SMALL-SCALE FISHERIES IN THE AMAZON BASIN: GENERAL PATTERNS AND DIVERSITY OF FISH LANDINGS IN FIVE SUB-BASINS

 

Giulia Cristina dos Santos LOPES¹; Michel Fabiano CATARINO1; Álvaro Carvalho de LIMA1; Carlos Edwar de Carvalho FREITAS1

 

ABSTRACT

The commercial fisheries existent in the sub-basins of the Madeira, Purus, Juruá, high Solimões and low Amazonas rivers was studied, aiming to build an integrated scenario of fishing at the Amazon Basin. The data were collected in 2012 at the main docks in the cities of Humaitá, Boca do Acre, Juruá, Tabatinga and Parintins. The common name of the fish species was registered, along with other information such as catch (kg), fishing gear, origin and fishing effort. In general, migratory Characiformes were the most abundant. Boca do Acre on the Purus River showed a dominance of Siluriformes, mainly surubim (Pseudoplatystoma spp.). In general, fishlandings were higher during the  falling water season. Gillnets and a kind of purse seine (locally called “redinha”) concentrated the captures and River and lakes were the most explored fishing grounds. The CPUE (catch per unit effort) varied between 12 and 216.5 kg fisher.day-1, with high averages in the Parintins and Juruá Rivers.

Key words: inland commercial fisheries; catch composition; fishing effort; geographical distribution; Amazon

 

A PESCA DE PEQUENA ESCALA NA BACIA AMAZÔNICA: PADRÕES GERAIS E DIVERSIDADE DOS DESEMBARQUES DE CINCO SUB-BACIAS

RESUMO

A pesca comercial das sub-bacias dos rios Madeira, Purus, Juruá, Alto Solimões e Baixo-Amazonas foi estudada com o objetivo de traçar o perfil integrado da atividade pesqueira na Bacia Amazônica. Os dados foram coletados em 2012, nos principais portos de desembarque das cidades de Humaitá, Boca do Acre, Juruá, Tabatinga e Parintins. O nome comum das espécies foi registrado, assim como a captura (kg), os apetrechos, os pesqueiros e esforço de pesca. Em geral, o desembarque foi dominado por Characiformes migradores. Em Boca do Acre, no rio Purus, os Siluriformes foram mais importantes, com destaque ao surubim, (Pseudoplatystoma spp.). Os desembarques foram maiores nos períodos de vazante. Redes de emalhar e um tipo de rede de cerco (chamado localmente de “redinha”) concentraram as capturas. Rio e Lagos foram os pesqueiros mais explorados. A CPUE variou de 12 a 216,5 kg homem.dia-1, com maiores valores médios nos municípios de Parintins e Juruá.

Palavras-chave: pesca interior; composição da captura; esforço de pesca; distribuição geográfica da pesca; Amazonas

 

 

 Artigo Científico: Recebido em 25/09/2015 – Aprovado em 03/05/2016

1 Department of Fisheries Sciences, Federal University of Amazonas (UFAM). 3000 Rodrigo Otávio Avenue, Coroado-Zip Code: 69077-000–Manaus–AM–Brazil. E-mail: giulia.lps@live.com; michelcatarinofish@gmail.com; alvlima@yahoo.com.br; freitasc50@gmail.com  


INTRODUCTION

In Amazonia, fishing is one of the extractive activities that involves large amounts of people, generating around 200,000 direct jobs and total estimated annual revenue of USD 200 million (FISCHER et al., 1992). It supplies regional urban centers with fish (GONÇALVES and BATISTA, 2008; RUFFINO, 2014), the most important source of animal protein for people in the region, particularly rural inhabitants living on the banks of rivers and lakes (SHRIMPTON and GIULIANO, 1979; CERDEIRA et al., 1997; ISAAC and ALMEIDA, 2011).

