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Fish SciDOI 10.1007/s12562-015-0853-z

ORIGINAL ARTICLE

The panorama of artisanal fisheries of the Araguaia River, Brazil

Carlos Eduardo Zacarkim · Pitágoras Augusto Piana · Gilmar Baumgartner · José Marcelo Rocha Aranha

Received: 7 July 2014 / Accepted: 18 December 2014 © Japanese Society of Fisheries Science 2015

that both Araguaia River hydrology and fisher gender should be taken into consideration in developing manage-ment strategies for achieving sustainable yields. Of note, our results for fishery yields were 305 % higher than offi-cial Brazilian estimates for the entire Araguaia basin over the same period, which suggests underestimation in the official statistics.

Keywords Amazon River basin · Araguaia–Tocantins system · Fishery yields · Fisher gender

Introduction

Seasonal changes in the composition of fish assemblages may occur as a result of natural fluctuations in the hydro-logical regime, thereby affecting the distribution and abun-dance of freshwater species [1–3]. These effects have been linked to factors such as the duration, frequency, and perio-dicity of the hydrological regime, local and regional geo-morphology and zoogeography, changes in habitat, human interventions, and climate change [4–6]. According to Salas and Gaertner [7] and Snelder and Lamouroux [8], such sea-sonal variation can alter patterns of small-scale commercial fishing between high- and low-water regimes, affecting the size and distribution of fishing efforts.

A common type of analysis used by water resource man-agers involves the evaluation of fishery landings at ports and landing sites. Although the information collected in this manner does not measure the fishing effort exerted, it does allow evaluation of exploited species, number of fish caught per period, and birthplace, gender, and age demo-graphics of fishers [9–11]. In addition to obtaining landing data, the quantification of small-scale commercial fishing efforts makes it possible to interpret changes in the amount

Abstract Seasonal changes in composition and yield of artisanal fishery catches may occur due to natural fluctua-tions in hydrological regime, fishers, and gear used. In this context, the present study aimed to test the hypothesis that the hydrological cycle of the Araguaia River influences the activity of small-scale commercial fishing by examining the following predictions: fishery yield is influenced by the hydrological regime; the main species exploited through artisanal fishing can change with variations in hydrological regime; and there are differences between male and female fishers in both yield and main exploited species due to dif-ferences in the sites that they explore and the gear that they use. Results from the study demonstrated a significantly higher fishery yield during the low-water season, when the catch per unit effort (CPUE) was 24.8 kg/fisher/day, com-pared to an ebb season CPUE of 19.9 kg/fisher/day. The main species caught by artisanal fisheries was indeed influ-enced by the hydrological regime of the Araguaia River and the fisher’s gender, which was associated with differences in fishing locations and gear used. These findings suggest

Fisheries

C. E. Zacarkim (*) Laboratory of Ecology, Fishing and Ichthyology (Laboratório de Ecologia, Pesca e Ictiologia, LEPI), Federal University of Paraná (Universidade Federal do Paraná), Pioneer Street, 2153, Palotina, Paraná 85.950-000, Brazile-mail: zacarkim@ufpr.br

P. A. Piana · G. Baumgartner State University of West Paraná (Universidade Estadual do Oeste do Paraná, UNIOESTE), Faculdade Street, 645, Toledo, Paraná 85.903-000, Brazil

J. M. R. Aranha Graduate Program in Zoology, Federal University of Paraná (Universidade Federal do Paraná), Pioneer Street, 2153, Palotina, Paraná 85.950-000, Brazil

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of fish captured, to assess the impacts of new fishing prac-tices, tackle types, and changes in the abundance of stock, and to regulate fishing efficiency to maximize profits and minimize overfishing [7].

In Brazil, artisanal fisheries play a key role in fish pro-duction, accounting for over 60 % of continental landings. The northern region is responsible for 55.7 % of Brazilian freshwater fish production, which totaled 248,911 t in 2010, and which is driven by the states of Amazonas (70,896 t) and Pará (50,949 t). A large proportion (~40 %) of the arti-sanal fishers of Brazil are also concentrated in this region, particularly in the states of Pará and Tocantins, which are home to 223,501 and 6,263 fishers, respectively [12, 13].

An unusual feature observed in the riverine communi-ties of the Amazon basin is that fishing is a vital food and income source for entire families, where in almost 100 % of cases their livelihoods depend on fishing activity. Fami-lies in these communities are generally large, with five or more members, consisting of one adult couple and at least three children, and where participation in fishing activi-ties involves all family members, with the men fishing along the river while women and children fish on the banks near their homes as a means of supplementing the family income [10, 38].

