NOTES 447

V. M. J A N I K , ~ School of Environmental and Evolutionary Biology, University of St Andrews, Fife KYl6 9TS, United Kingdom; S. M. VAN PARIJS and P. M. THOMPSON, University of Aberdeen, Department of Zoology, Lighthouse Field Station, Cromarty, Ross-shire IV11 8YJ, United Kingdom. Received 8 December 1998. Accepted 25 August 1999.

Current address: Woods Hole Oceanographic Institution, Biology Department, MS 34 Red- field, Woods Hole, Massachusetts 02543, U.S.A.; e-mail: vjanik@whoi.edu.

MARINE MAMMAL SCIENCE, 16(2):447-452 (April 2000) 0 2000 by the Society for Marine Mammalogy

TUCUXI (SOTALZA FL UVZATZLZS) OCCURS I N NICARAGUA, 800 KM NORTH OF ITS PREVIOUSLY

KNOWN RANGE

The previously recorded distribution of the tucuxi (Sotalia jiwiatilis) ex- tended from Santa Catarina, Brazil, on the Atlantic coast (27"35'S, 48"34'W) (Simaes-Lopes 1987, 1988), north to the Caribbean Sea off central Panama (9"22'N, 79"54'W) (Bossenecker 1978, Borobia et al. 1991). This note reports records that extend the known range some 800 km to the northwest in north- eastern Nicaragua, where it is apparently an established part of the cetacean fauna.

Aerial surveys along coastal segments of northeastern Nicaragua were con- ducted in March, May, and June of 1992. Standard aerial survey techniques were employed as described by Rathbun (1988). A single-engine airplane was used for each flight, flying at an altitude of 250 m and at an air speed of 90 knt. When animals were sighted the pilot circled the area several times while three observers (one in the right front seat and one in each of the left and right rear seats) recorded data on species, number, and behavior directly onto charts of the study area. More than 190 km of the Miskito Coast Reserve (Fig. l), including coastline, lagoons, estuaries, and rivers, were surveyed to count manatees and dolphins. Boat surveys and interviews with local inhabitants familiar with aquatic life also were conducted. The interview protocol followed methods similar to those outlined in Carr et al. (1982).

These were the first aerial surveys for marine mammals in the waters off the eastern coast of Nicaragua. During 19 h of combined flight survey time over five days in March-June 1992, 136 sightings of dolphins were recorded. Interviews and boat surveys were conducted after each flight; observations and positive identification of the dolphins were corroborated with photographs. Based on the small size, coloration and low triangular dorsal fin (Jefferson et al. 1993; da Silva and Best 1994, 1996) all dolphins were identified as Sotalia. No sightings of bottlenose dolphins (Tarsiops tranratas), which have higher,

448 MARINE MAMMAL SCIENCE. VOL. 16. NO. 2 . 2000

Leimus NICARAGUA

- 84 W , 83W

83-W 84 W I

15 N

14 N

Figare 1 . Map of Miskito Coast Reserve, Nicaragua, showing locations and num- bers of dolphins observed during aerial surveys conducted on 29-30 May 1992.

NOTES 449

falcate dorsal fins, were made. The northernmost sighting was of a single dolphin in the backwaters of Leimus Lagoon (14"35'31"N, 83°14'54'fW). This discovery of S. fltlviatzlis in Nicaragua documents a new northernmost occur- rence for the species. The maximum count was 63 animals sighted on 29-30 May (Fig. 1). Dolphins were located near shore and in the coastal lagoons of the Miskito Coast Reserve. Most of the sightings (61.5%) were in lagoons and backwater bays and estuaries of the study area, while the remainder (38.5%) were in the sea just outside the surf line. Behavior of the dolphins varied. Social interaction between individuals, jumping, traveling, and feeding were observed.

Group size ranged from 1 to 20 individuals, with a mean of 8.0 2 6.1 (SD). All dolphins sighted were estimated to be <3 m in total length. The largest group of 20 dolphins was observed feeding on small schooling fish and possibly shrimp along the west shore of Waunta Lagoon. A group of dolphins was present in the same location for at least three consecutive days. Water depth in this brackish area is 1 2 m and the bottom is composed of soft mud.

A 187-cm male tucuxi was found dead just north of the mouth of the Layasiksa River, west side of Waunta Lagoon (1 3"40'00"N, 83'36'40"W) on 1 June 1992 and necropsied. It was positively identified as S. flZlviatilis using diagnostic keys of Jefferson et al. (1993) and da Silva and Best (1994, 1996) that utilize size, coloration, dorsal-fin shape, shape of teeth, and cranial mea- surements. The specimen was in fresh condition; the cause of death was not determined. The animal was slate-gray on the dorsal surface and white on the ventrum. Complete morphometrics were collected following Norris (1961) (Table 1). No parasites were observed. The stomach contents consisted of three small finfish, too decomposed for species identification. Local fishermen indi- cated that these dolphins feed on mullet, small schooling fish, and shrimp commonly found in the lagoons. Borobia and Barros (1989) suggested that this species feeds in inshore waters, predominantly on demersal teleosts and cephalopods. Previous reports of strandings in the Caribbean of tucuxi are very rare (van Bree 1975, Casinos e t al. 1981). The entire skeleton, stomach con- tents, and photographs were collected and sent to the Smithsonian Institution, Washington, DC (Catalog Number NMNH 57 1558), where morphological examination of rhe skull of the specimen verified field identification.