The Amazon Basin is a huge network of aquatic environments, with water chemistry of the rivers, lakes and streams determined by the soils found in each particular watershed (JUNK et al., 1989). The most abundant fish populations are found in white water flood plains, such as the Solimões-Amazonas River, whose headwaters originate in the Peruvian Andes. (IRION et al., 1997). Although the Solimões-Amazonas floodplain is relatively homogeneous between Tabatinga in the upper Solimões and Parintins in the middle reach of the Amazonas River, the fishing catch of commercial species could exhibit marked differences dictated by market preferences and fisher behavior. The large seasonal fluctuation in water level (> 10 meters) offers dynamic variability in aquatic habitats and fishing grounds. Amazonian fishers’ in-depth knowledge of the behavior of commercial species is demonstrated by their use of a wide arsenal of artisanal fishing gear, which varies based on changes in the hydrological cycle and the type of fishing ground being exploited (FREITAS et al., 2002; BATISTA and PETRERE, 2007).

 Commercial fishing takes place along river banks and channels, on beaches and ressacas, as well as in flooded areas, such as lakes, furos and paranás. It is carried out in large and medium-sized boats that can travel over 500 km, as well as small wooden canoes better for  travelling shorter distances and managing the nets (PETRERE, 1978b; BATISTA et al., 2012; CARDOSO and FREITAS, 2012; INOMATA and FREITAS, 2015). Approximately 200 species of fish are procured for food consumption along the Solimões-Amazonas River (BARTHEM, 1995; BARTHEM and FABRÉ, 2004), where catch composition varies widely according to the specific region (BATISTA et al., 2012). This variation is linked to several factors, including fluctuations in the hydrological cycle, floodplain extension, number of floodplain lakes, seasonal movements of target species, and overfishing (CASTELLO et al., 2013), As well, extrinsic factors such as market preferences and individual knowledge of fishers also influence catch composition. .

Due to population growth in the Amazon over the last four decades and the consequent increase in fishing effort to meet the demand for fish in expanding urban centers, some species have already been overfished, which results in a reduced number of landings and smaller fish being caught (PETRERE, 1983; MÉRONA and BITTENCOURT, 1988; BARTHEM and GOULDING, 1997; RUFFINO and ISAAC, 1999; PETRERE et al., 2004; FREITAS et al., 2007; CASTELLO et al., 2011; CAMPOS and FREITAS, 2014; CATARINO et al., 2014; SANT’ ANA et al., 2014).

The lack of cooperation among different authorities and the discontinuance of fishery-monitoring programs have prevented a more comprehensive synopsis of the fleets’ activities. Therefore, it is extremely important to renew regular monitoring efforts, to be able to track fishing activity in large urban centers and also in the interior. Amazonas State is the largest in Brazil, covering more than 1.5 million square meters and encompassing large variability in aquatic systems. Fishing activity in the state is influenced by market demand, which, consequently, is a product of economic, social and cultural factors.

Preliminary and fragmented studies showed that fish landings in urban centers in the central part of the Amazon primarily consist of migratory Characiformes, especially prochilodontids (BITTENCOURT and COX-FERNANDES, 1990; BATISTA and PETRERE, 2003), while Siluriformes are more common in urban centers in the lower reach of the Amazon, in the Amazonas River estuary (BARTHEM and FABRÉ, 2004) and in the upper Solimões (PETRERE et al., 2004). Therefore, this study sought to analyze the similarities and differences in commercial fishing in different areas of Amazonas State, based on fish landings in urban centers representing the five largest sub-basins of the Solimões-Amazonas River. This comparative analysis was based on information about total and per-species catch, fishing grounds, fishing gear used and fishing effort. We hypothesized that there would be differences in catch composition in relation to fishing gear used  and catch per unit effort among small scale commercial fisheries along the Solimões-Amazonas River

MATERIAL AND METHODS

Study area

Data on fish landings were collected in the cities of Boca do Acre, Humaitá, Juruá, Tabatinga and Parintins. These are the administrative centers of the principal municipalities of the Purus, Madeira and Juruá rivers and of the central channel of the Solimões/Amazon River, respectively (Figure 1). These sub-basins are typical of whitewater rivers and account for most of the commercial fish production in the state of Amazonas.

