INTRODUCTION
Striped dolphins (Stenella coeruleoalba Meyen, 1833) are widely distributed in temperate, subtropical and tropical seas. The species is found worldwide and, in the Atlantic, it ranges north to Newfoundland, southern Greenland, Iceland, the Faroes and Denmark (Rice, Reference Reid, Kitchener, Ross and Herman1998), with the northern limit on the eastern seaboard of North America changing as a function of the Gulf Stream (Archer, Reference Archer and Perrin2002). There have been occasional sightings in Norwegian waters (Isaksen & Syvertsen, Reference Hohn, Lockyer, Bjørge and Donovan2002), and strandings of this species have been recorded as far north as Iceland and the Faroe Islands (Bloch et al., Reference Bloch, Desportes, Petersen and Sijurjónsson1996). Striped dolphins are typically found outside the continental shelf, usually over the continental slope and over oceanic waters (Archer, Reference Archer and Perrin2002). It tends to occur in sea depths of 1000 m or deeper, but has been recorded in waters of 60 m or less (Forcada et al., Reference Evans, Stirling and Evans1990); when found close to land it is usually seen in deep water.
In UK waters, the species is classed as rare (Reid et al., Reference Perrin and Myrick2003). Its normal distribution appears to reach its northern limits at 50°N, with most records coming from the Western Approaches (off the south-west of England) and off Southern Ireland, although it has been recorded as far north as Shetland and in deep waters off the continental shelf north to 62°N (Evans, Reference Desportes1992; Reid et al., Reference Perrin and Myrick2003). It was not recorded among the 15 cetacean species sighted off the north and west of Scotland between 1979 and 1998 by Weir et al. (Reference Weir, Pollock, Cronin and Taylor2001) or among nine cetacean species identified off north-west Scotland in July/August 1998 (Macleod et al., Reference MacLeod, Bannon, Pierce, Schweder, Learmonth, Herman and Reid2003), or the eight species encountered off the west coast of Ireland between May and September 2004 (Wall et al., Reference Wall, O'Brien, Meade and Allen2006). During the 1994 Small Cetacean Abundance in the North Sea and Adjacent Waters (SCANS) survey, which included the North Sea (including waters north to 62°N), Skagerrak, Kattegat, western Baltic Sea, Channel and Celtic Shelf, striped dolphins were encountered only in the Celtic Sea, in relatively deep waters over the continental shelf off France (Hammond et al., Reference Goujon, Antoine and Collet1995). Striped dolphins have been identified during observations from seismic surveys in UK waters; these sightings include a group of about 18 individuals north of Shetland in 1996, a group of approximately 13 individuals on the edge of the continental shelf to the west of Ireland in 1998, a group of 18 dolphins in the southern North Sea in 1999 and, during seismic surveys in 2000, ‘possible’ striped dolphins occurred in deep waters in the Faroe–Shetland Channel and in shelf waters to the west and east of Shetland (Stone, Reference Spitz, Richard, Meynier, Pusineri and Ridoux1997, Reference Stone2000, Reference Stone2001, Reference Stone2003).
The striped dolphin appears to be a relatively recent addition to the Scottish cetacean community, with the first stranding recorded on the Isle of Lewis, Western Isles in 1988 (Reid et al., Reference Reid, Evans and Northridge1993; Sheldrick et al., Reference Sheldrick1994). The first evidence of striped dolphins (euphrosyne dolphin) stranding on the British coast was in 1923 at Criccieth on the Lleyn Peninsula, Wales (Fraser, Reference Fraser1974). In Ireland, the first published record of a striped dolphin was in 1985, although they may have been present as early as 1912 (Berrow & Rogan, Reference Berrow and Rogan1997).
García-Martínez et al. (Reference Fraser1999), in a genetic study using mtDNA restriction analysis to determine the status of the species in European waters, found evidence for the existence of two distinct populations, one in the Mediterranean and one in the Atlantic Ocean, with very low gene flow between them. In the early 1990s, striped dolphins were a significant component of the cetacean by-catch in the Atlantic French tuna-drift-net fishery (Goujon et al., Reference García-Martínez, Moya, Raga and Latorre1993). In the Mediterranean, between 1990 and 1992, more than 1100 striped dolphin carcasses were recorded on beaches extending from the Spanish Mediterranean coast to the Tyrrhenian and Aegean Seas (Aguilar & Raga, Reference Aguilar and Raga1993). This massive die-off affected only the striped dolphin and it has been linked to an infection by a morbillivirus similar to the one that causes distemper in carnivores (van Bressem et al., Reference Stone2001).
