Population of Formosan salmon falls

The number of endangered Formosan Landlocked Salmon (櫻花鉤吻鮭), also known as the national treasury fish, in rivers in Shei-Pa National Park (雪霸國家公園) has been cut by more than half following two devastating typhoons this summer, according to a scientific survey released yesterday.

Before the typhoon season this year, about 3,200 of the fish were counted in a survey of Chichiawan Stream (七家灣溪) near Wuling Farm (武陵農場) in Taichung County. However, abnormally heavy rains brought by Tropical Storm Mindulle in early July and Typhoon Aere in late August have put the species in danger.

Tzeng Chyng-shyang (曾晴賢), an associate professor at National Tsing Hua University, found about 1,475 fish after conducting a survey this fall. This is less than half of the 3,228 recorded in the summer, and the lowest number reported since 2002.

With the rise of conservation advocacy in Taiwan, efforts to revive the population of the endangered fish culminated in 2002, when the number of fish exceeded 4,000. However, the count declined to about 3,180 last year because of habitat damage from typhoons in 2002.

Tzeng has researched the relation between the fish population and natural disasters, and stressed that floods have been identified as one of the major factors. Tzeng presented the information at a conference on ecological conservation and natural disasters held yesterday by the Kingcar Education Foundation and National Taiwan Normal University.

Tzeng said his team found the situation this year following the typhoons to be quite similar to the aftermath of the devastating Typhoon Herb in 1996.

That autumn, there were about 1,245 survivors.

"It means that when floods come, natural refuges available to the fish in these habitats are limited," Tzeng said.

Tzeng said that after a flood, the carrying capacity of habitats was seriously affected because the of reduced diversity in the aquatic environment.

"Many kinds of water creatures' reproduction in the ecological system is affected. Food scarcity has led to a decline in the population of the Formosan freshwater salmon since the passage of typhoons this summer," Tzeng said.

However, Tzeng predicts that the population might increase in the following years, because members washed away were relatively small and young.

"Surviving adult salmon can still reproduce effectively, if the impact of typhoon disasters can be minimized by appropriate human efforts," Tzeng said.

Tzeng said habitat management has been improved in recent years and certain dams have been removed in order to diversify the environment.

Tzeng said the distribution of the endangered fish this fall was similar to a decade ago.

The precious salmon now mainly survive in an 8km section of Chichiawan Stream (七家灣溪) and some can be seen in nearby Kaoshan Creek (高山溪) and Yusheng River (有勝溪).

Lin Young-fa (林永發), head of the park's administration, said yesterday that managers will create a breeding stock of the species near rivers next year to ensure the survival of the delicate salmon. The next survey of the fish population will be conducted in June.