Age, growth, and mortality of the Atlantic goliath grouper Epinephelus itajara in French Guiana

Abstract

The age and growth of the Critically Endangered Atlantic goliath grouper Epinephelus itajara of equatorial French Guiana was determined by a non-lethal aging method using dorsal fin rays. Goliath grouper deposit 1 complete annulus per year, with the translucent zone of the annulus laid down at the beginning of the dry season (July). Two readers independently applied the method; there was full agreement between the two for 52% of the fish, and agreement of ± 1 yr for 82%. Comparison of ages derived from paired samples of otoliths and fin rays were identical (n = 6). The mean age of goliath grouper was 4.2 yr (range = 1 to 17 yr; n = 229); 82% of the individuals were under the size/age of sexual maturity. Goliath grouper in French Guiana are larger at a given age and reach their asymptotic length (L ∞ = 192.3 cm) faster (k = 0.20 yr −1 ) than goliath grouper from the west coast of Florida, USA (L ∞ = 200.6 cm, k = 0.126). Total mortality, estimated from a catch curve of the age distribution, was about 0.65 both in the Grand Connetable Island marine protected area in French Guiana (where fishing is prohibited) and outside of the reserve, suggesting that the reserve does not protect goliath grouper from illegal fishing. However, the estimates of total mortality in both fished and protected sites likely includes emigration, because goliath grouper may use rocky sites in French Guiana as a nursery habitat and may not remain there once they mature.

Food supplementation protects Magnificent frigatebird chicks against a fatal viral disease

“…A first scenario suggests that during the developmental period local food resources are limited and adult frigatebirds struggle to feed their chicks. In addition to the decline in shrimp fishery activity, illegal fishing is also leading to the decline of large marine predators (Artero et al., ; IUCN, ), to which frigatebirds may rely on for opportunistic feeding. A second scenario points out a potential very variable investment of the male into reproduction (18–161 days; Osorno, ), which would make some females in trouble to provide enough food to their offspring after the male abandons the nest.…”

Diving into archival data: The hidden decline of the giant grouper (Epinephelus lanceolatus) in Queensland, Australia

“…(iii) optimum length fish ranged between 163 and 200 cm TL. This size range was calculated from the following equation: $$$ {L}_{opt=}{10}^{1.0421\kern.5em \ast \kern.5em \log \left({L}_{\infty}\right)-0.27422}\pm 10\% $$$ (Froese & Binohlan, 2000), where $$$ {L}_{\infty }=192 $$$ represents the asymptotic length (cm) in the von Bertalanffy growth function (Artero et al, 2015). This category was defined as the ideal length at which the stock can be fished without compromising the productivity and reproductive capacity of the population (Froese, 2004).…”

“…L opt¼ 10 1:0421 Ã log L∞ ð ÞÀ0:27422 AE 10% (Froese & Binohlan, 2000), where L ∞ ¼ 192 represents the asymptotic length (cm) in the von Bertalanffy growth function (Artero et al, 2015). This category was defined as the ideal length at which the stock can be fished without compromising the productivity and reproductive capacity of the population (Froese, 2004).…”

Dorsal Fin Spines and Rays for Nonlethal Ageing of Goliath Grouper Epinephelus itajara

“…Ray ageing has been well documented in cold-temperate species, where the annual banding patterns are relatively wide and distinct [18][19][20]. More recently, ray and spine ageing has been applied successfully to tropical and warm-temperate species [21][22][23][24]. External structures are increasingly being used because the sampling is nonlethal, which is especially important for sportfish species with catch-and-release fisheries [16,25,26] and threatened or endangered species [27,28].…”

“…Alternative ageing structures for Goliath Grouper have shown promise but previous studies have been limited either in the range of ages available or in sample size [17,21,29]. For example, Brusher and Schull [29] compared scales, otoliths, and dorsal fin rays and spines from Goliath Grouper and determined that spines were the preferred external ageing structure (with otoliths as the reference).…”