Traditional botanical knowledge of artisanal fishers in southern Brazil

Local knowledge is being lost by many cultures in areas of high biodiversity, especially when activities related to the use of natural resources are gradually abandoned in favor of specializing in market-related activities [1]. Research on the knowledge, use, and management of natural resources by local populations is important because it confirms the value of these cultures and contributes to the self-sufficiency of these populations.

Several researchers have gathered ethnobotanical knowledge from communities located in the coastal area of the Brazilian Atlantic Forest, including the knowledge and use of plants [2–8], the knowledge and use of medicinal plants [9–12], plant management [13], and fishing ecology [1], among others. However, most studies in the coastal area of the Atlantic Forest have been restricted to the southeast coast, and few have addressed fishing communities [14]. Although other studies have examined the ethnobotany of similar groups that practice artisanal fishing (which are characterized by small scale production, the use of small vessels, and work within the immediate family, other relatives or neighborhood groups in which the produce is usually sold to intermediaries without the involvement of industry in marketing and fish processing [15], culturally, these groups can be quite different [14, 16].

In Rio Grande do Sul State, southern Brazil, approximately 12,200 active artisanal fishers depend on fishing as their main economic activity [17]. The most extensive lagoon system in Latin America is located on the coastal plain of the state, including the Lagoa dos Patos, also called the “mar de dentro” [“the inland sea”] [18]. Depending on location, fishers living in the lagoon area do not fish in the ocean but share limited fishing territories in the lagoon. The Lagoa dos Patos, according to Kalikoski et al.[19], is an important nursery ground for many commercially important species of fish and crustaceans. During the twentieth century, the lagoon was a center of artisanal fishing in southern Brazil and contributed significantly to national fish and shellfish production.

Urbanization is increasingly frequent in developing countries [20]. In these transformations, rural areas begin to be included in the urban area, producing a new category: rural-urban areas.

In Rio Grande do Sul, many fishing communities have experienced this process [21, 22]. Simultaneously, several studies have examined artisanal fishing in sea [23, 24] and inland [25–28] waters, but none have focused on the ethnobotany of these fishing communities. The present study attempts to answer the following question: is the local botanical knowledge of the artisanal fishers of the rural-urban district of Lami still active, even since the district’s insertion into the metropolitan region of Porto Alegre? In this context, the objectives are as follows: a) to characterize the history of the development of socio-economic activities in Lami, emphasizing artisanal fishery; b) to characterize the local botanical knowledge of the artisanal fishers from Lami and to determine any changes in knowledge in relation to preceding generations; and c) to characterize traditional knowledge about medicinal plants and identifying species that are more important to the fishing communities.

The artisanal fishing community of Lami comprises 15 families, in which the mean age of the subjects was 50 years, ranging from 31 to 75 years. Most subjects had not completed elementary school. Two fishers were natives of Lami, and six were from nearby regions, including other neighborhoods of Porto Alegre and the nearby municipality of Viamão. The remaining fishers were from other cities in Rio Grande do Sul. Most of the subjects had lived in Lami for several years (mean = 35); the oldest resident had lived there for approximately 60 years and had fished for 47 years; the newest resident had fished there for four years.

Most species are acquired exclusively by cultivation (64 spp.), extractivism (25 spp.), or purchase (9) (Figure 2). Significant differences were observed in these proportions (χ² = 40.75; p < 0.0001), reinforcing the importance of cultivation as the main method by which the Lami fishers acquire plants. Only 13 species were obtained in more than one way (Figure 2, Table 2).

Most native plants are acquired through extractivism (32 spp.), although a nearly identical number of native plants are cultivated (26 spp.) (Figure 2). These proportions did not differ significantly (χ² = 0.21; p = 0.76), indicating that the use of native plants in the region cannot be understood as a primarily extractivist activity because the arboreous species are obtained by extractivism and the herbaceous species are obtained by cultivation. In contrast, most of the exotic plants are cultivated (47 spp.), and only three are obtained by extractivism in non-managed areas (Figure 2), with significant differences in these values (χ² = 38.72; p < 0.0001). According to our interview subjects, the exotic species collected in non-managed areas include the trees Cinnamomum verum, Eucalyptus sp., and Punica granatum (Table 2).