Studies throughout the range of striped dolphins indicate that mating is seasonal, with gestation lasting from 12 to 13 months and lactation between 12 and 18 months. The inter-birth interval is 3–4 y. Body length at birth has been estimated to be between 93 and 100 cm, with adults reaching body lengths of 2.0–2.4 m. In general, males appear to reach sexual maturity between 7 and 15 y of age, possibly around 9 y, and estimates for the age of sexual maturity for females are between 5 and 14 y (Archer, Reference Archer and Perrin2002; Evans & Stirling, Reference Evans2002). The maximum estimated age for both males and females is 30–35 y, but may be as old as 57.5 y (Archer & Perrin, Reference Archer and Perrin1999; Evans & Stirling, Reference Evans2002). In the western Pacific, a complex schooling system has been documented, in which adult and mixed (juvenile and adults) schools are separated into breeding and non-breeding schools (Miyazaki & Nishiwaki, Reference Miyazaki, Kusaka and Nishiwaki1978; Archer, Reference Archer and Perrin2002).
Striped dolphins feed on a variety of pelagic and benthopelagic fish and squid. Regional variations in the diet have been reported, with myctophid fish dominating the diet off the coasts of Japan and South Africa while in the Mediterranean the species tend to feed primarily on squid (Archer & Perrin, Reference Archer and Perrin1999). In the eastern North Atlantic the diet consists of a variety of mesopelgaic and benthic fish, squid and crustaceans (Desportes, Reference Collet, Saint-Girons and Perrin1985; Berrow & Rogan, Reference Berrow and Rogan1995).
The present study summarizes information on life history and diet of the species at the northern limit of its distribution, as derived from strandings along the Scottish coast during 1992–2003. We analysed geographical, seasonal, sex- and size-related variation in diet.
MATERIALS AND METHODS
During 1992–2003, 52 striped dolphin strandings were recorded in Scotland, species identity being positively confirmed in 42 cases. Strandings locations were mapped using ARCVIEW.
Necropsies were carried out on 33 animals and samples of stomach contents were obtained from 20 of these (Table 1). Teeth and gonad samples were also available for some animals (6 dolphins and 12 dolphins respectively, Table 2). Necropsy procedures, sampling and data collection, as conducted by the Scottish Agricultural College (SAC), followed the recommendations of the European Cetacean Society (Kuiken & Hartmann, Reference Isaksen and Syvertsen1991) and the UK Marine Mammal Project (Law, Reference Kuiken and Hartmann1994). Cause of death was determined when possible.
Table 1. Striped dolphins (Stenella coeruleoalba) stranded around the Scottish coast (1992–2003) for which stomach samples were obtained.
Table 2. Striped dolphins (Stenella coeruleoalba) stranded around the Scottish coast (1992–2003) for which teeth and gonad samples were available.
Teeth were removed from the middle of the lower jaw and preserved in 10% neutral buffered formalin. Tooth preparation methods were adapted from Hohn & Lockyer (Reference Härkönen1995) and Lockyer (Reference Learmonth1995) and age was estimated by counting growth layer groups (GLG), which are thought to be laid down annually in odontocetes (Perrin & Myrick, Reference Perrin, Brownell and DeMaster1980).
The ovaries were removed and preserved in 10% neutral buffered formalin during the post-mortem examination of females, and any evidence of lactation or presence of a foetus was recorded. Both ovaries were examined externally and internally to record the presence and number of corpora lutea (CL) and corpora albicantia (CA). Females were classed as sexually immature if there were no corpora present. Females were considered sexually mature if the ovaries contained at least one corpus luteum or albicans. Pregnancy was established by the presence of a foetus. The assessment of female reproductive status was based on the procedures and terminology recommended by the International Whaling Commission (Perrin et al., Reference Miyazaki and Nishiwaki1984).
The testes were removed and preserved in 10% neutral buffered formalin during the post-mortem examination of males. Sections, approximately 2 × 2 × 0.5 cm, were dissected from the middle of each testis with its associated epididydmis, and stored in 70% ethanol before histological processing. The tissue sections were dehydrated, embedded, and cut into 7 µm sections. The mounted sections were then stained with haematoxylin and eosin. The reproductive status was classified as: (i) immature; (ii) pubescent; (iii) active mature; or (iv) resting mature; based on the mean diameter of the seminiferous tubules and the relative proportion (low, medium and high) of Sertoli cells, interstitial tissue, and germinal cells such as spermatogonia, spermatocytes, spermatids and spermatozoa, as described by Collet & Saint-Girons (Reference Clarke1984) for common dolphins.
