Journal of Mammalogy, 95(6):1289–1298, 2014 Clymene dolphins (Stenella clymene) in the eastern tropical Atlantic: distribution, group size, and pigmentation pattern CAROLINE R. WEIR,* PHIL COLES, AMY FERGUSON, DUNCAN MAY, MICK BAINES, INÊS FIGUEIRDO, MAREN REICHELT, LUIS GONCALVES, MARIJKE N. DE BOER, BARRIE ROSE, MATT EDWARDS, SUE TRAVERS, MIKE AMBLER, HUGO FÉLIX, DAVE WALL, VALERIA A. A. AZHAKESAN, MIKE BETENBAUGH, LEA FENNELLY, SIGBJØRN HAALAND, GUUS HAK, TERJI JUUL, ROB W. LESLIE, BRIAN MCNAMARA, NICHOLA RUSSELL, JACLYN A. SMITH, HEATHER M. TABISOLA, ALEXANDRA TEIXEIRA, ELS VERMEULEN, JULIET VINES, AND ANDY WILLIAMS Ketos Ecology, 4 Compton Road, Kingsbridge, Devon TQ7 2BP, United Kingdom (CRW) Department of Zoology, School of Biological Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen, AB24 2TZ, United Kingdom (CRW) c/o Ketos Ecology, 4 Compton Road, Kingsbridge, Devon TQ7 2BP, United Kingdom (PC, AF, DM, MB, IF, MR, LG, MNDB, BR, ME, ST, MA, HF, DW, VAAA, MB, LF, SH, GH, TJ, RWL, BM, NR, JAS, HMT, AT, EV, JV, AW) * Correspondent: caroline.weir@ketosecology.co.uk The Clymene dolphin (Stenella clymene) is endemic to warm Atlantic Ocean waters and is one of the least known delphinids. We reviewed existing published data (primarily strandings, captures, and bycatch) and unpublished sightings to examine the distribution, habitat, group size, seasonality, and pigmentation patterns of Clymene dolphins within the eastern tropical Atlantic (ETA). Following photographic verification, 84 confirmed and 8 probable at-sea sightings of ETA Clymene dolphins were analyzed. The documented records ranged from ~198N in central Mauritania to 14826 0 S in southern Angola, confirming 14 ETA range states. At-sea sightings occurred in water depths of 437–5,000 m and at distances from shore of 21–937 km, corresponding with a continental slope and oceanic habitat. Sightings within the wider ETA region had year-round occurrence. Group size ranged from 3–1,000 animals, with 60.9% of groups comprising  50 animals. Photographic examination revealed a complex and variable pigmentation pattern in ETA Clymene dolphins, which contrasts with the simple tripartite pattern often described for this species. In particular, most ETA animals had a dark gray lateral stripe extending diagonally along the flank from the beak to the genital area and a conspicuous dark gray eye– flipper stripe of varying intensity and thickness. The at-sea sightings documented here significantly extend current knowledge of the distribution, ecology, and appearance of the Clymene dolphin. Key words: Africa, conservation status, flank markings, Gulf of Guinea, habitat, seasonality, sightings, water depth Ó 2014 American Society of Mammalogists DOI: 10.1644/14-MAMM-A-115 The Clymene dolphin (Stenella clymene) was first described by Gray (1846) from a single skull originating from an unknown locality. The species was only validated in 1981 (Perrin et al. 1981), and until recently its occurrence was documented from fewer than 200 verified records (Fertl et al. 2003). Clymene dolphins are endemic to tropical and subtropical waters of the Atlantic Ocean, including the Caribbean Sea and the Gulf of Mexico (Perrin et al. 1981; Perrin and Mead 1994; Fertl et al. 2003; Jefferson 2009). Published records are strongly biased toward the western Atlantic (Fertl et al. 2003), where surveys in the Gulf of Mexico (Davis et al. 1998; Mullin and Fulling 2004; Maze-Foley and Mullin 2006), off the Atlantic United States coast (Mullin and Fulling 2003), and off the coast of Brazil (Moreno et al. 2005) have revealed a regular oceanic presence of this species. In contrast, the occurrence of the Clymene dolphin in the eastern tropical Atlantic (ETA) is poorly documented (Jefferson 2009; Weir 2010). In their global review of the species, Fertl et al. (2003) reported 2 capture records from the midAtlantic (Lütken 1889; Perrin et al. 1981) and 12 sighting, stranding, and capture records from ETA waters. However, 2 of the ETA capture records reported in their appendix 3 (on 20 July 1957 and 27 October 1981, respectively—Cadenat and Doutré 1958; Robineau et al. 1994) were erroneously 1289 www.mammalogy.org 1290 JOURNAL OF MAMMALOGY Vol. 95, No. 6 FIG. 1.—Eastern tropical Atlantic countries (including Exclusive Economic Zones) and the location of all verified Clymene dolphin (Stenella clymene) records. The southern border of the Gulf of Guinea extends from Cape Palmas in Liberia to Cap Lopez in Gabon (IHO 1953). Verified range states are shown in dark gray. Countries: 1—Mauritania, 2—Senegal, 3—Cape Verde Islands, 4—The Gambia, 5—Guinea-Bissau, 6— Guinea, 7—Sierra Leone, 8—Liberia, 9—Côte d’Ivoire, 10—Ghana, 11—Togo, 12—Benin, 13—Nigeria, 14—Cameroon, 15—Equatorial Guinea (including Bioko and Annobón), 16—São Tomé and Prı́ncipe, 17—Gabon, 18—Republic of the Congo, 19—Democratic Republic of the Congo, 20—Angola (including Cabinda), 21—Ascension Island, 22—Saint Helena. duplicated as strandings in their appendix 2, resulting in only 10 ETA records. Since that review, a number of bycatch records (Debrah et al. 2010) and a handful of at-sea sightings (Weir 2006, 2011a, 2011b; de Boer 2010) have been published for the ETA, but information remains scarce. The International Union for Conservation of Nature (IUCN) recently classified Clymene dolphins as a Data Deficient species (Hammond et al. 2012). However, the paucity of records in the ETA and documented mortality of the species in Ghanaian fisheries (Debrah et al. 2010) led to the addition of the ETA Clymene dolphin to the Conservation of Migratory Species of Wild Animals Appendix II in 2008, as a migratory species that needs, or would significantly benefit from, international cooperation. Given concern regarding the conservation status of ETA Clymene dolphins (Van Waerebeek and Perrin 2007), information on their distribution and ecology is urgently required. This paper reviews previously published records and presents a significant number of unpublished ETA sightings in order to document ETA range states, provide information on habitat, investigate seasonality, and assess behavior and group size. Additionally, the pigmentation patterns of Clymene dolphins photographed in the ETA were examined in order to describe color pattern and to assess the potential for confusion with other species during ETA sighting surveys. MATERIALS AND METHODS Study area.