Both active and passive human interactions with reef fish communities are increasingly recognized to cause fish behavioural changes. However, few studies have considered how these behavioural adaptations impact standard reef survey techniques, particularly across natural gradients of interest to ecologists and reef managers. Here we measure fish abundance, biomass and minimum approach distance using stereo-video surveys to compare the effects of bubble-producing open-circuit scuba vs near-silent closed-circuit rebreathers. Surveys extended across a shallow to upper-mesophotic gradient on the fringing reefs of Utila, Honduras, to explore how the effects of diver gear choice vary with depth. For most fish families we recorded similar abundances and biomass with the two diving techniques, suggesting that open-circuit transects are generally appropriate for surveying western Atlantic reefs similar to Utila with regular tourist diving but no spearfishing. Despite no overall significant difference in fish abundance or biomass, we identified several fish families (Labridae, Pomacentridae, Scaridae) that allowed closed-circuit rebreather divers to approach more closely than open-circuit divers. In addition, smaller fish generally allowed divers to approach more closely than larger fish, and in most cases divers could approach fish more closely on mesophotic than shallow reefs. Despite these significant differences in approach distances, their magnitude suggest they are unlikely to affect reef fish detectability during normal fish surveys for most families. Our findings highlight the importance of considering variation in fish behavioural adaptations along natural gradients such as depth, which otherwise has the potential to cause biases when surveying by traditional monitoring programmes.

Temporal variations over short and medium time scales play an important role in fish assemblage dynamics, but have been poorly investigated in tropical estuaries. This study evaluates the hypothesis that fishes co-occurring on a tidal mudflat have different patterns of temporal segregation at short- and medium-term scales that optimize resource use and habitat partitioning. A total of 6222 individuals and 66 fish species were caught during different hours covering the entire 24 h cycle, tidal regimes and the wet and dry seasons. Biomass and species richness, and to a lesser extent CPUE and evenness, showed statistically significant interactions across short- and medium-term scales. Biomass was higher during the dry season and its oscillation along tidal cycles revealed distinct patterns over the photoperiod in each season. A similar complex pattern was also observed for species richness, which showed distinct temporal patterns between high and low tides over the photoperiod in each season. Overall, shorter-term variations on fish assemblage attributes were correlated mainly with photoperiod and, to a lesser extent, tidal regime. Medium-term variations in fish abundance and species richness, in contrast, could result from seasonality in recruitment patterns and higher availability of allochthonous food resources during the wet period.

The diet and feeding behaviour of the forkbeard Phycis phycis was studied based on 246 stomachs collected between May 2011 and April 2012 from a commercial fleet operating off the central west coast of Portugal. A total of 44 prey items were identified in the stomachs which were merged into major groups to avoid problems with low expected frequencies. The following taxonomic categories were considered: non-decapod Crustacea, Caridea, Anomura, Munida spp., Processa spp., Brachyura, Pisces, Trisopterus luscus. In order to investigate possible diet differences between fish size classes, a cluster analysis was performed using the mean abundance of each prey group by forkbeard 5 cm length class, and three length groups (LG) were obtained: <22.5, 27.5–37.5 and >42.5 cm. Seasonally, Caridea was the main prey group during winter and autumn while Pisces was predominant during the rest of the year. Caridea was the most important prey group for LG1 and LG2 while in LG3 Pisces was the principal one. The forkbeard feeding behaviour may be characterized as presenting a shift pattern from a more generalist diet (small Crustacea, mainly Caridea) in the young adults to a more specialist strategy (teleosts) in the adults.

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.

Studies of species assemblages and community structure are of vital importance in the deep-sea realm. Data for the present study were collected during the research expedition of FORV ‘Sagar Sampada’ in the latitude 8.02°N and 11.58°N, longitude 74.16°E and 78.35°E. High Speed Demersal Trawl – Crustacean Version (HSDT-CV) was used for the operations at a depth of 200 and 1000 m. The total catch came to 2148.35 kg from 10 stations. An analysis of the catch composition was made. Total catch was dominated by Priacanthus hamrur (27.66%) followed by Neoepinnula orientalis (15.57%), Psenopsis cyanea (10.05%), Glyptophidium oceanium (3.55%), Lamprogrammus niger (3.17%), Narcine timlei (3.08%), Lamprogrammus sp. (2.6%), Pterigotrygla hemisticta (2.17%). About 76 species recorded from 22 orders were identified. The diversity indices, Cluster analysis, k-dominance plot were analysed using PRIMER v6 software. The diversity indices including Margalef richness index (d), Shanon index (log e2), Pielou's evenness index (J′) and Simpson diversity index (1 − λ) were calculated. Diversity indices were compared with the previous studies in the same area, and this can be a reference point for future studies.

The shovelnose guitarfish (Pseudobatos productus) is the most abundant and economically important batoid in Gulf of California fisheries. Despite the importance of the guitarfish in the demersal ecosystem, its trophic relationships are poorly understood. Results from stomach content and stable isotope analysis indicate P. productus is a specialist predator that feeds on coastal benthic organisms, mainly crustaceans, followed by fishes and cephalopods in the Upper Gulf of California. Males and females did not differ in dietary composition and isotopic values. Pseudobatos productus displayed ontogenetic changes in the diet, with smaller, immature individuals having a more specialized diet and mature individuals becoming generalist predators. Size classes I (<570 mm) and II (>570 mm) fed almost exclusively on crustaceans (99.78% and 82.37 %IRI, respectively). Size class III (>832 mm) increased consumption of fishes (22.11 %IRI) and squid (6.54 %IRI). Ontogenetic diet shifts were strongly supported by the SIAR mixing model. Stomach content and stable isotope analyses classify P. productus as a second-order predator.

