Sawfish (Pristidae) records along the Eastern Amazon coast

Sawfishes are the most endangered cartilaginous fishes on the planet. Their external morphology facilitates entanglement in fishing nets and their K-selected life history hinders the recovery of exploited populations. The Eastern Amazon coast (EAC) is known to be an area where sawfishes occur in Brazil, but few studies have been conducted in the area to better understand their biology and ecology. The present study reports sawfish captures along the coast of Brazil’s second largest state. Data were collected from interviews with fishermen, a literature review, and media reports. In total, 23 captures were recorded between 1984 and 2016. Records include adults, a pregnant female with near-term embryos, juveniles, and young-of-the-year specimens. Most catches were reported in the Canal do Navio, an area under strong human pressure. Sawfish saws are valuable items and, for many anglers in precarious economic and social situations, high market prices eclipse the fishing prohibitions laid down under federal laws. Urgent research is required to understand sawfishes’ life history, identify their critical habitats, and effectively manage and conserve these species along the EAC.


INTRODUCTION
Sawfishes are large cartilaginous fishes, easily recognized by an enlarged rostrum shaped as a saw. They are distributed across coastal areas, estuaries, and freshwaters from tropical to subtropical regions -especially in shallow, sandy, or muddy bottoms. The saw is used mainly for feeding purposes, such as to scour the bottom for benthic prey or to capture free-swimming ray-finned fishes (Wueringer et al. 2012, Poulakis et al. 2017. However, rostral ex pansion is also the main cause of entanglement in fishing nets (Dulvy et al. 2016).
Sawfish populations are extremely susceptible to fisheries exploitation due to their K-selected life history (e.g. late sexual maturation, low fecundity, and long lifespan) (Thorson 1976). Currently, Pristidae is the most threatened elasmobranch family in the world, with 3 of its 5 species considered Critically Endangered (Pristis pectinata, P. pristis, and P. zijsron) and the other 2 species considered Endangered (Anoxypristis cuspidata and P. clavata) (Dulvy et al. 2016).
In Brazil, only P. pristis and P. pectinata occur (Charvet & Faria 2014). Their distribution seems to be restricted to northern areas of the country (Palmeira et al. 2013), where viable populations of sawfishes have been reported (Burgess et al. 2009, Charvet & Faria 2014). Fishing of both species is prohibited by Brazilian legislation (IN 05, MMA 2004, www. mma.gov.br/estruturas/179/_arquivos/179_ 051 22008033927.pdf). However, they continue to be caught off the northern coast. Fisheries in this region are mainly artisanal with small to medium-sized vessels of little autonomy using mostly drift nets (Begossi et al. 2012). According to Pauly & Zeller (2016), the fact that artisanal fisheries data are overlooked by regulating agencies leads to underestimation of catches, and is thus a major cause for the paucity of elasmobranch catch data worldwide, including the Brazilian coast.
Since there are limited data available for artisanal fisheries in the area, local ecological knowledge (Anadón et al. 2009) becomes useful for directing future research. In addition, local knowledge is essential to the evaluation of critical habitat for endangered species in areas lacking in scientific data (Reis-Filho et al. 2016). The present study aims to trace records of sawfish catches in the second largest coastal state of Brazil, Maranhão, through local ethnological knowledge, news reports, fisheries landings observations, and a literature review.

Study area
Locally known as Reentrâncias Maranhenses, the Maranhão Amazon coast (MAC) area consists of several estuaries forming indented areas with mangrove-dominated channels (Lessa et al. 1999). MAC is a dynamic area, with macrotidal interference (4− 7 m). In addition, the region includes the largest area of mangrove forests in Brazil, comprising an esti-mated 5414.31 km 2 (Souza-Filho 2005). The main mangrove species in the region are Rhizophora mangle, R. racemosa, R. harrissonii, Avicennia germinans, A. schaueriana, and Laguncularia racemosa. MAC has 2 distinct seasons: a wet season from January to June and a dry season from July to December. However, the average temperature year-round is 26°C, regardless of season (Teixeira & Souza-Filho 2009).
The Gulf of Maranhão ( Fig. 1) is the most important zone of MAC, both socially and economically. The area is highly productive (Azevedo et al. 2008), consisting of 3 estuaries under the influence of strong currents (Teixeira & Souza-Filho 2009). Fisheries in the MAC area are artisanal and target mainly the acoupa weakfish Cynoscion acoupa, tarpon Megalops atlanticus, and Brazilian Spanish mackerel Scom beromorus brasiliensis using drift nets (Lessa et al. 2016). Nutrient contents follow patterns observed for other rivers of the Amazon system, such as high organic matter input and turbidity (Azevedo et al. 2008). The Gulf of Maranhão suffers from pollution discharges from adjacent metropolitan areas (Silva et al. 2011). In addition, the gulf has a major channel (Canal do Navio) used for transportation of commodities through the Porto do Itaqui (one of the largest cargo ports of Brazil), with heavy and incessant traffic of cargo ships (www. emap. ma. gov. br/ porto-do-itaqui/ operacoesportuarias/ movimenta cao-de-carga).

