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African Journal of Marine Science

ISSN: 1814-232X (Print) 1814-2338 (Online) Journal homepage: https://www.tandfonline.com/loi/tams20

Local ecological knowledge demonstrates shifting baselines and the large-scale decline of (Pristidae) in

G Braulik, M Kasuga & G Majubwa

To cite this article: G Braulik, M Kasuga & G Majubwa (2020) Local ecological knowledge demonstrates shifting baselines and the large-scale decline of sawfishes (Pristidae) in Tanzania, African Journal of Marine Science, 42:1, 67-79, DOI: 10.2989/1814232X.2020.1728379 To link to this article: https://doi.org/10.2989/1814232X.2020.1728379

Published online: 25 Apr 2020.

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Full Terms & Conditions of access and use can be found at https://www.tandfonline.com/action/journalInformation?journalCode=tams20 African Journal of Marine Science 2020, 42(1): 67–79 Copyright © NISC (Pty) Ltd Printed in South — All rights reserved AFRICAN JOURNAL OF MARINE SCIENCE ISSN 1814-232X EISSN 1814-2338 https://doi.org/10.2989/1814232X.2020.1728379

Local ecological knowledge demonstrates shifting baselines and the large-scale decline of sawfishes (Pristidae) in Tanzania

G Braulik1,2* , M Kasuga2,3 and G Majubwa4

1 University of St Andrews, St Andrews, Fife, United Kingdom 2 Wildlife Conservation Society Tanzania Program, , Tanzania 3 Open University of Tanzania, , Tanzania 4 Ambakofi, , Tanzania * Corresponding author, e-mail: [email protected]

Sawfishes are coastally distributed rays that grow to very large sizes. All five are assessed as Endangered or as a result of population declines caused mainly by entanglements in fishing gear and by habitat degradation. Three species occur in the western Indian Ocean, but their populations are believed to have declined drastically in many areas and little is known about their presence in Tanzania. Fisher interviews were conducted to provide an overview of the status of sawfishes in Tanzania and to highlight where conservation actions should be focused to conserve sawfishes nationally. In total, 386 interviews were conducted: 296 at 31 villages in four on Tanzania’s mainland, and 90 interviews at 12 villages in four regions of . Less than half (46%) of the fishers were familiar with sawfishes and could identify one from a photograph. A precipitous decline in abundance in Tanzania could be inferred from the age-related decline in local knowledge of their existence; all fishers aged between 70 and 80 years were familiar with sawfishes, whereas only 10% of fishers younger than age 20 had ever heard of them. A total of 29 sawfish records were compiled, comprising 16 rostra and 14 catches that occurred between 2002 and 2014 (one record included both a catch and a ). All rostra examined were from the pristis. Since 2002, the sawfish catches occurred in three locations, all on the mainland coast: in the southern , in the vicinity of the Rufiji Delta, and at Bagamoyo on the Zanzibar Channel. Interview data and rostra evidence suggest that the Rufiji Delta may be a largetooth sawfish nursery area, and confirmation of this should be a priority.

Keywords: biodiversity conservation, Endangered marine , elasmobranch, , gillnets, participatory research, Pristis pristis rostrum, rapid assessment

Introduction

The cartilaginous (class ) face a global entanglements in gillnets and coastal trawl fisheries conservation crisis, with an estimated one-quarter of species (Harrison and Dulvy 2014; Dulvy et al. 2016). Bycaught threatened with extinction (Dulvy et al. 2016). Among the sawfishes are usually retained because the large quantity of most threatened of these are sawfishes ( Pristidae), flesh can be lucrative, the rostra can be sold as curios, and giant coastal, -like rays (up to 7 m total length [TL]) the fins are considered valuable within the shark-fin trade that are characterised by a distinctive long rostrum on (Clarke 2008). Their coastal distribution and dependence the front of the head, with numerous large teeth on each on habitats prone to high levels of human impact, such as side. Globally there are five recognised species that occur river mouths, and , means they are also throughout coastal and estuarine waters of the tropical susceptible to the impacts of coastal and estuarine habitat Pacific, Atlantic and Indian oceans (Faria et al. 2013). All degradation (Simpfendorfer 2005; Moore 2015). Declines five species are listed as either Critically Endangered or are compounded by the inherent biological vulnerabilities Endangered on the IUCN Red List of Threatened Species of many shark and ray species, in that they are long-lived, (e.g. Carlson et al. 2013; Kyne et al. 2013; Simpfendorfer grow and reproduce slowly, and mature late, with the result 2013). Sawfishes were formerly widespread and abundant, that populations can be slow to recover (Harrison and Dulvy but populations of all species have been declining steadily 2014; Dulvy et al. 2016). Northern and are since the 1960s and 1970s (but possibly earlier) when the the only areas where viable sawfish populations are believed use of gillnets in global marine fisheries started to expand to remain (Harrison and Dulvy 2014; Devitt et al. 2015). dramatically (Klust 1973; Potter and Pawson 1991; FAO Despite the undeniable conservation priority of this group 2012). The elongated, toothed rostrum, or saw, which of charismatic and severely threatened elasmobranchs, can be up to 1.5 m in length, easily becomes hooked and few detailed studies have been published on their status entangled in fishing nets, and in many places sawfishes throughout vast areas of their circumtropical distribution have declined as a result of both targeted and accidental (Moore 2015). There is an urgent need for information on