—The ETA is defined here according to the eastern section of the tropical Atlantic biogeographic realm characterized by Spalding et al. (2007). It comprises the west coast of Africa from Mauritania south to Angola, including oceanic islands (Fig. 1). For completeness, we include the midAtlantic island of Ascension. Consequently, there are 22 December 2014 WEIR ET AL.—CLYMENE DOLPHINS IN THE AFRICAN ATLANTIC TABLE 1.—Criteria used to allocate sightings (n ¼ 104) to 5 verification categories. ‘‘Experienced observers’’ were defined as those with considerable cetacean field experience that specifically included previous encounters with Clymene dolphins (Stenella clymene; as evidenced by photographs). Category 1 2 3 4 5 Criteria No. records Photograph or video available, sufficient to confirm identification. Accepted. Animals viewed at very close proximity while bow-riding by an experienced observer allowing all key features to be noted, but photographs were inconclusive or unavailable due to weather (e.g., sun glare or torrential rain). Accepted. Animals were positively identified in the field by experienced observers and photographs were provided that were suggestive, but inconclusive (due to poor light or distance). Accepted as probable record. Photograph provided but animals could not be unequivocally identified as Clymene dolphins due to poor image quality (usually due to distance of the animals). Observer uncertain or lacked previous experience with the species, or both. Rejected. Photographs provided of ‘‘Clymene dolphins’’ proved to be misidentifications of other delphinid species. Rejected. 80 4 8 8 4 potential Clymene dolphin ETA range states including 18 mainland countries and 4 island states and territories (Cape Verde, São Tomé and Prı́ncipe, Ascension Island, and Saint Helena). The offshore islands of Annobón and Bioko are governed by, and considered with, Equatorial Guinea. Four geographic regions were defined for analysis: 1) north-west Africa (Mauritania to Liberia); 2) northern Gulf of Guinea (Côte d’Ivoire to Equatorial Guinea); 3) southern Gulf of Guinea to south-east Atlantic (Gabon to Angola); and 4) international waters seaward of the Exclusive Economic Zones (EEZ). Literature review.—A literature review searched for published Clymene dolphin records in scientific journals and in available ‘‘gray’’ literature (e.g., International Whaling Commission papers). Where records involved skeletal remains, strandings, captures or bycatch, the species verification was carried out by the authors of the studies in question and specimen samples were usually stored in museums (Supporting Information S1, DOI: 10.1644/ 14-MAMM-A-115.S1). Where records included published photographs, species identification was verified by the lead author (CRW). Unpublished sightings.—Experienced Marine Mammal Observers were contacted directly by the lead author during 2012 to request information on Clymene dolphin sightings. Open requests were posted on the Marine Mammal Observer Association forum (www.mmo-association.org) on 27 January and 27 November 2012. Opportunistic sightings were also reported to the lead author during the course of investigations into cetacean occurrence in the ETA region between 2004 and 1291 2011 (Weir 2011b). Initial examination checked that the following minimum data were available: supporting photograph or video, date, global positioning system position, and group size. Sightings without this information were omitted from the study. Verification methods.—Fertl et al. (2003) emphasized the difficulties in identifying Clymene dolphins to species level and the importance of verification using photographs or video. Key features used to identify Clymene dolphins from photographs included tripartite color pattern comprising a dark gray dorsal cape, mid-gray lateral field, and white ventral surface; a rounded convex dip in the ventral margin of the dorsal cape below the dorsal fin; gray eye–flipper stripe that widens toward the flipper; pale stripe extending from the blowhole to the apex of the melon; dark beak tip and lips; dark dorso-mesial surface to the beak bordered by paler gray; and distinctive ‘‘moustache’’ marking located one-third of the way from the melon to the beak tip on the dorsal surface of the beak (Perrin et al. 1981; Perrin and Mead 1994; Carwardine 1995; Jefferson 1996; Reeves et al. 2002; Shirihai and Jarrett 2006; Jefferson et al. 2008). A single person (CRW) allocated sightings to 1 of 5 verification quality categories using the criteria outlined in Table 1 and the key features described above. Categories 1 and 2 were accepted as Clymene dolphins. Category 3 sightings were accepted as probable records. Category 4 and 5 sightings were rejected. Additional information was requested for Category 1–3 sightings including water depth and behavioral notes (specifically including the presence or absence of bowriding and spinning behaviors). Data analysis.