The discovery of Sotalia in Nicaragua represents the occurrence of a popu- lation more than 800 km north of the closest previously known range in the Caribbean off Panama (Bossenecker 1978). It is suspected that distribution of this species could be influenced by temperature, as well as other variables (Borobia et al. 1991). Borobia (1989) postulated the existence of two forms of Sotalia: a larger coastal marine form and a smaller freshwater form, with dif- ferences in cranial measurements as well as total length. The mean adult body size for the freshwater form is 1.2 2 0.2 m, and for the marine form 1.7 2 0.2 m (da Silva and Best 1994). The length of the specimen from Nicaragua clearly places it within the coastal marine group. Condylobasal length (CBL) for this specimen was 37.1 cm.

Local residents and fishermen call the dolphin "lam" and report that it is

450 MARINE MAMMAL SCIENCE, VOL. 16, NO. 2, 2000

Table 1. External measurements of a male Sotalia flzlviatilis (NMNH 57 15 58)

% of total

cm length

Snout to fluke notch 187 100 Snout to apex of melon 11 6 Snout to center of right eye 28 15 Snout to center of left eye 28 15 Snout to right auditory meatus 33 18 Snout to anterior origin of right flipper 43 23 Snout to tip of dorsal fin 117 63 Snout to center of anus 132 71 Length of mouth (smile) 22 12 Maximum gape 24 13 Center right eye to right auditory meatus 7.0 4 Length of blowhole 2.8 1 Width of blowhole 2.3 1 Length of right flipper along anterior edge 32 17 Length of right flipper along posterior edge 25 13 Maximum width of right flipper 12 6 Dorsal fin height 18 10 Length of dorsal fin at base 36 19 Greatest width of flukes 14 7 Length of fluke, tip to tip 46 25 Depth of fluke notch 3.8 2 Maximum width of rostrum 5.7 3 Center of eye to eye, over head 19 10 Girth at eye 64 34 Girth at axilla 97 52

commonly sighted throughout the year. Some fishermen indicated that they think there are two kinds of dolphins: a smaller one found near shore and often in fresh water, and a larger one (over 200 cm in length) more typically found off shore. There does not appear to be any direct hunting pressure exerted by local fishermen; however, animals may become accidentally entan- gled in gill nets, which are used extensively in this region of Nicaragua. Techniques employed in local fishing practices should be reviewed to assess the impact on regional dolphin populations.

We strongly recommend that additional surveys and interviews be con- ducted to obtain further data on abundance and distribution for this popula- tion, as well as to reveal the extent of the range of Sotalia beyond the bound- aries of this study area. Detailed studies should be carried out to determine suitable habitat and establish baseline data in the event that sanctuaries are necessary in these areas. Additionally, educational programs to train local bi- ologists in marine mammal assessment studies should be initiated. Pamphlets and posters should be produced to help educate local inhabitants and visitors to the area. Local biologists and managers should devise and implement a

NOTES 45 1

protection plan to ensure the future preservation of this unique dolphin pop- ulation.

ACKNOWLEDGMENTS

This study was made possible by generous financial support from the U. S. Agency for International Development, the U. S. Marine Mammal Commission, and the Liz Claiborne and Art Ortenberg Foundation. The success of the fieldwork was aided by the steadfast logistical support and good humor contributed by Charlie Luthin, Carlos Espinoza, and Stern Robinson of the Caribbean Conservation Corporation (CCC). With- out the support afforded us by the staff of the Instituto Nicaraguence de Recursos Naturales y del Ambiente (IRENA) and the Miskito Indian Environmental NGO (MIKUPIA), this work would not have been possible. Denis Castro of the CCC staff arranged the day-to-day research itinerary and coordination. We are grateful to James Mead and Charles Potter of the Smithsonian Institution for their assistance in obtaining the specimen. Cathy Beck, Charles Deutsch, and Lynn Lefebvre of the USGS Sirenia Project were kind enough to read the paper prior to submission. We are grateful to Nelio Barros, John Heyning, and William Perrin for their constructive comments during the review process.

LITERATURE CITED

BOROBIA, M. 1989. Distribution and morphometrics of South American dolphins of the genus Sotalia. M.S. thesis, McGill University, Montreal, Quebec, Canada. 8 1 PP.

BOROBIA, M., AND N. B. BARROS. 1989. Notes on the diet of marine Sotaliafluviatilis. Marine Mammal Science 5:395-399.

BOROBIA, M., S. SICILIANO, L. LODI AND W. HOEK. 1991. Distribution of the South American dolphin Sotalia fluviatilis. Canadian Journal of Zoology 69: 1025-1039.

