Timor-Leste is located in the south-east of the Indonesian archipelago and comprises the eastern part of Timor Island, the exclave of Oecusse-Ambeno, and the islands of Atauro and Jaco (Figure 1). Timor-Leste gained independence in 2002 after several centuries of Portuguese colonization and 25 years of Indonesian occupation. It is now governed under a democratically elected national government and 13 Municipalities. The smallest administrative unit is the suco (‘village’), each comprising multiple aldeia (‘hamlets’). There are over 15 distinct ethnolinguistic groups across the country, some with multiple dialects; Tetun (Tetun Dili) is the lingua franca (Williams-van Klinken and Williams, 2015). Over 70% of Timor-Leste’s 1.2 million population live in rural areas, where the majority of households engage in various small-holding agricultural activities (Williams et al., 2017). Engagement in fisheries is low compared with other small island countries (López-Angarita et al., 2019). There are an estimated 5,000 boat-based fishers, many of whom fish as part of a mixed livelihood strategy, which may include agriculture, small business and/or occasional paid employment (Alonso et al., 2012; Mills et al., 2017). Fishing is almost entirely small-scale and nearshore (within 5 km from shore), using paddle and motorized canoes (2–7 m in length) and manual-operated gears such as handlines and gill nets. Small pelagic fish, including short-bodied mackerels, sardines, halfbeaks and scads, comprise the majority of landings (López-Angarita et al., 2019). Higher levels of fishing activity, indicated by higher percentage of household boat ownership, occur along the north coast of Timor Island and around Atauro Island, with pockets along parts of the south coast (Mills et al., 2013).

This study was conducted at sites along both north and south coasts of Timor-Leste, with in-depth investigation of two fisheries on the north coast, ‘Loes’ and ‘Comoro’, associated with nearshore fishing grounds immediately offshore from the mouths of Loes and Comoro Rivers respectively (Figure 1). Both were selected as fisheries known to target sardines (among other species) and accessible from the nation’s capital and urban center, Dili. Loes fieldwork was conducted predominantly in Tasimean and Tutubaba, two adjacent hamlets in rural Aidaba-leten village, Bobonaro Municipality, which has a combined population around 2,500 and high household boat ownership (22% at village level, GOTL, 2016). Kemak is the dominant language (Williams-van Klinken and Williams, 2015). The majority of fishers in the two hamlets carry out boat-based fishing on a seasonal basis with sardines the main target species, as well as agricultural activities such as rice farming. Comoro fieldwork was conducted mainly at fishery landing beaches to the east of Comoro River mouth in Metin I hamlet, Bebonuk village, Dili Municipality, which has a population of nearly 2,000 and household boat ownership similar to the Timor-wide average (<2% at village level, GOTL, 2016). This area is part of urban Dili and has been settled by people from around Timor-Leste. Tetun is the most common language spoken (Williams-van Klinken and Williams, 2015). The majority of fishers fish on a part-time or seasonal basis, combined with other occupations, for example as security guards, carpenters and laborers. Sardines are one of several fish families caught in the Comoro fishing grounds, often within 500 m of the river mouth and adjacent beaches. Fourteen other sites were also visited along the Timor-Leste coast (at least one in each coastal Municipality except Oecusse-Ambeno) and three inland Municipality capitals (Figure 1), based on the advice of fishery officials, fish traders and others, and/or opportunistic observations of fishery-associated activities while traveling through the area.

Timor-Leste has a tropical monsoon climate, responsible for seasonal changes in winds and waves, and marked variation in rainfall (DNMG, 2015). Rainfall patterns, sea conditions and nearshore marine environments differ on the north and south coasts. The north coast, adjacent to the Ombai-Wetar Strait (commonly referred to as the ‘female sea’ or tasi feto in Tetun), is characterized by extreme bathymetry, with narrow reef flats (often <60 m wide) partly occupied by seagrass and coral, dropping to depths of 3,000 m within 20 km of the coast (Boggs et al., 2009). Annual rainfall is relatively low (<1,000 mm), typically occurring during a 4–6 month wet season starting in December (Barnett et al., 2007). The south coast, adjacent to the Timor Sea (the ‘male sea’ or tasi mane), has a wide and sloping continental shelf and is characterized by long beaches, larger waves and more turbid conditions (Boggs et al., 2009). Annual rainfall is higher (∼1,500 mm) and occurs over a 7–9 month wet season with two peak periods around December and May (Barnett et al., 2007). Along both coasts, the roughest sea conditions occur in July–August, associated with strong south-easterly trade winds (DNMG, 2015).