Stomach contents were removed during necropsy and stored frozen or in 70% alcohol prior to analysis. Prey remains comprised mainly fish and cephalopods, also some crustaceans and polychaetes. Otoliths and bones of fish and mandibles (beaks) of cephalopods were identified using reference material and published guides (Clarke, Reference Calzada, Aguilar, Lockyer and Grau1986; Härkönen, Reference Hammond1986; Watt et al., Reference Watt, Pierce and Boyle1997). Fish were enumerated by counting otoliths and other paired bones, notably jaw bones, using the structure that yielded the higher number. Cephalopods were enumerated based on the number of upper or lower beaks, whichever was higher. Crustacean material (found in three stomachs only) was usually well-digested and could not be further identified.
Prey lengths and weights were estimated by applying standard regressions: regressions for fish were based on various sources as summarized by Brown & Pierce (Reference van Bressem1998), while those for cephalopods derived mainly from Clarke (Reference Calzada, Aguilar, Lockyer and Grau1986). It was not possible to estimate weights for crustaceans or polychaetes and their contribution is assumed to be minimal. Some bobtail squid (Sepiolidae) were identified to family from upper beaks, for which no general regression was available. It is assumed for the purpose of weight estimation that the animals had the same average weight as sepiolids for which lower beaks were found. Where large numbers of otoliths were present, a random sub-sample of at least 30 was measured (length or width). Length distributions of the main prey were calculated.
Dietary importance of each prey category was expressed as frequency (F, the number of stomachs in which it occurred), number of individuals summed across all stomachs (N), and the estimated weight of all individuals from otolith measurements summed across all stomachs (W). These indices were also expressed as percentages, %F expressing the percentage of stomachs in which a prey category occurs while %N and %W are based on sums of prey importance across all categories.
Statistical analysis (to relate diet to sex, season and body length) was based on data for numerical importance together with data on the median size of the two main prey species (whiting and Trisopterus) eaten by dolphins and used Kruskal–Wallis tests and Spearman's correlations. For comparison of seasons, the year was divided into two periods, ‘summer’ (April–September) and ‘winter’ (October–March). Body lengths were arbitrarily divided into three classes: ≤175 cm, 176–200 cm and >200 cm. Stranding locations were divided into ‘east coast’ (east of 4°W) and ‘west coast’ (west of 4°W). A length–weight relationship was derived for the stranded animals.
RESULTS
Between 1992 and 2003 the total number of stranded and by-caught cetaceans in Scotland was 1575 of which 1549 were identified to species. Of these, 52 animals were identified as Stenella coeruleoalba (3.4% of the total identified cetaceans). Strandings of striped dolphins occurred all around the Scottish coast (Figure 1) but with the majority of strandings recovered from the west coast. Strandings were recorded in every month of the year, with highest numbers being recorded in January–March and August. Twenty of the 52 strandings occurred between 1992 and 1997, with 32 between 1998 and 2003. Sex was determined for 41 dolphins, 17 females and 24 males. There was no difference in the seasonal pattern of strandings of males and females (Figure 2).
Fig. 1. Locations of striped dolphin strandings (Stenella coeruleoalba) around the Scottish coast (1992–2003). Dark circles indicate animals for which stomach contents were obtained.
Fig. 2. Seasonal distribution of striped dolphin (Stenella coeruleoalba) strandings around the Scottish coast (1992–2003).
Of the 33 striped dolphins examined, at least 29 had live-stranded. Pathologies recorded in some of the animals stranded included meningoencephalitis and Brucella meningitis. Seventeen of the 29 live-stranded dolphins were male, 11 were female and the sex was not determined for one animal. There was one ‘group’ stranding involving two females that stranded together at Glenelg Beach, Highland on 17 January 2002. Both females were immature, with body lengths of 152 cm and 160 cm and aged two years old. One of these animals was diagnosed with Brucella meningitis.
The length distribution of stranded striped dolphins is illustrated in Figure 3. The stranded animals ranged between 143 cm and 242 cm in length. The seven largest animals were all males, contributing to males having significantly greater average length than females (Student's t-test, t = 2.41, P = 0.021). The relationship between body weight and length (based on 26 individuals for which both length and weight were available) was:
Fig. 3. Length distribution of stranded striped dolphin (Stenella coeruleoalba) around the Scottish coast (1992–2003).