Herbaceous plants were the most species-rich group (43 spp.), followed by trees (38 spp.), shrubs (24 spp.), climbers (5 spp.), and epiphytes (1 spp.) (Figure 3). The richness of herbaceous plants was not significantly different from that of trees (χ² = 0,31; p = 0.66) but was statistically greater than that of the remaining groups (p < 0.05). Thus, the proportions of herbaceous and arboreal species mentioned by members of the community are similar. Most of the herbaceous and shrubby plants mentioned are exotic (26 and 14 species, respectively), but this richness is not significantly different from the number of native plants that was recorded for these two groups (17 and 10 species, respectively) (Figure 3) (herbaceous: χ² = 1.88; p = 0.22; shrubby: χ² = 0.67; p = 0.54). Despite this similarity, it appears that exotic herbs and shrubs are most strongly represented in the repertoire of local knowledge. In contrast, the group of arboreal species comprises predominantly native species (26 spp.), significantly more than the richness of exotic arboreal plants (12 spp.) (Figure 3) (χ² = 5.16; p = 0.03).

Most of the plants mentioned by the fishers were collected for medicinal use (69 spp.), followed by use as human food (32 spp.) and use in activities related to fishing (17 spp.) (Figure 4). All 15 interviewed fishers cited plants in the medicinal category. The richness of medicinal species mentioned was higher than that of all other categories identified in this study (p < 0.05). This finding can be understood if we consider that the medicinal category includes a wider variety of indications of use than other categories, requiring a larger repertoire of plants for treatment.

Analysis of the relationship between the origin and the growth habit indicated that among medicinal plants, native and exotic species contribute similar proportions of species (Figure 4) (χ² = 0.36; p = 0.63); this was also true for the human food category. However, species used for fishing activities and as fuel are predominantly native to the region. Plants used as condiments, for mystical purposes, and as animal food are exclusively exotic species (Figure 4).

Comparison between the usage categories and the methods of obtaining the plants showed that the Lami fishers obtain most of their medicinal plants through cultivation (51 spp.), followed by extractivism (21 spp.) and purchase (8 spp.) (Figure 5); these numbers were significantly different (χ² = 36.47; p < 0.0001). Extractivism was the main method used to obtain plants used for fishing and firewood (Figure 5). Few species are used for firewood, i.e., few are subject to this type of harvesting pressure. Curiously, the usage category associated with fishing included the most species acquired by purchase (Figure 5), although these were mostly native species (Figure 4).

Medicinal use

The largest numbers of medicinal plant species were used to treat ailments of the digestive system (20 spp.), followed by the respiratory system (16 spp.), genitourinary system (15 spp.), parasitic and infectious diseases (14 spp.), skin lesions (13 spp.), and diseases of the circulatory system (11 spp.) (Figure 6).

Aloe arborescens was considered the most versatile plant, being indicated for six categories of disease (Table 3), followed by Foeniculum vulgare, Cymbopogon citratus, and Aristolochia triangularis, each of which was indicated to treat five bodily systems. However, most of the medicinal species mentioned (65%) were indicated for only one ailment category.