The study design comprised both qualitative research methods and collection of fish specimens and photographs for taxonomic identification, and focused predominantly on the Loes and Comoro fisheries with briefer investigations elsewhere (Figure 1). Field research was carried out by the lead author over a 15-month period in 2017 and 2018, with a week-long follow-up visit in mid-2019. Frequent multi-day visits were made to the hamlets associated with Loes and Comoro fisheries (total 50+ days), while visits to other sites ranged from an hour to 3 days (Figure 1, further details in Supplementary Table 1.1). Guidance and assistance with community engagement, cultural protocol, translation and interpretation were provided by a Timorese research assistant. Several individuals, all university students or recent graduates recruited by word-of-mouth, were engaged throughout the fieldwork period. This study was part of a broader research project on the operation and importance of small-scale sardine fisheries in Timor-Leste. Research activities were approved by the Democratic Republic of Timor-Leste Ministry of Agriculture and Fisheries (MAF; letter from Director General of Fisheries dated 15 December 2016) and endorsed by village and hamlet leaders. Research Ethics Clearances were provided by Charles Darwin University’s Human Research Ethics Committee (approval H16111) and Animal Research Ethics Committee (approval A17024).

Local names and knowledge of the main tropical sardine species caught in Timorese fisheries were documented through focus group discussions and informal conversations, the former with groups of two to 12 fishers at Loes (n = 5), Comoro (n = 1), and four other sites (n = 5). At all sites, participants were identified by hamlet leaders, approached by the research team or recruited by other fishers; all were male, reflecting the male-dominated nature of boat-based fishing on mainland Timor-Leste. Loes participants ranged from 20 to 65+ years; some older fishers were (at least) second generation fishers, others were first generation. Comoro participants were generally younger (20–30 years) second or third generation fishers. Informal conversations were held with fishers, fish traders, fisher wives, hamlet leaders and consumers approached at landing sites, fish markets and in adjacent residential areas. Several Municipality fishery officers were also interviewed. In total, over 118 men (35 in Loes, 16 in Comoro, and 67 across the 15 other sites) and 16 women (4 in Loes, 2 in Comoro, and 10 elsewhere) contributed information to this study through participation in discussions and/or conversations (further details in Supplementary Table 1.1). Participant observations were frequently carried out while assisting to remove fish from nets, as well as while accompanying fishers on several fishing trips at Comoro.

The study aimed to explore the breadth of Timorese local knowledge on sardines. Discussion and conversation topics included the types of sardines present and their importance for local fisheries; their physical appearance and relative size; their seasonality in fishing grounds and interannual fluctuation in landings; their occurrence (or availability) in different habitat types; timing of reproduction-associated observations, such as eggs; and post-harvest characteristics in relation to perishability. All discussions and conversations were conducted in Tetun; other local languages were occasionally used to clarify questions. Initial discussions were challenging as some topics and key words did not translate easily to Tetun. Ways of asking questions and introducing the discussion topics evolved as the research team learnt and adapted to the language and terminology used and understood by the fishers. Not all topics were addressed by all groups or individuals at all sites due to the flow of discussions, participant engagement and time constraints. In initial discussions fishers were asked about local names based on photographs in fish identification guides (MAF and FAO, 2008; White et al., 2013). However this produced mixed results probably due (at least in part) to the highly similar appearance of many species particularly in small, two-dimensional photographs. Fishers also commented that not all types caught were depicted. Subsequently, after September 2017, photographs of sardines from Timorese fishers’ catches (scaled to actual size) were used to document local names at each site and stimulate local knowledge discussions. Additional photos were added over the fieldwork period as additional species were observed (Supplementary Figure 1.1). Wherever possible, local names were verified based on actual specimens at landing sites and fish markets.