African Journal of Marine Science is co-published by NISC (Pty) Ltd and Informa UK Limited (trading as Taylor & Francis Group) Published online 25 Apr 2020 68 Braulik, Kasuga and Majubwa their status from data-deficient areas, most of which are in Mozambique, and the Rufiji, which is one of the 10-largest developing nations with intensive shallow-water fisheries rivers in Africa and has one of the largest deltas and (Harrison and Dulvy 2014; Dulvy et al. 2016). stands in the East Africa region (WWF-EAME In eastern and southern Africa, three sawfish species are 2004). Marine fisheries in Tanzania are almost exclusively known to occur: the largetooth sawfish Pristis pristis, green artisanal and are conducted predominantly using gillnets, sawfish P. zijsron, and narrow sawfish Anoxypristis cuspidata purse-seines, hook-and-line, traps and longlines (Ministry (Dulvy et al. 2016). During the 1930s, sawfishes were of Livestock Development and Fisheries 2010). The reported as being common in KwaZulu-Natal Province, South only industrial fishery that existed in Tanzania was the Africa, and Maputo Bay (formerly Delagoa Bay), Mozambique prawn-trawl fishery, which began operating in the Rufiji (von Bonde 1934, as cited by Everett et al. 2015). In Delta in 1988. Effort increased steadily to a peak of 25 KwaZulu-Natal, largetooth sawfish and green sawfish vessels in 2003/4, but the fishery was closed in January were still relatively regular catches in the 1950s and 1960s 2008 owing to the collapse of prawn stocks (Muir and but they have now disappeared, with the last confirmed Ngatunga 2008). Trawling has not been conducted regularly record being from 1999 (Everett et al. 2015). Their local anywhere else along the coast of Tanzania. extinction is thought to be due to anthropogenic changes to the most important estuarine ecosystems, gillnets set for Fisher interviews bather protection, and illegal harvesting. Two key sites In 2014, interviews with local fishers were conducted to for sawfishes in Mozambique were identified where recent gather semi-quantitative information on the location and captures and numerous rostra suggest that largetooth sawfish timing of bycatch of marine megafauna. Gillnet fishers still persist, but elsewhere in the country they appear scarce were the primary target of the interviews because this (Leeney 2017). There are no recent sawfish records reported gear type has by far the highest bycatch rates for marine from Kenya (Pierce 2014). Sawfishes are known to occur in megafauna generally, and sawfishes specifically (Lewison Tanzania (Richmond 2011) and dried rostra were noted to be et al. 2004; Harrison and Dulvy 2014). Given that there regularly displayed for sale as curios in mainland Tanzania is no industrial fishery in Tanzania, we obtained all our and the in the 1990s (Barnett 1997; information from artisanal fishers. Time and budget Dulvy 2014; Pierce 2014), but recent monitoring of fish allowed for representatives of approximately 3–5% of landing sites in Zanzibar failed to record a single sawfish the fishing fleet to be interviewed (Ministry of Livestock (Temple et al. 2019). Reflecting the general lack of current Development and Fisheries 2010), and a target was set systematic or reliable information, green and largetooth of 15 interviews from each of two villages chosen in each sawfish were documented as ‘presence unknown’ in Tanzania district. The rapid bycatch assessment questionnaire in a recent comprehensive global review (Dulvy et al. 2016). developed by Moore et al. (2010) was used, and interviews The present study was initiated to fill this important were conducted in Kiswahili by Tanzanian researchers data gap, specifically by conducting fisher interviews to not known to the fishers, one-on-one at fish landing sites. gather information to: (i) confirm the occurrence of sawfish The questions related to catches and the use of dolphins, species in Tanzania; (ii) determine which species occur; whales and dugongs (all reported in Braulik et al. [2018]) (iii) examine the spatial and temporal distribution of records as well as sawfishes (reported here). Each interview lasted by life-stage throughout the country; and (iv) document approximately 30 minutes, and sawfishes were the last recent catches and highlight any important remaining species group addressed by the interviewers. There were refuges for sawfishes. The overall aim was to provide 12 questions that related specifically to sawfishes, and an overview of the status of sawfishes in Tanzania and these took 6–8 minutes to be completed. Respondents highlight where conservation activities should be focused to were informed that the interview was anonymous and best conserve sawfishes nationally. that they did not have to answer any question if they were uncomfortable. As recommended by Moore et al. (2010), Methods we requested the community to send the most experienced fishers and boat captains to be interviewed, as these Study area individuals would have the greatest knowledge about the The study area comprised the entire 800-km coast of ocean and the longest memories of past events. mainland Tanzania (from approximately 4 to 10° S) as well Interviews addressed the following topics: as the coasts of Pemba, (collectively the Zanzibar 1. Background questions about age, fishing-gear use and Archipelago) and Mafia islands (Figure 1). Tanzania’s experience. coastline is dominated by the warm, northward-flowing, 2. Questions to ascertain whether the informant knew what nutrient-poor East African Coastal Current and is subject a sawfish was: could they identify it in a photograph, to two seasonal monsoons, the northeast monsoon differentiate it from other similar (e.g. from December to February and the southeast monsoon or marlin) by describing the size and the rostrum, or from June to September, interspersed with calm, rainy accurately describe it? inter-monsoon periods (Mahongo et al. 2012). Sea surface 3. Questions to ascertain where, when, and in what temperatures range from 24 to 30 °C, with the highest circumstances they had seen or caught a sawfish. temperatures in March and the lowest in September 4. Questions referring to how sawfishes are perceived and (Mahongo and Shaghude 2014). There are numerous used by the community. small estuaries along the coast, but the largest are the 5. Requests for information about the location of sawfish Ruvuma, which forms the border between Tanzania and rostra. African Journal of Marine Science 2020, 42(1): 67–79 69

Figure 1: Map of the coast of Tanzania showing locations of the records of sawfish rostra and documented catches since 2002, as well as locations of the interviews with fishers. Numbers 1–15 and 28 refer to rostra records (listed in Table 1), and numbers 16–29 refer to sawfish catch records (listed in the Appendix)