Figure 1. Geographic location of the administrative centers of the municipalities in the Amazon basin. 1 = Parintins, Lower Amazon river; 2 = Humaitá, Madeira river; 3 = Boca do Acre, Purus river; 4 = Juruá, Juruá river; and 5 = Tabatinga, Upper Solimões river.

Data collection

Fish landing data were collected daily with a structured questionnaire between January and December 2012 in the municipalities of Juruá (368 questionnaires applied) and Tabatinga (748 questionnaires). In Boca do Acre (333 questionnaires), Humaitá (382) and Parintins (482), the data for 2012 were completed with records from September to December 2010. The questionnaires were applied in interviews with the person in charge of each boat when fish was being landed. The information recorded covered production (kg) per species, fishing gear used, fishing grounds exploited, number of people who took part and duration of each trip. Some of the forms only contained catch data as respondents did not provide information about the fishing gear used.

Mean monthly water levels, provided by the Brazilian Mineral Resource Research Company (CPRM), were used to describe the hydrological cycles in the sub-basins from the years 2010 to 2012. With the exception of the municipality of Juruá, where this information was not available, we therefore used the data for Tabatinga, the closest municipality to it.

Data analysis    

A list of the common names of the fish species recorded and their possible taxonomic identity was drawn up based on the current literature (REIS et al., 2003) and by consulting specialists at the Federal University of Amazonas (UFAM) and the National Amazonian Research Institute (INPA). Total fish landings (kg) were calculated for each municipality. They were then broken down by type of fishing ground, fishing gear and month and also compared with the annual hydrological cycle. Catch per unit effort (CPUE) was calculated dividing the catch per fishing trip (kg) by fishing effort expressed as number of fishers multiplied by the number of days spent in the fishing trip) (PETRERE, 1978).

RESULTS

Catch composition

Seventy-six common names of fishes were recorded. This number potentially corresponds to a larger number of species because the same common name can be used to designate different species.  The greatest variety of fish in landings was recorded in Humaitá (36) and Juruá (35) followed by Parintins and Boca do Acre, with 34 types of fish each (common names), and Tabatinga with 22. Slightly over 10% of the species (mainly migratory Characiformes) were found in landings in all the municipalities (Table 1).

Fish landings

In Parintins, Juruá and Humaitá, around 80% of fish landed were Characiformes, in contrast to Boca do Acre, where Siluriformes were the most common (Table 2). In Tabatinga, the most common fishes were salada, a grouping that corresponds to a variety of species of little commercial value. Curimatã (Prochilodus nigricans), jaraquis (Semaprochilodus spp.), pacu (Mylossoma spp.) and (Metynnis spp.) and matrinxã (Brycon amazonicus) accounted for over half of overall production in the municipalities. They were also the species or species group that accounted for more than 10% of total production in Parintins, Juruá and Humaitá, Pseudoplatystoma spp., representing a species group known as pintado, surubim and caparari, was the only catfish (order Siluriformes) to account for over 10% of landings in one of the municipalities. Parintins was the municipality with the largest landings, followed by Boca do Acre, Tabatinga, Juruá and Humaitá (Table 2). Mean monthly landings were 63.0 t ± 7 in Parintins, 12.7 t ± 7 in Boca do Acre, 8.5 t ± 12 in Tabatinga, 7.5 t ± 4 in Juruá and 5.5 t ± 4 in Humaitá. In general, production peaks in the municipalities were associated with the falling-water period with the exception of Parintins, where the largest values were recorded in the flood period. In Boca do Acre, the largest landings were for surubim (Pseudoplatystoma spp.), which represented 12.5% of production in May and 13.7% in July. Cuiú-cuiú (Oxydoras niger) accounted for 11.8% of landings in May, and mandí (Pimelodus spp.) for 15.6% in July (Figure 2). In Humaitá, jaraqui (Semaprochilodus spp.) accounted for 86% of the total catch landed in April, while in May jaraqui (Semaprochilodus spp.) and jatuarana (Brycon melanopterus) were the most important species, accounting for 23.4% and 22.3%, respectively (Figure 3). In Tabatinga, production peaks were in July (99.4%) and October (84%), when a variety of species, commonly referred to as salada, were landed (Figure 4). In Juruá peaks were recorded in March, April and May. In March, jaraqui (Semaprochilodus spp.) represented 45.5% of the landings, followed by matrinxã (Brycon amazonicus) with 40.3%. In April, matrinxã and curimatã (Prochilodus nigricans) were responsible for 30% and 24.5%, respectively, while in May pacús (Mylossoma spp.) and (Metynnis spp.) were more important, accounting for 49.8% of landings (Figure 5). In Parintins, the species that accounted for the largest proportion of landings in the months of April and May were jaraqui (Semaprochilodus spp.) and curimatã (P. nigricans) with 46% and 30%, respectively. Another peak was observed in July, when curimatã (P. nigricans) (51.2%) and pacu, (Mylossoma spp.) and (Metynnis spp.) (17.7%) were the most common fishes (Figure 6).