As fish assemblages change with variations in nature (e.g., hydrology), fishers use different fishing gear for tar-geted species based on natural environmental conditions, indicating a “learning ability of fishers” to adapt to natural fluctuations. Men also generally travel by motorized boats to fish far from their homes, while women and children practice marginal fishing using other types of gear, such that captured species would be expected to differ between genders. In this context, the present study aims to test the hypothesis that the hydrological cycle of the Araguaia River influences the activity of small-scale commercial fishing. We predict the following: fishery yield is influenced by the hydrological regime; the main species exploited through artisanal fishing varies with the hydrological regime; and both yields and main exploited species vary between male and female fishers due to differences in fishing sites and gear used.

Materials and methods

Study area

The Araguaia River rises in the Caiapó hills near Emas National Park at the municipality of Mineiros in the state of Goiás (GO), and empties into the Tocantins River, form-ing an extensive river system linking the Brazilian Mid-west Region with the north of Brazil. The river acts as a natural boundary, first between the states of Mato Grosso

and Goiás, then between Mato Grosso and Tocantins, and finally, between Pará and Tocantins. Over 2,000 km in length, the river is largely navigable, and can be divided into upper (450 km), middle (1,505 km), and lower (160 km) sections [14].

To implement this study, interviews were conducted with fishers from nine fishing settlements situated along the so-called lower Araguaia River, encompassing the munici-palities of Palestina do Pará, São Geraldo do Araguaia, and Piçarra in the state of Pará, and Ananás, Araguatins, Ara-guanã, Aragominas, Riachinho, and Xambioá in the state of Tocantins. The section of the river evaluated encompassed an area of approximately 16,000 km2 (190 × 85 km) and a distance of approximately 270 km along the Ara-guaia River, with central coordinates of 6°8′14.62″S and 48°19′52.86″W (Fig. 1).

Hydrological regime

In the Araguaia River near the city of Xambioá–TO, the lowest recorded flow occurred in 1971 and the highest in 1979 (Fig. 2). According to Cetra and Petrere [15], the cycle of flooding in the Araguaia River can be divided into four periods: a high period (H) from February through April, when the river enters the floodplain and fishing activity begins; an ebb period (E) from May through July, when the flow of the river begins to slow; a low period (L) from August through October, when flows are reduced and the river is restricted to its main channel, exposing large beaches; and a rising period (R) from November through January, when the rains begin and the river level starts to rise. The rising period marks the beginning of reproductive migration, and fishing activity is therefore prohibited in the region at this time.

Data collection and processing

Data collection was performed by means of interviews con-ducted with 562 artisanal fishers (195 women and 367 men) between March and June 2009, encompassing the areas of operation of nine fishing colonies on the lower Araguaia River. The interview process included completing a ques-tionnaire to gather data regarding the fishing sites, species caught, fishing gear used (net, longline, handline, cast net, or rod), time periods of operation (high, ebb, or low), and yield per period. The interviews were conducted during scheduled meetings at the fishing colonies and in visits to riverside communities, as well as by approaching fishers at major fish landing sites, as was suggested by Camargo and Petrere [16] and Silva [17].

To identify the main species captured, a structured ques-tion was asked of fishers in which they were to rank the five most frequently captured species in each fishing period.

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This information was summarized via correspondence anal-ysis (CA, described in McCune and Grace [18]) to obtain the largest gradients of variation among the main species catches. These gradients were subsequently analyzed using bi-factorial analysis of variance (ANOVA), followed by Tukey’s post hoc test, considering fisher gender and fishing period as sources of variation, with a 5 % significance level.

The correspondence analysis was performed with the aid of PC-ORD version 4.0 software [19], and the factorial ANOVA followed by Tukey’s post hoc test was conducted using Statistica™ version 7.0 software. The influence of

fisher gender and the period of the hydrological regime on the total fish yield was evaluated using bi-factorial ANOVA followed by Tukey’s post hoc test using Statistica™ ver-sion7.0 software.

To quantitatively assess the fishing gear used for cap-tured species, fishers were asked another structured ques-tion in which they were to rank the five most frequently captured species by each type of gear. This information was also summarized using correspondence analysis (CA, described in McCune and Grace [18]) to obtain the largest gradients of variation in the gear.

