Abstract/Summary

1. Anthropogenic activities and climate change are affecting marine ecosystems worldwide, but systematic biodiversity assessments through periodic biomonitoring can be challenging and costly. Local ecological knowledge (LEK), obtained from experienced residents, can complement other approaches and provide improved understanding of the conservation status of marine areas. Here we explore the value and limitations of LEK to assess the status of several flagship species of tourism interest: cetaceans, sea turtles, whale sharks, and sea snakes in a unique tropical fiord and biodiversity hotspot, Golfo Dulce, Costa Rica. 2. We analysed interviews conducted with fishermen and tour-boat guides in 2010 and 2020 and compared their responses to biomonitoring data obtained through boat-based sighting surveys during in the same two time periods. Our questionnaire asked for estimates of sighting frequencies in both years, and in 2020 it also inquired about perceived changes over the time gap. 3. A key limitation was that many interviewees from 2010 could not be relocated in 2020, though 13 repeat participants served as a panel. Their responses suggest shifts in abundance that vary across taxa. For example, changes in reported sighting frequencies from 2010 to 2020 indicate a possible decline in whales but an increase in sea snakes. Those changes were also reflected in our biomonitoring data, suggesting respondents were fairly accurate in their reports of current abundance. However, when asked about perceived changes over the decade we found their answers were not consistent with changes detected through their reported frequencies nor though biomonitoring. 4. Our results suggest LEK can be a good source of information for current assessment but highlight the potential biases of perceptions of change. Evaluating changes through LEK may best be done by obtaining interview data at multiple points in time and systematically assessing trends, though, notably, there can be challenges with acquiring consistent sample sizes. Interviews should not replace but can complement biomonitoring while also providing further value via community engagement and as an avenue to gain insights into local opinions regarding conservation measures.