FAO capture production for Naso unicornis from Saudi Arabia recorded 126 tonnes in 2000 to 191 tonnes in 2001, catch decreased from 2002-2004 with 133, 145 and 113 tonnes respectively; it has increased since then with 195 tonnes recorded in 2007. There are no capture production records prior to 2000. Density of N. unicornis was 3-10 times greater after marine reserves around five islands in New Caledonia were protected from fishing for 4 yrs (Wantiez et al. 1997). In the central Philippines, there were two orders of magnitude difference in mean biomass between fished areas and marine reserves (0.5 to 11 years protection) (Stockwell et al. 2009).
In Saipan, this species was the most abundant fish in the surveys with landings accounting for 14% of the total fish landings, and 50% of the acanthurids landings (P. Houk unpublished data). Census data from seven sites around Saipan using timed visual surveys on SCUBA revealed N. unicornis was extremely rare at 0.05% of the total acanthurid abundance. A similar result was found on Guam, where this species made up 17% of the acanthurid fishery but was rarely recorded during visual surveys. In these and other locations where spearfishing is the primary fishing method, daytime visual surveys using fixed length transects might be inappropriate.
In the Federal States of Micronesia, particularly Yap, N. unicornis accounts for approximately 12% of the total catch landed from the sheltered coastal reefs and lagoons at two sites Yyin and Riiken (Kronen et al. 2006). On Pohnpei, this species is the second most abundant acanthurid in the fishery (26% of all acanthurids) (Rhodes et al. 2008). Analysis of longterm fishery data (1984-2007) from Guam reveal no decline in mean individual weight for this species (Division of Aquatic and Wildlife Resources unpub. data). An average of 7,700 kg/year is landed in Hawaii (Division of Aquatic Resources unpub. data). This species is collected as an aquarium fish in West Hawaii. The total number of individuals caught from FY 2005-2009 was 24 with a total value of $68 (Walsh et al. 2010).
This species was recorded as occasional in terms of relative abundance in Palawan Province, Philippines and the northern Bismarck Sea, Papua New Guinea (Werner and Allen 2000, Palawan Council for Sustainable Develeopment, Allen 2009). It is moderately common in Milne Bay Province, Papua New Guinea and in Raja Ampat, Indonesia (Allen 2003, 2003b). In Moorea, French Polynesia, SPOT satellite images allowed estimation of the surface area of fringing reef (1,076 ha), barrier reef (3,788 ha) and outer slop (493 ha). A total of 21,346 individuals were recorded in this area in fish visual surveys conducted from 1990-1993 (Lecchini et al. 2006).
In the Nabq Managed Resource Protected Area, South Sinai, Egyptian Red Sea, mean abundance of this species was higher in the fished areas than in the no-take zones across 3 and 10 m depths. This can be attributed to a result of reduced predation or competition (Ashworth and Ormond 2005). In a stock assessment conducted at the northern province of New Caledonia by Letourneur et al. (2000), density and biomass was higher in the north zone and on barrier reefs (17.5 g m-2 and 129 Ã10-4 individuals m-2) compared to other areas surveyed and other reef types.