Fig. 1 Region surrounding the lower Araguaia River, which acts as a natural division between the states of Pará and Tocantins, showing the munici-palities where interviews were conducted with fishermen

Fig. 2 Time-series of the water level of the Araguaia River between 1970 and 2009, with emphasis on the mean and the 2009 series. Source: modified from Agência Nacional de Águas [ANA] (National Agency of Waters) [14]

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Results

Among the species recorded in the artisanal fisheries, the most important were from the order Characiformes, from the families Anostomidae for Leporinus friderici, Characi-dae for Myleus sp., and Prochilodontidae for Prochilodus nigricans. In the order Siluriformes, the family Auchenip-teridae, particularly the species Ageneiosus inermis, stood out in terms of the fishing catch. A list of the main spe-cies caught among artisanal fisheries in the lower Araguaia River region is shown in Table 1.

The correspondence analysis summarized 40 % of the total variability in the rankings of the main species catches between men and women during the high, ebb, and low periods. Axis 1 accounted for 23 % of the asso-ciated variability, primarily separating the species Myleus sp., Leporinus spp., and Ageneiosus inermis from Prochilo-dus nigricans, Hydrolycus armatus, and Serrasalmus spp. Axis 2 accounted for 17 % of the variability, where the spe-cies Prochilodus nigricans, Myleus sp., Semaprochilodus brama, and Leporinus spp. were scored with more positive values, while Ageneiosus inermis, Cichla spp. and Ser-rasalmus spp. showed more negative coefficients. Twelve other species were concentrated in the central region of the ordination (Fig. 3).

According to bi-factorial ANOVA applied to the axes, the gender of the fishers and the fishing period showed no interactive effects, but the main effects of both fisher gen-der and fishing period were significant in relation to axis 1 (F(1, 1680) = 11; p < 0.001; F(2, 1680) = 68; p < 0.001, respec-tively), while only the fishing period had an effect on axis 2 (F(1, 1680) = 35; p < 0.001, Fig. 4). These results indicate that a greater proportion of the Myleus sp., Leporinus spp., and Ageneiosus inermis specimens were captured by men, while women captured a larger percentage of Prochilodus nigricans, Hydrolycus armatus, and Serrasalmus spp.

During the high-water period, a greater proportion of Myleus sp., Prochilodus nigricans, Semaprochilodus brama, and Leporinus spp. were captured, whereas more Ageneiosus inermis, Cichla sp., and Serrasalmus spp. were captured during the low-water period. The remaining 12 species were more predominant during the ebb period. With regard to species composition of catches per fishing period, the species caught during the low and ebb periods were similar, and differed from those captured during high water levels.

Table 1 List of species caught through artisanal fishing in the lower Araguaia River

Taxonomic group Code

Order Characiformes

Family Anostomidae

Leporinus friderici/Leporinus spp. Lepor

Family Characidae

Myleus sp. Myleu

Serrasalmus maculatus/Serrasalmus spp. Serra

Family Curimatidae

Psectrogaster amazonica Psect

Family Cynodontidae

Hydrolycus armatus Hydro

Family Erythrinidae

Hoplias malabaricus Hopli

Family Hemiodontidae

Anodus orinocensis Anodu

Family Prochilodontidae

Prochilodus nigricans Proch

Semaprochilodus brama Semap

Order Perciformes

Family Cichlidae

Cichla kelberi/Cichla piquiti Cichl

Geophagus sp. Geoph

Family Sciaenidae

Plagioscion squamosissimus Plagi

Order Siluriformes

Family Auchenipteridae

Ageneiosus inermis/Ageneiosus ucayalensis Agene

Family Doradidae

Pterodoras sp. Ptero

Family Loricariidae

Baryancistrus sp. Barya

Family Pimelodidae

Pseudoplatystoma reticulatum Pseud

Hypophthalmus marginatus Hypop

Zungaro zungaro Zunga

Phractocephalus hemioliopterus Phrac

Pinirampus pirinampu Pinir

Fig. 3 Ordination of species caught by men and women during the high, ebb, and low periods by correspondence analysis (CA) on axis 1 (CA 1) and axis 2 (CA 2). Species codes are identified in Table 1

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When the total fishery yield per day per fisher was assessed using bi-factorial ANOVA, no significant inter-action was observed between fisher gender and period of the hydrological cycle. However, a significant main effect was observed for the hydrological cycle (F(2, 1680) = 36; p < 0.001), showing differences among the three phases (Fig. 5): the fishery yield was significantly higher in the low-water season, when the catch per unit effort (CPUE) was 24.8 kg/fisher/day, compared with 19.9 kg/fisher/day in the ebb period and 13.8 kg/fisher/day during high water levels.

