Report of the Second Workshop on The Biology and Conservation of ...

Needs for additional researchStock identity research is badly needed, especiallygiven <strong>the</strong> possibility <strong>of</strong> shared populationsbetween SE Asia and Japan, where <strong>the</strong>re arelarge-scale directed catches <strong>of</strong> this species. Someassessment is also needed <strong>of</strong> <strong>the</strong> effects <strong>of</strong> bycatchin large-mesh driftnet fisheries, particularlyin deep coastal waters <strong>of</strong> Taiwan. The illegalharpoon catches in Taiwan should be investigatedfur<strong>the</strong>r.2.2.8 Stenella longirostrisDistributionThe spinner dolphin has been confirmed to occurin Malaysia (Doc. 10). Smith noted that <strong>the</strong> dwarfsubspecies <strong>of</strong> <strong>the</strong> spinner dolphin (S. longirostrisroseiventris - Perrin et al. 1999), described from<strong>the</strong> Gulf <strong>of</strong> Thailand and <strong>the</strong> Arafura and TimorSeas, may be present in <strong>the</strong> Gulf <strong>of</strong> Tonkin waters<strong>of</strong> Vietnam, based on a single sighting. Wangreported that dwarf spinners also may be presentin shallow waters <strong>of</strong>f <strong>the</strong> sou<strong>the</strong>rn and easterncoasts <strong>of</strong> Taiwan (Wang et al. 2001a). These areas,if confirmed as part <strong>of</strong> <strong>the</strong> subspecies’ distribution,would represent large range extensions. It hasnow been reported from Cambodian waters (Doc.34).Population/stock structureNo new information.Population statusDolar (1999a) provided abundance estimates forTañon Strait (3,214; CV=33%) and <strong>the</strong> easternSulu Sea (29,966; CV=29%). An estimate for <strong>the</strong>sou<strong>the</strong>rn Sulu Sea is 3,979 (CV=59%; Dolar etal. 1997). Chen (2001) calculated an abundanceestimate <strong>of</strong> 1,490 individuals (CV=25%) fornor<strong>the</strong>astern Taiwan.Habitat statusThe nearshore reef habitat <strong>of</strong> <strong>the</strong> dwarf subspeciesis highly vulnerable to human impacts in SE Asia.Wang reported that high-speed watercrafts havebeen observed chasing dwarf spinner dolphins(tentative identification) in sou<strong>the</strong>rn Taiwan andthat <strong>the</strong> coral reef ecosystem <strong>of</strong> sou<strong>the</strong>rn Taiwanhas experienced great destruction by humanactivities.Directed catchesThis is one <strong>of</strong> <strong>the</strong> most commonly harpoonedspecies <strong>of</strong>f Taiwan (Doc. 6), and directed catchesare also known from <strong>the</strong> Philippines (Doc. 28).The spinner dolphin is one <strong>of</strong> several species<strong>of</strong> dolphins that may be hunted for food byimmigrants in Sabah, Malaysia (Doc. 10).By-catchesBy-catches <strong>of</strong> three spinner dolphins are knownfrom Vietnam, <strong>of</strong>f <strong>the</strong> Con Dao Islands (Doc.4). The species is also taken in driftnets in Taiwan(Doc. 6). Perrin noted that <strong>the</strong>re are still no dataon <strong>the</strong> by-catch <strong>of</strong> dwarf spinner dolphins in <strong>the</strong>Taiwanese shark gillnet fishery that operates inIndonesian territorial waters. This is <strong>the</strong> samefishery that previously operated in Australianterritorial waters and was ejected because <strong>of</strong>causing a large by-catch <strong>of</strong> dolphins <strong>the</strong>re (Doc.16). By-catch occurs in purse seines, driftnets,and longlines in many areas <strong>of</strong> <strong>the</strong> Philippines(Doc. 19).Needs for additional researchThere should be a detailed study <strong>of</strong> whale-templespecimens to examine <strong>the</strong> possibility <strong>of</strong> <strong>the</strong>presence <strong>of</strong> <strong>the</strong> dwarf form in Vietnam. The bycatchin <strong>the</strong> shark gillnet fishery in Indonesianwaters is <strong>of</strong> serious concern, and should beinvestigated as a matter <strong>of</strong> urgency. Wheneverpossible sightings <strong>of</strong> <strong>the</strong> dwarf spinner dolphin aremade in Taiwan, effort should be made to collect74 CMS Technical Series Publication Nº 9 - 2005