This study described the myliobatids caught in artisanal beach seine fisheries in southern Brazil. Fieldwork was carried out from spring 2012 to winter 2014 in Cassino Beach (Rio Grande, Brazil). Both retained and discarded specimens were identified to species level, and sex, maturity and disc width (DW in cm) were recorded. A total 359 specimens of Myliobatis spp. were recorded, of which 43.4% were from fishery discards, 31.5% from beach seine and 25.1% from drifting gill-net (‘lance de praia’, a fishery that has developed recently in the study area). Catches of myliobatids were higher in the spring and autumn. A total of 94 Myliobatis goodei (24 males, 69 females (eight pregnant) and one unsexed), and 179 Myliobatis ridens were recorded (24 males, 148 females (17 pregnant) and seven unsexed). Myliobatis goodei ranged in size from 45.0–65.0 cm DW (males) and 43.3–115.0 cm DW (females). Myliobatis ridens were 45.0–59.0 cm DW (males) and 41.2–98.0 cm DW (females). Both beach seine and gill-net fisheries operated in potential nursery areas for these myliobatid rays, as indicated by the proportionally high number of mature females (including pregnant females) and juveniles found in this study. The rays probably feed and give birth during the warmer seasons of the year (spring and summer) in these areas.

We examined the skulls of Arctocephalus australis, Callorhinus ursinus and Otaria byronia with the objectives of (1) estimating the development and growth rates and comparing these parameters among the species; (2) describing the development for each linear measure, for each species and sex; (3) determining which variables are best correlated with age; (4) determining age of physical maturity. We employed traditional and geometric morphometric techniques to study the skulls. In A. australis and C. ursinus, skulls of females mature at about 6 years of age, and those of males at about 8 years. Otaria byronia matures later, at about 9 years. Using geometric morphometric data sets, the rate and constant of growth in A. australis did not differ between the sexes. Callorhinus ursinus and O. byronia showed rates significantly different between sexes concerning growth (and in the constant as well), but only O. byronia differed between sexes in both developmental model parameters (rates and constant). Comparisons between the growth and developmental models showed significant differences in slope and constant. In both treatments employed, a relationship between size and shape dimorphism could be inferred for the skulls of all three species. We conclude that rates or timing of growth and development evolves within a conserved spatiotemporal organization of morphogenesis.

Gorgona National Park (GNP) protects the only known feeding aggregation of juvenile green turtles Chelonia mydas on the Pacific coast of Colombia. This study was undertaken to compare the diet of the two known C. mydas morphotypes (black and yellow), and to determine availability, selectivity, and quality of food resources at GNP. Oesophageal lavages and isotopic analysis of epidermal tissue were performed on turtles captured between February and December 2012. Food quantity was estimated by determining per cent cover in quadrats randomly placed on the reefs. Food quality of algae species was estimated by proximate analysis. Food selection was estimated using Ivlev's electivity index, and the trophic level of sea turtles at GNP was calculated. A total of 30 black (mean = 63.9 cm SCL) and 47 yellow (mean = 54.3 cm SCL) morphotype turtles were lavaged. Eight invertebrate and nine algae food items were identified in oesophageal contents. The most frequently found and abundant items in lavages were terrestrial plants, plastic fibres, invertebrates and algae. A total of 27 items, including 15 algae species, were identified on the reefs, of which Cladophora sp. was selected by black turtles, and Hypnea pannosa and Dictyota sp. were selected by both morphotypes; the latter species had the highest protein and lipid content, and low lignin content. A trophic level of 3.5 for black and 3.4 for yellow turtles was calculated. No significant difference in diet between the two morphotypes could be determined through lavage or isotopic analysis.

Belize contains important habitat for Antillean manatees (Trichechus manatus manatus) and provides refuge for the highest known population density of this subspecies. As these animals face impending threats, knowledge of their dietary habits can be used to interpret resource utilization. The contents of 13 mouth, six digestive tract (stomach, duodenum and colon) and 124 faecal samples were microscopically examined using a modified point technique detection protocol to identify key plant species consumed by manatees at two important aggregation sites in Belize: Southern Lagoon and the Drowned Cayes. Overall, 15 different items were identified in samples from manatees in Belize. Five species of seagrasses (Halodule wrightii, Thalassia testudinum, Ruppia maritima, Syringodium filiforme and Halophila sp.) made up the highest percentage of items. The red mangrove (Rhizophora mangle) was also identified as an important food item. Algae (Ulva sp., Chara sp., Lyngbya sp.) and invertebrates (sponges and diatoms) were also consumed. Variation in the percentage of seagrasses, other vascular plants and algae consumption was analysed as a 4-factor analysis of variance (ANOVA) with main effects and interactions for locality, sex, size classification and season. While sex and season did not influence diet composition, differences for locality and size classification were observed. These results suggest that analysis of diet composition of Antillean manatees may help to determine critical habitat and use of associated food resources which, in turn, can be used to aid conservation efforts in Belize.