Perceptions of trends in Seychelles artisanal trap fisheries: comparing catch monitoring, underwater visual census and fishers' knowledge

Abstract

SUMMARYFisheries scientists and managers are increasingly engaging with fishers' knowledge (FK) to provide novel information and improve the legitimacy of fisheries governance. Disputes between the perceptions of fishers and scientists can generate conflicts for governance, but can also be a source of new perspectives or understandings. This paper compares artisanal trap fishers' reported current catch rates with landings data and underwater visual census (UVC). Fishers' reports of contemporary 'normal' catch per day tended to be higher than recent median landings records. However, fishers' reports of 'normal' catch per trap were not significantly different from the median CPUE calculated from landings data, and reports of 'good' and 'poor' catch rates were indicative of variability observed in landings data. FK, landings and UVC data all gave different perspectives of trends over a ten-year period. Fishers' perceptions indicated greater declines than statistical models fitted to landings data, while UVC evidence for trends varied between sites and according to the fish assemblage considered. Divergence in trend perceptions may have resulted from differences in the spatial, temporal or taxonomic focus of each dataset. Fishers may have experienced and understood behavioural changes and increased fishing power, which may have obscured declines from landings data. Various psychological factors affect memory and recall, and may have affected these memory-based estimates of trends, while different assumptions underlying the analysis of both interview data and conventional scientific data could also have led to qualitatively different trend perceptions. Differing perspectives from these three data sources illustrate both the potential for 'cognitive conflicts' between stakeholders who do not rely on the same data sources, as well as the importance of multiple information sources to understand dynamics of fisheries. Collaborative investigation of such divergence may facilitate learning and improve fisheries governance.

Assessing Changes in Fisheries Using Fishers’ Knowledge to Generate Long Time Series of Catch Rates: a Case Study from the Red Sea

“…In this case, interviews gave more accurate results than official statistics. Daw et al (2011) compared CPUE data from interviews, official reports, and underwater visual censuses and found disagreement among them. They concluded that each data source had its own limitations and biases, and that none could be taken at face value.…”

“…They concluded that each data source had its own limitations and biases, and that none could be taken at face value. Even the most independent abundance measurement, the underwater visual census, had sampling problems, e.g., depth limitation, and there was also a mismatch between the area sampled by the visual census and the fishing grounds (Daw 2008, Daw et al 2011. O'Donnell et al (2012) compared CPUE data from interviews, logbooks, and official catch landing records.…”

Collaborative Engagement of Local and Traditional Knowledge and Science in Marine Environments: A Review

“…Silvano and Valbo-Jorgensen argue that divergent results should prompt new studies rather than lead to the assumption that one knowledge system has the right answer. Daw et al (2011) compares fishers' reports of catch rates with official landings data and underwater visual census (UVC) in the Seychelles, finding that each data source gave different perceptions of trends in the biomass of fish and catches over the study period. Other such studies have compared seasonal abundance patterns (Manajarréz-Martínez et al 2010) and seabird chick emergence and size (Moller at al.…”

The importance of targeted spawning aggregation fishing to the management of Seychelles’ trap fishery

“…The CAS is a stratified catch, effort and species composition statistical system implemented since 1985 but modified in 1991 (Mees, 1990;Grandcourt and Cesar, 2002;Daw et al, 2011). Trap data are disaggregated into active and static trap-types.…”

“…They are the most important fish family in the coastal trap fishery with an estimated catch of 190 metric tonnes (t) in 2008 (Seychelles Fishing Authority, 2009), and S. sutor is the main target species (Grandcourt and Cesar, 2002). Three types of traps are used in the fishery, of which two are sturdily constructed, fixed (static) traps with soak times of up to 3 days, while active traps are of lighter construction and are soaked for several hours only (Daw et al, 2011). The fishery is subject to minimum mesh size requirements (40 mm) but otherwise is unmanaged.…”