Nitrogenous wastes including ammonia-N, nitrite-N, and nitrate-N are increasingly becoming a global issue in aquatic ecosystems due to escalating anthropogenic activities and are a ubiquitous concern in aquaculture. These pollutants are interrelated via the nitrification cycle, with the direct metabolic product ammonia-N generally being the most toxic with high species specificity. Furthermore, while environmental factors influencing nitrogenous waste toxicity are similar, the causative underlying mechanisms are often substantially different. In this review, we focus on decapod crustaceans due to their high commercial value and likelihood of encountering these pollutants in their benthic or near-benthic habitat. While a large body of publications exists in this area, to date a comprehensive literature review on relative toxicities of all three nitrogenous wastes, physiological consequences, and adaptive mechanisms of crustaceans is lacking. Understanding these processes will likely have implications for environmental/fisheries management and the aquaculture industry. Additionally, there are strong indications that theoretical “safe” values, traditionally used for predicting toxicity thresholds, substantially underestimate the impact of nitrogenous waste on the growth and physiological condition of crustaceans. These consequences will be emphasized along with various methods of uptake, elimination, and detoxification that ultimately explain differences in nitrogenous waste toxicity to decapod crustaceans.

The prevalence of cannibalistic behavior among many commercially important decapod crustaceans is one of the biggest limiting factors to their culture productivity and profitability in aquaculture. Various biotic and abiotic factors influence cannibalism including stocking densities, molt status, size heterogeneity, photoperiod, light intensity, and availability to refuge and food; however, their relative efficacies are often species or stage dependent. For instance, although generally penaeid shrimp are seldom cannibalistic when food and space are sufficient, this does not apply to many crab, lobster, and some crayfish species. This review will first discuss the cannibalistic prevalence among commercially important crustacean species followed by a brief review on the current knowledge regarding chemical cues that trigger cannibalism. The main focus will then be on various mitigating methods to improve survival for each of the three main aquaculture phases, that is hatchery, nursery, and grow-out, respectively. Throughout, areas in which one method may have applications to other species or life stages will be highlighted. A final section discusses possible future directions that include individually farming high-value crustaceans and the potential to manipulate hormones associated with aggression. It is hoped that such discussions as well as identifying knowledge gaps will prompt research to help expand and diversify the crustacean farming industry.