Age was determined for six animals: five females and one male. Ages ranged from 2 to 14 y (Table 2). The reproductive status was determined for six females and six males (Table 2). Five females were immature and one female was pregnant with a 90 cm male foetus. The immature females had body lengths between 152 and 194 cm, were aged 2–7 y, and were recovered from the North Sea and west coasts in the 1st, 3rd and 4th quarters. The pregnant female was aged 14 y, had a body length of 206 cm and was recovered from Skye on the west coast of Scotland in September 2001. Of the six males for which reproductive status was analysed: two were classed as immature, three were pubescent and one was mature and sexually active. The two immature males had body lengths of 185 cm and 186 cm and age was determined for one immature male, which was 6 y old. Both immature males were recovered from the west coast, one in the 1st quarter and one in the 4th quarter. The three pubescent males had body lengths between 183 cm and 208 cm; they were recovered during the 1st, 2nd and 3rd quarters on Shetland, the west and Irish Sea coasts. The mature and sexually active male had a body length of 223 cm and was recovered from the North Sea coast in May.
Numbers of prey recorded in the stomach samples ranged from 1 to over 600, with up to 11 different taxa identified in individual stomachs. At least 21 different taxa were identified overall, of which fish of the family Gadidae were the most important numerically and in terms of biomass (Table 3). Whiting (Merlangius merlangus) comprised 32% of the diet by number and 58% of the diet by weight while Trisopterus spp. accounted for 36% of prey numbers and 13% of prey biomass. The most important cephalopods, numerically, were sepiolids (2.1%). In terms of biomass, Gonatus sp. (probably G. steenstrupii) were the most important cephalopods (10%), although they were found in only one stomach—an animal stranded in Shetland.
Table 3. Summary of diet composition. Indices of importance for each prey taxon are as follows: F, frequency of occurrence; N, minimum number of individual prey recovered from the set of stomachs; and W, reconstructed weight based on otoliths and beaks only. The indices are also expressed as percentages.
There was no difference between summer and winter, east or west coasts, or between dolphin length-classes, in the average numerical importance of whiting, Trisopterus or sepiolids. The numerical importance of these species in the diet was not correlated with dolphin body length. The number of Trisopterus present in stomachs was significantly higher in females than in males (Kruskal–Wallis test, H = 5.99, P = 0.014), although no such difference was observed for whiting or sepiolids. None of the other prey taxa occurred sufficiently frequently to allow such comparisons to be made.
Similar analysis was carried out on the median size of whiting and Trisopterus eaten by dolphins. Trisopterus eaten in winter were larger than Trisopterus eaten in summer (Kruskal–Wallis test, H = 4.41, P = 0.036). Both Trisopterus and whiting eaten on the east coast were bigger than those eaten on the west coast (Kruskal–Wallis test, H = 5.40, P = 0.020; H = 5.81, P = 0.016, respectively).
The estimated size of whiting eaten ranged from 2.5 cm to 18.5 cm (Figure 4), with evidence of as many as four size modes. The majority of Trisopterus eaten were under 12 cm in length, with modes around 6–7 cm (Figure 4). Note that these sizes are based on uncorrected otolith measurements.
Fig. 4. Reconstructed length distributions for the main prey taxa in the stomach contents of striped dolphins (Stenella coeruleoalba) stranded around the Scottish coast (1992–2003).
DISCUSSION
Striped dolphins were not reported in Scottish waters until 1988 (Reid et al., Reference Reid, Evans and Northridge1993; Sheldrick et al., Reference Sheldrick1994). It has been suggested that Stenella coeruleoalba, a warm water species, could have recently expanded its distribution northwards. MacLeod et al. (Reference López2005), in their analysis of changes in the cetacean community on the north-west Scottish coast, noted that it was highly unlikely that the species would have been simply unrecorded prior to 1988 if it was present in Scottish waters. The authors also comment on the current frequency of the strandings of striped dolphins in the area (double the number of those of white beaked dolphins, Lagenorhynchus albirostris) and note that the species is also occasionally sighted at sea. Macleod et al. (Reference López2005) proposed that increased sea temperatures caused by climate change could explain this shift in distribution. Forcada et al. (Reference Evans, Stirling and Evans1990) analysed the water temperature at which a total of 69 sightings of striped dolphins had taken place in the north-eastern Atlantic and the authors found that it ranged from 10° to 21°C with a mode at 19°C.