BOSSENECKER, P. J. 1978. The capture and care of Sotalia guianensis. Aquatic Mammals 6: 13-17.

BREE, P. J. H. VAN. 1975. Preliminary list of the cetaceans of the southern Caribbean. Studies on the fauna of Curafao and other Caribbean islands 48:79-87.

CARR, A,, A. MEYLAN, J. MORTIMER, K. BJORNDAL AND T. CARR. 1982. Surveys of sea turtle populations and habitats in the Western Atlantic. NOAA Technical Mem- orandum NMFS-SEFC-91. 98 pp.

CASINOS, A., F. BISBAL AND S. BOHER. 1981. Sobre tres ejemplares de Sotaliafluviatilis del lago de Maracaibo (Venezuela) (Cetacea, Delphinidae). Publicaciones del De- partamento de Zoologia de Barcelona 23:263-274.

JEFFERSON, T. A., S. LEATHERWOOD AND M. A. WEBBER. 1993. FA0 species identifi- cation guide. Marine mammals of the world. FAO, Rome.

NORRIS, K. S., ED. 1961. Standardized methods for measuring and recording data on the smaller cetaceans. Journal of Mammalogy 42:47 1-476.

RATHBUN, G. B. 1988. Fixed-wing versus helicopter surveys of manatees Trichechus manatus. Marine Mammal Science 4:7 1-7 5.

DA SILVA, V. M. F., AND R. C. BEST. 1994. Tucuxi-Sotaliafluviatilis (Gervais, 1853). Pages 43-69 in S. H. Ridgeway and R. Harrison, eds. Handbook of marine mammals. Volume 5. The first book of dolphins. Academic Press, London.

DA SILVA, V. M. E, AND R. C. BEST. 1996. SotaliafEllviatilis. Mammalian Species 527:

SIM~ES-LOPES, P. C . 1987. Sobre a ampliagzo da distribuigzo do gsnero Sotalia, Gray, 1866 (Cetacea, Delphinidae) para as iguas do estado de Santa Catarina, Brasil. Pages 87-88 in Proceedings of Segunda ReuniHo de Trabalho de Especialistas em

1-7.

45 2 MARINE MAMMAL SCIENCE. VOL. 16, NO. 2. 2000

Mamiferos Aqudricos de AmCrica do Sul, 4-8 August 1986, Rio de Janeiro, Brad . FundaGiio Brasileira para a Conservagiio de Natureta. Rio de Janeiro, Brazil.

SIMOES-LOPES, P. c. 1988. Ocorrencia de uma populafgo de Sotaha fluviadis, Gervais, 1953 (Cetacea, Delphinidae) no limite sul de sua distribuigzo, Santa Catarina, Brad . Biotemas 1:57-62.

THOMAS CARR, Caribbean Conservation Corporation, P. 0. Box 2866, Gaines- ville, Florida 32602, U.S.A.; ROBERT K. BONDE,~ U.S. Geological Survey- Biological Resources Division, Florida Caribbean Science Center, 4 12 N.E. 16th Avenue, Room 250, Gainesville, Florida 32601, U.S.A.; e-mail: robert-bonde@usgs.gov. Received 12 November 1998. Accepted 29 July 1999.

Corresponding author.

MARINE MAMMAL SCIENCE, 16(2):452-459 (April 2000) 0 2000 by the Society for Marine Mammalogy

CONFIRMED SIGHTINGS OF DUSKY DOLPHINS (LAGENORHYNCHUS OBSCURUS) IN SOUTHERN

AUSTRALIAN WATERS

Dusky dolphins (Ldgenorhynchw 06sczlrzl.r) are widely distributed in southern cool temperate waters. Their presence has been confirmed previously in this habitat off the coasts of New Zealand, South Africa, Peru, Chile, and Argen- tina, as well as around the Chatham, Auckland, Falkland (Malvinas), and Prince Edward Islands, and Campbell, Gough, Amsterdam, and St Paul Islands (Gaskin 1968, Brownell 1974, Wiirsig and Wiirsig 1979, Baker 1983, Leath- erwood and Reeves 1983, Van Waerebeek 1993a, Van Waerebeek et al. 1995, Wiirsig et al. 1997). A supposed dusky dolphin stranded on Kerguelen Island in 1951 was re-identified by Robineau (1989) as a Commerson’s dolphin Ce- phalorbyncbzrs commwsoni. A skull from Tasmania attributed to L. obsczlrzls was subsequently identified as that of LissodeLphis pwonii (Van Waerebeek 19936). Brownell (1974) proposed that the distribution of this species comprised a circumpolar series of isolated geographic stocks. Recent morphometric work suggests subspecific status for stocks from the southeastern Pacific, south- western Africa, and New Zealand (Van Waerebeek 1993a).

Given their widespread distribution in southern cool temperate waters, dusky dolphins could be expected to occur in the waters surrounding Austra- lia. New sightings of this species in Australian waters are described here, including the first ones with photographic records, and are discussed in the context of previous records. The records reported here confirm that L. obsczlrus does occur in Australian waters and is properly included in the region’s faunal list.