in the main channel, beaches and river banks of the Caquetá River near Araracuara, where spawning grounds of dourada and piramutaba are thought to exist. Gold extraction is also reported for the Guainiá River (Negro River), the Putumayo River and the Traira River on the frontier of Colombia and Brazil.⁹¹⁰ These activities are not only destroying valuable spawning habitat of fish and turtles, but are also likely contributing substantial mercury pollution to the area.

Planting of illegal crops in rainforest lands is increasing in the headwaters of large important tributaries like the Caquetá and Putumayo. Riparian vegetation is being destroyed and soils are becoming destabilised,

⁹⁰⁸ CIFSA, 1995

⁹⁰⁹ Barthem et al., 1991

⁹¹⁰ TCA, 1995

affecting the water flows and quality, and local people are being displaced by the associated violence. The main threat to fish, however, is the increasing use of large quantities of herbicides like glycophosphate (Roundup) to eradicate illegal crops. Roundup is prohibited in many countries because of high environmental toxicity and is likely to have dramatic effects in an aquatic environment.

Much of the Colombian fishery for migratory species relies on fish that come from Brazil, so that Brazilian programs for assuring the health of migratory stocks are important. In this regard, a program to prevent ecological degradation of the Amazon estuary has yet to be enforced. While information regarding the magnitude of tidal forest logging is insufficient, the threat is already clear.⁹¹¹

MANAGEMENT AND MITIGATION

Management

Sustainable use and conservation of migratory fish diversity is a goal that is proving to be extremely difficult to achieve, even with management systems that are supported by high-quality information. Unfortunately, data on occurrence and management of fish in Colombia are hugely deficient. Nevertheless, some research and management agencies within the National Environmental System (SINA) are attempting to set out general guidelines for conservation and sustainable use.

Groups involved in fish conservation and management at different levels include indigenous organisations, fishing interests, scientists from universities, research institutes and national or international NGOs, and government management institutions (Table 8). What co-operation exists is still, however, more the result of the efforts of independent individuals, rather than of organized inter-institutional activities.

⁹¹¹ Barthem & Goulding, 1997

TABLE 8. Principal institutions working on fish-related issues in the Colombian Amazon

Legislation for Protection of Migratory Fish Species

Fisheries in Colombia are regulated under Agreements 015/INDERENA/ 1987 and 075/INDERENA/1989. The General Statute of Fisheries (Law 13 of 1990, Decree 2256 of 1991) prohibits:

• The exploitation of resources protected by natural reserve areas or closed seasons.
• The use of illegal fishing methods including toxic materials.
• The drying, dyking or damming of rivers, streams, lakes or lagoons and any other water bodies, without the permission of the relevant authority.
• The dumping of materials or pollutants in water ecosystems that interfere with the life cycles of aquatic organisms and/or navigation.
• The fishing, processing and marketing of individuals of less than the minimum size.

Limitations on catch, fishing effort and storage quotas have not been imposed; their effectiveness would be expected to be limited. It is clear

TABLE 9. Size restrictions for fishing nets in the Colombian Amazon⁹¹²

that a more effective system of information and management is required. Lack of financial resources and institutional capacity has limited the development of participatory strategies. In the Colombian Amazon, closed seasons, restrictions on fishing gear and minimum fish sizes for capture have all been used:

• Fishing activities in all lakes and streams in natural and indigenous reserves are restricted to subsistence purposes.
• Net sizes are restricted (Table 9).
• Drift nets are prohibited between December and April.
• Beach seines are prohibited in the Caquetá River.
• The use of nets is prohibited in the rapids of Araracuara and Cordoba in the Caquetá River.
• There is a minimum capture size for some species (Table 10).

Colombian National Biodiversity Policy

By way of enforcing the mandate of the CBD, adopted by Colombia in Law 165 of 1994, the Ministry of Environment began a National Inventory of Biodiversity in 1997. This project analysed the threats to biodiversity and set down guidelines for the establishment of a National Policy of Biodiversity based on the knowledge, conservation and sustainable use of its components. Unfortunately, no particular reference is made to fish species in the Inventory.

The 1995 Colombian report to TCA (International Treaty on Amazon Co-operation) proposed fisheries conservation in four main areas:

1. To preserve catch diversity in highly fished zones, maintain maximum catches in zones of low pressure, establish areas for the

⁹¹² Agreements 015/87 & 075/87

development of commercial fisheries, and aim for maximum sustainable yields.

2. To improve the organisational framework and promote participatory management schemes through the establishment of a network of fishing communities and other receptive groups.

3. To promote the development of fisheries through capacity building and technical assistance.

4. To implement an information network to improve the exchange of statistics, co-ordinate activities, harmonise management measures at national and international levels, harmonise technology transfer programs, and encourage research co-operation.

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