—All records were mapped in ArcView 3.2 (Environmental Systems Research Institute, Inc. [ESRI] 1998) Geographic Information System (GIS) using global positioning system positions (sightings) or locality descriptions (stranding and bycatch records). Each was assigned to a range state using an EEZ shapefile (Flanders Marine Institute 2012). The depth of most Clymene dolphin sightings (n ¼ 75) originated from the vessel echosounder. For the remaining sightings (n ¼ 17) water depth was calculated from the General Bathymetric Chart of the Oceans Digital Atlas 2003 (General Bathymetric Chart of the Oceans [GEBCO] 2003) contour data using GIS (see Weir 2011a). The distance of each sighting from shore was calculated using a custom-design script in GIS, and assigned to neritic or pelagic habitat. Neritic was defined as the waters extending from the coast to the shelf edge (, 200 m depth), whereas pelagic referred to open waters seaward of the shelf edge. Depth-related habitat is defined throughout this paper as continental shelf/neritic (, 200 m depth); upper slope (200– 999 m); lower slope (1,000–2,000 m); and deep oceanic (. 2,000 m). Aqua Modis monthly composites (4-km resolution) of sea surface temperature (SST) data were downloaded from the National Aeronautics and Space Administration Ocean Color Web site (Ocean Color Web 2014) for every month and year for which sightings were reported. A value was extracted for each sighting (except one 1972 record that occurred prior to the 1292 JOURNAL OF MAMMALOGY Vol. 95, No. 6 TABLE 2.—Depths, distance from shore, sea surface temperature (SST), and group sizes of 92 Clymene dolphin (Stenella clymene) sightings in 4 regions: 1) northwestern Africa (Mauritania to Liberia); 2) northern Gulf of Guinea (Côte d’Ivoire to Equatorial Guinea); 3) southern Gulf of Guinea to southeastern Atlantic (Gabon to Angola); and 4) international waters. Water depth (m) Distance (km) SST (8C) Group size Region n X̄ SE Median X̄ SE Median X̄ SE Median X̄ SE Median 1 2 3 4 All 17 36 35 4 92 2,429 2,521 1,666 4,560 2,267 154.0 158.0 92.9 38.2 101.0 2,261 2,368 1,721 4,555 2,123 116.8 88.2 116.5 908.2 139.9 6.1 11.6 6.2 23.4 18.0 113.4 66.8 118.8 928.4 108.3 21.4 27.7 27.9 27.9 26.6 0.67 0.23 0.12 0.37 0.31 20.4 27.1 27.9 28.0 27.7 62.8 47.1 108.2 39.0 72.9 10.1 7.0 29.0 18.4 11.8 50.0 40.0 50.0 35.0 47.5 availability of SST data) using a custom-designed script in GIS. Statistical tests to analyse variation in water depth, distance from shore, SST and group size between geographic regions were carried out using Minitab 16 statistical software (Minitab Inc. 2010). RESULTS Summary of records.—Eight specific nonsighting records of ETA Clymene dolphins were found during the literature review: 2 capture records, 2 strandings, 3 calvaria, and 1 skeleton of unknown origin (probable bycatch—Supporting Information S1). Additionally, 2 capture records (one involving 2 animals) are documented from mid-Atlantic waters northwest of Ascension (Supporting Information S1). These records span the period from ~1846 to 1995. More recently, a cetacean landing (bycatch and direct takes) monitoring program in Ghana has photographically verified 52 Clymene dolphin specimens between 1994 and 2010 (Supporting Information S1; Debrah et al. 2010) and reported 13 cranial specimens in the University of Ghana collection (Van Waerebeek et al. 2009). A total of 104 (12 published and 92 unpublished) ETA sightings were evaluated, of which 84 were accepted as confirmed Clymene dolphins and 8 were accepted as probable Clymene dolphins (Table 1). Ninety-two sightings were therefore used for analysis (Supporting Information S2, DOI: 10.1644/14-MAMM-A-115.S1). Four sightings were clear misidentifications and comprised common dolphin (Delphinus sp.; n ¼ 2) and pantropical spotted dolphin (Stenella attenuata; n ¼ 2). One published ‘‘probable’’ sighting (de Boer 2010) could not be photographically verified because of distance of the animals and poor image quality, and was not included further. Range states.—At-sea sightings occurred between latitudes of 18834 0 N (central Mauritania) to 14826 0 S (southern Angola [Fig. 1]). When nonsighting records were also considered, the northern range limit extended to ~198N. Published nonsighting records confirmed 4 ETA range states: Mauritania, Senegal, The Gambia, and Ghana (Supporting Information S1). The mid-Atlantic captures were located in international waters outside of the Ascension Island EEZ. Verified sightings occurred in 12 ETA range states: Mauritania, Guinea-Bissau, Sierra Leone, Liberia, Côte d’Ivoire, Ghana, Togo, Benin, Nigeria, Equatorial Guinea, Gabon (including 1 sighting reallocated from the Republic of the Congo—Weir 2006, 2011b), and Angola (Supporting Information S2). Four sightings were located in international waters outside of the EEZ. The combined sighting and nonsighting records confirmed 14 Clymene dolphin ETA range states. Habitat.—The 89 sightings occurred in water depths ranging from 437 to 5,000 m (X̄ ¼ 2,267 m, SE ¼ 101 m, median ¼ 2,123 m) and at distances from shore of 20.6 to 937.4 km (X̄ ¼ 139.9 km, SE ¼ 18.0 km, median ¼ 108.3 km). No sightings were recorded in neritic habitat. Four records occurred in international waters far from shore in deep water (Fig. 1; Table 2). SST values for the sightings ranged from 19.68C to 31.18C (X̄ ¼ 26.68C, SE ¼ 0.318C, median ¼ 27.78C; Table 2). There were statistically significant differences in water depth (Kruskal–Wallis test: H2 ¼ 23.42, P , 0.0001) and distance from shore (Kruskal–Wallis test: H2 ¼ 15.78, P , 0.0001) of sightings between regions 1–3 (Table 2). Mann–Whitney tests revealed significant differences in water depth between regions 1 and 3 (P ¼ 0.0001) and regions 2 and 3 (P , 0.0001), and in distance from shore between regions 1 and 2 (P ¼ 0.0016) and regions 2 and 3 (P ¼ 0.0005). Sightings in the northern Gulf of Guinea (region 2) occurred closest to shore, whereas sightings between Angola and Gabon (region 3) were in the shallowest water (Fig. 2). There was a statistically significant difference in SST between regions 1–3 (Kruskal–Wallis test: H2 ¼ 33.68, P , 0.0001), and Mann–Whitney tests revealed that these differences were highly significant between regions 1 and 2 (P , 0.0001), and regions 1 and 3 (P , 0.0001). Temporal distribution.