Ordination of main species caught by gear type using correspondence analysis (CA) summarized 80 % of the variability in two axes (axis 1 = 46 % and axis 2 = 34 %). Axis 1 grouped the species Zungaro zungaro, Pinirampus pirinampu, Ageneiosus inermis, and Pseudoplatystoma reticulatum with handline and longline fishing gear types,

while Prochilodus nigricans and Baryancistrus sp. were caught more frequently with cast nets. The other species were located in more central positions in the correspond-ence analysis, most of which were caught using gill nets, except for Leporinus spp. and Hoplias aff., which were largely caught using rods (Fig. 6).

Discussion

The range of species caught and the diversity of gear used among men and women in the artisanal fisheries of the lower Araguaia River demonstrate a lack of a single

Fig. 4 Mean values ± 95 % confidence interval for axis 1 (horizontal bars) and axis 2 (vertical bars), according to a fisher gender (M men, W women) and b fishing period (H high, E ebb, L low). Non-overlapping bars show significant differences according to Tukey’s test

Fig. 5 Mean values ± 95 % confidence interval for fishery yield (CPUE) according to fisher gender and fishing period. Non-overlap-ping bars indicate significant differences according to Tukey’s test

Fig. 6 Ordination of the main species caught by fishing gear type (GN gill net, CN cast net, LL longline, HL handline, R rod) through correspondence analysis (CA)

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target species and illustrate the multiple efforts expended in fishing activities. Our results show 13 families and 20 fish species among catches from these fisheries. The order Characiformes was the most frequently captured, followed by Siluriformes and Perciformes. Among the recorded families, Pimelodidae (23 %), Cichlidae (14 %), and Characidae (14 %) were the most common in catches. The predominance of Characiformes and Siluriformes compared to other orders has also been found in ichthyo-faunal surveys conducted in tropical regions [20, 21], and the families Prochilodontidae and Pimelodidae were previ-ously recorded as a component of fishery landings in the Tocantins River basin [15, 22].

The fish fauna caught by the artisanal fisheries of the lower Araguaia River included a mixture of lowland Amazon river species, including Phractocephalus hemio-liopterus, Prochilodus nigricans, and Semaprochilodus brama, and other species typical of the Tocantins River basin such as Cichla kelberi, Cichla piquiti, and Hypoph-thalmus marginatus. In this respect, the species diversity represents a peculiar combination, reflecting both high abundance and species richness [21, 23, 24]. The preva-lence of Characiformes in the composition and structure of fish populations of the Araguaia–Tocantins and other tropical basins has been well described in the literature, as have the seasonal changes related to variations in river flow [16, 20, 25].

The results of this work demonstrate that the diversity of species caught by artisanal fisheries of the Araguaia River is indeed influenced by the hydrologic regime. Similar results have been observed in upland rivers, where seasonal variations in water levels can, to a varying degree, deter-mine food and shelter availability, reproduction, growth, mortality, competition, and predation [26–30]. In addition, species display different reproductive strategies, and the flood pulse is a critical determinant of the composition and structure of these fish assemblages, as increases in ampli-tude and duration of the flood pulse and the level of distur-bance in flooded regions acts to increase species richness [6, 8, 31–33]. Studies by Agostinho [31] and Suzuki [34] conducted in the floodplain of the Paraná River found that major flooding was associated with greater species rich-ness, without affecting the diversity index (Shannon) for the various habitats of the region.

The prevalence of Prochilodus nigricans, Myleus sp., and Semaprochilodus brama across the entire catch period can be explained by the formation of schools that are suitable for recruitment after the end of the reproductive period (rising water levels). The catch success for these species was observed in the Tocantins River basin by Cetra and Petrere [15], who found that Prochilodus nigricans and Semaprochilodus brama accounted for 70 % of land-ings. According to Brazilian national fishery statistics for

inland production by species, the fish resources showing the greatest numbers of landings in 2010 were Prochilo-dus nigricans (28,432 t) and Semaprochilodus brama (16,435 t).

Species richness increased during the low-water and ebb seasons. With reduced river water levels, there is an increase in fish density and a reduction in escape sites, thus enhancing the odds of capture. During these periods, fish-ing in the lower Araguaia River occurs close to the Santa Isabel and Piçarra waterfalls, where fishers camp on the islands formed in the main body of the river, while in the rainy season the waters invade the margins, favoring the dispersal of species [15].

