Assessing discards in an illegal small-scale fishery using fisher-led reporting

Rev Fish Biol Fisheries https://doi.org/10.1007/s11160-022-09708-9 ORIGINAL RESEARCH Assessing discards in an illegal small‑scale fishery using fisher‑led reporting T. Mendo · J. Mendo · J. M. Ransijn · I. Gomez · P. Gil‑Kodaka · J. Fernández · R. Delgado · A. Travezaño · R. Arroyo · K. Loza · P. McCann · S. Crowe · E. L. Jones · M. A. James Received: 8 April 2021 / Accepted: 28 February 2022 © The Author(s) 2022 Abstract About a third of all marine fish in the world are caught in Small-Scale Fisheries (SSF). SSF are increasingly recognised as essential for food security and livelihoods for vulnerable and economically fragile communities globally. Although individual SSF vessels are usually perceived as having little impact on the ecosystem, the cumulative impact of gear type and number of vessels may be substantial. Bottom trawling is a common fishing method that can greatly influence the marine ecosystem by damaging the seafloor and generating high levels of discards. However, appropriate sampling coverage using onboard observer programmes to collect these data from Supplementary Information The online version contains supplementary material available at https://doi. org/10.1007/s11160-022-09708-9. T. Mendo (*) · J. M. Ransijn · M. A. James Scottish Oceans Institute, University of St Andrews, East Sands, Fife KY16 8LB, UK e-mail: J. Mendo · I. Gomez · P. Gil‑Kodaka · J. Fernández · R. Delgado · A. Travezaño · R. Arroyo · K. Loza Facultad de Pesquería, Universidad Nacional Agraria La Molina, Av. La Molina s/n, Lima, Peru P. McCann · S. Crowe IT Services, University of St. Andrews, Walter Bower House, Guardbridge KY16 0US, UK E. L. Jones Biomathematics and Statistics Scotland, Peter Guthrie Tait Road, Edinburgh, UK SSF are rare, as they are expensive and pose logistical constraints. A mobile App was used to assess whether self-reporting by fishers could provide reliable fine-scale information on fishing effort and discards over time in an illegal shrimp trawling fishery in northern Peru. Maps depicting the spatial distribution of trawling effort and the proportion of discards from observers and fishers were compared using the Similarity in Means (SIM) Index, which ranges from 0 when spatial patterns differ completely to 1 when spatial patterns are very similar. High levels of agreement between spatio-temporal patterns of effort (SIM Index = 0.81) and discards (0.96) were found between fisher and observer maps. Moreover, far greater spatial coverage was accomplished by fishers, suggesting that self-reporting via an App represents a useful approach to collect reliable fisheries data as an initial step for effective monitoring and management of these fisheries. Keywords Effort · Tracking · Bycatch; mobile Application · Blue agenda · Trawling Introduction Bottom trawling, where fishing gear such as beam, otter trawls or dredges are towed over the seafloor, is the most widespread human source of physical disturbance affecting seabed habitats (Amoroso et al. 2018). Among the main impacts associated with Vol.: (0123456789) 13 Rev Fish Biol Fisheries bottom trawling are the alteration of habitat structure, reduction of faunal biomass, productivity and species richness (Collie et al. 2017; Sciberras et al. 2018) which can lead to changes in the trophic structure and function of ecosystems (Thrush and Dayton 2002; Tillin et al. 2006; Pusceddu et al. 2014). In addition, high discard rates (where species or sizes of species that are not targeted are thrown overboard usually dead or dying) are attributed to bottom trawls. It is estimated that bottom trawl fisheries contribute to 45% of all discards (4.2 million tonnes) (Pérez Roda 2019). Discarding practices are controversial resulting in waste, juveniles of other commercial species are overexploited (usually affecting co-occurring fisheries), and biodiversity and protected and endangered species are threatened (Dayton et al. 1995; D’Agrosa et al. 2000; Lewison et al. 2004; Harrington et al. 2005). Most of what we know about the impacts of bottom trawling come from studies of large scale fisheries. Even though Small-Scale Fisheries (SSF) contribute to about a third to half of all fish caught in the sea (Kelleher et al. 2012; Pauly and Zeller 2016), data on discards are limited (Lewison et al. 2014; Suuronen and Gilman 2020). While in general, it is acknowledged that SSF contribute very little to global discarding (Zeller et al. 2018) and have low discard rates (~ 4%) (Kelleher 2005), it is increasingly recognised that the magnitude of their impact on the ecosystem is more likely related to the quantities of vessels involved in the activity and the types of gear used (Shester and Micheli 2011; Belhabib et al. 2018). Thus, shrimp trawling by SSF can have discard rates comparable to those observed in industrial fisheries (Pérez Roda 2019). Several methods are used to monitor discards worldwide, including at-sea observer programmes, remote electronic monitoring (REM), logbook or smartphone reporting, fisheries collaborative sampling schemes and interviews (Mangi et al. 2015; Suuronen and Gilman 2020). Independent on-board observer programmes have generally been depicted as the most reliable means to assess discards (Pérez Roda 2019; Suuronen and Gilman 2020). This remains the most widely used method, and in the Food and Agriculture Organisation (FAO) third assessment of global marine fisheries discards, more than 78% of the discard rates were obtained from this source (Pérez Roda 2019). While on-board observers Vol:. (1234567890) 13 provide accurate and comprehensive information on discards and associated information (e.g. assessment of probability of post-release survival, environmental variables, vessel information) they remain an expensive method to monitor discards (Suuronen and Gilman 2020). In SSF, the large number of vessels, the remote and dispersed nature and vessel size constraints (i.e. sufficient deck space to host an observer) limit appropriate sampling coverage by this means. In recent years, REM which includes on-board cameras, have been used as an alternative method to obtain reliable information on bycatch and discards (Kindt-Larsen et al. 2011; Glemarec et al. 2020). One of the advantages of REM is to provide spatial information, from which main fishing grounds and effort can be estimated. While REM has been proven effective to assess bycatch in SSF (Bartholomew et al. 2018), their wide-scale deployment is hindered by the relatively high price of the equipment compared to SSF revenue, the number of vessels involved and the capacity of authorities to manage and utilise large quantities of image data in an operational context. For SSF, fisher-led reporting on discards may allow a wider, more cost-effective sampling coverage. The use of logbooks and more recently smartphones has allowed fishers to self-record data on bycatch and discards which is sent to managers in real or near real-time (Merrifield et al. (...truncated)