Details of the fishers’ accounts of sawfish catches and rostrum and teeth; and (iii) the size and arrangement of the sightings were carefully scrutinised and then included in the gaps between the teeth. Species identifications were later final database only if the fisher had convincingly described verified by a sawfish expert who examined the photographs the and the rostrum. When rostra were located, they and measurements (R Leeney, Natural History Museum, were photographed, and the length and number of teeth London, pers. comm.). The owner of each rostrum was recorded. Identification to species level of the rostra, and questioned about its capture location and date. Given that sawfish species nomenclature, followed Faria et al. (2013) rostra can be traded and transported long distances from the and was based on: (i) tooth counts; (ii) size and shape of the original catch location, care was taken to clarify where each 70 Braulik, Kasuga and Majubwa rostrum originated. Where catch information was lacking, the other gear types (e.g. purse-seines, hook-and-line, longline current location of the rostrum was depicted on Figure 1 (see or traps) were represented in lower numbers. The average Table 1 for details of rostra locations, and the Appendix for age of respondents in the entire study was 43 years (SD 13). catch locations). The range of mean age of respondents across the coastal regions was 37–48 years and was not uniform across the Historical information country (ANOVA, df = 5, F = 3.96, p < 0.05); respondents In an effort to locate additional rostra on display in public in the Coast region (Figure 1) (mean age 48 years) were places or that were privately owned, messages were significantly older than those in Dar es Salaam (mean age posted on social media (Facebook and Twitter) asking for 37 years) (Tukey, p < 0.01) and in the Tanga region (mean information. To gather historical information on sawfish age 40 years) (Tukey, p < 0.01), but in all other regions the occurrence and catches, national fisheries experts and mean age of respondents was similar (Table 2). Of those regional shark specialists were contacted. Bibliographic interviewed, 95% (n = 367) were fulltime fishers, but just items were searched in electronic archives (e.g. Google over half also had another source of income, with agriculture Scholar, ISI Web of Knowledge), and online biodiversity being the most common (37%, n = 143). Boat captains databases were also searched, including the Ocean comprised 63% (n = 243) of respondents and 36% (n = Biodiversity Information System (OBIS), the Global 139) were crew, while 4 individuals did not specify their role. Biodiversity Information Facility (GBIF) and FishBase. Outboard motors were present on the boats of 29% (n = 112) The Sawfish Conservation Society, and the International of the interviewees, and the remaining 71% (n = 274) had Sawfish Encounter Database (ISED; Florida Museum of oar- or sail-powered boats. Natural History, University of Florida) were also consulted. The Kiswahili name for sawfish is ‘papa upanga,’ which The largest Tanzanian national libraries were searched for translates to ‘machete shark’ in English. Species that published and unpublished information on sawfishes, with fishers sometimes confused with sawfishes were the giant searches including the entire collection of the Tanzanian Rhynchobatus djiddensis (‘fuanda’/’charawanzi’) Notes and Records, the Journal of the East African and and swordfish Xiphias gladius (‘sansuli’), so interviewers Ugandan Natural History Society, and the Journal of the East took care to carefully describe the differences. Nearly half African Natural History Society dating from the early 1900s. of the fishers interviewed (46%, n = 178) had never heard of the existence of sawfishes and could not recognise one Analysis of interview data from a diagram (Table 2). Age of the fisher was a highly The locations of sawfish catches and rostra were plotted significant predictor of whether they knew what a sawfish onto Figure 1 using QGIS 3.4 to display their spatial was; all fishers between ages 70 and 80 years were familiar distribution. We used an ANOVA to examine whether the with sawfishes, but only 10% of fishers younger than age age of fishers that were interviewed differed significantly 20 had ever heard of them (binomial GLM, age: p < 0.0001) according to coastal region, followed by Tukey’s honest (Figure 3). Of those who answered a question regarding significance test to explore specifically which regions trends in the abundance of sawfishes, almost all (99%, n = were significantly different from one another. A binomial 174) stated that they thought the fish are declining in number. generalised linear model, with the predictor variable coded as ‘0’ if a fisher did not know what a sawfish was and Sawfish records could not recognise it from a photograph, or as ‘1’ if they A total of 29 sawfish records from Tanzania were compiled. did know and could recognise sawfish, and the explanatory These comprised 16 rostra, and information from fishers variable Fisher Age was used to explore whether the age about 14 catches (one record included both a catch and a of a fisher influenced their knowledge of sawfishes. Models rostrum) that occurred between 2002 and 2014 (13-year were implemented using R 3.6.1 with the logit link function period) (Table 1; Appendix). The records were fairly evenly (R Core Team 2019). distributed along the entire coast of the country, including from Unguja and Mafia islands (Figure 1); however, there Results were no records from Pemba Island.