Studies by Lamberth [35] and Gillson and Suthers [3] have shown that drought and flood events cause fluctua-tions in fishery resources, resulting in altered species com-position of landings and changes in capture techniques employed and revenue generated. Other factors reported to be associated with differences in fishing captures between high- and low-water periods are related to changes in tur-bidity and dissolved oxygen availability due to a greater availability of organic matter in flooded margins [8, 20, 21].

Considering the fishery yields (kg/fisher/day) for the high-water, ebb, and low-water seasons in the lower Ara-guaia and the number of active artisanal fishers in the region (562 fishermen, Nsample = 98 %), and taking into account only the days fished (Ø = 5 days), we estimate that the average fishery landings for 2009 amounted to 1,278.55 t during the high-water season, 1,868.65 t during the ebb sea-son, and 2,458.75 t during the low-water season, for a total of 5,605.95 t of fish for the assessed period. According to national fishing statistics [13], the annual yield from conti-nental extractive fishing in the state of Tocantins—referring to the Araguaia and Tocantins Rivers—is 1,836.9 t. Thus, in the present analysis, the recorded yield for the fisheries is 305 % of the official annual estimate, evidence that the official landing data for the region’s fisheries are underes-timated, which leads to erroneous or delayed decisions on the part of public managers. The method for determining official statistics in Brazil should be reviewed in order to avoid such issues in the future.

The fact that fishery yield is influenced by the hydro-logical regime suggests that disruptions in the hydrological regime of the Araguaia River may also cause a reduction in landings [21, 33, 36, 37]. Thus, identifying and quantifying the relationships between biological characteristics, yields, and hydrological regimes are essential steps for the man-agement of fisheries in rivers and reservoirs [8, 32].

Based on the species ordination according to fisher gender and the selection of fishing gear used for artisa-nal fishery catches in the Araguaia River, it was possible to determine that gill nets and cast nets were the types of

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equipment used most frequently among men and women, with men making use of gill nets and handlines, while women used cast nets and rods more often. Gill nets and longlines are employed passively along the banks of the Araguaia River and its tributaries, while cast nets, rods, and handlines are employed at specific times and during certain periods. As was observed by Cetra and Petrere [15], gill nets are used in two ways in the Araguaia–Tocantins basin: passively, placed on the river margins; and actively, where fishers place the net between two canoes, taking advantage of the current.

The fact that women use cast nets and rods as their pre-ferred equipment is a reflection of both the species that they capture and their lifestyle. Women remain in the home, which is often situated on the banks of the Araguaia, taking care of their children and fishing only at certain times of the day. Men, on the other hand, travel greater distances in search of fish, nearly 50 km, until they reach the uninhab-ited areas of the Santa Isabel and Piçarra waterfalls, where they remain in groups of three to five fishers for entire weeks at a time. Fishing in these areas is focused mainly on species that occur in smaller proportions in regions near their homes, such as Myleus sp., Leporinus spp., and Age-neiosus inermis, and is conducted passively, with gill nets and longlines, and actively with handlines, cast nets, and rods. In the Tocantins basin, the combination of gill nets and cast nets has been reported to be responsible for over 90 % of fishery yields during the low-water season [15, 38].

In Brazil, the reproductive migration of fish occurs between November and February during the rising water period in the Araguaia River basin, which is regulated through normative decrees, and onboard fishing is prohib-ited. Fishing from the banks of rivers, however, is allowed. Our results thus indicate that this type of fishing would still be exercised, as fishing by women largely occurs on the banks of the Araguaia River, capturing smaller species such as Prochilodus nigricans, Hydrolycus armatus, and Serras-almus spp. Therefore, it is important to monitor stock con-ditions among these fish species and to identify future stock management needs.

The results of this study indicate that flood events influ-ence the activities of artisanal fisheries of the Araguaia River, corroborating the hypothesis that fishery yields and main exploited species vary among the phases of the hydro-logical cycle (high, ebb, and low). Although we found no difference between fisher genders with regard to yields, we did observe differences in the main species caught. The study results also confirmed our hypothesis that differences between fishermen and fisherwomen in species composi-tion of catches were influenced by the types of gear used and fishing sites explored. Such knowledge may assist water resource managers in the regulation of fishery land-ings with regard to both species exploited and amount of

fish caught per period as well as with developing strategies for yield optimization.

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