—Sightings occurred throughout the year within the wider ETA (Fig. 3a). They were recorded in 10 months in the northern Gulf of Guinea and in the waters between Gabon and Angola, and in 6 months (primarily July– November) off northwestern Africa (Fig. 3a). Group size and behavior.—Sightings comprised groups of 3–1,000 animals (X̄ ¼ 72.9 animals, SE ¼ 11.8 animals, median ¼ 47.5 animals, n ¼ 92). Most (60.9%) groups contained  50 animals (Fig. 3b). Comparing regions 1 to 3 only (due to low sample size in region 4), there was no significant difference in group size according to depth (categories: , 1,000 m; 1,000– 2,000 m; . 2,000 m; Kruskal–Wallis test: H2 ¼ 1.61, P ¼ 0.447), distance from shore (categories: , 100 km; 100–150 km; . 150 km; Kruskal–Wallis test: H2 ¼ 3.06, P ¼ 0.216), or geographic area (Kruskal–Wallis test: H2 ¼ 5.31, P ¼ 0.070). The behavior most commonly recorded during sightings (n ¼ 76; 82.6%) was travel or porpoising. Aerial behavior was December 2014 WEIR ET AL.—CLYMENE DOLPHINS IN THE AFRICAN ATLANTIC 1293 FIG. 2.—Relationship between water depth and distance from shore of Clymene dolphin (Stenella clymene) sightings (n ¼ 88) in 3 regions: 1) northwestern Africa; 2) northern Gulf of Guinea; and 3) southern Gulf of Guinea to southeastern Atlantic. logged for 54 (58.7%) sightings. Bow-riding (34.8%) and spinning (32.6%) were each noted in around one-third of sightings. Only 1 mixed-species assemblage was reported: 12 Clymene dolphins and 7 common dolphins identified within a large group of 350 dolphins off Angola (Weir 2006). Pigmentation pattern.—We observed several pigmentation characteristics in ETA Clymene dolphins that had not been emphasized in most previous descriptions of the species. Dorsal cape. Previous studies had noted that the margin of the dorsal cape dips ventrally beneath the dorsal fin (Perrin et al. 1981; Perrin and Mead 1994; Carwardine 1995; Reeves et al. 2002; Jefferson et al. 2008). However, in most ETA Clymene dolphins the lowest point of the ventral margin was located slightly further forward, below the base of the leading edge of the dorsal fin (Fig. 4; Supporting Information S3, DOI: 10.1644/14-MAMM-A-115.S1). Dark lateral stripe. The presence of a dark diagonal lateral stripe was a prominent feature on most ETA Clymene dolphins, but had not been noted in many previous studies (e.g., Perrin et al. 1981; Perrin and Mead 1994; Carwardine 1995; Fertl et al. 2003). Jefferson et al. (2008, p. 238) noted that there ‘‘may also be an indistinct dark band running diagonally along the side, from the anus forward,’’ while Shirihai and Jarrett (2006, p. 184) noted the presence of a ‘‘dark, ill-defined band . . . on mid body.’’ We found that a distinct dark gray lateral stripe was conspicuous on many ETA individuals, extending from the posterior edge of the beak and curving upward through the eye toward the dorsal fin, reaching its highest point above the flipper. The stripe angled diagonally downward along the length of the animal toward the genital area (Fig. 4; Supporting Information S3), and strongly demarcated the lateral and dorsal fields from the white ventral field in most ETA individuals. The demarcation was particularly marked toward the rear of the ventral field, and was more muted behind the flipper. The lateral stripe was highly variable in intensity and extent. In individuals where the eye–flipper and lateral stripes were pronounced, the stripes converged behind the eye to produce a characteristic ‘‘masked’’ appearance (Supporting Information S3). Mid-gray lateral field. The presence of a mid-gray lateral field is a key component of the tripartite coloration pattern often reported for this species. However, this feature varied in extent and distinctiveness in ETA Clymene dolphins (Supporting Information S3). In some individuals the ventral margin of the dorsal cape merged with the upper edge of the lateral stripe so that no clear area of mid-gray lateral field was present below the dorsal fin. Eye–flipper stripe. Fertl et al. (2003) reported that Clymene dolphins have an ‘‘indistinct’’ eye–flipper stripe. However, most ETA animals had a conspicuous dark gray eye– flipper stripe of varying intensity and thickness, usually broadening toward the flipper (Fig. 4; Supporting Information S3). Above the dark eye–flipper stripe was a narrow, welldefined white stripe extending from the back of the eye to the trailing edge of the flipper. In some animals the area between the merging eye–flipper and lateral stripes was relatively ‘‘clean’’ and the eye–flipper stripe terminated at the flipper (Fig. 4A). However, in others this area was a dusky gray color (often causing the white eye–flipper stripe to stand out Fig. 4B), and in some a dark gray streak extended backward above the flipper into the ventral field (Fig. 4C). 1294 JOURNAL OF MAMMALOGY Vol. 95, No. 6 FIG. 3.