The implementation of consistent and continuous biodiversity survey efforts over a long period of time is imperative to the examination of temporal diversity patterns and the evaluation of existing conservation measures' effectiveness. In Hong Kong, a marine biodiversity hotspot in the South China Sea, reef fish diversity has been poorly documented due to inconsistent and sparse biodiversity surveys, posing considerable challenges to long-term monitoring of biodiversity dynamics. To fill in the data gap, regular scuba underwater visual surveys were conducted across 55 dive sites in Hong Kong during the wet seasons from 2018–2021. After ~3171 hours of underwater survey, 31 reef fish species from 14 families that are new to Hong Kong have been recorded, including species from Acanthuridae, Chaetodontidae, Diodontidae, Gobiidae, Labridae, Mullidae, Nemipteridae, Pinguipedidae, Pomacanthidae, Pomacentridae, Ptereleotridae, Solenostomidae, Tetraodontidae and Tetrarogidae. As Hong Kong sits within the natural distribution range of the newly recorded species, the possibility of artificial release was eliminated after careful consideration. These species were all found outside the currently established Marine Protected Areas (MPAs) in Hong Kong, indicating the need for comprehensive research to identify potential marine reef fish hotspots in areas that are unprotected thus far. Our findings demonstrate the need to establish a long-term monitoring programme that can fill in data gaps of local marine biodiversity to enable the establishment of effective MPAs, and to lay down a baseline for future research and monitoring, so as to safeguard Hong Kong's marine biodiversity in the long term.

Resource partitioning is considered one of the main processes driving diversification in ecological communities because it allows coexistence among closely related and ecologically equivalent species. We combined three complementary approaches, i.e. the evaluation of foraging behaviour, diet composition and nutritional condition (RNA:DNA ratio), to assess feeding by two closely related (sister) butterflyfishes that are syntopic in Puerto Rico. Chaetodon capistratus had a higher abundance and higher bite rate and selected octocorals and hard corals for feeding, whereas Chaetodon striatus fed preferentially on sandy substrates. Cnidarians and polychaetes were the most representative diet items for both species, but C. capistratus preferred the former (Feeding Index of 74.3%) and C. striatus the latter (Feeding Index of 60.4%). Similar RNA:DNA ratios for both species suggest that, although they differ in feeding rates and diet, C. capistratus and C. striatus have similar nutritional fitness. Therefore, these species are both zoobenthivores but show clear differences in their substrate selection. The differences in the use of foraging substrate by C. capistratus and C. striatus, despite their close phylogenetic relationship and similar diets, suggest that these species coexist by resource partitioning.

Age and growth of Agassiz's parrotfish Sparisoma frondosum captured off Brazil (Pernambuco) were estimated using sagittal otoliths from 251 specimens. Sex of each specimen was determined and showed that 130 specimens were females (13.1 to 36.8 cm TL) and 121 were males (17.5 to 36.6 cm TL). The otolith marginal increment analysis indicated a single translucent ring formed every year. Parameters of growth curves were derived for the von Bertalanffy (VBGF) and Gompertz models. Based on the Akaike information criterion (AIC), both models were suitable for describing the growth of this species. VBGF parameters were estimated for males L ∞ = 39.74 cm TL, K = 0.22, t 0 = −1.63 years, females L ∞ = 32.38 cm TL, K = 0.44; t 0 = −0.23 years; and for the sexes combined L ∞ = 33.66 cm TL, K = 0.41, t 0 = −0.27 years. The study showed that 55% of individuals were 3 and 4 years of age, with maximal age of 9 years. Mature females (>17.6 cm TL) accounted for 45% of the sample. The age at first maturity for females was 1.6 years. For males the size at first maturity was not determined as immature individuals were not present in the overall sample. Also, primary males (PM) and specimens with gonads undergoing sexual transition were not found. The age structure and growth parameters for S. frondosum are an important contribution to the assessment of the state of exploitation of this species.

Here we report two types of skeletal deformities, ‘pughead’ and ‘short-tail’, observed for the first time in the adult Atlantic goliath grouper (Epinephelus itajara). Photographic documentation of these deformities was made for only three individuals during our studies of their spawning aggregations. ‘Pugheadedness’ was documented in Brazil and Florida, and the ‘short-tail’ deformity was documented only in Brazil. Skeletal deformities are rare, have very low frequencies in wild populations and appear to be initiated during early development. There was no apparent effect of the condition on the adult goliath grouper, as they appeared robust and healthy.

We report here, for the first time, the predation activity of the French angelfish Pomacanthus paru on the jellyfish Chrysaora lactea on Brazilian rocky reefs. The activity involved a group of 14 P. paru and was documented by pictures. We believe that temporarily available food resources benefit species with a more generalist diet.

We report here, for the first time, the existence of a white colour morph Elacatinus figaro, an endemic threatened cleaner goby from the Brazilian Coast. The specimen from this study lived in a cleaning station along with other E. figaro. Records were made based on pictures and the specimen was collected and preserved for genetic studies. Although the strong bright yellow colour is of vital importance for attracting other fish to the cleaning station, we speculate that living alongside regular-coloured individuals can diminish the disadvantage of not having the flashy stripe.