Fishers’ knowledge of sawfishes Sawfish rostra Interviews with fishers were conducted at landing sites Of the 16 records of rostra, one was reported by an between the northern and Dar es Salaam, international shark expert, three were museum records from 22 April to 4 May 2014; between Dar es Salaam and published by Faria et al. (2013), six were discovered during the southern , from 17 to 27 June 2014; and the fisher interviews, and another six were discovered on Pemba Island, from 22 to 27 September 2014 (Figure 1). either through contact with local marine biologists or Time, budget and logistical constraints meant that fishers opportunistically in hotels and elsewhere in the course of on Mafia and Unguja islands were not interviewed. A total several years of marine conservation work in Tanzania. of 386 interviews were conducted, all with male fishers Published research on fisheries and elasmobranchs in (women in Tanzania do not fish from boats): 296 interviews Tanzania is extremely limited and almost nothing was in 31 villages in four regions on the Tanzanian mainland, discovered in these sources. Similarly, nothing was and 90 interviews in 12 villages in four regions of Pemba discovered through social media. All the rostra that Island. A total of 71% (n = 274) of those interviewed used were located were determined to be largetooth sawfish gillnets as their primary gear type, and another 10% (n = 39) Pristis pristis, based, in every case, on tooth counts, the used gillnets as their secondary gear type; those who used large gap between the first and second tooth at the tip of African Journal of Marine Science 2020, 42(1): 67–79 71 Notes ZMB 33551 and see Appendix; Figure 2b) in Dar es Salaam island owned in Cambridge, UK house of man in village sale at Tsh180 000 (≈US$80) Lindi River in 1993; stored in fisher’s house 2013 ( collection of the Rijksmuseum van Natuurlijke Historie, Netherlands (RMNH D3080) Berlin Zoological Museum, Germany ( ZMB 14882) Stored in fisher’s house Very old rostrum, privately owned Hanging in fishing camp on the Sawfish killed in 1994; privately Privately owned For sale Privately owned Displayed in hotel More than 30 years old; kept in Displayed in the hotel Displayed in the market and for Sawfish caught in a gillnet Young sawfish caught by fisher in Isolated rostrum in the Rostra in the collection of strum length described by Faria et al. (2013) Catch location Island Bagamoyo Zanzibar Mkwaja Mafia Island Not known; likely Unguja Songo Nungwi Not known Mbegani, Bagamoyo Not known Kigombe Not known Not known Lindi Nyamisati, Rufiji Delta Not known; possibly Not known; possibly Species P. pristis P. pristis P. pristis P. pristis P. pristis P. pristis P. pristis P. pristis P. pristis P. pristis P. pristis Not known Not known Not known Pristis pristis (m) a b b b b 1.36 1.0+ 0.89 1.32 1.0+ 0.97 1.252 1.16 1.13 1.0+ 1.025 0.229 1.0+ Length of Not known Not known rostrum 18/19 18/18 21/20 18/19 16/15 18/18 18/19 19/19 20/19 18/19 17/17 21/21 (left/right) Not known Not known Not known Tooth count Lindi Coast Coast Coast Tanga Tanga Tanga Region Zanzibar Zanzibar Mafia Island Mafia Island Unguja Island Unguja Island Dar es Salaam Dar es Salaam

Current rostrum location Place useum record from 1960, noted in Faria et al. (2013) Faria et al. (2013) Mafia Island Langi Langi, Nungwi Songo Nungwi Mbegani, Bagamoyo Fumba Mitwero, near Ras Kera Kigombe Kingfisher Hotel, Kigombe Dar es Salaam curio market Mkwaja Nyamisati M Two museum records, noted in Dar es Salaam Details of the sawfish rostra found in Tanzania, either examined directly or with photographic supporting evidence (locations are shown Figure 1). Tsh = Length refers to the distance from rostrum tip base where it was detached body, which approximates measurement of total ro When length was not measured but photographs were available to gauge size, the approximate size simply estimated as ‘greater than’ (+) 5 6 15 28 ID no. a b 13 14 Table 1: 7 1 2 3 4 8 9 10, 11 12 72 Braulik, Kasuga and Majubwa

Table 2: Summary of fishers’ knowledge of sawfishes, by Tanzanian region

Region Total Tanga Dar es Salaam Coast Lindi Mtwara Pemba Island No. of fisher interviews 121 22 71 50 32 90 386 Average age of 40 (SD 15, 37 (SD 10, 48 (SD 17, 45 (SD 16, 44 (SD 14, 43 (SD 13, 43 (SD 15, interviewees (years) range 16–72) range 23–53) range 20–80) range 15–83) range 25–72) range 18–68) range 15–80) Interviewees that 45% (55) 41% (9) 79% (56) 74% (37) 69% (22) 32% (29) 54% (208) could recognise a sawfish (n) Interviewees having 20% (24) 9% (2) 27% (19) 30% (15) 13% (4) 7% (6) 18% (70) caught a sawfish in their lifetime (n)

(a) (b)

Figure 2: (a) The largest (125 cm TL) and (b) the smallest (22.5 cm TL) Pristis pristis rostra that were located in Tanzania (Photograph: G Braulik)

the saw (visible even in very small rostra), and the broad rostra were measured, but no precise length measurement rostrum width relative to length (Figure 2a, b). Tooth counts was available for the remainder. Of those that either were per side of the rostra ranged from 17 to 21. Nine of the measured or where the approximate size could be gauged African Journal of Marine Science 2020, 42(1): 67–79 73 from photographs, all were at least 1 m in length, except for 1.0 record No. 8 (Table 1) which was only 22.9 cm long. The rostra provided no evidence that any other sawfish species is extant in Tanzania. WFISHES 0.8 Sawfish catches Throughout the coast of Tanzania there was some traditional knowledge of sawfishes in almost every 0.6 community, although catches were extremely rare. A total of 14 sawfish catches made since 2002 were documented. Only one of the documented catches was identified to species (largetooth sawfish), based on a photograph 0.4 (Figure 4). The records of sawfish catches made between 2002 and 2014 are listed in the Appendix. Many fishers FISHER KNOWS OF SA travel long distances, and consequently some reported 0.2 that their own sawfish catches in Tanzania had occurred hundreds of kilometres from the interview location. All recent catches have been primarily in three locations: on