—A) Temporal distribution and B) group size of Clymene dolphin (Stenella clymene) sightings (n ¼ 92) in 4 geographic regions: 1) northwestern Africa (Mauritania to Liberia); 2) northern Gulf of Guinea (Côte d’Ivoire to Equatorial Guinea); 3) southern Gulf of Guinea to southeastern Atlantic (Gabon to Angola); and 4) international waters. Dorsal fin shape and color. Dorsal fin shape showed considerable variation, ranging from small and triangular to noticeably falcate or tall and erect (Supporting Information S3). Some individuals had pale inner areas on the dorsal fin. DISCUSSION Eastern tropical Atlantic range states and distribution.—In their 2007 review, Van Waerebeek and Perrin verified 6 ETA range states for the Clymene dolphin: Mauritania, Senegal, Gambia, Ghana, Gabon (record reallocated from the Republic of the Congo—Weir 2011b), and Angola. The sightings reported here increase the documented range states to 14 (north to south): Mauritania, Senegal, Gambia, Guinea-Bissau, Sierra Leone, Liberia, Côte d’Ivoire, Ghana, Togo, Benin, Nigeria, Equatorial Guinea, Gabon, and Angola. We were unable to locate any records for Cape Verde (a sighting reported from Cape Verde actually comprised pantropical spotted dolphin [see Hazevoet et al. 2010]), Guinea, Cameroon, the Republic of the Congo, the Democratic Republic of the Congo, or Saint Helena, despite those being listed as range states by some assessments (Culik 2011; Hammond et al. 2012). However, given confirmed northern and southern limits in central Mauritania and southern Angola, respectively, Clymene dolphins are likely to occur in all intermediate range states. Our records indicate that Clymene dolphins are widespread in the ETA and that the scarcity of earlier records was likely due to paucity of survey effort (as noted by Robineau et al. 1994) and confusion with other delphinids. Effort-related analyses of this data set were not appropriate because of variation in survey methods, observers and platforms, and unknown potential impacts from anthropogenic sound (seismic survey vessels were the platform for most sighting records). However, those countries with the highest number of at-sea December 2014 WEIR ET AL.—CLYMENE DOLPHINS IN THE AFRICAN ATLANTIC 1295 FIG. 4.—Pigmentation pattern of eastern tropical Atlantic Clymene dolphins (Stenella clymene) based on photographs of live animals (illustrations by Phil Coles): a) generalized overall appearance of flank pattern; a) and b) head where eye–flipper and lateral stripes are well defined and converge at the eye to produce a distinct ,-shape; and c) head where eye–flipper and lateral stripes merge behind the eye and extend back into the ventral field as a dark band. sightings (i.e., Angola, Gabon, Côte d’Ivoire, and Mauritania) were those where Marine Mammal Observers have been most frequently utilized by industry in recent years. Clymene dolphins occur as far south as 29859 0 S in the southwestern Atlantic off Brazil (Moreno et al. 2005), but 14826 0 S is the southernmost ETA latitude currently documented. It seems unlikely that Clymene dolphins routinely occur much farther south than Angola, because of the cold-water Benguela Current influence off Namibia. However, their range may potentially extend northward from the ETA into warm temperate waters off Western Sahara, the Canary Islands, and beyond. For example, sightings of another tropical delphinid, Fraser’s dolphin (Lagenodelphis hosei), have recently been recorded off Madeira and the Azores (~388N—Gomes-Pereira et al. 2013). Examination of the data showed that Clymene dolphins occur year-round in the wider ETA and support a probable year-round occurrence in both the northern Gulf of Guinea and the waters from Gabon to Angola. The reported sightings between Mauritania and Liberia were strongly seasonal (May to November), most likely due to temporal variation in survey effort in that region. Systematic year-round survey effort is required throughout the ETA to assess seasonal movements. Eastern tropical Atlantic habitat.—The Clymene dolphin is usually considered to be an oceanic species occurring seaward of the continental shelf (Perrin et al. 1981; Perrin and Mead 1994; Davis et al. 1998; Fertl et al. 2003). Sightings off Brazil occurred over 1,050- to 4,500-m water depth (Moreno et al. 2005), whereas those in the Gulf of Mexico ranged from 612 to 1,979 m (X̄ ¼ 1,261 m—Davis et al. 1998) and from 688 to 3,065 m (X̄ ¼ 1,692 m—Maze-Foley and Mullin 2006). The 94 sightings analyzed by Fertl et al. (2003) had a depth range of 44–4,500 m (X̄ ¼ 1,870 m, median ¼ 1,675 m); however, the sighting in 44 m was considered to be ‘‘atypical.’’ The depth distribution of the sightings reported here was consistent with those studies, confirming an occurrence in slope and deep oceanic habitat in the ETA. Slight differences in depth range and distance from shore were apparent between the 3 geographic regions considered. Because the distribution of cetacean survey effort was not available, the significance of the observed trends cannot be evaluated. However, it is likely that some differences do occur due to the bathymetric variation between the geographic regions. Although much of central and northern Angola and Gabon has a shelf of around 60-km width, the shelf off Togo, Benin, and Côte d’Ivoire in the northern Gulf of Guinea is often less than 30 km wide. Seabed topography is usually steeper in these areas of narrow shelf, so that water deepens rapidly relatively close to shore. Consequently, although occupying deep, oceanic habitat throughout the ETA, the steepness of the seabed and the width of the shelf are likely to be key influences on the exact water depths and distances from shore that Clymene dolphins are recorded in each region. The distribution of Clymene dolphins appears to be restricted to warm waters (Fertl et al. 2003; Moreno et al. 2005). SST during sightings in the Gulf of Mexico ranged from 22.18C to 29.28C (X̄ ¼ 25.98C—Maze-Foley and Mullin 2006), whereas off Brazil it ranged from 258C to 28.58C (Moreno et al. 2005). We recorded a slightly wider SST range for the species in ETA waters, varying from 19.68C to 31.18C. The coldest SSTs recorded (19.5–20.68C) were for the 14 sightings off Mauritania. The southernmost sighting recorded had a SST of 25.08C, 1296 JOURNAL OF MAMMALOGY Vol. 95, No. 6 FIG. 5.