Species	Disease category	Number of citations foruse(s) of species	Number of citations of the most-mentioned use	AMU	CF	AMUC
Aloe arborescens	Skin lesions, hair treatment, parasitic and infectious diseases, respiratory system, digestive system, neoplasms	21	11	52.4	1.90	100
Plectranthus barbatus	Digestive system	8	8	100	0.72	72.72
Dodonaea viscosa	Digestive system	7	7	100	0.63	63.63
Plectranthus ornatus	Digestive system	7	7	100	0.63	63.63
Eugenia uniflora	Digestive system	6	6	100	0.54	54.54
Foeniculum vulgare	Digestive system, circulatory system, nervous system, genitourinary system, nutrition and metabolism	11	6	54.5	1	54.54
Cunila microcephala	Respiratory system, nervous system, parasitic and infectious diseases	7	5	71.4	0.63	45.45
Mikania laevigata	Respiratory system	5	5	100	0.45	45.45
Achyrocline satureioides	Digestive system, respiratory system, nervous system	8	5	62.5	0.72	45.45
Psidium guajava	Digestive system	4	4	100	0.36	36.36
Bromelia antiacantha	Respiratory system	4	4	100	0.36	36.36
Citrus sp.	Respiratory system	4	4	100	0.36	36.36
Anredera cordifolia	Aphrodisiac, skin lesions, circulatory system	5	4	80	0.45	36.36
Persicaria hydropiperoides	Musculoskeletal system and conjunctive tissue, skin lesions, poisoning	5	4	80	0.45	36.36
Casearia sylvestris	Circulatory system, nutrition and metabolism, abortive, skin	6	4	66.7	0.54	36.36
Cymbopogon citratus	Circulatory system, digestive system, respiratory system, nervous system, parasitic and infectious diseases	12	4	33.3	1.09	36.36
Aristolochia triangularis	Skin lesions, poisoning, digestive system, mouth and throat, circulatory system	8	3	37.5	0.72	27.27
Microgramma sp.	Genitourinary system	3	3	100	0.27	27.27
Citrus sinensis	Respiratory system	3	3	100	0.27	27.27
Alternanthera brasiliana	Parasitic and infectious diseases	2	2	100	0.18	18.18
Psidium cattleianum	Digestive system	2	2	100	0.18	18.18
Persea americana	Hair treatment, skin lesions, skin	4	2	50	0.36	18.18
Artemisia absinthium	Digestive system	2	2	100	0.18	18.18
Sechium edule	circulatory system	2	2	100	0.18	18.18
Phyllanthus tenellus	Genitourinary system	2	2	100	0.18	18.18
Punica granatum	Digestive system	2	2	100	0.18	18.18
Dolichandra unguis-cati	Genitourinary system, respiratory system, digestive system	4	2	50	0.36	18.18
Malva sylvestris	Mouth and throat	2	2	100	0.18	18.18
Euphorbia tirucalli	Neoplasms	2	2	100	0.18	18.18
Aloysia citriodora	Circulatory system, digestive system, respiratory system, parasitic and infectious diseases	5	2	40	0.45	18.18
Ruta sp.	Abortive, poisoning, skin lesions	2	1	50	0.18	9.09
Petiveria alliacea	Poisoning, skin lesions	1	1	100	0.09	9.09
Plantago sp.	Parasitic and infectious diseases	1	1	100	0.09	9.09
Plantago tomentosa	Parasitic and infectious diseases, genitourinary system	1	1	100	0.09	9.09
Aloysia gratissima	Respiratory system	1	1	100	0.09	9.09
Aloe maculata	Skin lesions	1	1	100	0.09	9.09
Vitex megapotamica	Nutrition and metabolism, genitourinary system, circulatory system, respiratory system	4	1	25	0.36	9.09
Sida rhombifolia	Genitourinary system, circulatory system	2	1	50	0.18	9.09
Ocimum carnosum	Digestive system	1	1	100	0.09	9.09
Ocimum americanum	Respiratory system	1	1	100	0.09	9.09
Gamochaeta sp.	Skin lesions	1	1	100	0.09	9.09
Ficus cestrifolia	Skin	1	1	100	0.09	9.09
Origanum majorana	Respiratory system	1	1	100	0.09	9.09
Rosmarinus officinalis	Nervous system, circulatory system	2	1	50	0.18	9.09
Equisetum hyemale	Circulatory system	1	1	100	0.09	9.09
Piper sp.	Genitourinary system, parasitic and infectious diseases	2	1	50	0.18	9.09
Gymnanthemum amygdalinum	Digestive system	1	1	100	0.09	9.09
Euphorbia prostrata	Genitourinary system	1	1	100	0.09	9.09
Tanacetum vulgare	Parasitic and infectious diseases, skin lesions	2	1	50	0.18	9.09
Pelargonium graveolens	Parasitic and infectious diseases	1	1	100	0.09	9.09
Erythroxylum argentinum	Respiratory system	2	1	50	0.18	9.09
Zea mays	Genitourinary system	1	1	100	0.09	9.09
Petroselinum sativum	Genitourinary system	1	1	100	0.09	9.09
Chaptalia nutans	Skin lesions	1	1	100	0.09	9.09
Sideroxylon obtusifolium	Nutrition and metabolism	1	1	100	0.09	9.09
Costus spiralis	Genitourinary system, parasitic and infectious diseases	1	1	100	0.09	9.09
Leandra australis	Digestive system	1	1	100	0.09	9.09
Jodina rhombifolia	Genitourinary system, respiratory system	2	1	50	0.18	9.09
Baccharis sp.	Genitourinary system, nutrition and metabolism	1	1	100	0.09	9.09
Melissa officinalis	Parasitic and infectious diseases	1	1	100	0.09	9.09
Mentha sp.1	Parasitic and infectious diseases	1	1	100	0.09	9.09
Morus nigra	Genitourinary system	1	1	100	0.09	9.09
Solanum sp.	Digestive system, parasitic and infectious diseases	2	1	50	0.18	9.09
Mentha sp.2	Nervous system	1	1	100	0.09	9.09
Ocimum gratissimum	Digestive system	1	1	100	0.09	9.09
Passiflora sp.	Nervous system	1	1	100	0.09	9.09
Achillea millefolium	Skin lesions, poisoning	2	1	50	0.18	9.09
Helianthus annuus	Skin lesions, skin	1	1	100	0.09	9.09