the southern coast in the Mtwara region, in the vicinity of PROBABILITY the Rufiji Delta, and around the coastal port of Bagamoyo 20 30 40 50 60 70 80 on the Zanzibar Channel. A large sawfish (6 m TL) was AGE OF FISHER (y) landed in the mouth of a river just southeast of Bagamoyo (near the Mbegani Fisheries Institute) in 2013. There were Figure 3: Proportion of interviewed fishers who knew about the two records, one from 2010 and one from April 2014, from existence of sawfishes, according to their age near the Mozambique border where the large Ruvuma River estuary is located. In the northern Tanzanian region of Tanga there were reports of sawfish catches at the villages of Kigombe, Pangani and Mkwaja from 15–20 years ago, but no evidence of any catches since the early 2000s. Fishers stated that sawfishes were caught in gillnets, but one respondent recalled a catch in a prawn trawler when the commercial fishery at Rufiji was still operational. In Nyamisati village in the northern part of the Rufiji Delta, all but one of the fishers interviewed (93%, n = 14) were familiar with sawfishes. This was the highest level of sawfish knowledge among the locations visited during the survey. There were three independent reports from this village that small sawfish (<1 m TL) are currently caught regularly in the shallow water of smaller channels in the delta. This was corroborated by the discovery of a relatively small rostrum, Figure 4: Largetooth sawfish brought in by fishers to the village 22.9 cm in length, retained by a fisher after a catch he of Nungwi on Unguja Island, Tanzania, on 24 September 2004, described in 2013 (Figure 2b). The respondents in Nyamisati showing that the origin of the first is anterior to the pelvic- suggested certain months when catches of juvenile sawfish fin origin, confirming identification of this animal as Pristis pristis were most common, but there was little congruence in their (Photograph: C Goodwin) statements. There was no evidence that juvenile sawfish were caught at any of the three other villages (Jaja, Kiomboni and Pombwe) visited in the Rufiji Delta. Rufiji Delta and the Ruvuma River, respectively (Table 2). Sawfish catches were recalled along most of the mainland Spatial distribution of sawfish records coast, but the recent records were so few that it was not Fishers in the central and southern areas of the mainland possible to identify hotspots. coast were the most familiar with sawfishes, with 70–80% of respondents in those areas recognising them, in Use of sawfishes by communities comparison with fishers along the northern coastline and Although sawfish catches are rare, the landing of such on Pemba Island where less than 50% had heard of them a large fish is a notable event in a fishing community. (Table 2). The proportion of fishers that reported having Interview respondents claimed that a sawfish was too seen or caught a sawfish was lowest on Pemba and in the large to eat themselves, and therefore all who answered a large port city of Dar es Salaam, suggesting that sawfishes question about what they would do with a sawfish after it are rarest in these locations. The largest percentages was caught (n = 110) agreed they would sell the meat and of fishers reporting that they had either caught or seen fins. Sawfish fins, like shark fins, are valuable and often first-hand a sawfish catch in their lifetime were in the Coast sold to local dealers immediately after capture. In Tanzania, (27%) and Lindi (31%) regions, in the vicinity of the large it is common practice for the , internal organs and 74 Braulik, Kasuga and Majubwa intestines of cetaceans, and non-targeted fishes to Gambia, and -Bissau (Leeney and Poncelet be stored in barrels; months later this mixture (called ‘sifa’) 2015; Leeney and Downing 2016; Leeney 2017), as well as is used as a protective varnish on wooden boats. One fisher in other regions of the Indian Ocean (Hossain et al. 2015; in Bagamoyo (Coast region) noted that sale of the sifa he Moore 2015; Jabado et al. 2017) and southwestern Atlantic produced from a 6-m sawfish that he caught in 2013 had Ocean (Manir Feitosa et al. 2017; Cuevas et al. 2019), been more lucrative to him than the sale of all other sawfish reflecting the rapid global decline of these threatened parts combined. Some fishers sell the rostra, though many species and the consistent pattern of the potential to will keep this part as a decoration in their home. Reportedly, become locally extinct. four sawfish rostra (1.2–1.8 m in length) were for sale in the Dar es Salaam in 1993; the traders claimed that Largetooth sawfish distribution these sawfish were captured in the Mafia and Songo Songo All rostra that were discovered were of the largetooth sawfish island group (Dulvy 2014). The sale of sawfish rostra at the P. pristis and this is certainly the most common sawfish same fish market continues to the present. species extant in Tanzania. Although some distribution maps of the green sawfish P. zijsron include Tanzania Discussion (Simpfendorfer 2013), Dulvy et al. (2016) noted that their presence is uncertain. We found no evidence that green Decline of sawfishes in Tanzania: shifting baselines sawfish currently occur or ever did occur in Tanzania. This study provides a first summary of the status of Despite the lack of evidence, it is possible that the species sawfishes in Tanzania, documents only sporadic catches in a is still present but is extremely rare, or that it once occurred recent 13-year period (2002 to 2014), records an apparently but became locally extinct sufficiently long ago that no rostra precipitous decline in sawfish abundance, and provides remain. However, our information suggests that Tanzania evidence of a possible nursery area for Pristis pristis. should be removed as a range state for green sawfish. Declining knowledge among fishers of the very existence of We generated sawfish records from all of the coastal sawfishes in Tanzania’s marine environment, such that only regions of Tanzania, including all five mainland regions 10% of respondents under age 20 had ever heard of these and those of the Mafia and Unguja islands. Notably, the fish, in contrast to 100% of those aged 70 and above, also interviews generated no evidence of sawfishes at Pemba provides convincing evidence that sawfishes are increasingly Island (neither rostra nor anecdotal evidence of catches). rare locally, have declined rapidly, and are possibly In addition, the proportion of respondents that could approaching . recognise a sawfish was significantly lower on Pemba The shifting baseline syndrome that we recognise for (32%, n = 90) compared with all other places in the country sawfishes in Tanzania represents a well-known phenomenon: (Table 2). Both Mafia and Unguja are continental islands once even charismatic megafaunal species cease to be separated from the African mainland by shallow waters, encountered on a fairly regular basis, they are rapidly whereas Pemba is an oceanic island separated by a forgotten by local communities (Knowlton and Jackson 2008; channel approximately 1 000 m deep (Figure 1). Largetooth Turvey et al. 2010). For example, community interviews sawfish are generally restricted to shallow (<10 m) coastal, along the Yangtze River showed that informants’ age was estuarine and fresh waters; therefore, it is possible that a strong predictor of whether they had ever heard of the Pemba has never been a habitat for sawfishes. Sawfishes recently extinct Yangtze River dolphin Lipotes vexillifer or were also thought unlikely to have ever been present the Chinese paddlefish Psephurus gladius, with younger around other oceanic islands in the western Indian Ocean, informants being substantially less likely to recognise either including at Réunion, Mauritius and the Seychelles (Dulvy species. On the Yangtze River, a marked decrease in local et al. 2016); however, those locations are far more isolated knowledge about local freshwater megafauna occurred at than Pemba. the same time as major population declines of these species, from the 1970s onwards (Turvey et al. 2010). In 2014, 100% Largetooth sawfish nursery areas of the interviewed fishers aged 70–80 were knowledgeable The small rostrum (Figure 2b) that was located at Nyamisati about sawfishes, which suggests that these fishes were still in the Rufiji Delta falls within the size range documented relatively common in Tanzania when these interviewees were for young largetooth sawfish or young of the year (<24 cm) young (i.e. approximately in the 1940s and 1950s), and the (Thorburn et al. 2007; Last and Stevens 2009; Moore 2015). finding suggests that sawfishes have been steadily declining Fishers reported ‘numerous small sawfishes in small narrow in abundance since that time. The timing of the onset of channels’ of the delta which are present on an annual and the decline from the 1950s onwards corresponds well with regular basis. It is known that mature largetooth sawfish the introduction of gillnets to the Indian Ocean region and the occur primarily in marine environments and that they move rapid expansion of Tanzania’s coastal fisheries (Tarbit 1984). into estuaries to pup, and that rivers and estuaries provide Furthermore, extensive fisheries catch surveys and market important nursery areas for juveniles (Peverell 2005; Kyne surveys around the Mafia and Songo Songo islands in the et al. 2013; Fernandez-Carvalho et al. 2014). Juvenile early 1990s did not record any sawfishes (Dulvy 2014), which sawfish have an affinity for very shallow water and for corroborates our conclusion that sawfishes have been rare in shoreline habitats with overhanging vegetation, such as Tanzania for several decades. mangroves, probably because of the protection provided The phenomenon of declining local knowledge of from predators such as sharks (Poulakis et al. 2011; sawfishes that was seen in Tanzania has been observed Simpfendorfer et al. 2011). The information generated by in many other parts of Africa, including in Mozambique, this study is insufficient to show definitively whether the African Journal of Marine Science 2020, 42(1): 67–79 75