Data collection
In January 2016 and 2017, eight traditional fishermen from the cities of Raposa and Vitória do Mearim where sawfish captures have been reported were interviewed using open questions regarding sawfish captures. Questions related to estimated total length (TL) and sex of the specimens, location and year of capture, and fishing gear used. Information about other areas of MAC was also provided by traditional fishermen from Raposa. These fishermen were considered qualified to provide data based on their knowledge acquired over decades of fishing across MAC and constant communication with fishermen from surrounding regions.
In addition, a literature review of published papers, books, and media reports about Maranhão State's elasmobranch fauna was carried out. Only records containing, at the least, capture location data were considered. Records of 2 rostra exposed in museum collections (Orla Viva NGO, a non-governmental organization and educational project for marine life conservation in São Luís, Maranhão) were also included in this analysis. Standard rostrum length was measured and TL estimated following Whitty et al. (2014). Specimens were identified following Faria et al. (2013). Life stage was estimated based on specimens' TL: birth (72-90 cm), juvenile (91-280 cm), and adult size (> 280 cm) (Last et al. 2016).

RESULTS
Between 1984 and 2016, a total of 23 sawfish catches were recorded in the study area. Specimens varied in size between 80 and 700 cm TL (Figs. 2 & 3; see also Fig. S1 in the Supplement at www. int-res. com/ articles/ suppl/ n034 p229 _ supp. pdf), comprising young-of-the-year individuals (80 cm TL), juveniles (100−300 cm TL), unsexed mature individuals (> 300 cm TL), and 1 gravid female (Table 1). It is important to note that no record of Pristis pectinata was obtained among the identifiable specimens. Nine specimens (39%) were reported from the Canal do Navio, at depths varying between 20 and 91 m. Fourteen specimens were caught in other areas of MAC. The other locations were the Mearim River (n = 7; 30%), Farol de Santana (n = 4; 17%), Baia de Turiaçu (n = 1; 4%), Baia de Cumã (n = 1; 4%), and the Gurupi River mouth (n = 1; 4%) ( Fig. 1). Records from the Farol de Santana consisted of 4 adult specimens of about 400 cm TL in 2010, the largest number of specimens caught in a single year among the records we obtained.

DISCUSSION
Sawfish populations are in decline worldwide (Dulvy et al. 2016). Data regarding where these elusive creatures have sustainable populations are scarce (Fernandez-Carvalho et al. 2014). Conservation concerns in our study area arise due to the proximity of the sawfish capture points to the coast and human settlements. Human demographic growth in the region has been intense and has compromised much of the local ecosystem. Thus, sawfish stocks across the MAC are often subjected to habitat degradation as a result of mangrove deforestation, pollution (Silva et al. 2011), and strong artisanal fishing pressures. Areas such as the Canal do Navio, where 3 juvenile specimens and a gravid female were caught, and Mearim River, where all catches consisted of juveniles, should be recognized as priority areas for research and conservation purposes. Despite the lack of data on sawfish biology and ecology, and the absence of continuous fishery-independent surveys in these areas, as recommended by Heupel et al. (2007), our data suggest that the Canal do Navio and the Mearim River might be potential nursery grounds for sawfish along the Amazon coast.
Present data demonstrate the ongoing practice of environmental crimes by the fishing communities of Maran hão State. This occurs mainly due to the lack of inspection both on board fishing vessels and at their landing points. Moreover, artisanal fishing in the MAC area is practiced by economically deprived people with little or no education. Since sawfish saws are extremely valuable as collection pieces, often being sold for more than US$800 (Charvet− Almeida & Faria 2008), fishermen are easily impelled to commercialize these items, even though they recognize and fear the illegality of the act. Nevertheless, one exception to the lack of law enforcement oc curred. The fisherman responsible for the capture of a large adult specimen in 2015 (Fig. S1 in the Supplement) suffered the punishment required by Brazilian law, being fined approximately US$9000 (current exchange rate) for illegal fisheries. Ac cording to interviewed anglers, a group of fishermen, fearing the same consequences, released alive a large sawfish specimen caught later in the same year and area. Fin trade, on the other hand, was not reported by the interviewees, al though the removal of pectoral fins was observed photographically (Fig. S2 in the Supplement). In general, little has been done by regulatory agencies to manage and protect sawfish stocks or their habitat.
Preservation of the natural environments that function as remote refuges for sawfish species present a great challenge. Conservation initiatives are overwhelmed by increasing fishing pressure, habitat destruction caused by urban development, lack of oversight by regulatory agencies, and critical social issues. We therefore endorse the need for urgent research here. Genetic diversity, population size, sex ratio, movement patterns, habitat use, and trophic ecology data are crucial to fully understand sawfishes and thus establish policy measures to protect their populations in the MAC and Eastern Amazon coast (EAC) areas. Acknowledgements. We thank the fishermen who agreed to be interviewed, Orla Viva NGO for allowing data collection, FAPEMA, São Luís, Ma ran hão, for providing a productive scholarship, and Patrício Getúlio Garcia Neto for figure preparation.