—Comparison in cape and lateral stripe patterns of: a) Clymene dolphin (Stenella clymene), and b) striped dolphin (Stenella coeruleoalba) off Angola. Both species have a dark lateral stripe from eye to anus; however, the stripe of the striped dolphin runs almost horizontally along the side whereas that of the Clymene dolphin slopes diagonally downward. The stripe is also finer and better defined around the eye on the striped dolphin compared with the Clymene dolphin. The striped dolphin usually has a distinct shoulder blaze sweeping forward from the cape (b, left-hand animal). However, in some individuals this is muted and indistinct (b, center animals) and may potentially cause confusion with the dipped dorsal cape of the Clymene dolphin. suggesting that the species’ range may extend some way southward of that location in central Angola. Differences in the SST of sightings between the 3 regions is likely the result of oceanographic differences, with Mauritanian waters comprising the Sahelian upwelling zone (Spalding et al. 2007) and having lower water temperatures than the other regions. Group size.—We recorded group sizes in the ETA of 3– 1,000 animals, but most groups comprised fewer than 50 animals. This correlates well with observations of group size elsewhere, including Brazil (8–300 animals—Moreno et al. 2005) and the Gulf of Mexico (1–68 animals—Maze-Foley and Mullin 2006). In 105 sightings analyzed by Fertl et al. (2003), group size ranged from 1 (in a mixed-species school with spinner dolphins [Stenella longirostris]) to 1,000 animals. The mean (72.9 animals) and median (47.5 animals) group sizes recorded in the ETA are remarkably similar to those reported by Fertl et al. (2003) for the western Atlantic (76.1 and 47.0 animals respectively). Pigmentation pattern.—Few publications have provided a detailed description of the coloration pattern of the Clymene dolphin, and previous descriptions have been based on animals photographed or stranded in the western Atlantic, primarily within the Gulf of Mexico (Perrin et al. 1981; Perrin and Mead 1994; Jefferson 1996; Jefferson et al. 2008). We observed a complex and highly variable pigmentation pattern in ETA Clymene dolphins, which contrasts with the simple tripartite pattern often described for this species. In other delphinid species such intraspecific variation in coloration has been shown to relate to factors including individual, age, sex, and geographic location (Perrin 2009). The complexity was particularly evident in the intensity and extent of, and intersection between, the lateral stripe, lateral field, and the eye–flipper stripe. Even at distance, complex lateral patterns, rather than defined tripartite coloration, were apparent on leaping Clymene dolphins. Although the beak moustache marking may be the species’ single most diagnostic external feature (Fertl et al. 2003), we suggest that the combined dipped dorsal cape, dark lateral stripe, and ‘‘clean’’ throat appearance may be the best means of identifying this species at distance in the ETA. Confusion species.—Misidentifications of Clymene dolphins occur by experienced cetacean biologists (see Fertl et al. 2003; Hazevoet et al. 2010) and by experienced (as defined by regulator standards—Joint Nature Conservation Committee [JNCC] 2010) Marine Mammal Observers (this study). It is likely that the number of misidentifications reported by Marine Mammal Observers industry-wide is much higher than indicated here, because this paper specifically targeted the most experienced personnel. Both scientific and Marine Mammal Observer surveys should routinely collect photographic or video data to facilitate independent verification of species, and these should be assessed prior to data use to ensure adequate standards of data quality. December 2014 WEIR ET AL.—CLYMENE DOLPHINS IN THE AFRICAN ATLANTIC Previous studies have identified spinner and common dolphins as potential confusion species (e.g., Perrin and Mead 1994; Reeves et al. 2002; Fertl et al. 2003; Jefferson et al. 2008). We also note superficial similarities in pigmentation pattern with the striped dolphin (Stenella coeruleoalba) in ETA waters (Fig. 5). Similarities in skull and body shape led previous studies to note that Clymene dolphins appeared intermediate between spinner and striped dolphins (Perrin et al. 1981; Jefferson et al. 2008; Jefferson 2009). Recent genetic evidence indicates that the Clymene dolphin may have originated through natural hybridization between spinner and striped dolphins (Amaral et al. 2014). Our observations of pigmentation patterns in the ETA (Fig. 5) may lend further support to taxonomic similarities between these species. Conservation status.—The status of the Clymene dolphin is unknown throughout its range. Hammond et al. (2012) noted that there are bycatch and directed takes in West Africa of ‘‘unknown, but likely escalating, scale.’’ We were able to locate only 2 published capture records in the ETA (both from Senegal) and a further 2 records from the mid-Atlantic, none of which were recent (Supporting Information S1). Evidence for bycatch in ETA fisheries currently originates solely from Ghana (Supporting Information S1), where the proportion (of the total cetacean bycatch) of Clymene dolphins landed in drift gill-net and purse-seine fisheries has variously been calculated as 34.5% (Ofori-Danson et al. 2003; Van Waerebeek et al. 2009) and 24.5% (Debrah et al. 2010). The occurrence of bycatch in other range states is undocumented, but may be significant. Additionally, Maigret (1981) and Weir and Pierce (2013) underlined the lack of information on dolphin bycatch in industrial tuna purse-seine fisheries in the Gulf of Guinea. The ‘‘West African population’’ of Clymene dolphins was recently added to the Conservation of Migratory Species of Wild Animals Appendix II, due to the scarcity of ETA records and evidence of high bycatch in Ghana (Van Waerebeek and Perrin 2007). However, given the publication of 2 mid-Atlantic capture records (Lütken 1889; Perrin et al. 1981), an occurrence in offshore deepwater habitat (. 4,000 m—Fertl et al. 2003; Moreno et al. 2005; this study), and an absence of genetic or taxonomic studies to support regional differentiation, it is currently unclear whether considering Clymene dolphins as separate western and eastern Atlantic ‘‘populations’’ is the optimal management approach. In this paper we documented a widespread occurrence of Clymene dolphins in the ETA, indicating that the previous paucity of records reflected an absence of survey effort (and identification difficulties) rather than a genuine rarity of the species in the region. Nevertheless, verified records remain relatively scarce in relation to other ETA cetacean species (e.g., comprising only 1.0% of 617 sightings of positively identified delphinid species in Angola [Weir 2011b]). Robust information on the spatiotemporal movements, abundance, population structure, and mortality levels of Clymene dolphins is needed before a full evaluation of conservation status can be made. As noted by Van Waerebeek and Perrin (2007), the Clymene dolphin appears to be a wide-ranging, mobile species for which 1297 coordinated transboundary conservation plans covering multiple range state Exclusive Economic Zones will be required for effective management within the ETA. ACKNOWLEDGMENTS We thank the following companies (alphabetical) for their permission to include previously unpublished data from their surveys in this paper: BP Exploration (Angola) Ltd., Chevron (Nigeria and Angola), China National Offshore Oil Company, Compagnie Béninoise des Hydrocarbures, ConocoPhillips, ENI (Togo and Angola), Kosmos Energy, Maersk Oil Angola, Ophir Energy, Petrobras Oil and Gas BV—Benin, Petroleum Geo-Services (PGS) Multi-Client (comprising BP Exploration (Angola) Ltd., Sonangol, Statoil and Total (Angola)), Shell Benin Upstream Ltd., Shell International Exploration and Production B.V., TGS NOPEC Angola, Total (Côte d’Ivoire and Angola), and Tullow Oil (Ghana and Mauritania Ltd.). R. Compton (RPS), N. Grosse (Geomotive), and A. Hyam (GeoGuide) provided helpful assistance in gaining data permissions. Thanks to the two reviewers whose comments improved this manuscript. SUPPORTING INFORMATION SUPPORTING INFORMATION S1.—Published stranding, capture, and skeletal records (by date) of the Clymene dolphin (Stenella clymene) in the eastern tropical Atlantic. Found at DOI: 10.1644/14-MAMM-A-115.S1 (40 MB DOC) SUPPORTING INFORMATION S2.—Verified sighting records (n ¼ 92) of the Clymene dolphin (Stenella clymene) in the eastern tropical Atlantic. Presented by range state (north to south) and then by date. Found at DOI: 10.1644/14-MAMM-A-115.S1 (40 MB DOC) SUPPORTING INFORMATION S3.—Individual variation in the pigmentation patterns of eastern tropical Atlantic Clymene dolphins (Stenella clymene). Found at DOI: 10.1644/14-MAMM-A-115.S1 (40 MB DOC) LITERATURE CITED AMARAL, A. R., G. LOVEWELL, M. M. COELHO, G. AMATO, AND H. C. ROSENBAUM. 2014. Hybrid speciation in a marine mammal: the Clymene dolphin (Stenella clymene). PLoS ONE 9:e83645. CADENAT, J., AND M. DOUTRÉ. 1958. Notes sur les Delphinidés ouestafricains. I. Un Prodelphinus ? indéterminé des côtes du Sénégal. Bulletin de l’Institut Français d’Afrique Noire 20:1483–1485. CARWARDINE, M. 1995. Whales, dolphins and porpoises. Dorling Kindersley Limited, London, United Kingdom. CULIK, B. 2011. Odontocetes—the toothed whales. CMS Technical Series 24. United Nations Environment Programme/Convention on Migratory Species of Wild Animals (CMS)/Agreement on the Conservation of Small Cetaceans of the Baltic and North Seas (ASCOBANS) Secretariat, Bonn, Germany. DAVIS, R. W., ET AL. 1998. Physical habitat of cetaceans along the continental slope in the north-central and western Gulf of Mexico. Marine Mammal Science 14:490–507. DE BOER, M. N. 2010. Cetacean distribution and relative abundance in offshore Gabonese waters. Journal of the Marine Biological Association of the United Kingdom 90:1613–1621. DEBRAH, J. S., P. K. OFORI-DANSON, AND K. VAN WAEREBEEK. 2010. An update on the catch composition and other aspects of cetacean exploitation in Ghana. Paper SC/62/SM10 presented to the Scientific Committee of the International Whaling Commission, Agadir, Morocco, 2010. 1298 JOURNAL OF MAMMALOGY ENVIRONMENTAL SYSTEMS RESEARCH INSTITUTE, INC. [ESRI]. 1998. ArcView GIS 3.2. Environmental Systems Research Institute, Inc., Redlands, California. FERTL, D., T. A. JEFFERSON, I. B. MORENO, A. N. ZERBINI, AND K. D. MULLIN. 2003. Distribution of the Clymene dolphin Stenella clymene. Mammal Review 33:253–271. FLANDERS MARINE INSTITUTE. 2012. MarineRegions.org., version 7. www.marineregions.org Accessed 20 November 2012. GENERAL BATHYMETRIC CHART OF THE OCEANS [GEBCO]. 2003. General Bathymetric Chart of the Oceans digital atlas (GDA). British Oceanographic Data Centre, Liverpool, United Kingdom. GOMES-PEREIRA, J. N., R. MARQUES, J. CARVALHO, AND A. MARTINS. 