Rufiji Delta is a sawfish nursery area; however, the small anecdotes. Despite this, imperfections in memory, lack of rostrum, reported regular recent sightings and catches of trust for outsiders, as well as cultural and other factors, mean very small sawfish collectively suggest that this may be the that the local ecological knowledge collected from interviews case. This is plausible because Rufiji, the largest delta in alone cannot be relied upon as an indicator of species East Africa, includes the most extensive shallows along the prevalence, distribution and trends (McKelvey et al. 2008). Tanzanian coast and has beds and mangroves, Another aspect to consider is that our respondents which for example are known to favour might have mistakenly reported ( (Simpfendorfer et al. 2010), and the entire estuary has high Pristiophoriformes) as sawfishes. Sawsharks are productivity and diversity (Howell et al. 2000; Doody and substantially smaller than sawfishes (generally <1.7 m TL, Hamerlynchk 2003). There are few nursery areas known compared with up to 6 m for sawfishes) and commonly for any sawfish species outside Australia and Florida, occur in deeper marine waters, but are morphologically and, given the extreme level of threat faced by sawfishes similar (Compagno 1984). distribution is not globally, it is important to conduct the scientific studies well known in Tanzania though several specimens were necessary to conclusively determine whether the Rufiji Delta caught on long lines off the south coast of Zanzibar is a largetooth sawfish nursery ground. Confirmation would (Unguja Island) in 2017 and 2019 (P Berggren, Newcastle provide a sound basis from which to launch the habitat and University, UK, pers. comm.). The majority of participants species protection that would be required to protect that in the artisanal Tanzanian fishing fleet that we interviewed area. Although the Rufiji Delta contains a series of protected used non-motorised vessels, and fishing mostly occurs mangrove reserves, the clearing of mangroves continues in nearshore areas where sawfishes occur. Thus, these to occur (Richmond et al. 2002) and several large for fishers would less frequently venture into sawshark habitat, hydropower generation have been approved for the Rufiji which is deeper and consequently more risky for them River basin, which will change the freshwater-flow regime to access (Jiddawi and Öhman 2002). The majority of the into the estuary, and both are circumstances that will change sawfish catches reported were of large individuals that and degrade sawfish habitat (Simpfendorfer et al. 2011; were too large to have been a sawshark. The records and Duvail et al. 2014). reports of small-sized sawfishes from the Rufiji Delta are unlikely to have been misidentified sawsharks because Local ecological knowledge: reliability of the the shallow-water habitat is not believed to be suitable for information collected sawsharks. However, given that the physical description of Interview-based collection of local ecological knowledge both taxa is very similar, it is not possible to rule out that a can be a useful monitoring method for assessing population few of the smaller sawfish records that we report might have trends of distinctive aquatic species, and is especially been sawsharks. Nonetheless, the large sample size of appropriate in regions where resources for regular surveys interviewees, and general consistency of the findings across are limited (Turvey et al. 2013; Aylesworth et al. 2016). In the country, lend weight to the reliability of the dataset. addition, once species become extremely rare they are This study was conducted opportunistically and without increasingly difficult to detect during field surveys, such funding, and the questions about sawfishes were added as those at fish landing sites (Temple et al. 2019) or by to interview surveys that were part of a larger study to vessel-based sampling surveys (Cuevas et al. 2019), and conduct a rapid assessment of cetaceans in Tanzania. interviewing experienced fishers might be the only way to A dedicated and funded study specifically focusing on gain current or retrospective knowledge. The collection of sawfishes would likely have generated more data, allowed local ecological knowledge can quickly and cost-effectively more sophisticated analysis, and possibly provided more provide information on the presence of distinctive species insights into hotspots. However, what was generated with across wide geographic areas. However, the information relatively little effort or cost helps to fill a significant data gathered needs to be carefully verified. For example, fishers gap and provides a basis for moving ahead with sawfish might fear the consequences (such as prosecution) of conservation and targeted research work. The major threats providing information that suggests they have knowledge facing most marine megafauna species, including sea about the mortality of a threatened species, which turtles, many large chondrichthyans and marine mammals, might lead them to conceal information or provide false are linked to fisheries bycatch, primarily in gillnets information (Silver and Campbell 2005). In Guinea-Bissau, (Lewison et al. 2004), and, given the extreme conservation Leeney and Poncelet (2015) used people from the local concerns and high level of threat that these animals face, community to conduct interviews, on the assumption that it is important for single-taxon specialists to look for more interviewees would be more comfortable—and therefore opportunities to use existing surveys to collect information more candid—when speaking to someone known to them on other, threatened taxa. or their community. In the present study, questions about sawfishes were asked at the end of a longer interview that Conservation and research priorities included questions about the bycatch of dugongs, dolphins Sawfishes are not explicitly protected in Tanzania and whales. Whereas most respondents were aware that (Government of the United Republic of Tanzania 2009), marine mammals are protected, and might therefore have but relevant legislation is being revised and this might been wary about providing information about the mortality be rectified in the near future. However, even with