This study identifies differences in fishing efficiency of vessels operating in the Nha Trang purse seine fishery in Vietnam. The deterministic DEA methodology is used to assess relative capacity utilization of the fishing fleet. Double bootstrap DEA method is adopted to overcome some of the drawbacks of nonparametric DEA methodology and provide consistent inference regarding factors affecting the capacity utilization. The study is based on a survey of cost and earning data from 52 purse seiners in Nha Trang, Vietnam in 2016, and reveals that the vessels had an average profit margin of 11.2%. The mean capacity utilization while assuming variable returns to scale is 0.724, using the double bootstrap DEA. Corresponding capacity utilization rate when adopting the deterministic DEA method is 0.813. These results suggest that it is possible to sustain the catches with reduced use of input factors in the fishery. The study indicates that factors influencing the capacity utilization are size of vessel, fishing experience and family size of skipper. The two latter are interpreted as proxies for skilled crew and low crew costs.