Nassau groupers are found in tropical and subtropical waters of the western North Atlantic. These include Bermuda, Florida, the Bahamas, the Yucatan Peninsula and the entire Caribbean to southern Brazil. There was a verified report of Nassau groupers in the Gulf of Mexico at the Flower Gardens Bank. They usually live under shallow reefs, but can be found at depths of up to 426 feet. The Nassau grouper can live up to 29 years. Males and females usually mature when they reach about 15 to 17 inches. Most reach sexual maturity when they are about 20 inches long and about 4 to 5 years old. Nassau groupers go through a juvenile bisexual phase and then mature directly as males or females. While adult Nassau groupers can change sex after hormone injection, the natural sex change has not been confirmed. Other relevant impacts of the identification of critical habitat, which we considered in accordance with section 4(b)(2) of the ESA, include impacts on the efforts of private and public entities involved in the management or conservation efforts of listed species. In cases where a federal context exists (such as a federal grant or permit), the identification of critical habitat may require consultation with NMFS to progressively address the impact of management or conservation activities on critical habitat. In such cases, these entities may need to allocate resources to fulfill their consultation obligations under section 7 as a third party to the consultation – including the administrative burden of consultation and potentially modifying projects or conservation measures to avoid adverse changes to critical habitat – that, without the identification of critical habitat, are based on management or conservation efforts for the benefit of listed species. would apply.
Therefore, the possibility of reallocating the resources of these private and public entities would be limited to the additional administrative costs of section 7 consultations that would take place without critical habitat for Nassau groupers. Therefore, we do not expect that the identification of critical habitat for Nassau Grouper will affect the ability of private and public institutions to conserve Nassau Grouper. Large fish are more likely to return to aggregation sites and spawn in consecutive months than small fish (Semmens et al. 2007). Nassau groupers have been shown to have high fidelity to an aggregation site, with 80% of tagged Nassau groupers returning to the same aggregation site, Bajo de Sico, each year during the 2014-2016 follow-up period in Puerto Rico (Tuohy et al., 2016). The area occupied by Nassau groupers during spawning is smaller at Bajo de Sico than at Grammanik Bank off St. Thomas. Acoustic detections of Nassau tagged groupers showed southwest movement from the Puerto Rican plateau to Bajo de Sico in a narrow corridor (Tuohy et al., 2017). In summary, there is considerable basic protection in the proposed areas for critical habitat for Nassau groupers.
The incremental impact on the proposed designation should reflect the additional administrative burden required for section 7 consultations to address the impact on critical habitat. Given several assumptions and uncertainties, the total cost projected over the next decade is approximately $380,000 (annualized $54,000), with a discount rate of 7%. Despite the uncertainty underlying the projection of incremental costs, the results provide an indication of potential activities that could be affected and a reasonable forecast of future costs. The best-known habitats of the Nassau grouper are where adult males and females congregate at predictable times during the winter full moon for exclusive breeding purposes. These spawning grounds are occupied by Nassau groupers during winter periods of full moon from about November to May (NICU) (Nemeth et al. 2006). Aggregations consist of hundreds, thousands, or historically tens of thousands of individuals. Some groupings have been systematically formed at the same sites for 90 years or more (see references in Hill and Sadovy of Mitcheson, 2013). All known breeding activities of Nassau groupers occur in aggregations; Spawning of pairs was not observed.
Approximately 50 spawning groups have been recorded, mainly in the island areas of the Bahamas, Belize, Bermuda, the British Virgin Islands, the Cayman Islands, Cuba, Honduras, Jamaica, Mexico, Puerto Rico, the Turks and Caicos Islands and the USVI; however, many may no longer form (Figure 10 in Hill and Sadovy of Mitcheson 2013). Although the size and number of spawning accumulations have decreased, spawning still occurs in some locations (NMFS 2013). Nassau groupers are medium-sized fish with large eyes and a robust body. Coloration varies, but adult fish are usually light beige with five dark brown vertical bars, a large black spot at the base of the tail, and a series of black spots under and behind each eye. A dark band forms a tuning fork pattern on the top of the head, which starts at the front of the upper jaw, extends through each eye, and then curves to meet the corresponding band in front of the dorsal fin. Juveniles have a color pattern similar to that of adults. They are distinguished from other groupers by the vertical bars and dark coloration of the saddle along the dorsal part of the area preceding the tail. The color pattern can change in minutes from almost white to two-tone to dark brown evenly, depending on the behavioral state of the fish. A characteristic two-tone pattern appears when two adults or an adult and a large juvenile meet, and is often observed at spawning gatherings.