Herein, we describe the use of scars to photo-identify the goliath grouper, Epinephelus itajara. Three individuals were photo-identified and re-sighted several times at the same site along the Brazilian coast, including the longest report for site fidelity, with more than four years.

We present a species checklist, characterizing the ichthyofaunal composition of four coastal archipelagos in waters off the metropolitan area of Rio de Janeiro, Brazil. Data were obtained from ~120 h of underwater observations, published and unpublished information, including new species records. A total of 197 fish species (78 new records), belonging to 130 genera and 61 families, were observed. The family Carangidae (17) dominated in number of species, followed by Labridae and Serranidae (10 each), Epinephelidae and Scaridae (9 each). Most species are distributed along the tropical western Atlantic (51.8%) or on both sides of the Atlantic Ocean (20.5%). A minor part is endemic to Brazil (9.7%) or range to temperate rocky reefs of Patagonia (6.7%). Fourteen species are threatened, according to the IUCN, and listed under the Brazilian Ministry of the Environment red list (6.6%). Despite an increment of fish species listed herein, and the recent establishment/creation of a Marine Protected Area (Monumento Natural das Ilhas Cagarras—MoNa Cagarras), research efforts are clearly needed along these archipelagos, as nearshore environmental threats increase due to lack of regulatory practices.

Reef fish usually display a remarkable variety of colours and coloration patterns. The colour patterns are largely used for species identification, and some morphologically conservative genera are highly dependent on coloration for this purpose. In this context, this paper aims to briefly describe unusual colour patterns recorded for territorial damselfish of the genus Stegastes in the south-western Atlantic Ocean. Four unreported coloration pattern types were observed in three species (S. fuscus, S. rocasensis and S. pictus). The pale morph which is characterized by individuals presenting whitish marks over the regular coloration pattern was recorded in S. fuscus in north-eastern reefs and S. rocasensis in Fernando de Noronha archipelago. On the other hand, S. fuscus and S. pictus presented other types of unusual coloration patterns, which are characterized by an irregular cover (blue or dusky) over the regular colour pattern. Another type of unusual coloration pattern was recorded for S. fuscus, which presented a yellowish/reddish dorso-anterior band. Additionally, two distinct colour patterns of adult S. variabilis, from the south-eastern and north-eastern Brazilian reefs are reported.

A biogenic structure ecosystem of extensive worm tubes of Chaetopterus sp. harbouring different fish species was investigated at Anacapa Island, southern California to determine the numerical abundance, species composition, body size, and seasonality of the ichthyofauna associated, and their relation with the worm patch size. Bimonthly, a 30-m swimming transect and a quadrat-based survey estimated the length of each fish, the type of habitat it occupied, and the worm tube patch size-class. Larger worm mats harboured higher densities of fish, mainly the dominants Rhinogobiops nicholsii and Chaenopsis alepidota, which live inside the worm tube patches. Fish population density varied between the ‘inside’ and ‘edge’ of Chaetopterus beds as smaller and younger individuals were hindered from reaching the middle of the patch by larger, older and territorial individuals. The prevalence of positive and significant correlations between the abundance of smaller individuals of R. nicholsii and specific habitat features (e.g. edge) suggests that the abundance and distribution of juveniles might be habitat-dependent besides intraspecific competition between older and younger individuals. There was a decreasing density of R. nicholsii at greater than 20 cm away from worm tubes and there were no individuals beyond 6 m away from structure. Chaenopsis alepidota was not recorded when the patch size was less than 50% tube coverage. Our results revealed that complex habitat structure had a positive influence on the abundance of juvenile and adult of C. alepidota and R. nicholsii, and suggest that these structured areas are preferentially utilized, which contributes to its patchy distribution pattern. The presence of biological structures in low-relief sedimentary habitats can have critical functional significance even for reef fish. These important habitat features may need to be identified and protected.

Here we studied the activity budgets of nine common reef fish in the oceanic archipelago of Fernando de Noronha, off north-east Brazil. Species were variable in their behaviour between different sites and similarities in their activity budgets were not necessarily associated with their trophic group. For four species we investigated the relationship of their activity budgets to wave exposure and substratum composition. Staying close to the substratum was positively correlated to wave exposure for most species and foraging was negatively correlated to exposure for two species. By behaving this way, these fish may save energy by avoiding swimming in higher water flux. In contrast to relationships with wave exposure, the responses to substratum composition were species specific. Our results highlight that the activity budgets of fish living in oceanic rocky reefs can be variable and influenced by the local and temporal variation in environmental variables.