Participants gave written or oral consent to participate in the research and data were anonymized. Focus group discussions and interviews were conducted by a research assistant and the lead author, audio-recorded and transcribed. Informal conversations were mainly carried out by the lead author with notes written at the time or shortly after. Observations were recorded in a field diary, organized chronologically. Additional notes on sardine local knowledge at the Comoro study site were made, in Tetun, by two part-time fishers based on their personal observations and discussions with family members. Local knowledge data from all sources were translated into English with significant words and phrases retained in Tetun, coded using NVivo 11 (QSR International Pty Ltd) by local sardine name and knowledge topic, and summarized. Throughout the fieldwork period we sought to build on, validate and compare (across sites) the local knowledge shared with us in earlier discussions; this was carried out more extensively at sites visited several times (Figure 1). Where summarized local knowledge accounts were inconsistent, conflicting, unclear or inconclusive, the lead author decided whether to note the variation, seek clarification from key informants or not include data on that knowledge topic. Specimen photographs and local knowledge summaries on each locally distinguished sardine type were reviewed by key informants at Loes and Comoro sites in July 2019, and revised or clarified as necessary. Cross-validation of names was also carried out with MAF-WorldFish field staff. All data presented were cross-validated with more than one source. Maps were created using QGIS Desktop 3.10.5 and Inkscape 1.0.

To relate local names to Latin species names, specimens (n = 31) of nine locally distinguished sardine types were obtained from landing sites and fish markets in 2017 and 2018 (Supplementary Table 2.1). Specimens were fixed in 10% formalin and/or 70% ethanol and transported to Darwin, Australia with a MAF export permit and in accordance with airline and Australian Government import requirements. Specimens were identified to genus or species level by the Museum and Art Gallery of the Northern Territory (MAGNT) using available taxonomic keys (Munroe et al., 1999; Stern et al., 2016). Additional specimens (n = 7) and photographs (40+) were examined by the lead author to assign genus or species level taxonomy to local names across study sites. We follow recent taxonomic revisions which consider Clupeidae (sardines, herrings, shads and allies), Dussumieriidae (round herrings) and Spratelloididae (sprats or small round herrings) as three separate families in the Clupeoidei suborder (Lavoué et al., 2014, 2017; Egan et al., 2018; Fricke et al., 2020).

Across Timor-Leste, fishers distinguished over nine types of sardines, with some differences in local names between sites. We found these corresponded to at least eight species from three genera in the Clupeidae family—Sardinella (subgenera Clupeonia and Sardinella), Amblygaster and Herklotsichthys; and one Dussumieria species from the Dussumieriidae family (Table 1). Identification within these genera is challenging due to morphological similarities and overlapping distributions (Whitehead, 1985; Stern et al., 2016; Hata and Motomura, 2019b). Without genetic analyses, not all specimens collected could be conclusively identified to species-level. To accommodate these uncertainties, we present our findings in terms of four groups of species aggregated at either genus or subgenus level, as per Hunnam (2021): Flat-bodied Sardinellas, Round-bodied Sardinellas, Tropical Pilchards and Tropical Herrings. We further split the Flat-bodied Sardinellas into three groups based on distinctive external characteristics (or lack thereof), to reflect distinctions made by Timorese fishers.

