First record of a spawning aggregation for the tropical eastern Pacific endemic grouper Mycteroperca olfax in the Galapagos Marine Reserve

This study provides direct and indirect evidence of temporally and spatially consistent spawning aggregations for the grouper Mycteroperca olfax. Recently reported declines in population numbers, probably related to the direct targeting of aggregations by artisanal fishermen, highlight the urgent need for species‐specific management actions in the Galapagos Marine Reserve, such as minimum and maximum landing sizes, and the importance of protecting key aggregation sites with the declaration of no‐take areas and the establishment of total fishing bans during the reproductive season.     

Life‐history strategies of the rock hind grouper Epinephelus adscensionis at Ascension Island

Epinephelus adscensionis sampled from Ascension Island, South Atlantic Ocean, exhibits distinct life‐history traits, including larger maximum size and size at sexual maturity than previous studies have demonstrated for this species in other locations. Otolith analysis yielded a maximum estimated age of 25 years, with calculated von Bertalanffy growth parameters of: L_∞ = 55·14, K = 0·19, t₀ = ?0·88. Monthly gonad staging and analysis of gonad‐somatic index (I_G) provide evidence for spawning from July to November with an I_G peak in August (austral winter), during which time somatic growth is also suppressed. Observed patterns of sexual development were supportive of protogyny, although further work is needed to confirm this. Mean size at sexual maturity for females was 28·9 cm total length (L_T; 95% C.I. 27·1–30·7 cm) and no females were found >12 years and 48·0 cm L_T, whereas all confirmed males sampled were mature, >35·1 cm L_T with an age range from 3 to 18 years. The modelled size at which 50% of individuals were male was 41·8 cm (95% C.I. 40·4–43·2 cm). As far as is known, this study represents the first comprehensive investigation into the growth and reproduction of E. adscensionis at its type locality of Ascension Island and suggests that the population may be affected less by fisheries than elsewhere in its range. Nevertheless, improved regulation of the recreational fishery and sustained monitoring of abundance, length frequencies and life‐history parameters are needed to inform long‐term management measures, which could include the creation of marine reserves, size or temporal catch limits and stricter export controls.     

Reproductive biology of squaretail coralgrouper Plectropomus areolatus using age‐based techniques

The squaretail coralgrouper Plectropomus areolatus was identified as a fast‐growing, early maturing and relatively short‐lived aggregation‐spawning epinephelid. Examinations of sectioned otoliths found females and males first maturing at 2 and 3 years, respectively, suggesting protogynous hermaphroditism; however, no transitionals were observed in samples. Age distribution for the two sexes was similar and both were represented in the oldest age class; however, significant sex‐specific differences in size‐at‐age were identified. Both sexes fully recruit into the fishery at age 4 years and reach 90% of asymptotic length by age 3 years. Underwater visual assessments, combined with the gonado‐somatic indices, revealed a 5 month reproductive season, with interannual variability observed in the month of highest density within the spawning aggregation. Catch restrictions on adults during spawning times and at reproductive sites, combined with gear‐based management and enhanced enforcement, are recommended to maintain spawning stocks. Based on the available evidence, the sexual pattern for this species is unresolved.     

Distribution,relative abundance and size composition of the threatened serranid Epinephelus daemelii in New South Wales,Australia

The aim of this study was to undertake baseline surveys on the distribution, relative abundance and total lengths (L_T) of a threatened epinephelid species, black cod Epinephelus daemelii, in New South Wales (NSW), Australia, their westernmost distribution. Diving surveys at 83 sites where E. daemelii were expected to occur were undertaken from 2009 to 2011 using 45 min roving diver counts. Sites were spread through northern NSW, including Lord Howe Island (LHI). Individual fish were measured using stereo‐video, enabling accurate length measurement. Surveys were repeated at a sub‐set of sites to assess temporal variation across days, seasons and years. A total of 117 E. daemelii were recorded during baseline surveys, occurring at 42% of the surveyed sites. Across all surveys, the highest numbers recorded (14–18 individuals at a site) were at the outer Solitary Islands and Fish Rock (Smoky Cape). Fewer E. daemelii were found southwards, but two sites in the Port Stephens–Great Lakes Marine Park had consistent numbers (three to six) over four annual surveys. Only 12 E. daemelii were recorded from eight of the 18 sites at LHI. The numbers observed at re‐surveyed sites were generally stable over years. There were latitudinal and cross‐shelf differences in L_T. Individuals in the north were found to be significantly larger than those further south, and fish offshore were significantly larger than those inshore. The largest measured fish was 135 cm, smaller than the maximum L_T(c. 170 cm) recorded for this species. The smallest fish was 26 cm. Overall, it is considered that the abundance of E. daemelii is low compared to anecdotal data even though they have been protected for c. 30 years in NSW. These findings provide an essential benchmark to assess ongoing status and response to protective management.     

Spawning aggregations of three protogynous groupers in the southern Gulf of Mexico

Spawning aggregations of red hind Epinephelus guttatus, tiger grouper Mycteroperca tigris and yellowfin grouper Mycteroperca venenosa were identified at two coral‐reef systems: Arrecife Alacranes (emergent bank reef) and Bajos del Norte (submerged bank reef) on the continental shelf of the Yucatan Peninsula (Campeche Bank), Mexico. At both reefs, E. guttatus forms large spawning aggregations between February and March. At Bajos del Norte, M. tigris reproduces in a small, low‐density aggregation in May, while M. venenosa aggregates at high densities for spawning between March and May. Multi‐species use of an aggregation site by E. guttatus and M. venenosa was observed at Bajos del Norte. The identified spawning aggregations are apparently stable in location over time, and all three species were commonly observed to spawn within 1 week following the full moon. Development and survival of the larvae spawned in these aggregations are probably aided by a seasonal (spring–summer) upwelling in the north‐east Campeche Bank. A permanent area closure at Bajos del Norte, currently outside any specific fisheries management area or regulations, would provide protection needed for the spawning aggregations of these three species.     