 

Table 1. Types of fish and total fish landings (in kg) in the municipalities in 2012.  BA = Boca do Acre; HU = Humaitá; JU = Juruá; PA = Parintins; TA = Tabatinga.

 

Species

Common name

BA

HU

JU

PA

TA

Subtotal

Acestrorhynchus spp.

Peixe cachorro

193

4

50

247

Leporinus spp.

Piau; Aracu cabeça gorda

3830 

55

4711

111

8707

Leporinus fasciatus

Aracu flamengo

20

20

Schizodon fasciatus

Aracu comum

130

1795

32522

34447

Arapaima gigas

Pirarucu

4471

4471

Ageneiosus spp.

Fidalgo; Mandubé; Bocão

4876

700

30

5606

Ageneiosus spp.

Boca de bolsa

5867

5867

Hoplosternum littorale

Tamoatá

392

1200

1592

Brycon amazonicus

Matrinxã

18209

214

10222

41681

830

71156

Brycon melanopterus

Jatuarana

4317

72

4389

Colossoma macropomum

Tambaqui; Ruelo

971

714

1379

19780

1280

24124

Mylossoma spp.; Metynnis spp.; Myleus spp.

Pacu

12151

8181

23692

41452

1975

87451

Piaractus brachypomus

Pirapitinga

8335

17

4537

19972

659

33520

Pygocentrus nattereri

Piranha caju

552

552

Serrasalmus spp.

Piranha; Piranha preta

1197

899

301

1891

25

4313

Triportheus spp.

Sardinha

412

2807

1252

3616

190

8277

Astronotus spp.

Acará açu

1493

959

1046

6198

9696

Chaetobranchus spp.

Acará branco

36

58

94

Cichla spp.

Tucunaré, Tucunaré amarelo

6599

1098

4323

11222

23242

Crenicichla spp.

Jacundá

20

20

Geophagus spp.

Acará tinga

140

140

Heros spp.

Acará roxo

29

29

Boulengerella lucius

Peixe agulha

12

12

Potamorhina spp.

Branquinha; Chorão

37

6022

2690

8362

1660

18771

Rhaphiodon vulpinus

Saranha

150

150

Lithodoras dorsalis

Bacu pedra

220

220

Oxydoras niger

Cuiú cuiú; Cujuba

13773

28

860

1091

15752

Pterodoras granulosus

Bacu liso

11

11000

105

11116

Hoplerythrinus unitaeniatus

Jejú

35

35

Hoplias malabaricus

Traíra

221

688

40

949

Anodus spp.; Hemiodus spp.