Flat-bodied Sardinellas, Sardinella (subg. Clupeonia) spp., with no distinctive markings corresponded to two locally-distinguished sardine types: small fish caught in 1′′ (25 mm) mesh nets, which grow into larger fish caught in 1.25′′ (32 mm) mesh nets and on jigging lines (Table 1). Based on lengths at first maturity reported elsewhere in the IWP (Hunnam, 2021), these probably refer to juveniles and adults respectively. Both small and large specimens collected were identified as S. gibbosa, however we suspect landings of this group in Timor-Leste comprise at least two taxonomic species. Loes fishers and community members described two varieties based on differences in scale-shedding characteristics and pigmentation around the eyes and nostrils. Slight variations in pigmentation, shading extent on caudal and dorsal fin tips and body depth were also evident from photographs taken at different sites and occasions, and sometimes between specimens from a single catch. While S. gibbosa has been noted to vary in body depth and fin coloration across its Indo-West Pacific distribution, several other species within the Clupeonia subgenus are highly similar and overlap in distribution (Stern et al., 2016). Evidence of cryptic species within S. gibbosa has also been reported (Thomas et al., 2014). Non-deciduous scales have only been noted in S. fimbriata (Stern et al., 2016; Hata and Motomura, 2019b), which is now thought to be an Indian Ocean endemic (Hata and Motomura, 2019b; Fricke et al., 2020). Further sampling and genetic analyses are therefore required to confirm species composition in Timor-Leste. Discussions and observations indicated that this species-group is widely caught in nearshore fisheries around the country (Figure 2). It was reported as the dominant species-group landed each year in Loes and relatively abundant in Comoro, Laclo (Manatuto–Obrato) and Caraulun (Betano–Hato-udo) fisheries.

Flat-bodied Sardinellas, S.(subg. Clupeonia) spp., with a distinctive black-tipped tail corresponded to a single locally distinguished sardine type (Table 1). Specimens collected were identified as S. melanura. However, one had a black mark at the base of its dorsal fin, a feature not present in either S. melanura or the highly similar S. atricauda, which is also present in the region (Munroe et al., 1999). While two species, S. hualiensis and S. electra, do have a dorsal fin spot and shaded black-tipped caudal fins, neither are known to occur outside Taiwan and the Philippines (Willette et al., 2011) and Japan (Hata and Motomura, 2019a) respectively. This group may therefore contain more than one taxonomic species in Timor-Leste, but confirmation through further sampling is required. Discussions and observations indicated that this species-group is caught regularly in some north coast fisheries including Comoro and Laclo, but it was not mentioned by south coast fishers (Figure 2).

Flat-bodied Sardinella, S. (subg. Clupeonia) sp., with a deep body and a black mark posterior to the upper gill cover was preliminarily identified from photographs taken on the south coast. This species corresponded to a single locally distinguished sardine type, reportedly caught commonly in Suai Loro and Caraulun fisheries. Fishers described its scales as rough. North coast fishers rarely recognized photographs of this species, suggesting it is uncommon in north coast fisheries.

Round-bodied Sardinella, S. (subg. Sardinella) lemuru was identified from specimens collected on the north coast. This species corresponded to a single locally distinguished sardine type. Fishers only distinguished large specimens, caught in 1.25′′ (32 mm) or 1.5′′ (38 mm) mesh. Based on lengths at first maturity reported elsewhere in the IWP (Hunnam, 2021), these are probably adults. Juvenile S. lemuru may not be present in Timor-Leste’s nearshore waters, or may not be distinguishable from other small sardines caught. S. lemuru was not identified as a regular dominant component of current fisheries in Timor-Leste, although both Comoro and Loes fishers reported abundant catches have occurred some years. Large quantities observed in Dili markets over the fieldwork period were reportedly imported from Indonesia via the West Timor border – these had darker coloring, presumably from prolonged storage on ice.

Tropical Pilchards, Amblygaster spp., were distinguished as two sardine types by fishers at some sites, including Comoro: small fish caught in 1′′ (25 mm) mesh nets, which grow into larger fish caught mainly in 1.25′′ (32 mm) or 1.5′′ (38 mm) mesh nets (Table 1). Based on lengths at first maturity reported elsewhere in the IWP (Hunnam, 2021), these probably refer to juveniles and adults respectively. Both small and large specimens collected were identified as probable A. leiogaster. Photographs of fishers’ catches also indicated the presence of A. sirm. Highly similar A. clupeoides, which also occurs in the region and is only distinguishable from A. leiogaster by number of lower gillrakers (Munroe et al., 1999), may also be present. Discussions and observations indicated that both small and large Tropical Pilchards are landed regularly at some north coast fisheries including Comoro and Laclo. In Loes, fishers only distinguished large specimens and suggested this sardine type is typically only caught in low numbers in their fishery. Neither small or large specimens were mentioned in discussions with south coast fishers (Figure 2).

