Detection of Japanese flounder-specific DNA from gut contents of potential predators in the field

Predation by invertebrates may be one of the major factors influencing the mortality of released flounder juveniles in the field. We developed a polymerase chain reaction (PCR)-based technique for the detection of Japanese flounder material from the gut contents of potential predators in the field. The PCR primers used here are flounder specific and encompass a 153 bp region from the right domain of the mitochondrial control region. With these oligonucleotide primers, PCR reactions yielded specific amplification products from the gut contents of some putative predators, including Matuta lunaris, Portunus gladiator, Sepioteuthis lessoniana, Suggrundus meerdervoorti, Platycephalus sp. and Rhyncopelates oxyrhynchus. Many animals with gut contents of unidentified fish material showed indication of predation on the flounder after release of hatchery reared flounder juveniles. The technique developed in the present study is useful not only for the survey of predation on the flounder by known species, but also for the search for novel potential predatory species in the field.