Behavioral response and retinal adaptation of Blue swimming crab (Portunus pelagicus) exposed to LED lights – Led light as a potential artificial attractant in trap fishing

Abstract

Trap fishing offers many potential benefits such as high catch quality and the possibility to release unwanted catch alive. The use of wild fish as a bait in trap fishing, however, can be troublesome and may involve sustainability concerns. There is a need for accessible and sustainable alternative attractant that is not based on marine resources which can be used for human consumption. To reduce reliance on natural bait and to improve the catch rate of traps, underwater LED lights have recently been tested with promising results in several trap fisheries targeting crustaceans. We investigated in laboratory conditions the response and behavior of blue swimming crab towards different LED light colors and a natural bait. Our results suggest that blue swimming crab has a high preference for blue LED light. The frequency of crab moving toward attractant was highest with blue light, followed by natural bait, red light, and green light. Trap equipped with blue LED light captured 3,5 times more crabs than trap with red light. In addition, during the 60-min exposure time, a trap with blue LED light was equally effective as a trap with natural bait to retain crabs caught in a trap. Furthermore, our study shows that the rhabdom layer of blue swimming crab eyes was more pigmented with a blue light than green and red light which indicates that its eye is more sensitive to blue light. Our experiments suggest that the use of blue LED light as an attractant would be a potential alternative to natural bait. Further research, however, is required through fishing trials in natural conditions to verify the effectiveness of LED light as artificial bait to blue swimming crab.