Tropical Herring Herklotsichthys quadrimaculatus was identified from specimens collected in north coast fisheries. This species corresponded to a single locally distinguished small sardine type caught in 1′′ (25 mm) mesh net. Based on lengths at first maturity reported elsewhere (Hunnam, 2021), these are probably adults. Discussions and observations indicated that H. quadrimaculatus occurs regularly in some north coast fisheries including Comoro and Laclo, and occasionally Loes and Atauro Island. However it was not mentioned by south coast fishers (Figure 2). Some Comoro fishers described a second, less common variety of the same local name, but it was unable to be sampled or photographed for identification.

Other:Dussumieria species (formerly Clupeidae family, now Dussumieriidae, Fricke et al., 2020) was commonly mentioned by south coast fishers. It also appeared occasionally in the Comoro fishery (Figure 2). A specimen collected was identified as Dussumieria elopsoides. Photographs of other specimens were also probably D. elopsoides, since the similar D. acuta is not thought to occur as far south as Timor (Munroe et al., 1999; Fricke et al., 2020).

Others: Specimens of other genera from the Clupeidae family were occasionally observed in fishers’ mixed-species catches, such as gizzard shad, Anodontostoma sp. near Suai Loro. Photographs of fishers’ catches taken after the main fieldwork period also indicated the presence of sardine and herring species additional to those documented here. This is unsurprising given over 40 species from the Clupeidae family are known to occur in marine and brackish habitats in the Indo-West Pacific region (Hunnam, 2021).

Based on comparison across sites, we found that the occurrence of sardine species-groups in local fisheries and their reported relative importance varies across Timor-Leste (Figure 2). For instance, Comoro and Laclo fishers noted several sardine species-groups (as well as other small pelagic fishes) as important components of landings each year. In contrast, Loes fishers indicated their fishery is usually dominated by large Flat-bodied Sardinellas with no distinctive markings, while other sardine species-groups are typically only caught occasionally, for short periods and/or in low numbers. This likely reflects different ecosystem characteristics and species-specific habitat requirements. For instance, the Loes River mouth area is characterized by long, sandy, surf beaches, while Comoro is adjacent to a bay with areas of intertidal seagrass, coral reef and mangroves (DesRochers et al., 2017); river catchment size and flow also differ.

Many Timorese fishers have considerable knowledge on the different types of fish they commonly catch, particularly on aspects relevant to their seasonal abundance, fish behavior, and post-harvest qualities, as discussed below and summarized in Table 1. Details of fishers’ observations and knowledge by site and locally distinguished sardine type are provided in Supplementary Tables 1.3, 1.4, 1.5.

Fishers in Timor-Leste have considerable knowledge relevant to the successful operation, development and management of their local fisheries. This knowledge, largely gained through practical experience, trial and error, observations and exchanges within their community and families rather than through formal education or training, forms a significant resource that should be valued, supported, and developed.

Timor-Leste’s complex history of colonization, conflict and associated movement of people, as well as post-independence nation building, is reflected in the different types of knowledge, experience and engagement with fishing as a livelihood among fishers (and others), and differing degrees of shared knowledge within fishing communities. This context differs to those typically investigated in early local knowledge studies (e.g., Inglis, 1993; Johannes et al., 2000; McWilliam, 2003), which tended to focus on the ancient wisdom of elders; more recent framing of local knowledge as a dynamic process opens up broader avenues of research (Lauer, 2017). In the Loes area, where some families have fished for multiple generations, there appeared to be greater cultural connections with sardines, including the existence of rules and rituals to govern fishing activities. These shared cultural or spiritual beliefs also influenced local thinking about fisheries resources, including aspects such as seasonal movement. In contrast, fishers in Vemasse often mentioned their inland origin—they had moved to the coastal area during Indonesian occupation and only started fishing in the last 40 years, largely out of necessity to adapt to living in the arid, marginal coastal lands. Fishers’ observations here were more varied and at times contradictory, for instance regarding associations between fish and turbidity, suggesting weaker shared fishing-related narratives. Local knowledge and explanations for observations were also shaped by fishers’ backgrounds. In Comoro, our key participants were predominately young and literate (some with university education) with access to television and internet, which they drew on and referenced in our discussions. While our study took a broad, exploratory, inclusive approach, factors such as age, experience and background have been shown in previous studies to have important implications for investigations into local knowledge and fisher knowledge (Johannes et al., 2000; Berkström et al., 2019).