2013. The little-known Fraser’s dolphin Lagenodelphis hosei in the North Atlantic: new records and a review of distribution. Marine Biodiversity 43:321–332. GRAY, J. E. 1846. On the cetaceous animals. Pp. 13–53 in The zoology of the voyage of H.M.S. Erebus and Terror, under the command of Captain Sir James Clark Ross (J. Richardson and J. E. Gray, eds.). E. W. Janson, London, United Kingdom, 1(3). HAMMOND, P. S., ET AL. 2012. Stenella clymene. In: IUCN 2013. IUCN Red list of threatened species. Version 2013.2. www.iucnredlist. org. Accessed 12 February 2014. HAZEVOET, C. J., ET AL. 2010. Recent data on whales and dolphins (Mammalia: Cetacea) from the Cape Verde Islands, including records of four taxa new to the archipelago. Zoologia Caboverdiana 1:75–99. INTERNATIONAL HYDROGRAPHIC ORGANISATION [IHO]. 1953. International Hydrographic Organisation special publication 23, limits of oceans and seas. 3rd ed. International Hydrographic Organisation, Monaco, Monaco. JEFFERSON, T. A. 1996. Morphology of the Clymene dolphin (Stenella clymene) in the northern Gulf of Mexico. Aquatic Mammals 22:35– 43. JEFFERSON, T. A. 2009. Clymene dolphin Stenella clymene. Pp. 234– 236 in Encyclopedia of marine mammals (W. F. Perrin, B. Würsig, and J. G. M. Thewissen, eds.). Academic Press, London, United Kingdom. JEFFERSON, T. A., M. A. WEBBER, AND R. L. PITMAN. 2008. Marine mammals of the world: a comprehensive guide to their identification. Academic Press, Elsevier, London, United Kingdom. JOINT NATURE CONSERVATION COMMITTEE [JNCC]. 2010. JNCC guidelines for minimising the risk of injury and disturbance to marine mammals from seismic surveys. Joint Nature Conservation Committee, Aberdeen, United Kingdom. LÜTKEN, C. F. 1889. Spolia Atlantica. Bidrag til Kundskab om de tre pelagiske Tandhval-Slaegter Steno, Delphinus og Prodelphinus. Kongelige Danske Videnskabs-Selskabet Skrifter, MathematiskNaturvidenskabelig 6:1–61. MAIGRET, J. 1981. Rapports entre les cétacés et la pêche thonière dans l’Atlantique tropical oriental. Notes Africaines 171:77–84. MAZE-FOLEY, K., AND K. D. MULLIN. 2006. Cetaceans of the oceanic northern Gulf of Mexico: distributions, group sizes and interspecific associations. Journal of Cetacean Research and Management 8:203–213. MINITAB INC. 2010. Minitab 16 statistical software. Minitab Inc., State College, Pennsylvania. MORENO, I. B., ET AL. 2005. Distribution and habitat characteristics of dolphins of the genus Stenella (Cetacean: Delphinidae) in the southwest Atlantic Ocean. Marine Ecology Progress Series 300:229–240. Vol. 95, No. 6 MULLIN, K. D., AND G. L. FULLING. 2003. Abundance of cetaceans in the southern U.S. North Atlantic Ocean during summer 1998. Fishery Bulletin 101:603–613. MULLIN, K. D., AND G. L. FULLING. 2004. Abundance of cetaceans in the oceanic northern Gulf of Mexico, 1996–2001. Marine Mammal Science 20:787–807. OCEAN COLOR WEB. 2014. NASA Ocean Color website. http:// oceancolor.gsfc.nasa.gov. Accessed 28 July 2014. OFORI-DANSON, P. K., K. VAN WAEREBEEK, AND S. DEBRAH. 2003. A survey for the conservation of dolphins in Ghanaian coastal waters. Journal of the Ghana Science Association 5:45–54. PERRIN, W. F. 2009. Coloration. Pp. 236–245 in Encyclopedia of marine mammals (W. F. Perrin, B. Würsig, and J. G. M. Thewissen, eds.). Academic Press, London, United Kingdom. PERRIN, W. F., AND J. G. MEAD. 1994. Clymene dolphin—Stenella clymene (Gray, 1846). Pp. 161–171 in Handbook of marine mammals. Vol. 5. The first book of dolphins (S. H. Ridgway and R. Harrison, eds.). Academic Press, San Diego, California. PERRIN, W. F., E. D. MITCHELL, J. G. MEAD, D. K. CALDWELL, AND P. J. H. VAN BREE. 1981 Stenella clymene, a rediscovered tropical dolphin of the Atlantic. Journal of Mammalogy 62:583–598. REEVES, R. R., B. S. STEWART, P. J. CLAPHAM, AND J. A. POWELL. 2002. Guide to marine mammals of the world. Alfred A. Knopf, New York. ROBINEAU, D., M. VÉLY, AND J. MAIGRET. 1994. Stenella clymene (Cetacea, Delphinidae) from the coast of West Africa. Journal of Mammalogy 75:766–767. SHIRIHAI, H., AND B. JARRETT. 2006. Whales, dolphins and seals: a field guide to the marine mammals of the world. A & Black, C London, United Kingdom. SPALDING, M. D., ET AL. 2007. Marine ecoregions of the world: a bioregionalization of coastal and shelf areas. BioScience 57:573– 583. VAN WAEREBEEK, K., P. K. OFORI-DANSON, AND J. DEBRAH. 2009. The cetaceans of Ghana, a validated faunal checklist. West African Journal of Applied Ecology 15:61–90. VAN WAEREBEEK, K., AND W. F. PERRIN. 2007. Conservation status of the Clymene dolphin in West Africa. Paper CMS/ScC14/Doc.5, 14th Meeting of the CMS Scientific Council, 14–17 March 2007, Bonn, Germany. WEIR, C. R. 2006. First confirmed records of Clymene dolphin, Stenella clymene (Gray, 1850), from Angola and Congo, south-east Atlantic Ocean. African Zoology 41:297–300. WEIR, C. R. 2010. A review of cetacean occurrence in West African waters from the Gulf of Guinea to Angola. Mammal Review 40:2– 39. WEIR, C. R. 2011a. Distribution and seasonality of cetaceans in tropical waters between Angola and the Gulf of Guinea. African Journal of Marine Science 33:1–15. WEIR, C. R. 2011b. Ecology and conservation of cetaceans in the waters between Angola and the Gulf of Guinea, with focus on the Atlantic humpback dolphin (Sousa teuszii). Ph.D. dissertation, University of Aberdeen, Aberdeen, United Kingdom. WEIR, C. R., AND G. J. PIERCE. 2013. A review of the human activities impacting cetaceans in the eastern tropical Atlantic. Mammal Review 43:258–274. Submitted 24 April 2014. Accepted 10 June 2014. Associate Editor was Jeanette A. Thomas.