Primary male development of two sequentially hermaphroditic groupers,Epinephelus akaara and Epinephelus awoara (Perciformes: Epinephelidae)

Gonad ontogeny of the Hong Kong grouper Epinephelus akaara (a bi‐directional sex changer) and the yellow grouper Epinephelus awoara (a protogynous hermaphrodite) was examined for the first time from post‐larval phase until first sexual maturation, by histology. Approximately 20 specimens of each species were collected randomly every 2–7 weeks from rearing tanks with natural sea water and temperature between June 2013 and June 2014. The paired gonadal primordia (GP) were observed at 6 weeks after hatching (wah) for both species; however, gonia were first observed in GP at 16 wah for E. akaara and at 8 wah for E. awoara. The timings for the appearance of primary‐growth stage oocytes (O1) and the completion of ovarian lumen (OL) varied; both at 27 wah for E. akaara, and at 18 and 23 wah for E. awoara respectively. A bisexual‐phase gonad with an OL, O1 and scattered spermatogenic cysts (SC) was observed at 27–29 wah for both E. akaara and E. awoara. Sexual differentiation was subsequently observed from the bisexual‐phase gonad at 34 wah for E. akaara, and 41 wah for E. awoara, with the appearance of cortical‐alveolus stage oocytes (O2) for developing female and the proliferation of SC for developing primary male (i.e. from juvenile directly). Ovaries of mature females contained the vitellogenic stage oocytes (O3) and scattered SC; testes of mature primary males had sperm in sperm sinuses within the gonadal wall and remained O1. Minimum age of first sexual maturation for both female and primary male of E. akaara was at 41 wah; minimum total length (L_T) of female (143 mm) was larger than that of primary male (137 mm L_T). Minimum age and size of first sexual maturation for female of E. awoara (47 wah and 149 mm L_T, respectively) were larger than those of E. akaara. Developing primary males of E. awoara were found at 41–58 wah, however, mature males were not observed, indicating inconsistency in first sexual maturation for E. awoara. This study provided strong evidences of primary male pathway in E. akaara and E. awoara; the latter is confirmed to be diandric.     

Similar cryptic behaviour during the early juvenile phase of two unrelated reef fishes: Epinephelides armatus and Bodianus frenchii

The juveniles of many reef fishes behave cryptically during critical juvenile stages in their life history and thus the microhabitats they often occupy are not well known. Comprehensive surveys of reef fishes on the temperate mid-west coast of Australia identified that juveniles of the unrelated Epinephelides armatus (Epinephelidae) and Bodianus frenchii (Labridae) < 100 mm total length both exhibit cryptic behaviour by exclusively swimming upside down under cave roofs and ledges. These individuals swam among the sponges and small algae in this microhabitat which would provide refuge from predation and also supply the dietary requirements of these two carnivores. Occupying this microhabitat would also reduce intra-specific competition, as individuals > 150 mm were only observed swimming ventrally oriented to the substrate in caves, under ledges or on open reef. Identifying the nursery habitats of fishery species, such as E. armatus and B. frenchii, is critical for understanding their life histories, but would also inform survey designs aimed at determining recruitment strength or variation.     

Age,growth and reproductive life-history characteristics infer a high population productivity for the sustainably fished protogynous hermaphroditic yellowspotted rockcod (Epinephelus areolatus) in north-western Australia

The yellowspotted rockcod, Epinephelus areolatus, is a small-sized grouper that is widely distributed throughout the Indo-Pacific, where it forms a valuable component of the harvest derived from multispecies fisheries along continental and insular shelves. Samples of E. areolatus were collected from 2012 to 2018 from commercial catches and research surveys in the Kimberley, Pilbara and Gascoyne regions of north-western Australia to improve the understanding of the life history, inherent vulnerability and stock status of this species. Histological analysis of gonads (n = 1889) determined that E. areolatus was a monandric protogynous hermaphrodite. Non-functional spermatogenic crypts were dispersed within the ovaries of 23% of mature functioning females; nonetheless, these crypts were not observed during the immature female phase. The length and age at which 50% of females matured were 266 mm total length (L_T) and 2.7 years, respectively. The spawning period was protracted over 10–12 months of the year with biannual peaks at the start of spring and autumn (i.e., September and March) when the photoperiod was at its mid-range (i.e., 12.1 h). Estimates of the lengths and ages at which 50% of E. areolatus change sex from female to male were very similar (i.e., <5% difference) between the Kimberley and Pilbara regions, i.e., of 364 and 349 mm L_T and of 7.9 and 7.3 years, respectively. A maximum age of 19 years was observed in all three regions, but there was significant regional variation in growth. These variations in growth were not correlated with latitude; instead a parabolic relationship was evident, where the smallest mean length-at-age and fastest growth rates (k) occurred in the mid-latitudes of the Pilbara region. In the Kimberley and Pilbara regions, individuals were not fully selected by commercial fish traps until 5–6 years of age, hence, several years after reaching maturity. These life-history characteristics infer a high population productivity, which underpins the sustainable harvest of this species, despite comprising the largest catches of all epinephelids in the multispecies tropical fisheries across north-western Australia.