Search for: All records

Local habitat availability can strongly affect animal communities. On coral reefs, the biodiversity of small, bottom-dwelling (‘cryptobenthic’) reef fishes and drivers of their community assembly have yet to be explored in many locations. Here, we investigate how local and regional factors shape the structure and composition of cryptobenthic reef fish communities in the Veracruz Reef System National Park (VRS) in the Gulf of Mexico (GoM). Focusing on five reefs in the VRS, we surveyed cryptobenthic reef fish communities at scales of reef outcrops (~ 3–5 m2) and isolated microhabitats, while also quantifying the benthic composition of each reef to determine microhabitat availability. We found no significant differences in species richness or abundance across park regions and reef zones, but community composition differed qualitatively across reef zones. Furthermore, we discovered strong differences in cryptobenthic reef fishes’ preferences for various microhabitats, which are likely to drive community assembly and provide evidence for species-specific vulnerabilities to reef degradation. Caves harbored the highest biodiversity and abundance of cryptobenthic fishes, while gorgonian soft corals and algae supported the fewest species and individuals. The endemic gobies Tigrigobius redimiculus and Elacatinus jarocho both showed high abundance and occurrence but displayed opposite patterns of microhabitat specialization; T. redimiculus was categorized as a microhabitat generalist, while E. jarocho was revealed as a cave-dwelling specialist species. Overall, our quantitative exploration of the cryptobenthic reef fish community in the southwest GoM provides a crucial baseline for habitat and biodiversity monitoring in the region and highlights E. jarocho as an emblematic, endemic indicator species that will be vulnerable to extinction if further reduction of habitat complexity occurs. 

Cross-ecosystem nutrient transfer can enhance coral reef functioning in an otherwise oligotrophic environment. While the influence of seabird-derived nutrients on coral reef organisms is increasingly recognized, how they are integrated into reef food webs remains unclear. Cryptobenthic reef fishes are crucial for energy transfer on coral reefs, and their fast life histories imply that they respond strongly to seabird-derived nutrients. Here, we investigate how variation in nearshore seabird nutrient subsidies affects coral reef fish communities. By comparing fish communities across locations differing in seabird nutrient inputs and using stable isotope analysis, we explore nutrient integration across depth, their influence on cryptobenthic and associated larger reef fishes and investigated the relative reliance of cryptobenthic fishes on seabird-enriched benthic and non-enriched pelagic pathways. We find that, near seabird colonies, cryptobenthic fishes’ diets can transition from pelagic to benthic dominance; cryptobenthic fish communities are larger; herbivores and all feeding groups comprising potential cryptobenthic fish predators have higher biomass. Collectively, our results stress the importance of seabirds in shaping energy pathways and suggest that, even in dynamic, ocean-swept reef systems, cryptobenthic fishes can mobilize seabird subsidies and potentially act as a nutritional bridge to higher trophic levels. 

Understanding how humans have altered coral reef food webs remains challenging due to the absence of prehistoric baselines. Here, we use fish remains preserved in fossil and archaeological deposits from Panamá and the Dominican Republic to explore how Caribbean reef fish mortality patterns have changed over millennia. By quantifying accumulation rates of shark dermal denticles (scales) and bony fish otoliths (ear stones) in reef sediments, we assess relative fish abundance, while otolith size serves as a proxy for body size at death. Comparisons of these death assemblages suggest a 75% decline in shark-derived material and a 22% reduction in the sizes of human-targeted fishes—consistent with historical exploitation. This evidence of decline in large-bodied, higher trophic level fish remains coincided with a doubling in prey fish otolith accumulation and a 17% increase in their reconstructed body sizes. These patterns in time-averaged death assemblages align with effects of release from predation, documenting an often assumed (but rarely shown) cascading effect. In contrast, otoliths of predator-sheltered cryptobenthic fishes showed no change in either accumulation or size, suggesting that ‘‘bottom–up”environmental factors were not responsible for the observed changes. Together, these data indicate that pre-exploitation predator communities strongly controlled exposed prey fishes, but this “top–down” effect diminishes rapidly toward the food chain base, especially in predator-resistant groups. Understanding trophic cascades on Caribbean reefs requires studying systems before predator depletion. 

During ontogeny, animals often undergo significant shape and size changes, coinciding with ecological shifts. This is evident in parrotfishes (Eupercaria: Labridae), which experience notable ecological shifts during development, transitioning from carnivorous diets as larvae and juveniles to herbivorous and omnivorous diets as adults, using robust beaks and skulls for feeding on coral skeletons and other hard substrates. These ontogenetic shifts mirror their evolutionary history, as parrotfishes are known to have evolved from carnivorous wrasse ancestors. Parallel shifts at ontogenetic and phylogenetic levels may have resulted in similar evolutionary and ontogenetic allometric trajectories within parrotfishes. To test this hypothesis, using micro-computed tomography (μCT) scanning and three-dimensional geometric morphometrics, we analyse the effects of size on the skull shape of the striped parrotfishScarus iseriand compare its ontogenetic allometry to the evolutionary allometries of 57 parrotfishes and 162 non-parrotfish wrasses. The youngS. iserihave skull shapes resembling non-parrotfish wrasses and grow towards typical adult parrotfish forms as they mature. There was a significant relationship between size and skull shapes and strong evidence for parallel ontogenetic and evolutionary slopes in parrotfishes. Our findings suggest that morphological changes associated with the ecological shift characterizing interspecific parrotfish evolution are conserved in their intraspecific ontogenies. 

Abstract Oligotrophic tropical coral reefs are built on efficient internal energy and nutrient cycling, facilitated by tight trophic interactions. In the competition for available prey, some small fishes have evolved to feed on apparently barren sand patches that connect hard‐substratum patches in many reef habitats.One strategy for obtaining prey from a particulate matrix is to sift out small prey items from the sediment (often called ‘winnowing’). Yet, the trophic link between small winnowing consumers and their prey are poorly resolved, let alone the morphological specialisations that enable this foraging behaviour.We used aquarium‐based feeding experiments to quantify the impact of winnowing by two sand‐dwelling goby species (Valenciennea sexguttataandValenciennea strigata) on meiobenthos abundance and diversity and examined their actual ingestion of meiobenthos using gut content analysis. To identify potential morphological structures involved in winnowing, we investigated the gobies' feeding apparatus with electron microscopy (SEM) and micro‐computed tomography (micro‐CT).After 4 days of sifting through the sand matrix, the two species significantly reduced meiobenthic prey abundance by 30.7% ± 9.2SE(V. sexguttata) and 46.1% ± 5.1SE(V. strigata), but had little impact on the meiobenthic diversity. The most abundant prey groups (copepods and annelids) experienced the greatest reduction in number, suggesting selection by size, shape and density of prey items. Furthermore, gut content analysis confirmed that winnowing gobies can efficiently separate meiobenthic prey from heavier inorganic particles (sand), likely facilitated by a specialised epibranchial lobe, pharyngeal jaws and highly abundant papillose taste buds in the oropharyngeal cavity.Our results provide important background on the trophic link between the meiobenthos and winnowing gobies on coral reefs. The revealed specialisations of the goby feeding apparatus facilitate sand‐sifting foraging behaviour and access to an otherwise inaccessible trophic niche of microscopic prey. By having evolved a specialised strategy to obtain nutritious and highly abundant prey from seemingly barren sand, we suggest that winnowing gobies act as an important conduit for sand‐derived energy to higher trophic levels. Read the freePlain Language Summaryfor this article on the Journal blog.