Charuto; Saúna

197

5590

5787

Pterygoplichthys pardalis

Acari  bodó

315

898

499

38484

510

40706

Osteoglossum bicirrhosum

Aruanã

143

437

5750

8696

15026

Brachyplatystoma capapretum; B. filamentosum

Filhote; Flecheiro; Piraíba

6970

671

330

630

8601

Brachyplatystoma platynemum; Goslinia platynema

Babão

446

446

Brachyplatystoma rousseauxii

Dourada

256

1105

18

1378

2757

Brachyplatystoma vaillantii

Piramutaba; Piaba

8742

3073

60

11875

Calophysus macropterus

Piracatinga

2000

2000

Hypophthalmus spp.

Mapará

721

15

17750

18486

Leiarius marmoratus

Jandiá

1847

68

1000

10

2925

Leiarius pictus

Jandiá preto

567

567

Phractocephalus hemioliopterus

Pirarara

1892

922

487

3301

Pimelodus blochii; Pimelodina flavipinnis

Mandí

10922

10922

Pinirampus pirinampus

Piranambú; Barbado; Barba chata

1322

93

160

100

1675

Platynematichthys notatus

Cara de gato

1391

1391

Pseudoplatystoma spp.

Pintado; Surubim; Caparari

21935

1319

2736

12865

120

38975

Sorubimichthys planiceps

Peixe lenha; Pirauaca

423

4

427

Zungaro zungaro

Jaú; Pacamom

4726

222

391

30

5369

Pellona castelnaeana

Apapá amarelo; Sardinha amarela; Arenga

2577

38

300

2915

Pellona flavipinnis

Apapá branco; Sardinha branca; Arenga

335

8

477

210

1030

Prochilodus nigricans

Curimatã

6772

6079

8694

251845

479

273869

Semaprochilodus spp.

Jaraqui; Jaraqui escama grossa; Jaraqui escama fina

200

21933

9629

180242

30

212034

Plagioscion squamosissimus

Pescada

1400

602

1741

21186

60

24989

Salada

91321

91321

Others

 

1729

103

20

 

 

1852

Number of species

34

36

35

34

22

Total

 

144396

65507

88598

754905

100805

1154211

 

Table 2. Total catch (in kg) of Characiformes (CH) and Siluriformes (SI) and their respective percentage of total catch by municipality. Species and common names that accounted for more than 10% of total production are shown separately.

Municipality

Total weight (1,000 kg)

CH

(1,000kg)

%

> 10%

SI

(1,000kg)

%

> 10%

Parintins

754.9

606.9

80.4

Curimatã (33%)

Jaraqui (23%)

95.7

13

Boca do Acre

144.4

52.7

36.5

Matrinxã (12%)

77.4

54

Surubim (10%)

Tabatinga

100.8

7.8

7.2

Salada (90%)

1.6

2,2

Juruá

88.6

69.8

78.7

Pacu (26%), Matrinxã (11%)

5.7

8

Humaitá

65.5

52.1

79.0

Jaraqui (31%),

Pacu (12%)

10.1

16

Total

1,154.2

789.3

190.6

 

 

 


Figure 2. Monthly commercial fish landings in Boca do Acre. Bars denote fish production and lines the river level.

Figure 3. Monthly commercial fish landings in Humaitá. Bars denote fish production and lines the river level. No data was available for September.

Figure 4.  Monthly commercial fish landings in Tabatinga. Bars denote fish production and lines the river level.

 

Figure 5. Monthly commercial fish landings in Juruá. Bars denote fish production and lines the river level.

Figure 6. Monthly commercial fish landings in Parintins. Bars denote fish production and lines the river level. No data was available for September and October.

Fishing grounds

        The Juruá and Parintins fishing fleets exploited a wider variety of fishing grounds. Beaches and rivers were exploited in all the sub-basins. Lakes were exploited by all the fleets, with the exception for the fleet of Boca do Acre. An island environment was only used by fishers in Parintins, and igapós only by fishers in Juruá (Table 3). The fishing grounds with the greatest production were rivers, lakes and paranás, while those with the lowest production were igapós and islands (Table 3).