The depth and consistency of fishers’ (and others’) knowledge also varied by topic. Seasonal occurrence and habitat associations were generally topics on which fishers had strong knowledge and observations. On other aspects, local knowledge appeared to be relatively weak and perhaps not used to guide or govern their fishing activities. For instance, understanding of life cycle characteristics was often vague or based on conjecture. While some fishers expressed concern that non-selective fishing gears catching very small fish may damage future generations of fish, we did not have any discussions in which fishers linked fishing pressure on small sardines with catches of large sardines of the same species (e.g., Tropical Pilchards ‘kostazul’ and ‘kobi’ in the Comoro fishery). However we also recognize that some in-depth knowledge was lost in translation—for instance on tides, currents and lunar cycles. This was due to working across the Tetun–English language interface (and at times a Tetun–Indigenous language interface); the multiple meanings of some Tetun words and the typically high-context communication style employed; as well as the broader challenge of articulating and discussing knowledge which is embedded in practical activity (Lauer and Aswani, 2009).

Establishing a clear understanding of local naming was key to holding successful discussions with fishers about their observations and experiences. Local names are closely linked to local knowledge. Local knowledge can emerge through the process of identifying local names (Davis and Ruddle, 2010) and names themselves can contain information on characteristics such as habitat, behavior and appearance (Foale, 1998). However, differences in naming across Timor-Leste due to the use and influence of multiple languages and historical separateness of some coastal communities, combined with the highly similar appearance of some sardine species, posed a considerable challenge for the research team. While fishers enjoyed looking through fish identification guides, we found this was not a reliable method on which to base our data collection due to the small photos, exclusion of some species and the subtle morphological differences between sardine species. Freshly caught specimens were most reliable, as found in other similar studies (e.g., Foale, 1998; Hamilton and Walter, 1999). Life-size photos of specimens taken in Timor-Leste also generally worked well, once we had collated sufficient photographs to represent most of the important species. Participation in fishery activities, such as assisting to remove fish from nets, was also beneficial as it not only allowed us to verify local names with a group of people simultaneously, but also often prompted conversations on distinguishing features less apparent in photographs, such as body shape and texture.

Relating local names with an accurate taxonomic identification (to species or genus level) is also important because it enables local knowledge to be compared and contrasted with other research, and can facilitate the use of information from elsewhere to fill knowledge gaps or provide the basis of hypotheses for future studies. It also enables the contribution of local knowledge to the broader set of information about a particular species. However, as we found, local names may not correspond neatly to an individual species—particularly for a group such as sardines where species within some genera are highly similar. Our species-group approach allowed us to account for both uncertainty in taxonomic identification and the fact that local names often are used for multiple species.

Finally, the process of accurately documenting local naming and knowledge required time and effort across social and natural science disciplines from fish taxonomy and biology to linguistic and cultural understanding. More time spent in the hamlets associated with the two case study fisheries meant we were able to build greater rapport with community members and this resulted in a greater depth of understanding compared to our briefer visits elsewhere.

Fishers’ local knowledge recorded in this study has immediate application in efforts to formalize fisheries monitoring, and in the broader consideration of potential impacts on Timor-Leste’s coastal fisheries from catchment developments, climate change and fishing pressure in neighboring Indonesia.

