Distribution and school size of dusky dolphins, Lagenorhynchus obscurus (Gray, 1828), in the Southwestern South Atlantic Ocean

CRESPO, ENRIQUE ALBERTO; PEDRAZA, SUSANA NOEMÍ; COSCARELLA, MARIANO ALBERTO; GARCÍA, NÉSTOR ANÍBAL; DANS, SILVANA LAURA; IÑIGUEZ, MIGUEL; REYES, LAURA MARINA; KOEN ALONSO, MARIANO; SCHIAVINI, ADRIAN CARLOS MIGUEL; GONZÁLEZ, RAÚL

Reports of the International Whaling Commission

International Whaling Commission

Lugar: Oxford; Año: 1997 vol. 47 p. 693 - 697

0143-8700

New records un the distribution of the dusky dolphin, Lagenorhynchus obscurus, off the coasts of Argentina, in the southwestern south Atlantic Ocean, are presented. School size and sympatry between dusky and Peale´s dolphins, Lagenorhynchus australis, are also discussed. Information was recorded by: (a) trained observers onboard oceanographic and fishing vessels nr from specimens entangled in fishing gear; (b) trained observers during aerial surveys: (e) fishermen un fishing vessels; (d) less-trained observers and previous records jo the literature. The information gathered included: date; location of sightings; entanglement or stranding; latitude; longitude; number of individuals; sex; sea state; weather conditions; etc. The northemmost record was at La Lucila del Mar, north of Buenos Aires Province (36019fS), and the southernmost record was at Bahía Nassau (55026´S 67018´W), near Cape Horn. Dusky dolphins have been sighted from the coast to just before the 200 n.miles Exclusive Economic Zone border, but the present information does not allow us to conclude whether this species´ distribution tends to be more coastal than offshore or vice versa due to the bias in coastal effort. Fishermen detected schools of > 50 individuals, mostly between noon and 1600hrs, while the schools sighted from airplanes were of