White-beaked dolphins (Lagenorhynchus albirostris) annual and seasonal distribution in Skjálfandi Bay, Iceland. Using opportunistic data from whale watching platforms.
Supervisor: Marianne Rasmussen (The University of Iceland’s Research Centre in Húsavík).
White-beaked dolphin (Lagenorhynchus albirostris) is endemic to the North Atlantic and the most sighted dolphin in Icelandic coastal waters. However, limited data is known about this species. An analysis was done from a fourteen-year period (2004-2017), of photo-identification and data collected from a whale watching opportunistic platform in Skjálfandi Bay, Iceland. A summary of annual recorded surveys presented a total of 2,434 trips, where only 24.4% (594 trips) included sightings of whitebeaked dolphins. Linear regression model explains a linear relation (R2=0.8329) in number of recorded trips (NSV) through time. However, for recorded trips with white-beaked dolphins (NWBD), linear regression didn’t follow that trend (R2=0.1344). To analyse effort spent of encounters with white-beaked dolphin an analysis of their annual sightings per unit effort (SPUE) was conducted. First analysis consisted of an annual SPUE analysis where only white-beaked dolphins breeding season (May to September) was analysed, and a second one including only the month of July for each year because it was the only month consecutively recorded. Throughout the annual analysis we concluded that there was a significant statistical difference among years (Kruskal-Wallis test χ2(13) = 106.51, p =< 2.2e-16). Boxplots showed that years 2014 onwards had a slightly lower median compared to previous years. However, to reduce bias even more, the annual analysis of the month of July confirmed that indeed there were decreasing SPUE during the last four years. Spearman correlation was performed on SPUE of white-beaked dolphins by sea surface temperature where we conclude that SST has no effect in SPUE of white-beaked dolphins in the bay. Furthermore, spatial and temporal trends were studied, where white-beaked dolphins’ distribution of sightings displayed no annual patterns, however kernel density monthly model during the breeding season (May-Sep) allowed to observe a clear affinity towards shallow areas with steep slopes in Skjálfandi Bay. Finally, a minimum abundance of 355 whitebeaked dolphins were identified as dorsal fin edge mark (DEM), from which only a 5.92% (n=21) were resighted among the subsequent years. All annual resighting were considered ‘rare’, since they didn’t exceed the three-year resighting threshold. These low frequencies may be explained because of its free-ranging population. Whale watching tourism in the bay has evolved greatly in these last fourteen years, and although it started in Iceland as an alternative and ‘sustainable’ service to increase local revenue, it still presents a set of challenges, and necessary scientific data should be provided to create standardised protocols for management and conservation. and large coastal distribution and because of the nature of the opportunistic sampling. Results on this study suggest and expansion of the area of study is required, and standardised data collection for future conservation projects should be applied.