Biological reference points in the management of North American sea urchin fisheries

The precautionary approach calls for both target and limit reference points (TRPs and LRPs, respectively) and notes the vulnerability of developing fisheries to excess effort. LRPs should reflect a population's ability to continue to persist, which depends on lifetime egg production (LEP) and current abundance. The unique characteristics of sea urchin fisheries, such as (i) tight ecological coupling, (ii) their being roe fisheries, (iii) protection of juveniles under adult spine canopies, and (iv) broadcast spawning, can influence their management. Most North American sea urchin fisheries developed rapidly. Their reference points include (i) several LRPs and TRPs based on the logistic or surplus production model, (ii) a unique TRP involving direct monitoring of the bathymetric position of their macro phyte food, and (iii) an LRP based on the fraction of natural, unfished LEP. The dominant effect of fishing down and serial depletion on catch and effort data from developing sea urchin fisheries adversely affects fits to the logistic model. Reference points based on tight ecological coupling will be useful only where food webs are simple and one-dimensional. Sea urchin fisheries developed in the future should consider the fraction of natural LEP as an LRP and attempt to limit early excess fishing capacity.