The majority of strandings occurred on the west coast (60%) and most animals stranded during the 1st and 3rd quarters. The month in which most strandings were recorded was August (15.4% of all records). This pattern of strandings could be explained if water temperature was playing a role in determining the distribution of the species in Scottish waters (i.e. highest numbers are recorded in summer and on the west coast where the warming effect of the Gulf Stream current is at its peak). Nevertheless, live strandings of striped dolphins have been recorded in all months of the year and not only on the west coast but also on the east coast and the northern islands, which would seem to indicate that at least some animals are present all year round. High numbers of strandings in the first quarter (winter) could have originated due to bad weather conditions affecting juvenile and/or weakened animals, a possibility already suggested by Isaksen & Syvertsen (Reference Hohn, Lockyer, Bjørge and Donovan2002) who found the highest number of stranded striped dolphins in January in Norway. Winter was also the period when most strandings of striped dolphins were recorded in Ireland (47% of all records from 1901–1995, Berrow & Rogan Reference Berrow and Rogan1997). Historic stranding records (1933–1992) from the British coast indicate that the majority of striped dolphins have stranded on the west coast and strandings were recorded throughout the year, except in March, May and June (Fraser, Reference Forcada, Aguilar, Evans and Perrin1946, Reference Fraser1953, Reference Fraser1974; Sheldrick, Reference Sekiguchi, Klages and Best1989; Sheldrick et al., Reference Sheldrick1994). In Ireland striped dolphin strandings have also been reported in all months except May and June (Rogan et al., Reference Ringelstein, Pusineri, Hassani, Meynier, Nicolas and Ridoux1997). Most near-shore sightings of striped dolphins in the UK have been recorded between July and December (Evans, Reference Desportes1992; Reid et al., Reference Perrin and Myrick2003).
There were a high number of live standings, at least some of which could have been partly caused by infectious diseases such as meningoencephalitis and Brucella meningitis, the latter condition having been recorded in one of the two female dolphins that live- stranded together in January 2002.
Striped dolphins can occur in large groups consisting of hundreds of individuals, although in European waters group sizes of 6–60 are most common. In British and Irish waters, however, most sightings are of single animals or small groups of fewer than 20 individuals (Stone, Reference Spitz, Richard, Meynier, Pusineri and Ridoux1997, Reference Stone2000, Reference Stone2001, Reference Stone2003; Reid et al., Reference Perrin and Myrick2003). The majority of striped dolphin strandings in this study and historic stranding records involved individual dolphins, with the exception of two females that stranded together at Glenelg Beach, Highland in January 2002 (Fraser, Reference Forcada, Aguilar, Evans and Perrin1946, Reference Fraser1953, Reference Fraser1974; Sheldrick, Reference Sekiguchi, Klages and Best1989; Sheldrick et al., Reference Sheldrick1994).
Several authors have found evidence of sexual dimorphism in this species, with males attaining bigger sizes than females. The recorded difference between the sexes varies with the area/population studied. Thus, males have been found to measure 11–15 cm more in length than females in the western Pacific but only 2 cm longer in the Mediterranean according to Miyazaki (Reference Macleod, Simmonds and Murray1984). Calzada et al. (Reference Brown and Pierce1997) estimated a 6 cm difference in length between males and females in the western Mediterranean and the author explained this sexual dimorphism as the result of males displaying continuous growth for several years after female growth has stopped. In the present study, males were also found to have significantly greater average length than females (the seven largest animals were all males) although the number of animals sampled was small. Similarly, in striped dolphins stranded and by-caught around Ireland males were larger than females, with a maximum length of 214 cm for females and 228 cm (Rogan et al., Reference Ringelstein, Pusineri, Hassani, Meynier, Nicolas and Ridoux1997).
Reproductive samples were analysed from six female and six male striped dolphins stranded around Scotland. Based on this limited dataset, it appears that female striped dolphins could attain sexual maturity at body lengths between 194 to 206 cm and ages of 7–14 y, while male striped dolphins could attain sexual maturity at body lengths of about 208–223 cm. This is consistent with data from striped dolphins in Irish waters, which suggest that the onset of sexual maturation in males occurs after 11 y of age and total body lengths greater than 201 cm, and where the youngest sexually mature female was 14 y old with a body length of 201 cm (Rogan et al., Reference Ringelstein, Pusineri, Hassani, Meynier, Nicolas and Ridoux1997). López (Reference Lockyer2003) recorded ten mature females from strandings in Galicia, Spain during 1990–1999 and estimated that matuity occurs at a length of around 200 cm and between the ages of 3 and 10 y. The single mature male recorded was 219 cm in length. In a subsequent study (2001–2003), four mature females were recorded from Galicia, with body lengths of at least 197 cm and aged 15 y or older, also three mature males with body lengths of 211 cm and over, aged 18 y or older (Learmonth et al., Reference Law2004).
