Effects of age, size, and density on natural survival for an important coral reef fishery species, yellow tang, Zebrasoma flavescens

Hundreds of thousands of juvenile yellow tang, Zebrasoma flavescens, are caught each year in the state of Hawai'i (USA) for the live aquarium trade. As part of an extensive adaptive management strategy built around a network of protected areas, an emphasis was placed on understanding this important species' life history. Multiple capture-mark-recapture techniques and a model selection approach to data analysis in Program MARK were used to estimate the effects of individual age and conspecific density on natural per-capita daily survival probabilities of yellow tang recruits (recently settled individuals, 30-50 mm total length) and the effects of body size and site on natural per-capita monthly survival probabilities for juveniles (58-127 mm total length). The models of recruit survival that included additive effects of density and age were best supported by the data and indicated an increase of survival with age and decrease of survival with increased conspecific density. At 1 day post-settlement, the model averaged daily per-capita survival probability ranged from 0.963 (95% CI: 0.932-0.981) at a low density of 0.1 recruits m⁻² to 0.848 (95% CI: 0.752-0.911) at a high density of 1.3 recruits m⁻². The best supported model of juvenile survival had no effect of fish length or site, with a constant monthly per-capita survival of 0.939 (95% CI: 0.925-0.950). Only about 1% of recruits may survive to adulthood when protected from fishing. These results can be used to better analyze and interpret data from protected area monitoring surveys and refine management practices. Continued long-term monitoring, combined with targeted life history studies and demographic modeling, is needed to further investigate the population level effects of fishing yellow tang juveniles.