Regarding the agreement on the main use (AMUc), Aloe arborescens (AMUc = 100%) (used to treat skin lesions), as well as Plectranthus barbatus (72.73%), Dodonaea viscosa (63.64%), Plectranthus ornatus (63.64%), Eugenia uniflora (54.54%), and Foeniculum vulgare (54.54%) (all used to treat digestive system ailments) (Table 2), exhibited high agreement. These plants may be interesting for pharmacological study regarding their possible therapeutic efficacy. Except for D. viscosa and E. uniflora, which are native plants acquired by extractivism, all of these plants are exotic cultivated species, emphasizing their importance in the local medical system.

Approximately 56% of the plants that were indicated to have medicinal properties exhibited AMUc values of less than 10% (Table 3). These species were all cited infrequently, i.e., they were known to a few or perhaps only one person. Furthermore, most of these plants are cultivated exotic (52%) or native species that are collected by extractivism (26%).

The similarity in the total richness of native and exotic species reveals the dynamism of the local botanical knowledge and an ability to adjust to the requirements of the local people, reflecting a pattern that has previously been documented in the literature. If the Lami fishing community live in an area of strong urban influence, this may contribute to the inclusion of species that are widely used in general society; however, if the fishers live near a biological reserve, this may allow them to have closer contact with native plants. Methods to encourage the use of exotic plants rather than native species have been discussed [48–50], but the data obtained in Lami show that the usage rate of these species is balanced. The same pattern was identified by Voeks [51] while studying the traditional pharmacopeia of an area of the Atlantic Forest in southern Bahia.

In Lami, the plants obtained through cultivation are not restricted to exotic species because many native plants are obtained from fields, backyards, and community gardens. Again, this practice may be related to the presence of the Lami Biological Reserve because although the reserve contributes to the maintenance of local knowledge regarding the native flora, it also limits access to these resources, and the local community must compensate by growing culturally important native species. This response indicates the adaptive nature of traditional botanical knowledge.

