Promoting community-based surveillance of economically important invasive species in lower-income economies: a case study of the suckermouth catfish (Pterygoplichthys pardalis) in Bangladesh

The distribution of invasive species in lower-income economies is relatively poorly understood, and many countries do not actively curate a list of species invasions or have programs to monitor or mitigate the effects of non-native species within their borders. Methods leveraging new technologies and expanding access to the internet may offer the opportunity to support low-cost and large-scale monitoring efforts. Here, we demonstrate how the use of online news coverage can support initial attempts to map the distribution of an economically-important, non-native freshwater fish in Bangladesh (Ptergoplichthys sp.), which is native to tropical regions of South America. By initiating new collaborations between the scientific and online journalism communities, governments and organizations may be able to enhance their abilities to map the distribution of non-native species and develop new programs to support public awareness of species invasion at relatively low cost.


Introduction
Published descriptions of biological invasions in poorer countries are relatively scarce , though no region of the globe appears to be free from the risk of invasion (Hughes et al. 2020). In lower-income economies, public awareness of species invasions and the ability of the scientific community to identify and monitor invasions has been limited (Nuñez and Pauchard 2010), and this has implications for early warning and rapid response which are essential in controlling the spread of invasive species (Pysek et al. 2020). An incomplete understanding of the geographical distribution of an invasive species influences the ability to accurately predict the consequences of invasions and the way in which policy makers should address invasion threats (Nagendra 2018). Research has suggested that tropical regions may be at less risk for invasion (Chong et al. 2021), Promoting community-based surveillance of economically important invasive species but more information is needed to assess if this pattern can be supported with data. Accurate invasion data are especially important when an invasion threatens economic stability (Angulo et al. 2021). For instance, the economic consequences of invasion in aquatic environments can compromise the sustainability of freshwater fisheries (Ramírez-Guevara et al. 2012). Increasing access to technology including, internet access, online content, and social media create potentially transformative opportunities for progress in invasive species management (Groom et al. 2019;van Rees et al. 2022), especially in poorer regions of the globe. Social media and other online resources may function as an informal real-time information source that can contribute to the detection of trends and early warnings in environmental problems (Edwards et al. 2021).
Rivers dominate much of Bangladesh's landscape and more than 50 transboundary rivers interact to form the world's largest delta (Rasul 2015). Much of the country's land mass was generated by alluvium from the Ganges and Brahmaputra watersheds (Brammer 2016). The country is home to more than 740 species of marine and freshwater fishes (IUCN 2015). The country also has a long history of species introductions from around the globe (Mukul et al. 2020).

Reported activities
We used widely available online news resources to test a new approach that could support monitoring efforts of economically important invasive species in lower-income economies. We identified reports of Pterygoplichthys (suckermouth catfish) invasion from local and national newspapers and online news portals since January 2007 (the year it was reported in the country for the first time) to March 2022. Suckermouth catfish in the family Loricariidae are native to Central and South America, but due to their popularity in the aquarium trade, have been introduced throughout the globe. In many regions, they have become invasive (Capps and Flecker 2015). Smallscale and subsistence fisheries have been negatively impacted by suckermouth catfish invasion (Ramírez-Guevara et al. 2012).
We conducted searches through Google search engine using the terms 'sucker fish', 'suckermouth catfish', 'devil fish', 'alien fish' and 'peculiar fish'. We also included the local names used for Pterygoplichthys, including 'birol mach', 'ajgubi mach' and 'doitto mach'. We only included news reports that reported the confirmation of the species by local experts in our analysis. To prevent repetition, news reports from multiple news sources covering the same area over the same time period were cross-checked and duplicate invasion reports were discarded. For the purpose of this study, news reports were defined as reports by local news reporters and journalists of regional-and national-level newspapers or online news portals, and local experts were defined as representatives from a district-level fishery officer from the government or an academic researcher with expertise in ichthyology, fisheries biology, or a related field. We also reviewed the photos and video included in each report and visually confirmed the presence of loricariid catfish. We used Google Earth Pro to obtain the geographic coordinates of the invasion that was documented in each report, and employed ArcGIS 10.8 to create a map of the distribution. The district-level shapefile of Bangladesh was derived from GeoDASH. We used the frequency of reported invasions within a given district to estimate the intensity of district-level invasions. If more than 19 unique locations were documented in a district, it was classified as 'dominant', and districts reporting between five and 18 locations were classified as 'abundant'. Districts reporting one to four locations were classified as 'rare' and districts with no reports were classified as 'not reported' (Fig. 1, Table 1).
Our results suggest that suckermouth catfish are widely distributed in Bangladesh. Our search documented them in 38 out of the 64 administrative districts in the country (Fig. 1). We documented a total of 111 distinct invasion locations using our approach (Table 1; Supplemental Table 1). Two districts were classified as 'dominant' two were classified as 'abundant' and 34 were classified as rare. Suckermouth catfish were detected in manmade ponds and lake ('inland waters') in 21 districts and in the rivers and  (Table 1, Fig. 1).

