Artisanal shrimp fishers’ local ecological knowledge is a largely social construct, reinforcing the importance of well-crafted public policies for efficient and socially equitable fisheries management. This calls for the incorporation of LEK as an important supporting information for conservation and sustainable use of socio-ecological systems [67, 68]. Our results also show that, as anticipated, LEK is greater among experienced prawn fishers, though this difference is less for directly applied themes as reproduction and migration, and greater for less applied themes such as feeding, growth and mortality. Another important consideration is the aggregating power of fishers’ specific local knowledge, generating connectivity linked to the sharing of similar bioecological knowledge about the exploited species.
LEK is known to be influenced by several factors, including fishers age [6]. However, in the context of small-scale artisanal shrimp fisheries, fishers were relatively knowledgeable about shrimp reproduction and migration, regardless how old they were. The fact that these species have a continuous reproductive cycle allow fishers to follow the species reproductive cycles during the year, mainly for white and pink shrimps that migrate into estuarine environments to reproduce [69–71]. The acquisition and evolution of LEK is expected to progress through passive adaptive processes according to the cumulative experiences in the environment [72, 73]. Our study suggests this only occurs for lower rated topic themes (feeding, mortality and growth) and older fishers (≥ 41 years). Thus, the experience acquired over the years by older fishers is mainly manifested in knowledge of more refined and difficult to observe bioecological topics.
The similarity in the quality of ecological information on exploited species indicates that there is considerable information sharing or homology of interests. The themes most often cited as part of LEK were similar across species, contrary to expectations due to known interspecific bioecological differences (e.g., Dall et al. 1990) and attention bias toward higher revenues [74], e.g., the higher priced shrimp species. The main bioecological difference between species, discriminated by hypothetical-deductive knowledge, is related to migration. White shrimp (P. schmitti) and pink shrimp (P. subtilis) need the estuary to complete the life cycle [38, 39, 75, 76], while the seabob shrimp (X. kroyeri) completes its life cycle exclusively at sea [33, 40, 77]. Another difference between species is the age at first maturation. Pink shrimps mature in 2 to 3 months [78]; white shrimp from 6 to 7 months [36], and the seabob shrimp in 12 months [79, 80]. Notwithstanding these bioecological differences, thematic knowledge was similar for all species as shrimp fisheries are multispecific allowing similar connection of fishers to all species life cycles. Thus, neither abundance nor sales value is as important as fishers interest and the frequency and constancy of observation.
There was high similarity in LEK between informants from different locations, consolidated in information networks on bioecological themes. This indicates that similar environmental conditions and experiences lived by fishers drive similarities in the acquisition, retention and sharing of knowledge (Berkes et al., 1993; Ruddle and Ruddle, 1991). Social actors involved in sharing ecological information interact at different scales [3], mainly at fishing harbors and fishers centers – called colonies or “colônias” in local language [83]. The intragroup similarity of fishers on bioecological information on species is consequently determined by the operational fisheries affinity. The fishing gear with greater power to catch shrimp is regionally similar, usually single or double bottom trawls [36, 37], not differing by species. The LEK similarity shows that the connection of knowledge between fishers is anchored in bioecological issues relevant to independent social groups, generating similarity of knowledge even though there is social and cultural heterogeneity between communities. Moreover, the fact that the seabob shrimp life cycle is specific, involving movements between estuaries and the open sea, does not apparently affect LEK about the species. This may be related to the lower interest in this species due to its lower economic value.
It is also noteworthy that these species are close to the limits of overfishing [38–40], and thus need to be effectively monitored. According to our findings, artisanal fishers’ LEK is focused on the themes on reproduction and migration. However, to information on growth and mortality is more restricted to more experienced fishers. Older fishers are typically less active, but have high status within the community, providing inputs to other fishers and acting as important nodes in local network.
Information sharing is essential in natural resource management processes that contain a wide variety of social actors, such as artisanal fishers. This sector is essential for coastal food security, using common resources that require participatory fisheries management [14] planned at local, and even regional, scales [84–86]. Possible reduction in the flow of ecological information could limit the wider dissemination of LEK [12, 13], generating subgroups affected by local species importance. Differences on species importance among harbors, e.g., white shrimp at Baía Formosa responding to 35,1% of shrimp yields; against 29,4% at Pontal do Peba and 25% at Sirinhaém [36], may generate differences on local community learning. Therefore, social networks feed by common needs potentially affect productivity and their social survival with high connectivity among the networks nodes. Facing results, reproduction and migration themes were considered essential in promoting intercommunity dialogue and with other decision makers aiming at participatory and effective fisheries management.
With respect to the main themes covered by the social networks, the intermediate centrality metric indicates information exchange in networks [23, 24]. Such exchange is essential for success in natural resource management planning and execution. The most relevant intermediate centrality metrics were on the themes of reproduction and species migration, and these themes could therefore be used to leverage collaboration among stakeholders. Networks must consider all existing knowledge, no matter coming from hypothetical-deductive methods or from LEK, either to improve fisher communities well-being, attending yield targets but also to conserve coastal biodiversity [72] that is essential to biological production. Therefore, for efficient management in the future, the themes of reproduction and migration could be considered as bridges for dialogue and decision-making, reconciling conservation of populations with sustainable economic revenues for the fishing communities.
The bioecological similarity in the LEK of the species evaluated in different areas suggests that regional level planning of resource management could be effectively implemented. Current legal determinations include different no-take reproductive periods on the Northeast coast during the last 20 years (e.g., Dias-Neto 2011; Santos et al. 2013). These clearly lack justification and must be concluded, reducing conflict due to the displacement of fleets between fishing grounds. A fisheries agreement validated by government authorities based mainly on experienced fishers LEK and supplemented by scientific advice will reduce conflicts and safeguard fisher communities. In addition, scientific research on topics where LEK is weak (e.g., growth and mortality), with participative dissemination of results to all stakeholders may improve management efficiency and the communication quality among networkers.
Ecological information provided by the fishers can and should be combined with that generated by experimental science to better support the assessment of fisheries [88] and even to predict changes in the spatial distribution of species [89] with positive social, economic and environmental outputs. Such co-production of research [90] can improves dialogue and the effectiveness of fisheries management. Following common-pool resources principles, mainly collective choice arrangements monitoring methods and eventual sanctions to illegal actions [91] are facilitated when managers value the knowledge of fishers [26, 92]. Researcher-manager-fisher cooperation should be used to make LEK and ecological science a basis for social and environmental sustainability, providing a robust information-driven platform to respond to challenges of climate change and other anthropogenic impacts.