Life‐history characteristics of an exploited bonefishAlbula glossodontapopulation in a remote South Pacific atoll

Abstract

Bonefishes Albula spp. are important components of subsistence fisheries and lucrative sport fishing industries throughout their circumtropical distribution. In Oceania, however, Albula spp. have historically been overexploited and there is a growing need to balance the demands of competing fishing sectors, making the description of their life history a regional priority. To this aim, we collected biological samples from Albula spp. of Anaa atoll, French Polynesia, to identify the species that compose the stock and estimate their life‐history parameters including age, growth, reproduction and natural mortality. Our results indicate that Albula glossodonta is the species of bonefish present, with a maximum age that is below the, 20 year longevity of the genus (8 years in males and 10 years in females). Differential growth patterns existed between the two sexes (L∞ = 58, 78 cm fork length (LF) and K = 0.38, 0.21 for males and females, respectively). Males attained sexual maturity at 43 cm LF (c. 3 years) whereas females matured at 48 cm LF (c. 4 years) and oocyte production was significantly related to body mass, with a maximum batch fecundity of 1,133,767 oocytes in a 4406 g (70 cm LF) female. The gonado‐somatic index of harvested fishes indicated that the spawning season extends from March through September. Based on the observation of a, 20 year bonefish at the proximate Tetiaroa Atoll and several empirical models, estimates of natural mortality ranged from 0.21 to 0.68; however, an estimate of 0.21 was deemed most appropriate. This information facilitated the resurgence of a Rahui (temporary fishing closure) and community‐based management to protect A. glossodonta during a critical portion of their spawning season and in this context our results provide an important demographic baseline in evaluating the recovery of this fishery.

Population dynamics of roundjaw bonefish Albula glossodonta at a remote coralline Atoll inform community‐based management in an artisanal fishery

“…Tag recoveries from the traps located in these migratory corridors indicate that bonefish travel long distances from their foraging habitats in all corners of the atoll to access these northern passes during their migrations to the outer reef, which is spatially consistent with long‐distance movements observed in pre‐spawning aggregations in the Atlantic (Boucek et al, ; Perez et al, ). Temporally, the peaks in the number of bonefish tagged and recaptured in the trap fishery coincide with the waning moon and indicate that the timing of movement towards offshore spawning locations overlaps with the gonad development observed in female bonefish across the lunar cycle (Filous, Lennox, Coleman, et al, ). Indeed, the GSI of bonefish recaptured in the trap complex was significantly higher than those subsampled during tagging events in the lagoon, which demonstrates that these movements are spawning‐related.…”

“…Furthermore, the predicted low level of natural mortality for age 7 fish is reasonable because bonefishes of the Genus Albula are long‐lived and specimens of >20 years have been found in unfished populations (Ault, Humston, et al, ; Ault, Moret, et al, 2007; Filous, Lennox, Coleman, et al, ), suggesting that natural mortality is less intense as the species reaches its growth asymptote and presumably becomes less vulnerable to predation (Sogard, ). On the other hand, the estimates of fishing mortality suggest that fishing mortality is negligible in age‐3 fish or less, and although some juvenile bonefish are captured in the artisanal trap fishery during high wind events, male and female bonefish are not fully recruited to the trap fishery until the age of 95% sexual maturity (A 95 ), 4 and 5 years, respectively (Filous, Lennox, Coleman, et al, ). The rapid and consistent increase in fishing mortality in age‐4 + bonefish predicted by the integrated Brownie–Petersen model is consistent with this aspect of the species life history and its interaction with the artisanal trap fishery.…”

“…Local fishermen were accompanied during monthly harvest events that coincided with bonefish spawning activity during the waning moon to record the number of bonefish captured and measure their FLs. After obtaining these FL frequency distributions, the age of fish harvested and tagged was determined by converting their FLs to age with the non‐sex‐specific von Bertalanffy growth parameters ( L ∞ = 76, K = 0.20, t 0 = −0.75) estimated from annual growth rings in otoliths (Filous, Lennox, Coleman, et al, ). The natal year for each fish was then back calculated and each fish was placed into age cohorts.…”

Length‐Based Assessment of an Artisanal Albulid Fishery in the South Pacific: a Data‐Limited Approach for Management and Conservation

“…Finally, generation time ( GT ) was estimated with the following equation: where AM is the age at first maturity (4 years) in females and T max (20 years) is the maximum recorded age (Depczynski and Bellwood ; Filous et al. 2019a).…”

“…Until recently, there was insufficient biological data to evaluate the impact of fishing on the stock; however, research into the life history of the species has filled these knowledge gaps and paved the way for its assessment with the data‐limited methods (Filous et al. 2019a).…”