Illegal fishing is often cited as a principal cause of the failure of fisheries management, expecially fishing efforts regulations in traditional fisheries management. Usually, illegal fishing problems are perceived to be equivalent to inadequate enforcement, and policy prescription then follow to strengthen enforcement programs. The purpose of this paper is to analyze the illegal fishing behavior relatively recent emphasis on fishing efforts regulations in traditional fisheries management. The analysis focuses on measuring, explaining and developing the effectiveness way of enforcement strategies responding to imperfectly managed fishing efforts regulations through illegal fishing behavior and avoid enforcement fishing efforts measures. A model of fishermen fishing behavior and profit-maximizing decision making is analyzed to determine optimal fishing at individual fisherman level in response to fishing efforts regulation. The results of economic analysis of the enforcement of illegal fishing in traditional fisheries management results are as follows: First, illegal fishing will occur only if enforcement effort is not so high as to remove the incentive to do so, and if the effectiveness of avoidance is not too great, nor its cost too low. Second, avoidance effort will occur at a level jointly proportional to the extent of illegal activity and of enforcement; for given levels of the latter, the desired avoidance effort increase with its effectiveness and decrease with its cost Third, to improve the effectiveness of enforcement, understanding avoidance behavior appears to be crucial to any efforts. Forth, enforcement and fishermen behavior interact depends strongly on characteristics of avoidance, specifically its cost and effectiveness. When avoidance is neither too cheap nor too effective, the interaction is regular. Fifth, in this case, at low levels of enforcement, fishers respond to increases in enforcement by increasing avoidance, but at higher enforcement levels, it becomes uneconomical to continue to do so, and avoidance decreases with enforcement. Sixth, illegal fishing activity decreases steadily with enforcement, so the fishery manager is able, in theory, to reduce illegal fishing toward zero by increasing enforcement. If, however, avoidance is very inexpensive and/or very efficient/ then the optimal level of avoidance will increase indefinitely with increasing enforcement. Finally, less fishery enforcement is required if fishermen have less incentive to overfish, and fishermen have less incentive to avoid fishery enforcement measures.