The effect of led lights on trap catches in signal crayfish fisheries

Abstract

Signal crayfish (Pacifastacus leniusculus) is a freshwater crayfish, originally from the west coast of North America. It is now widespread in Europe and it is listed as a harmful species in the list of invasive species of European Union concern. We tested the effect of LED lights in signal crayfish trapping in a large Finnish lake. Light attraction could be a cost-effective way of increasing crayfish catches in eradication programs and commercial trapping, but research results are largely lacking. Experiments were conducted in Lake Päijänne which has an abundant population of invasive signal crayfish. We tested whether white and green LED lights attached inside the baited traps increase crayfish catch per unit effort (CPUE) compared with baited traps without light. Mean CPUE was higher in traps only baited with a fish (2.7 ind. 24 h-1) compared to traps with a fish bait and a green LED light (1.5 ind. 24 h-1), and traps with a fish bait and a white LED light (1.9 ind. 24 h-1). Our results show that LED lights did not increase signal crayfish CPUE. Instead, lower catches in traps with LED lights indicate that crayfish were not attracted by the light. We observed significant variation in CPUEs, but without interaction between crayfish sex or size and light treatments. We conclude that LED lights do not increase the effectiveness of signal crayfish trapping.