Patterns and Trends in Cetacean Occurrence Revealed by Shorewatch, a Land-Based Citizen Science Program in Scotland (United Kingdom)

Abstract

Shorewatch is a citizen science project, managed by Whale and Dolphin Conservation (WDC), that records the occurrence of cetaceans during regular, standardized watches from a series of locations along the coast of Scotland (United Kingdom). Observer training and a clearly defined protocol help deliver a valuable source of information about cetacean occurrence and activity along the coast. Between 2005–2018, over 52000 watches generated over 11000 sightings of at least 18 cetacean species. Generalized Additive Models based on sightings for the five most commonly sighted species (bottlenose dolphin, harbor porpoise, minke whale, Risso’s dolphin, and common dolphin), at those sites with the longest time series, demonstrated seasonal, geographical and year-to-year differences in their local occurrence and relative abundance. Bottlenose dolphins are mainly present at observation sites located on the east coast of Scotland, being uncommon on the west coast, while harbor porpoise and minke whale are principally present at sites located on the west coast. The seasonality observed in cetacean occurrence is consistent with peak abundance in summer months described by previous studies in the area. Mean depth around the observation sites is the static variable that apparently has the greatest influence on species presence and number of sightings, except for Risso’s dolphin. All the species except bottlenose dolphin showed upward trends in occurrence and number of sightings over the period 2012–2018. Evidence of temporal autocorrelation was found between results from consecutive watches at the same site on the same day as well as between results from consecutive days at the same site. The power to detect declines in local abundance over a 6-year period depends on the underlying sighting rate of each cetacean species, the number of watches performed and the rate of decline. Simulations performed to determine the power to detect a decline suggest that the current intensity of observation effort in some observation sites, of about 2500 watches per year, may offer good prospects of detecting a 30% decline of the most frequently sighted species (95% of the time) over a 6-year period, although a more even distribution of observation effort in space and time is desirable. The data could potentially be used for monitoring and 6-yearly reporting of the status of cetacean populations.

Using citizen science to better understand Risso’s dolphin (Grampus griseus) presence in northeast Scotland and the Northern Isles

“…Risso's dolphins were found to be present in the region yearround, with a higher number of reported sightings in August, consistent with similar previous studies in the area (Evans et al, 2010), and with annual and seasonal trends seen in other regions such as the Outer Hebrides (Weir et al, 2019), Moray Firth (WDC Shorewatch, unpublished data 4 ) and East Grampian coastline (Evans et al, 2003;Genesis Oil and Gas Consultants, 2011;Anderwald and Evans, 2020;Gutieŕrez-Muñoz et al, 2021). Although with considerable spatiotemporal variation, initial photo-ID and reported sightings data suggests that Risso's dolphins are consistently recorded inshore at specific locations within the study area.…”

“…Between 2020-2021 alone, OMMRI launched in Orkney and saw sightings reports rise by at least three-fold in two years (OMMRI, unpublished data 1 ), WDC Shorewatch expanded into the Northern Isles, training 100 new volunteers in cetacean identification, and the "COVID-19 effect" influenced an increase in the overall number of citizen science observers. However, there is also previous evidence suggesting an upward trend in the occurrence of Risso's dolphin around Scotland from effort-corrected monitoring (Gutieŕrez-Muñoz et al, 2021). Changes in prey distribution due to climate change could also play a part (Hall et al, 2019;Evans and Waggitt, 2020b) and is worthy of further consideration, given the implications for future spatial protection.…”

“…Collaborating with wildlife photographers and the public can result in the contribution of quality images. Nevertheless, one constraint with this approach can be the consistency and quality of data received (Newman et al, 2003;Embling et al, 2015;Gutieŕrez-Muñoz et al, 2021). However, keeping volunteers engaged and providing guidance as to what is required for a valid photo-ID image can help to improve both of the above.…”

“…The use of citizen science to advance scientific understanding and enhance public participation is increasingly recognised (Evans, 1976(Evans, , 1980Evans et al, 2003;Silvertown, 2009;Merenlender et al, 2016;Gutieŕrez-Muñoz et al, 2021) and valued by governments, policy makers and the scientific community (Hecker et al, 2018).…”

Seas the DNA? Limited detection of cetaceans by low‐volume environmental DNA transect surveys

“…Each of these approaches includes inherent biases to data collection; acoustic monitoring can be spatially limited and focused toward only a portion of species depending on the device used (Barkley et al., 2021; Liu et al., 2022; Rice et al., 2021), whereas visual boat‐based surveys that cover a wider spatial area than acoustic monitoring, however, are limited to when animals surface to breathe, time of day and year, visibility, weather, sea state, observer bias, and vessel avoidance bias (Dalpaz et al., 2021; Forney et al., 1991; Marsh & Sinclair, 1989; Oliveira‐Rodrigues et al., 2022). In addition to these methods, citizen science, or community‐based monitoring initiatives, worldwide also contribute important data toward understanding cetacean distribution and abundance (Cheeseman et al., 2023; Gutiérrez et al., 2021; Mancini & Elsadek, 2019; Mwango'mbe et al., 2021; Pirotta et al., 2020; Rodriguez et al., 2021).…”