        Fishing on beach grounds, although exploited by all the fleets, made only a small contribution to fish landings. Igarapés, although found in most of the municipalities, followed a similar pattern. Igapós and islands were even less important and were only exploited in Juruá and Parintins (Table 3).

Fishing gear

Thirteen types of fishing gear were used. Hooks and gillnets were used in all the sub-basins. In Parintins, on the Lower Amazon River, 76% of the different types of fishing gear listed were used. In Boca do Acre, 23% were used on the Purus River, 46% on the Madeira River, 61% on the Juruá River and 38% on the Upper Solimões River. More than 95% of the fish were caught with gillnets or redinhas (61% and 36%, respectively). Hooks accounted for the third largest proportion of fish landings and for a particularly significant proportion in Boca do Acre and Humaitá (Table 4). Bottom longlines and handlines were not included in the table because they accounted for less than 100 kg year-1 of landings and were each used in only one of the sub-basins (Madeira River and Amazon River, respectively).

Catch per unit effort (CPUE)

CPUE varied from 12 to 216.5 kg man.day-1 throughout the year. Parintins, Juruá and Tabatinga had the highest mean CPUE values, followed by Boca do Acre and Humaitá. In Parantins two peaks in CPUE were recorded: one at the end of the flood period, in April and May, and another at the beginning of the falling-water period, in July. This pattern was similar to that found in Juruá. In Tabatinga the highest value was recorded at the beginning of the flood period, in the month of October. In Boca do Acre, the highest CPUE values were recorded at the end of the flood period, at the beginning of February, and during the falling-water period, between May and August (Table 5).  The highest CPUE values were recorded in the falling-water period in Boca do Acre, Juruá and Parintins, and in the flood period in Humaitá and Tabatinga. The start of the flood period was marked by low values of CPUE in Boca do Acre, Humaitá and Juruá, while in Tabatinga and Parintins the lowest figures were observed during the falling-water and dry seasons, respectively.


 

Table 3. Fish production (kg) for each type of fishing ground exploited by the fleets in each municipality.

Municipality

Igapó

Igarapé

Island

Lake

Paraná

Beach

River

Subtotal

BO

2,070

3,447

139,079

144,596

HU

43,452

3,773

18,282

65,507

JU

300

1,611

34,380

2,851

20

49,436

88,598

PA

450

255

155,559

121,415

400

476,826

754,905

TA

48,040

1,870

50,895

100,805

Total

300

4,131

255

281,431

124,266

9,510

734,518

1,154,411

 

 

Table 4. Types of fishing gear used and the amount of fish (in kg) landed with each type of gear in the municipalities studied. HK = hook; BA = bow and arrow; HP = harpoon; DN = dragnet; BO = boinha; RL = rod and line; BL = surface longline; GN = gillnet; RD = redinha; CN = castnet; SP = spear.

 

Municipality

HK

BA

HP

DN

BO

RL

LL

GN

RD

CN

SP

Boca do Acre

5199

140068

270

Humaitá

8238

126

190

54513

4542

Juruá

821

205

58

855

56794

31115

365

505

Parintins

258

884

3382

187

166

381

325767

374896

430

Tabatinga

264

 

 

35

 

 

50

112898

260

 

 

Total

14780

205

884

3601

187

166

1476

690040

410813

1065

505

 

 

Table 5. Variation in Catch per Unit Effort (CPUE) throughout 2012.

Sub-Basin

J

F

M

A

M

J

J

A

S

O

N

D

Purus

14.8

23.7

20.8

18.8

23.2

22.4

31.3

33.7

17

14.5

25.4

17.5

22 ± 6

Madeira

12.8

16.8

16

14.8

16.4

13.4

14.3

13.4

15.2

13.5

12.3

14.4 ± 1.5

Juruá

36.2

41

95

88.2

92.3

50.7

46.3

109.2

41.5

37.5

38.4

26

58.5 ± 28.8

Baixo Amazonas

26

36

36.2

31.3

44.3

43.8

216.5

71

94.8

12

61.2 ±  59.4

Alto Solimões

17

74

37.8

41.2

22

28.2

28.7

14.5

16.8

121.8

52.2

53

42.2 ± 30.8

 