The reproductive season for striped dolphins in Scottish waters is difficult to determine due to the small sample size, however, the period of conception appears to be in May, based on the mature and sexually active male that stranded at this time and the calving period may occur around September–October, based on pregnant female with near-term 90 cm foetus found in September. Rogan et al. (Reference Ringelstein, Pusineri, Hassani, Meynier, Nicolas and Ridoux1997) suggested that calving in Irish waters may occur from July to November, which is consistent with the findings of this study and the recovery of a lactating female in November 2002 on the Irish coast (Learmonth et al., 2004). Mature and sexually active male striped dolphins have been recovered from the coasts of Galicia and France between January and April and in June (Learmonth et al., 2004). This could indicate that the male reproductive period for striped dolphins in the north-eastern Atlantic extends up to six months or there could be regional variations in reproductive season, unfortunately sample sizes in all studies are too small to examine this further.
In the present study from the Scottish coast, whiting was the most important prey species of striped dolphins (by reconstructed weight). The diet of striped dolphins has been studied in several parts of the world, including Japan (Miyazaki et al., Reference Miyazaki1973), the Mediterranean (e.g. Desportes, Reference Collet, Saint-Girons and Perrin1985; Bello, Reference Bello1992; Würtz & Marrale, Reference Würtz and Marrale1993; Blanco et al., Reference Blanco, Aznar and Raga1995), South Africa (Sekiguchi et al., Reference Rogan, Gassner, Mackey and Berrow1992) and the north-eastern Atlantic (Desportes, Reference Collet, Saint-Girons and Perrin1985; Spitz et al., Reference Sheldrick, Chimonides, Muir, George, Reid, Kuiken, Iskjaer-Ackley and Kitchener2006). In general, the diet of the species includes oceanic fish, cephalopods and crustaceans, with the relative abundance of each major taxon in the diet changing with location. For example, Desportes (Reference Collet, Saint-Girons and Perrin1985) analysed the stomach contents of striped dolphins stranded on the French Atlantic (N = 25) and Mediterranean (N = 20) coasts. Desportes found fish to be the most frequent prey in the Atlantic samples but cephalopods were more frequent in the Mediterranean samples, with some seasonal variation. The most frequently recorded fish species was blue whiting (Micromesistius poutassou). In a sample of 60 striped dolphins by-caught in the French albacore fishery (1992–1993) squid dominated the diet, mainly Teuthowenia megalops and Histioteuthis spp. Fish made up around 40% of the diet, mainly mesopelagic species such as lanternfish (mainly Notoscopelus kroeyeri and Lobianchia gemellarii). Crustaceans, mainly mesopelagic shrimps Sergestidae and Pasiphaeidae, were also important (Ringelstein et al., Reference Rice2006).
Fourteen fish, ten cephalopod and two crustacean taxa were found in the stomachs of striped dolphins collected along the coasts of the Bay of Biscay (N = 23) (Spitz et al., Reference Sheldrick, Chimonides, Muir, George, Reid, Kuiken, Iskjaer-Ackley and Kitchener2006). Fish comprised 91% of the diet by number, with blue whiting and Atherina presbyter being the main fish species eaten and Gonatus steenstrupi and an unidentified Ommastrephidae as the main cephalopods taken.
Very little is known of the life history of the striped dolphin in Scottish waters. The population size is unknown and the present analysis, although based on a small sample size, arises from the study of stranded specimens over a 12 y period, and represents the first attempt to gather all the available information.
ACKNOWLEDGEMENTS
The UK Stranding Project and all work undertaken by the SAC on strandings research is funded by the UK Department for Environment, Food and Rural Affairs (Defra). Analysis of stomach contents material collected up to 1997 was funded by the Commission of the European Communities under Contracts ERB 4001 GT 93/3630 and ERB FMBI CT96/1373. Stomach contents analysis during 1998–2000 was funded under CEC DG XIV Study Project 97/089. Analysis of teeth, gonads and stomach contents during 2001–2003 was funded under CEC project EVK3-CT-2000-00027.