Fisheries monitoring programs need to account for differences in local naming across sites, and also acknowledge where local names may relate to more than one taxonomic species. A key example is provided by the local name ‘kobi’ or ‘sardiña kobi,’ which we found can refer to two different sardine genera or species-groups in Timor-Leste: large Flat-bodied Sardinellas with no distinctive marking in Loes and large Tropical Pilchards in Comoro. In addition, an existing national fish identification booklet records ‘sardiña kobi’ as the oxeye herring Megalops cyprinoides, an unrelated species from the Megalopidae family which shares some superficial similarities in appearance. Furthermore, Timorese common names listed on FishBase also include similar name ‘kopi’ for fusiliers of the Caesionidae family, as well as for Tropical Pilchard A. sirm (Froese and Pauly, 2020). National fisheries monitoring in Timor-Leste currently records landings at the family level due to the difficulties associated with accurately identifying mixed-species catches to species level across the country (Tilley et al., 2020). However, this example illustrates that the same or similar local name could relate to three different families. Findings from this study suggest landings of ‘sardiña kobi’ are most likely to be members of the Clupeidae family, either Sardinella spp. in Bobonaro municipality or Amblygaster spp. in Dili—but not ‘herring’ from the ‘Elopidae family,’ as currently recorded (Tilley et al., 2020; WorldFish and MAF, 2021). We cannot provide any insight on where this name may relate to fusiliers or oxeye herring. This current misidentification has potential fisheries management implications. While the two clupeids have similarly short life-spans (generally 1–4 years) and small maximum size (usually under 20 cm SL), M. cyprinoides can live up to 44 years and reach a maximum size around 110 cm SL (Froese and Pauly, 2020).

The strong association between sardine fishery productivity and seasonally turbid river plumes (or freshwater flow), recognized by fishers at several sites, emphasizes the need to consider coastal fisheries and fisher livelihood impacts in any catchment development proposals or assessments that may alter river flow or water quality. Rivers in Timor-Leste are currently largely unregulated, although some water is extracted for irrigation via free-intake and weir-based diversion systems. Post-independence policy targets to achieve food self-sufficiency and reduce malnutrition have led to a focus on water infrastructure development for agricultural use, including plans for new irrigation schemes and small and large dam construction (WB, 2018). Elsewhere, anthropogenic modification of catchments and river flows have caused major declines in coastal fisheries production, including tropical sardine fisheries (Loneragan and Bunn, 1999; Gillson, 2011). Findings from this study strongly suggest that changes to Timorese river flow regimes could have similar negative consequences for coastal fisheries. Catchment erosion due to land-use changes has already increased river sediment loads in Timor-Leste, and is suggested as one possible cause for perceived fisheries declines in some areas due to lower nutrient availability from sandier sediment (Alongi et al., 2009). River flow in Timor-Leste is highly dependent on rainfall, which is highly variable and may become more so with climate change (DNMG, 2015). Further research is required to understand the mechanisms underlying the observed relationship between rainfall, freshwater flows and sardine fishery productivity in Timor-Leste in order to elucidate likely responses to such changes. Due to the different life-cycles of different sardine species-groups, responses may be species-specific.

The seasonal movement patterns of fishes need to be considered (and better understood) in future fisheries management planning in Timor-Leste, given evidence that at least some sardine fisheries cross community, municipality and probably even national boundaries. Fishers in the Loes area have already expressed concern over increasing numbers of boats and nets, the non-appearance of juvenile sardines nearshore in their ‘usual season’ in some recent years, and the potential impact of the larger capacity mini-purse seine gear used in neighboring fishing communities. In the absence of resources to support fisheries governance and management in Timor-Leste, there are multiple examples where co-management partnerships between conservation organizations and local communities have tended to favor delineation of marine protected areas or no-take zones. For mobile fishes, like most sardine species-groups, such site-based protection may not be the most appropriate management mechanism (Tilley et al., 2019).

In conclusion, this study provides further evidence of the value of knowledge held by fishers, and demonstrates how local naming and knowledge can provide useful foundational knowledge to inform fisheries monitoring and management, and identify future research needs.