legal of those species, most respondents appeared by contrast protection in place, considerable effort would need to to be relaxed when finally asked questions about catching a be applied, in terms of education and raising awareness species about which they felt uninhibited to share stories and about sawfishes, by all levels of the fisheries departments 76 Braulik, Kasuga and Majubwa and within fishing communities. Also, given the rarity of from their respective fisheries departments. Helpful reviews of catch events, generally poor enforcement in the Tanzanian the manuscript were provided by Tim Davenport, Nick Dulvy and marine environment (Braulik et al 2017), and the high Amie Brautigam, as well as an anonymous reviewer. The work incentive to retain sawfish because of their value, it will be was funded through marine-mammal-targeted grants by the Pew Fellows Program in Marine Conservation, the Wildlife Conservation difficult to implement further protective measures. Fisheries Society, and the People’s Trust for . compliance in Tanzania is relatively poor; for example, it is one of the only countries in Africa where fishing with explosives is openly practised, with few repercussions for ORCID offenders (Slade and Kalangahe 2015; Braulik et al. 2017). We suggest that by far the best way to achieve effective Braulik: https://orcid.org/0000-0001-8919-4187 marine fisheries management is to use a bottom-up approach by working with village fisheries committees. With regard to sawfishes, conducting education and awareness- References raising activities with a focus on the species at the community level is the most likely way to be effective. Aylesworth L, Phoonsawat R, Suvanachai P, Vincent AC. Our study suggests that sawfishes are already 2016. Generating spatial data for marine conservation and extremely rare in Tanzania; therefore, introducing targeted management. Biodiversity and Conservation 26: 1–17. interventions is essential even though problematic. Barnett R. 1997. The shark trade in mainland Tanzania and Zanzibar. In: Marshall NT, Barnett R (eds), The trade in sharks The strategy that appears to have the greatest chance and shark products in the western Indian and southeast Atlantic of yielding positive impacts is to focus on community- oceans. Nairobi, Kenya: TRAFFIC East/Southern Africa. level interventions in those parts of the Rufiji Delta that pp 39–66. our interview findings suggest might represent a sawfish Braulik G, Wittich A, MacAulay J, Kasuga M, Gordon J, Davenport nursery area, based on the slightly higher frequency of TRB, Gillespie D. 2017. Acoustic monitoring to document the sawfish landings in the area than elsewhere in the country. spatial distribution and hotspots of blast fishing in Tanzania. A targeted outreach programme could be conducted at Marine Pollution Bulletin 125: 360–366. villages in the delta to increase awareness of the status Braulik GT, Kasuga M, Wittich A, Kiszka JJ, MacAulay J, and threats to sawfishes and to encourage fishers to Gillespie D et al. 2018. Cetacean rapid assessment: an approach release live sawfish from their nets. In Florida, use of to fill knowledge gaps and target conservation across large data deficient areas. 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Sharks last population in Tanzania in the Mafia–Rufiji area, and it of the world: an annotated and illustrated catalogue of shark is possible that sawfishes could be incorporated into this species known to date. Part 1 – to . FAO Fisheries Synopsis 125. Rome: Food and Agriculture network (West 2011). Despite the strong need for action, Organization of the United Nations (FAO). there is a clear need to undertake basic research to answer Cuevas JM, García M, Hozbor N, Faria VV, Paesch L. 2019. Tracing questions to assist with Tanzania’s management—for the occurrence of the Critically Endangered smalltooth sawfish example, to provide an understanding of the seasonal Pristis pectinata at its southernmost distribution in the southwest presence and distribution of sawfishes within the Rufiji Atlantic Ocean. Endangered Species Research 38: 1–9. Delta, so that this information is available to protect critical Devitt KR, Adams VM, Kyne PM. 2015. Australia’s protected area habitat at crucial times of the year. Acoustic tracking network fails to adequately protect the world’s most threatened of sawfish is a potentially useful means to answer some marine fishes. Global Ecology and Conservation 3: 401–411. essential questions; however, given the lack of reliable Doody K, Hamerlynchk O (eds). 2003. Biodiversity of Rufiji District sightings, finding sawfish to tag and track might be difficult – a summary. Unpublished report. Dar es Salaam, Tanzania: Rufiji Environment Management Project. and costly (Simpfendorfer et al. 2011). Therefore, we Dulvy NK. 2014. Sawfish rostra for sale in Tanzania. In: Harrison suggest that the best immediate course of action would LR, Dulvy NK (eds), Sawfish: a global conservation strategy. be to direct effort and resources to improving awareness Vancouver, Canada: Shark Specialist Group, International Union of sawfishes among coastal communities, developing for the Conservation of Nature Species Survival Commission. appropriate policies to protect these fish, and supporting p 57. implementation of those policies. Dulvy NK, Davidson LN, Kyne PM, Simpfendorfer CA, Harrison LR, Carlson JK, Fordham SV. 2016. Ghosts of the coast: global Acknowledgements — The community interviews were conducted extinction risk and conservation of sawfishes. Aquatic by MK, GM, and Nassoor Akida Ally. We would especially like to Conservation: Marine and Freshwater Ecosystems 26: 134–153. thank Ruth Leeney for guidance regarding the data collection and Duvail S, Mwakalinga A, Eijkelenburg A, Hamerlynck O, analysis, and for independently verifying species identifications. Kindinda K, Majule A. 2014. Jointly thinking the post- Thanks to Jason Rubens for guidance and suggestions on the future: exchange of local and scientific knowledge on the lakes work. Thanks to Sharif Mohammad and Mwanaidi Mlolwa for of the Lower Rufiji, Tanzania. Hydrological Sciences Journal 59: granting permission to undertake the work, as well as support 713–730. African Journal of Marine Science 2020, 42(1): 67–79 77