The similar richness of useful herbs and trees reveals the balanced proportion of tree and herbaceous species, similar to the balance between native and exotic species. This similarity may reflect a local adaptive process that occurs because the community lives in an area where the use of forest resources is restricted. Thus, it is advantageous to expand the repertoire of knowledge, including species from different habits and biogeographical origins, because this expansion increases the reliability of resources: a temporarily unavailable plant can be replaced by another species. This practice is consistent with the utilitarian redundancy hypothesis, which states that the use of functionally similar species can be part of a strategy to maintain the resilience of local knowledge [48]. Thus, we found that the two most important usage categories to the community (medicinal and food) comprised similar proportions of native and exotic species.

The above discussion characterizes artisanal fishing in the studied region in that published studies have reported that useful flora tend to be dominated by exotic herbaceous species, especially in the medicinal category [49, 51–54].

The use of plant species to build boats and construct fishing-net floats appears to have been an important practice in the past in various parts of Brazil. These uses have also been reported by fishers in the state of Alagoas, Northeast Brazil [55]. Traditional plants have been outmoded by new materials, resulting in the loss of this knowledge by fishers in Lami, because few fishers have reported these uses in the past. The same applies to boat building because “timbaúva” (Enterolobium contortisiliquum) and “cedro” (Cedrela fissilis) were used in Lami, and Hanazaki [14] reported that these species were also used for boat building by “caiçaras,” a term used to describe traditional fishers in southern Brazil.

The predominant medicinal use of plants related to the digestive system, in many cases reflecting the population’s sometimes unhealthy eating habits. Additionally, plants used to treat respiratory-system diseases were commonly mentioned, mainly because of the harsh and variable winter climate in southern Brazil. Similar data were found in other cities in Rio Grande do Sul [56, 57] and other parts of Brazil [52, 58–60], indicating that the residents use medicinal plants as the first line of treatment for most common diseases.

The plant described as the most versatile, Aloe arborescens, was indicated for six disease categories. A. arborescens is widely cultivated and used for medicinal purposes in Brazil [40].

According to floral assessments of the region’s biodiversity [31, 38, 61–66], 594 species have been identified, of which 507 are native (85.35%) and 87 are exotic (14.65%). In this study, the knowledge and use of 113 species by artisanal fishers were recorded, of which 50 are native and 61 are exotic. The preference for exotic species, in principle, indicates that collection does not exert a strong pressure on native species and that use is compatible with conservation. This preference can be explained by the Azorean descent of the fishers. Rio Grande do Sul is largely influenced by European colonization, which implies the use of traditional plants of European origin, mostly for medicinal purposes. Additionally, it is perceived that most species used for medicinal purposes in the fishing community are herbaceous or bushy and more easily collected or cultivated. This pattern of use is found in many communities in Rio Grande do Sul [56, 57, 67, 68].

This paper reveals that the use pattern of plant species by the fishers who live near conservation units in rural-urban areas is compatible with the maintenance of their lifestyles and with conservation, and this use pattern should be encouraged as a conservation strategy for the co-existence of traditional populations in rural-urban areas.

Although the fishing community of Lami is located in a large city with easy access to modern conveniences, the fishers clearly still value and perpetuate their local botanical knowledge, mainly for medicinal use, human food, and fishing-related uses.

Our interview subjects exhibited good knowledge of the remaining vegetation in the region and of the importance of conservation. They also identified environmental degradation as a problem that affects and reduces their fishing activity.

The rescue of local knowledge and the interest of academic researchers contribute to valuing and respecting the way of life conducted by the traditional fishing community of Lami. In this community, knowledge of the past is combined with knowledge that has been recently incorporated by the community, emphasizing the cultural changes that this area of the city is experiencing.