Assessing the effects of passive integrated transponders (PIT tags) on the survival of Po brook lamprey (Lampetra zanandreai) ammocoetes

Small-sized freshwater species with little or no direct economic value, such as many endemics, are poorly known in terms of habitat requirements, foraging strategies, distribution and movement behaviour. Passive Integrated Transponder (PIT) telemetry has proven useful for studying the ecology of small-sized species in confined environments. To use this technology in the wild, it is necessary to verify that PIT tags do not affect the survival and natural performance of tagged individuals. Such studies have been carried out on some small fish, usually showing low mortality and no effect on behaviour, but few have been carried out on lampreys. We investigated the effects of PIT-tagging on ammocoetes of Lampetra zanandreai, a freshwater lamprey endemic to northern Italy for which very little ecological knowledge is available. In a 2-week experiment, the tagged lampreys showed a high mortality rate (74%), while untagged controls showed no mortality. This result demonstrates that PIT-tagging is not a safe technology for ammocoetes of this species, at least not with the standard 12 mm tags.