FIELD STUDIES OF WHALES AND DOLPHINS IN FAXAFLÓI BAY, SOUTH-WEST COAST, ICELAND

Background

Although white-beaked dolphins (Lagenorhynchus albirostris) have been studied in Icelandic waters (Rasmussen, 1999; 2004; Magnusdottir, 2007; Bertulli, 2010), there is insufficient data to fully understand their abundance, population dynamics, habitat use and behaviour. Most studies have been conducted on the acoustics of white-beaked dolphins (Rasmussen & Miller, 2002; Rasmussen et al., 2002; Rasmussen et al., 2004; Rasmussen et al., 2006).

Photo Gallery
All photos copyright: ©Chiara G. Bertulli

In the north of Iceland, L. albirostris are routinely found in Skjalfandi Bay. In the south-west of Iceland, sightings have been reported from Faxafloi and from the west coast of Iceland. The east coast of Iceland remains un-surveyed. Observations from previous Icelandic field seasons revealed that significant numbers of white-beaked dolphin are present in Icelandic coastal waters year round (Salo, 2004; Magnusdottir, 2007). The likelihood of detecting white-beaked dolphins was much higher in Faxafloi than in Skjalfandi at the NE-coast of Iceland during the whale-watching seasons (from April to October).

Observations by Rasmussen (1999) during the 1997 to 1998 whale-watching season in Faxafloi, showed the greatest abundance of white-beaked dolphins in June, July and August. Bertulli later confirmed high frequency of L. albirostris sightings occurring from May to August (Bertulli, 2010).

Aerial surveys have been conducted to estimate the abundance of white-beaked dolphins in Icelandic waters, using large scale surveys during the summer months (NASS survey conducted from 1986-2001) resulting in an estimated 31653 animals in 2001 (95% CI:17679–56672) (Pike et al., 2009).

In 2004 two images of a white-beaked dolphin (one taken off the coast from Olafsvik in Brei?afjor?ur and one in Skjalfandi) were well matched indicating that it was the same individual in both locations (Tetley, 2006). Three individuals were re-matched between Faxafloi and Skjalfandi in 2010 (Bertulli, 2010) and up to eighteen individuals were confirmed during additional analysis (Bertulli et al., in prep). In August 2006 one male white-beaked dolphin captured in Faxafloi was tagged with a satellite transmitter, recording movements (Rasmussen et al., 2007). That individual travelled numerous times between Faxafloi, Brei?afjor?ur and the Westfjords between August and January. On one occasion the tagged dolphin ventured as far as the Westman Islands.

The photo-identification performed between 1998 and 2010 and the information gathered from the single satellite tagged dolphin suggest that white-beaked dolphins in Icelandic waters inhabit  coastal territories of relatively large scale, which they constantly scout. Based on information from the satellite track, one of these territories might extend between the south-west and north-west coast of Iceland.

Current research objectives

  • Determine the abundance of white-beaked dolphins in the Faxafloi population
    An intensive photo-identification study designed to minimize violation of mark-recapture assumptions can help to minimize bias and maximize precision of population estimates

  • Determine patterns of residency of white-beaked dolphins in the Faxafloi populations
    Using the photo-ID data for each year, it is possible to examine the number of days individual whales and dolphins are re-sighted; minimum residency time (the number of days between first and last sightings within the same season); and re-sighting rate (the proportion of individual whales/dolphins identified on more than one day within the same season)

  • Establish sex ratio estimates using genetic and/or hormone level data
    For most species, sex determination relies on the observation of the ventral region, which is a rare event in situ. The impracticality of morphological sex determination hinders a thorough understanding of important biological factors. Molecular sexing can close this gap and can be coupled with low impact sampling such as biopsy darting, which has proved to be safe and minimally invasive for free-ranging cetaceans

  • Investigating social structure of white-beaked dolphins in Faxafloi Bay
    The general procedure to convert long-term photographic identification databases into models of social structure, is to define and calculate association indices between all pairs of identified animals that together make up an association matrix. Using methodologies such as cluster analyses or sociograms, the association matrices for a particular dataset can be displayed. To test for preferred companionships, permutations of association measures can further be used

  • Investigate the prevalence of cutaneous disorders in white-beaked dolphins of Faxafloi Bay
    Skin diseases in free-ranging whales and dolphins have been studied using a variety of research methods including photographic identification (photo-id) surveys. Thus, photo-identification techniques can be extended to record the prevalence of certain signs of disease in whales and dolphins, and suggests that these methods could be used to complement other studies of disease in wild cetacean populations

  • Investigate the foraging behaviour of white-beaked dolphins and their association with seabirds during feeding bouts
    White-beaked dolphins are known to commonly engage in elaborate herding behaviour when feeding upon a shoal of fish

Background

Although white-beaked dolphins (Lagenorhynchus albirostris) have been studied in Icelandic waters (Rasmussen, 1999; 2004; Magnusdottir, 2007; Bertulli, 2010), there is insufficient data to fully understand their abundance, population dynamics, habitat use and behaviour. Most studies have been conducted on the acoustics of white-beaked dolphins (Rasmussen & Miller, 2002; Rasmussen et al., 2002; Rasmussen et al., 2004; Rasmussen et al., 2006).