Discussion of significance
Bangladesh is a water-rich country with extensive aquatic diversity. Freshwater fisheries in Bangladesh generate 3.61% of the national GDP and roughly 24.41% of the agricultural GDP (DOF 2017). Bangladesh is also one of the leading inland fish producers in the world (FAO 2018) and freshwater fisheries meet approximately 60% of the total animal protein demand of the country (DOF 2017). To support growing human populations, non-native fishes have been introduced to support nutritional needs, mosquito control efforts, or the ornamental fish trade and subsequently become established after release (Galib   Mukul et al. 2020). In Bangladesh, there has been no country-level inventory of invasive aquatic species. However, supporting surveillance and capacity building of government officials, promoting community awareness, and organized cooperation with neighboring countries have been identified as essential steps needed to minimize the spread and mitigate the threats of invasive aquatic species (Mukul et al. 2020). Suckermouth catfish are facultative air-breathers and can tolerate a wide range of physicochemical conditions (Capps et al. 2011); therefore, they have the capability to invade extremely degraded habitats. Research also suggests that they can alter the structure and function of invaded sites and negatively impact native species through competition for food and feeding on their eggs (Capps and Flecker 2013;Capps and Flecker 2015;Chaichana, Jongphadungkiet 2012). Hence, populations of other species may be negatively impacted by suckermouth catfish invasion. Seasonal flooding that occurs concomitantly with monsoons inundates more than 70% of the country (Agrawala et al. 2003) and may support the spread of the invasive catfish from more densely-packed urban regions to more rural areas of the country. Flooding and extensive annual and seasonal aquatic connectivity in the region may also have led to the movement of suckermouth catfish from India into Bangladesh (Hussan et al. 2016).Our study documented that the capital city, Dhaka, and nearby district of Narayanganj had the greatest number of reports and anecdotal observations by fishers. Experts in some of the reports also suggested that suckermouth catfish are the dominant species in reported invasion sites and relatively limited numbers of individuals of other fish species can be harvested (Supplemental Videos). Notably, rivers in these regions are highly degraded (e.g., dissolved oxygen (DO) as low as 1 mg L −1 and biological oxygen demand (BOD) as high as 55 mg L −1 ) (Bashar and Fung 2020) and they host the largest ornamental fish markets in Bangladesh. Natural resource managers should focus eradication efforts in the populated areas around Dhaka to prevent the additional spread of suckermouth catfish to new drainage areas.
The approach we used is limited in the biological information it provides about and invasion, and it can only be readily used in regions with access to the technology and media outlets needed to produce online coverage. We acknowledge these limitations and suspect that suckermouth catfish are more widely distributed in Bangladesh than our data suggest. Many districts, especially those in rural areas, have limited media coverage. Furthermore, the actual and relative abundance of suckermouth catfish cannot be decerned through this method. Future investigations that are funded to test similar techniques should ground truth the patterns documented through online investigation. They should also be encouraged to couple outreach and education efforts with monitoring efforts to test the efficacy of this approach in supporting awareness about invasive species.
Developing effective management and eradication strategies to mitigate the socioeconomic and ecological impacts of species invasion is dependent upon accurate mapping of species distribution (Nagendra 2018). However, reliable descriptions of biological invasions in developing economies are limited ). Here, we used publicly available online new stories to document the distribution of a wide-spread, economically-important invasive species in Bangladesh. Though the data generated through this process are relatively unrefined, we were able to use the method to visualize regions of the country with greater public awareness of the problem and to highlight potential regions of Bangladesh where management efforts could be focused to reduce further spread of suckermouth catfish. The process we document here could be used as an important first step in understanding the geographical distribution of aquatic invasive species. Our work suggests that increasing access to smart phones and online media can be leveraged to transform invasive species management in Bangladesh; lessons that could be applied to other regions of the world. Through collaboration with fishing cooperatives and online media outlets, the methods outlined here could be operationalized at a larger scale to support low-cost early warning programs for invasive species that are socially and/ or economically important species. Furthermore, the application of this approach could support more rapid responses to invasion threat in countries with limited financial resources.