Monitoring and managing fisheries discards: New technologies and approaches

Accurate data on discards, the proportion of the catch that fishers do not retain, is necessary to achieve socioeconomically and ecologically sustainable fisheries. We review conventional and emerging approaches to monitor and manage discards. At-sea human observer programs currently produce the most accurate data on discards. Electronic monitoring may become the most effective method to monitor discards, as it has the capacity to overcome most sources of statistical sampling bias of conventional human onboard observer programs. Other monitoring approaches, including logbooks, fishery-independent surveys and fisher interviews, produce relatively unreliable discard estimates, while port sampling only provides information on landed catch. Modifications to fishing practices and gear to increase selectivity are main approaches used to reduce discards. Managing the temporal and spatial distribution of fishing effort by employing tools such as dynamic spatial management and fleet communication are additional discards management tools. Landing obligations, retention bans, bycatch caps, effort limits and size restrictions are additional approaches for which strengths and weaknesses are discussed. Continual evaluation is necessary to understand ever-changing causes of fishers' discarding decisions so that important factors can be accounted for in designing monitoring programs and discard models, and guide the adaptation of measures to manage and reduce discards.