In the north of Iceland, L. albirostris are routinely found in Skjalfandi Bay. In the south-west of Iceland, sightings have been reported from Faxafloi and from the west coast of Iceland. The east coast of Iceland remains un-surveyed. Observations from previous Icelandic field seasons revealed that significant numbers of white-beaked dolphin are present in Icelandic coastal waters year round (Salo, 2004; Magnusdottir, 2007). The likelihood of detecting white-beaked dolphins was much higher in Faxafloi than in Skjalfandi at the NE-coast of Iceland during the whale-watching seasons (from April to October).

Observations by Rasmussen (1999) during the 1997 to 1998 whale-watching season in Faxafloi, showed the greatest abundance of white-beaked dolphins in June, July and August. Bertulli later confirmed high frequency of L. albirostris sightings occurring from May to August (Bertulli, 2010).

Aerial surveys have been conducted to estimate the abundance of white-beaked dolphins in Icelandic waters, using large scale surveys during the summer months (NASS survey conducted from 1986-2001) resulting in an estimated 31653 animals in 2001 (95% CI:17679–56672) (Pike et al., 2009).

In 2004 two images of a white-beaked dolphin (one taken off the coast from Olafsvik in Brei?afjor?ur and one in Skjalfandi) were well matched indicating that it was the same individual in both locations (Tetley, 2006). Three individuals were re-matched between Faxafloi and Skjalfandi in 2010 (Bertulli, 2010) and up to eighteen individuals were confirmed during additional analysis (Bertulli et al., in press). In August 2006 one male white-beaked dolphin captured in Faxafloi was tagged with a satellite transmitter, recording movements (Rasmussen et al., 2007). That individual travelled numerous times between Faxafloi, Brei?afjor?ur and the Westfjords between August and January. On one occasion the tagged dolphin ventured as far as the Westman Islands.

The photo-identification performed between 1998 and 2010 and the information gathered from the single satellite tagged dolphin suggest that white-beaked dolphins in Icelandic waters inhabit coastal territories of relatively large scale, which they constantly scout. Based on information from the satellite track, one of these territories might extend between the south-west and north-west coast of Iceland.

 

Current research objectives

  1. Determine the abundance of white-beaked dolphins in the Faxafloi population

An intensive photo-identification study designed to minimize violation of mark-recapture assumptions can help to minimize bias and maximize precision of population estimates.

  1. Determine patterns of residency of white-beaked dolphins in the Faxafloi populations

Using the photo-ID data for each year, it is possible to examine the number of days individual whales and dolphins are re-sighted; minimum residency time (the number of days between first and last sightings within the same season); and re-sighting rate (the proportion of individual whales/dolphins identified on more than one day within the same season)

  1. Establish sex ratio estimates using genetic and/or hormone level data

For most species, sex determination relies on the observation of the ventral region, which is a rare event in situ. The impracticality of morphological sex determination hinders a thorough understanding of important biological factors. Molecular sexing can close this gap and can be coupled with low impact sampling such as biopsy darting, which has proved to be safe and minimally invasive for free-ranging cetaceans

  1. Investigating social structure of white-beaked dolphins in Faxafloi Bay

The general procedure to convert long-term photographic identification databases into

models of social structure, is to define and calculate association indices between all pairs of identified animals that together make up an association matrix. Using methodologies such as cluster analyses or sociograms, the association matrices for a particular dataset can be displayed. To test for preferred companionships, permutations of association measures can further be used

  1. Investigate the prevalence of cutaneous disorders in white-beaked dolphins of Faxafloi Bay

Skin diseases in free-ranging whales and dolphins have been studied using a variety of research methods including photographic identification (photo-id) surveys. Thus, photo-identification techniques can be extended to record the prevalence of certain signs of disease in whales and dolphins, and suggests that these methods could be used to complement other studies of disease in wild cetacean populations

  1. Investigate the foraging behaviour of white-beaked dolphins and their association with seabirds during feeding bouts

White-beaked dolphins are known to commonly engage in elaborate herding behaviour when feeding upon a shoal of fish.