 


DISCUSSION

Our results show that at least 76 species or species groups were exploited by commercial fishers in the five sub-basins studied. This represents less than half of the number exploited by commercial and subsistence fishers throughout the Amazon Basin, which is estimated to be around 200 species (BARTHEM and FABRÉ, 2004). The number of species landed varied between 22 and 36. This variation appears to be a pattern throughout the basin, particularly along the Solimões/Amazon River channel, where 20 to 72 species have been recorded as being commercially exploited (PROVÁRZEA, 2006; BATISTA et al., 2012).

Fish landings in Parintins, Juruá and Humaitá consisted mainly of migratory Characiformes, especially jaraquis (Semaprochilodus spp.), matrinxã (Brycon amazonicus), pacus (Mylossoma spp.), (Metynnis spp.) and curimatã (Prochilodus nigricans). These species are very abundant in whitewater rivers (BATHEM and GOULDING, 2007), where they form large shoals during spawning migrations (ARAÚJO-LIMA and RUFFINO, 2003; RIBEIRO and PETRERE, 2006). Their population parameters and life strategies are typical of r-strategists (RIBEIRO and PETRERE, 2006; SANTOS-FILHO and BATISTA, 2009; CATARINO et al., 2014). Larvae and juveniles of these species use floodplains as nursery grounds, taking advantage of the food supply, which stimulates their fast growth. They generally reach maturity around two years of age, when they form large shoals and leave the floodplain to reproduce in the main channel of whitewater rivers (COX-FERNANDES, 1997). After reproducing, they return to the floodplain, where they feed until the start of the falling-water period, when they once again leave the floodplain in large shoals and migrate upstream in search of new areas where they can stay during the dry season (GOULDING, 1979; RIBEIRO, 1983; COX-FERNANDES, 1997; ARAÚJO-LIMA and RUFFINO, 2003). During these periods of reproductive and dispersive migration, the shoals are intensively exploited by the commercial fishing fleet (BATISTA, 2004).

In Parintins, Prochilodus nigricans, Semaprochilodus insignis and Semaprochilodus taenirus accounted for more than 10% of landings, a similar result to that found in 2003 in the same region (PROVÁRZEA, 2006). In Juruá, Brycon amazonicus, P. nigricans, S. insignis, S. taenirus and various species of Myleinae, commonly known as pacu, made up most of the production. In 2009/2010, only pacus (Mylossoma spp.) and (Myleus spp.) stood out in the landings recorded in this municipality (ALCÂNTARA et al., 2015). In Humaitá, jaraqui (S. insignis), (S. taenirus), pacu (Mylossoma spp. and Metynnis spp.) were the most-landed species, confirming the results observed in Manicoré, another town on the lower stretch of the Madeira River (CARDOSO and FREITAS, 2008). In Porto Velho, a municipality located upstream of Humaitá, dourada (Brachyplatystoma rousseauxii) and filhote, (Brachyplatystoma filamentosum) also accounted for a significant proportion of landings in 2004 (DORIA et al., 2012).

Fishing in Boca do Acre focused on various species of migratory catfish (Siluriformes), most notably surubim (Psudoplatystoma spp.) The importance of this group in landings in the Upper Purus has already been reported by ALMEIDA et al. (2012), who found that in addition to surubim (Pseudoplatystoma tigrinum), jandiá (Leiarius marmoratus), filhote (Brachyplatystoma filamentosum) and mandi (Pimelodus cf. altipinnis) were the most frequently caught species.

The importance of Siluriformes to fishing in the upper stretch of the Purus River corroborates findings in the estuary region of the Lower Amazon and Upper Solimões (BARTHEM and GOULDING, 2007). There are many fish processors in these regions that buy this type of fish, primarily to supply the Peruvian and Colombian markets (BARTHEM and GOULDING, 2007). Because Boca do Acre is close to Rio Branco, the capital of the state of Acre, catfish production in this municipality is probably shipped to Rio Branco.

