ORCID Profile
0000-0003-4418-6866
Current Organisation
James Cook University
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Publisher: MDPI AG
Date: 30-09-2020
DOI: 10.3390/D12100376
Abstract: Juvenile fish often use alternative habitats distinct from their adult phases. Parrotfishes are an integral group of coral reef fish assemblages, are targeted in fisheries, are sensitive to reef disturbances, and have been documented as multiple-habitat users. Considering the abundance of research conducted on parrotfishes, very little is known about their juvenile ecology at the species level due to their cryptic and variable coloration patterns. We collected juvenile parrotfishes in non-reef habitats (macroalgal beds, seagrass beds, and lagoons) in the Philippines and used DNA analysis to determine species composition. The results were then compared with data on adult parrotfish abundance from underwater visual census (UVC) surveys in coral reef and non-reef habitats. Collections identified 15 species of juvenile parrotfishes in non-reef habitats, and of these, 10 were also recorded in UVCs as adults. Informed by adult surveys, 42% of the 19 parrotfish species observed as adults were classified as multi-habitat users based on their presence in coral reef and non-reef habitats. When accounting for the occurrence of species as juveniles in non-reef habitats, 93% of the species collected as juveniles would be considered multi-habitat users. Species identified as juveniles in non-reef habitats comprised 50% of the average adult parrotfish density on coral reefs and 58–94% in non-reef habitats. The species richness of juveniles in non-reef habitats was greater than that of adults occupying the same habitats, and the most common adult species observed in UVCs was not collected as juveniles in non-reef habitats. Finally, UVC suggested that 97% of juvenile parrotfish -cm total length was present in non-reef habitats compared to coral reefs. These results provide further evidence for ontogenetic movement across habitat boundaries for parrotfish species in a erse and highly connected tropical seascape. This is one of the few studies to quantify links between nursery and adult habitat in parrotfishes, highlighting the importance of including non-reef habitats in ecological studies of an iconic group of coral reef fish.
Publisher: Wiley
Date: 13-01-2021
DOI: 10.1111/COBI.13636
Abstract: Understanding whether assemblages of species respond more strongly to bottom‐up (availability of trophic resources or habitats) or top‐down (predation pressure) processes is important for effective management of resources and ecosystems. We determined the relative influence of environmental factors and predation by humans in shaping the density, biomass, and species richness of 4 medium‐bodied (10–40 cm total length [TL]) coral reef fish groups targeted by fishers (mesopredators, planktivores, grazer and detritivores, and scrapers) and the density of 2 groups not targeted by fishers (invertivores, small fish ≤10 cm TL) in the central Philippines. Boosted regression trees were used to model the response of each fish group to 21 predictor variables: 13 habitat variables, 5 island variables, and 3 fishing variables (no‐take marine reserve [NTMR] presence or absence, NTMR size, and NTMR age). Targeted and nontargeted fish groups responded most strongly to habitat variables, then island variables. Fishing (NTMR) variables generally had less influence on fish groups. Of the habitat variables, live hard coral cover, structural complexity or habitat complexity index, and depth had the greatest effects on density, biomass, and species richness of targeted fish groups and on the density of nontargeted fishes. Of the island variables, proximity to the nearest river and island elevation had the most influence on fish groups. The NTMRs affected only fishes targeted by fishers NTMR size positively correlated with density, biomass, and species richness of targeted fishes, particularly mesopredatory, and grazing and detritivorous fishes. Importantly, NTMRs as small as 15 ha positively affected medium‐bodied fishes. This finding provides reassurance for regions that have invested in small‐scale community‐managed NTMRs. However, management strategies that integrate sound coastal land‐use practices to conserve adjacent reef fish habitat, strategic NTMR placement, and establishment of larger NTMRs will be crucial for maintaining bio ersity and fisheries.
Publisher: Wiley
Date: 19-11-2020
DOI: 10.1002/ECE3.6940
Abstract: Nonreef habitats such as mangroves, seagrass, and macroalgal beds are important for foraging, spawning, and as nursery habitat for some coral reef fishes. The spatial configuration of nonreef habitats adjacent to coral reefs can therefore have a substantial influence on the distribution and composition of reef fish. We investigate how different habitats in a tropical seascape in the Philippines influence the presence, density, and biomass of coral reef fishes to understand the relative importance of different habitats across various spatial scales. A detailed seascape map generated from satellite imagery was combined with field surveys of fish and benthic habitat on coral reefs. We then compared the relative importance of local reef (within coral reef) and adjacent habitat (habitats in the surrounding seascape) variables for coral reef fishes. Overall, adjacent habitat variables were as important as local reef variables in explaining reef fish density and biomass, despite being fewer in number in final models. For adult and juvenile wrasses (Labridae), and juveniles of some parrotfish taxa ( Chlorurus) , adjacent habitat was more important in explaining fish density and biomass. Notably, wrasses were positively influenced by the amount of sand and macroalgae in the adjacent seascape. Adjacent habitat metrics with the highest relative importance were sand (positive), macroalgae (positive), and mangrove habitats (negative), and fish responses to these metrics were consistent across fish groups evaluated. The 500‐m spatial scale was selected most often in models for seascape variables. Local coral reef variables with the greatest importance were percent cover of live coral (positive), sand (negative), and macroalgae (mixed). Incorporating spatial metrics that describe the surrounding seascape will capture more holistic patterns of fish–habitat relationships on reefs. This is important in regions where protection of reef fish habitat is an integral part of fisheries management but where protection of nonreef habitats is often overlooked.
No related grants have been discovered for Katie Sievers.