Skin Lesions,Injuries And Physical Deformities Of Indo-Pacific Humpback Dolphin In Jiangmen Waters

The Indo-Pacific humpback dolphin(Sousa chinensis)is a small cetacean that lives mainly in the coastal waters of the Western Pacific and Eastern Indian Ocean.It belongs to the Class I at the national protection level and is included in the "The IUCN Red List of Endangered Species"(The IUCN Red List).The number of existing Indo-Pacific humpback dolphin is estimated to be less than 6000.As a small cetacean living in estuaries and near shores,the habitat of Indo-Pacific humpback dolphin is more overlapped with human activities,and it is more affected by human activities compared with the other cetaceans,so it needs our extensive attention.This study was based on the data collected by our team from field surveys in Jiangmen Guangdong Chinese White Dolphin Provincial Nature Reserve and surrounding waters from spring 2013 to spring 2019.The population size and age structure,skin lesions,injuries and physical deformities of Indo-Pacific humpback dolphin in Jiangmen waters were studied.The population size and age structure of the Indo-Pacific humpback dolphin in the waters was described,and the skin lesions and injury deformities of them were systematically studied.This paper also analyzed the causes of lesions and injuries to cause teratogenesis,and put forward relevant protection suggestions.There were 664 identified individuals in Jiangmen waters.Judging by the age of the last record,there were a total of 477 adult individuals,including 49 Unspotted adult(UA),234 Spotted adult(SA),120 SA/SS and 74 Speckled animal(SS);96 juvenile individuals,including 28 SS/SJ,45 Spotted juvenile(SJ)and 23 Unspotted juvenile(UJ);And 91 Unspotted calf(UC)individuals.The total prevalence of skin lesions in Jiangmen population was 47.3%.The annual prevalence rate from 2013 to 2019 was in the range of 20.1%-41.8%,and there was no increasing trend with the year.Among them,the prevalence of skin lesions in 2017 was the highest,and the number of affected individuals was also the highest.The lesions included Infected rake mark(P=23.2%),orange film(P=14.6%),nodules 9.6%(n=64),pox-like lesions(P=8.7%),pale lesions(P=7.1%),ulcers(P=2.1%),dark lesions(P=1.5%).In terms of age groups,adult individuals had the highest prevalence rate of 51.8%(247/477),followed by juvenile individuals with a prevalence rate of 45.8%(44/96),and calf individuals had a prevalence rate of 25.3%(23/91).The main lesion types of adult individuals were infected rake mark(P=25.2%)and orange film(P=18.4%),the main lesion in juvenile was infected rake mark(P=25.0%),and there was no major lesion type in calf individuals,the most common disease in calf individuals was infected rake mark.According to the prevalence of various skin lesions in the three age groups of the Indo-Pacific humpback dolphin,nodule and orange film were more likely to occur in adult individuals,pale lesion changes were more likely to occur in juveniles,rake mark was more likely to occur in adults and juveniles.Pox-like lesion,ulcer and dark lesion had no obvious age tendency.There was no obvious seasonal difference in the number of individuals suffering from skin lesions.The general situation of various skin lesions in Jiangmen population was different from that of Hong Kong population and Taiwan population.Among the 664 identified individuals,51 individuals were injured or deformed.The total injury rate was 7.7%,the annual injury rate tended to decrease overall,and the annual injury rate was in the range of 1.3%-6.3%.The adult individual injury rate was 9.9%(47/477),and the juvenile individual injury rate was 4.2%(4/96),the calf individuals were not injured or deformed.The injury rate of the anterior and posterior dorsal fin was much lower than that of the dorsal fin.A total of 52 injuries were recorded.7 individuals were injured on the anterior dorsal fin,including 6 adults and 1 juvenile;42 individuals were injured on the dorsal fin,including 39 adults and 3 juveniles;3 individuals were injured on the posterior dorsal fin,all of which were adult individuals.5 adult individuals given birth after being deformed.The total prevalence of skin lesions was much higher than the total injury rate.The skin lesions and traumatic deformities of the Indo-Pacific humpback dolphin indicated that their health was under various pressures due to human activities.For example,the strangulation,wounds,ropes and fishing gear of the severely injured dolphins were the direct evidence caused by human activities.In addition to the direct effect like fishing gear and boat propeller damage,factors such as fishery resources,environmental pollution,and noise interference might also indirectly affect dolphins.Good fishery governance and protection actions are also vital to the endangered Indo-Pacific humpback dolphin.Therefore,it is necessary to limit the speed of fishing boats within the core habitat of the Indo-Pacific humpback dolphin,reduce the use of entangled fishing gear and monitor the discharge of pollutants.