Although the largest landing was recorded in Parintins, followed by Boca do Acre, Tabatinga, Juruá, and Humaitá, it was less than half that recorded in 2003 (1,730 t) (PROVÁRZEA, 2006). In Boca do Acre, total catch was similar to the figure for 2008, when 163 t were landed (PROVÁRZEA, 2006). In contrast, the value recorded in Tabatinga was much less than the 3,000 t recorded in 2003 (PROVÁRZEA, 2006). In Juruá, 88 t were landed, slightly more than the 60 t reported by ALCÂNTARA et al. (2015). In Humaitá production was 65 t, which was also less than the figure reported by the fisher association in the period 2001 to 2004 (DORIA et al. 2012).

The rivers and their floodplains, where the lakes are notable for their yield, were the most productive fishing grounds, although their importance varied from one sub-basin to the next. In Boca do Acre, the river was the main fishing ground used by the fishing fleet. In the other municipalities, lakes and paranás were of equal importance, as already reported by other authors (PETRERE, 1978b; BARTHEM and GOULDING, 2007).

A variety of fishing gear was used, of which more than one was normally used in the same fishing trip, indicating the multispecific nature of fishing in Amazonia (FREITAS et al., 2002; BATISTA and PETRERE, 2003). However, most of the fish landed was caught with gillnets and redinhas, corroborating the findings of other authors for the Amazon region (BATISTA and PETRERE, 2003). Gillnets are normally used throughout the year, particularly in lakes and flooded areas. Redinhas, on the other hand, are used primarily to catch species that form large shoals, particularly Characiformes, and are used predominantly in river fishing (PETRERE, 1978b; BARTHEM, 1999).

The unit of fishing effort measured in fisher per day is generally chosen to describe Amazonian fisheries because different type of gear are used in a same fishing trip, making it difficult to use more specific units of fishing effort (PETRERE, 1978a). CPUE in all the municipalities varied substantially throughout the year, probably because of changes in the spatial distribution of fishes at different stages of the hydrological cycle (BARTHEM, 1999; CARDOSO and FREITAS, 2007). In Parintins, mean CPUE was 61.2 kg fisher.day-1, significantly greater than the previous reference figure for the fleet in that municipality (10.6 kg fisher.day-1) (PROVÁRZEA, 2006), and very close to that reported for Tefé (63.6 kg fisher.day-1) (VIANA, 2004). In Juruá, mean CPUE was 58.5 kg fisher.day-1, slightly less than the 68.5 kg fisher.day-1 recorded by ALCÂNTARA et al. (2015), one of the largest figures for Amazonia. Although smaller than the estimated figures for Parintins and Juruá, the CPUE for Tabatinga was also high (42.2 kg fisher.day-1) and was greater than that recorded in 2003 (32.5 kg fisher.day-1) (PROVÁRZEA, 2006). Humaitá and Boca do Acre had the smallest mean CPUE, which may be related to ecological factors not investigated in this study.

CONCLUSION

The socio-economic importance of freshwater fishing in developing countries is frequently underestimated. The large variation observed in catch composition, especially in the catch accounted for each species, also in total fish production and types of fishing ground and fishing gear used, indicates that fisheries in the Amazon are very diverse. Altogether, various factors, such as the intensity and duration of the different hydrological periods, fishing effort, market preferences and the diversity and size of the different habitats influences the diversity of Amazonian fisheries.

This variability needs to be taken into account when developing effective management strategies, in this way it is recommended that management agencies should avoid generalist management policies that could prove ineffective or even adversely affect stock sustainability and fishing itself are avoided.

ACKNOWLEDGEMENTS

We would like to thank the project members who collected data as part of the State of Amazonas Fisheries Statistics Project for all their efforts, the Ministry of Fisheries and Aquaculture for providing financial support. The author CECF would also like to thank CNPq and FAPEAM for providing a research grant (ref. no. 302430/2012-1).

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