The horseshoe crab has the important roles as macrobenthos, but it is unfriendly for gillnets fisheries because it can damage the fishing net. The horseshoe crab is an ancient, rare, and protected animal so that the fishermen unable to utilize it, so the effort like mitigations need to be conducted like using red light LED. To avoid the learning behavior of horseshoe crab, so that the technology used is red light LED continuous then the red light led with flicker is used as a comparison. This study aims to determine the right type of red-light LED for horseshoe crab bycatch mitigation by the response pattern. The method used was a laboratory experiment. There are 20 adult horseshoe crabs used. The analysis used was descriptively comparative. The results showed that the red-light LED with flicker was most avoided by horseshoe crabs, which is 75%, while the fastest response of horseshoe crab in avoiding light was found in the light with a flicker effect of 22.97 seconds. Based on the horseshoe crab’s response, it can be concluded that the red LED light flicker is better than the red LED continuous as an alternative technology for the mitigation of horseshoe crab bycatch.