The barber goby Elacatinus figaro, native to the Brazilian Atlantic coast, is endangered due to over-exploitation by the ornamental industry. It is expected that once the technology for juvenile production is mastered, one could reduce fishing pressure by commercializing fish raised in captivity and stocking enhancement programmes can be established. This work was carried out in order to describe natural breeding, embryonic development and larviculture of barber goby in the laboratory. The first spawning was observed 24 days after the pairs were formed, thereafter barber goby spawned every 8 to 10 days at 26°C. Fecundity ranged from 430 to 1020 eggs per clutch with average hatching rate of 69 ± 16%. Fertilized eggs are elliptical in shape and present adhesive filaments at the proximal end and five protuberances at the distal end. Egg length averaged 1.81 ± 0.1 mm and mean width was 0.61 ± 0.03 mm. The embryonic developmental period lasted 7 days and newly hatched larvae measured 3.15 ± 0.07 mm, showing positive phototaxis. Larvae were fed with rotifers Brachionus plicatilis in green water culture along with the microalgae Nannochloropsis oculata from 1 to 20 days after hatching (DAH). Artemia nauplii were added to the diet 15 DAH, and 5 days later rotifers were no longer offered. The results of the present study demonstrate the viability to produce naturally spawned eggs of the barber goby E. figaro in captivity. Larvae settle to the bottom 28 to 35 DAH, when total length was equal to 8.5 mm in average.

We present a list with 10 new records of reef fish on the coast of Santa Catarina State, the southernmost site of tropical reef fish occurrence on the Brazilian coast. We also comment on the distribution-range of the recently described Halichoeres sazimai (Labridae).

I observed shark mackerel demonstrating multiple search and attack strategies. Strategies were categorized as three distinct types: (1) a linear search by single or groups of fish along reef features; (2) ambush from a stationary position on the seafloor; and (3) ambush from resting schools of co-occurring predators. Together these strategies were consistent with both information-sharing and producer–scrounger models of group foraging and indicate significant flexibility in individual fish foraging behaviour based on proximate conditions.

The cleaning behaviour of juveniles of the Brazilian wrasse Halichoeres penrosei (Labridae) is described for the first time in the present paper. Diurnal free dive observations and photographs were taken in the shallow reefs of Porto da Barra. The cleaners' sizes varied from 3 to 7 cm, and clients' fish size varied from 8 to 20 cm. The wrasses cleaned for 2 to 30 seconds, the flanks were the most explored area of the clients' bodies. The cleaning activity we described was rare and opportunistic. Therefore, it is unlikely that H. penrosei is a specialized cleaner.

Associations of the hairy blenny Labrisomus nuchipinnis (Labrisomidae) are described for the first time from different observations made on the coast of Brazil, South Atlantic. The first involved a majid crab cleaning the fish and the second, another fish following closely a foraging hermit crab of the genus Paguristes (Diogenidae).

The known geographic distribution of two reef fish species of Indo-Pacific affinity is increased: Acanthurus nigricans and Cantherhines dumerilii. These species are reported for the first time from the Acapulco coast, México. Collection data, and morphometric and meristic characteristics of the studied specimens are presented.

Lagoon fish in New Caledonia are mainly caught by artisanal fisheries and subsistence fishing. Reef fish are the major component of this catch. The present study aimed at estimating these reef fish standing stocks and at finding the main factors influencing the distribution of these fish. Sampling of 904 stations was stratified according to three zones (north, east and west) and three reef types (barrier, intermediate and fringing). Fish communities exhibited bold heterogeneity in their distribution, showing higher biomass (maximum of 447 g·m–2) and total standing stock (43000 tonnes) in the north zone than in the east and west zones. Similarly, observed patterns were dependent on reef types: higher biomass and total standing stock being observed on barrier reefs than on intermediate or fringing reefs. The total standing stocks, which were about 65000 t, were mainly composed of herbivorous fish families such as the Acanthuridae and Scaridae. The differences in the patterns of distribution of species, individuals and standing stocks between reef types may be explained by variations in terrestrial influences and reef morphology, whereas differences among zones were most likely due to accessibility of fishing areas and fishing pressure. The latter is almost non-existent in the north zone, which can thus be considered to be almost unexploited commercially. This most likely explains the high proportion, 77 %, of long-lived species in the biomass of this zone. The results might have implications in management of reefs elsewhere in the South Pacific, for which similar data are only scarcely available.

Despite its wide use in terrestrial ecology, distance sampling is as yet rarely used in underwater visual censuses. The present study attempts to compare density estimators based on distance sampling and on strip transects. Three stations with increasing densities of Chaetodontidae and Pomacanthidae were sampled twice by two divers of unequal experience, using two different transect types. A total of 96 transects and 2970 records of Chaetodontidae and Pomacanthidae were analysed. Nine estimators based on distance sampling were calculated and only the best fit (DT estimator) was kept for comparison with other estimators. These were either based on the average distance of the fish to the transect (AD estimator), or a 3-m- or 5-m-wide strip transect estimator (FW3 and FW5, respectively). There were no significant differences between the means found by DT, AD and FW3. Lower density estimates were given by FW5 in all cases. FW3 and FW5 did not detect several significant differences between stations which were otherwise detected by DT or AD. The number of transects needed to detect a significant difference between stations was four to ten times higher with FW3 or FW5 than with DT or AD. Diver experience was found to be a significant factor in density estimates. However, this factor was less important than the choice of the density estimator. Transect type or the day of sampling had no consequence for the estimates. The distance distributions of fish were divided into three different patterns which may be explained by a combination of detectability function and a behavioural component.