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Manuscript received March 2018 / revised November 2019 / accepted January 2020 African Journal of Marine Science 2020, 42(1): 67–79 79 Notes from interview Island, in 1990, 2002 and 2003 Nyamisati village, in 1995, 2000, 2001, 2002 and 2007; stated that sawfish live in the the in live sawfish that stated 2007; and 2002 2001, 2000, 1995, in village, Nyamisati estuary and that juveniles are sometimes caught in gillnets ~10 kg and sold the whole fish for Tsh45 000 (≈US$20) village, and then sold the rostrum large mesh; the specimen was between 4 and 6 m TL 2013, at Nyamisati village, and it was a juvenile; he stored the rostrum in his house (see Figure 2b) independently) Fisher caught a sawfish at Kikwetu village Brought to Nungwi village by fishers; rostrum now privately owned Fisher lives in Nyamisati village and caught sawfish in the Rufiji Delta and south of Mafia Fisher lives in Nyamisati village and caught sawfish the Rufiji Delta south of Mafia Fisher caught a sawfish at Mchinga village, near Lindi City Fisher caught sawfish in at least three different locations within the Rufiji Delta, all near Fisher caught sawfish in at least three different locations within the Rufiji Delta, all near Sold in the market Brought onto beach in fisher’s catch (reported by expat on Zanzibar) Fisher lives in Naumbu village; 3 years ago, near Mtwara Port, he caught a sawfish weighing a he caught ago, near Mtwara Port, years in Naumbu village; 3 Fisher lives Young animal, ~50 cm TL Fisher lives in Dar es Salaam but fishes elsewhere; he once caught a sawfish near Kisiju Brought to Dar es Salaam fish market and sold; unclear where it was captured originally Fisher caught a sawfish in river mouth not far from Bagamoyo, using a set gillnet with Fisher had a lot of experience, having caught sawfish 6 or 7 times; the last time was in April Brought to Mtwara fish market within the last three months (reported by several people people several by (reported months three last the within market fish Mtwara to Brought Lindi Lindi Coast Coast Coast Coast Coast Coast Tanga Region Mtwara Mtwara Unguja Island Unguja Island Dar es Salaam Kasera Nungwi Lindi City Lindi City Mtwara Port Mtwara Port Town/Village Dar es Salaam Mayuni, Matemwe Mbegani, Bagamoyo Kiomboni, Rufiji Delta Nyamisati, Rufiji Delta Nyamisati, Rufiji Delta Nyamisati, Rufiji Delta Kisiju, Mkuranga District 2002 2003 2006 2007 2008 2008 2010 2011 2012 2012 2013 2013 Apr 2014 24 Sep 2004 Date of catch Details of the documented sawfish catches made in Tanzania between 2002 and 2014 (locations are shown on the map in Figure 1; the ID nos. continue from numbering Detailsof of the documented sawfish catches made in Tanzania between 2002 and 2014 (locations are shown on map Figure 1; Appendix: rostra listed in Table 1, with No. 28 constituting both a catch record and rostrum). Tsh = Tanzanian shilling 29 28 27 26 25 24 23 22 21 20 19 18 17 16 ID no.