Browsing by Author "Nagelkerken, Ivan"
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Item Demography of fish populations reveals new challenges in appraising juvenile habitat values.(2013) Kimirei, Ismael; Nagelkerken, Ivan; Slooter, N.; Gonzalez, E. T.; Huijbers, Chantal; Mgaya, Yunus D.; Rypel, AndrewUnderstanding the ‘value’ of nursery habitats is increasingly perceived as essential to conservation management of marine ecosystems globally. Yet, most work on this topic has assumed that population dynamics are temporally and spatially static, which clearly oversimplifies some highly complex and integral ecological processes. We used size-frequency data of fish species from mangrove and seagrass habitats collected at various locations over a >2 yr period to explore demographic structure and variability along with potential factors (such as growth, food abundance, and relative predation risk) that might encourage such variability. While demographics were skewed predominantly towards juveniles, older fish (up to 13 yr) were regularly observed in some mangroves or seagrass beds, indicating relatively complex population demographics. Juvenile habitats varied substantially in both prey abundance and relative predation risk—an effect that appeared to give rise to habitat-specific differences in somatic growth rates and fish densities. Fish population size structure was further related to position within the seascape, suggesting complex spatial dynamics in the production of fish biomass. Our results demonstrate that effectively appraising juvenile habitats will be a more convoluted process than previously thought, as greater integration is needed between basic ecological processes (e.g. predation risk and food availability) and population demography. Whereas current approaches often identify and manage single, complete nursery habitats based on those that contribute most individuals to adult populations, our study shows that a more dynamic and spatially-explicit management approach is needed, as nurseries have divergent benefits for separate life stages, species, and locations.Item Different Fish Composition in Seagrass Beds Adjacent to Extensive Mangrove Areas as Opposed to Coral Reefs(2007) Dorenbosch, Martijn; Grol, Monique G. G.; Nagelkerken, Ivan; Lugendo, Blandina R.; Van der Velde, GerardLittle is known about fish assemblages on seagrass beds located adjacent to different habitats. Visual census surveys were used to study the fish composition of two types of seagrass habitats in Zanzibar (Tanzania): seagrass beds adjacent to extensive mangrove areas in an embayment (bay seagrasses) and seagrass beds situated on the continental shelf adjacent to coral reefs (reef seagrasses). At species level, 39 fish species were common in the seagrass habitats, of which nine showed significantly higher densities in bay seagrasses, and four species were exclusively observed in bay seagrasses. Seine net data supported these data a the connectivity with mangroves.Item Fish Community Composition of a Tropical Nonestuarine Embayment in Zanzibar, Tanzania(Wiley, 2007) Lugendo, Blandina R.; Nagelkerken, Ivan; Jiddawi, Narriman S.; Mgaya, Yunus D.; Van der Velde, GerardBy using a seine net, fish samples were taken from the nonestuarine Chwaka Bay (Zanzibar, Tanzania) from the mangroves, mud/sand flats and seagrass beds. Sampling was done twice per month between November 2001 and October 2002. In total, 150 fish species belonging to 55 families were identified. Diversity (H′) ranged from 1.9 in mud/sand flats to 3.4 within the Chwaka seagrass beds. Mean density of fishes was significantly higher in the mangrove creeks than in any other habitat (mean = 238.7 ind./1000 m2). Highest, but non-significantly different mean biomasses were recorded in the mangrove creeks (1.7 kg/1000 m2) and in the Marumbi seagrass beds (1.6 kg/1000 m2). The mangrove channel had the lowest biomass (0.6 kg/1000 m2). A high overlap in species composition (as high as 93.4% similarity) was found for adjoining habitats (i.e. mangrove creeks and mangrove channel), while habitats that were far apart showed low overlap (6.6% similarity for the Marumbi seagrass beds and mangrove creeks). On average, 58.4 and 63.2% in terms of abundance and biomass, respectively, of the fish assemblage of Chwaka Bay were of commercial fishery importance. Thus, Chwaka Bay appears to be an important juvenile habitat for various commercially important fish species.Item Habitat Utilization by Juvenile of Commercially Important Fish Species in a Marine Embayment in Zanzibar, Tanzania(2005) Lugendo, Blandina R.; Pronker, Anna E.; Cornelissen, Ilse; De Groene, Arjan; Nagelkerken, Ivan; Dorenbosch, Martijn; Van der Velde, Gerard; Mgaya, Yunus D.Habitat utilisation by juveniles of 13 commercially important fish species was studied in five habitats located in Chwaka Bay, Zanzibar: mangrove creeks, mangrove channel, sand/mud flats, a seagrass area close to mangroves, and a seagrass area far from mangroves. Fish samples were collected from each habitat using a seine net, and fish abundance and size were measured to determine habitat utilisation. The seagrass beds near to mangroves showed the most diverse fish assemblage of all habitats, possibly because it functions as a corridor between the mangroves and deeper parts of the embayment. Juveniles of Cheilio inermis, Hipposcarus harid, Leptoscarus vaigiensis, and Scolopsis ghanam inhabited seagrass beds only. Juveniles of Gerres filamentosus and Monodactylus argenteus were mainly found in the mangrove habitats. Lethrinus variegatus, Pelates quadrilineatus and Siganus sutor were found in more than two habitats, with highest abundances in seagrass beds. Juveniles of Gerres oyena, Lethrinus lentjan, Lutjanus fulviflamma and Sphyraena barracuda were the most generalist species and were found in all studied embayment habitats. Visual census surveys supported the seine net data showing that most fishes in the embayment habitats were juveniles or sub-adults. In terms of habitat utilisation by different size classes, five of the 13 species (Lethrinus lentjan, L. variegatus, P. quadrilineatus, Siganus sutor and Sphyraena barracuda) were found as small-sized individuals in shallow and turbid mangrove areas, whereas large-sized individuals were observed in deeper and less turbid seagrass beds. A possible explanation for this pattern could be an ontogenetic shift in habitat utilisation, although this could not be proven. The patterns observed in the present study show a high similarity to those observed in marine embayments in the Caribbean, indicating that similar mechanisms are at work which make these systems attractive juvenile habitats.Item Importance of different carbon sources for macroinvertebrates and fishes of an interlinked mangrove-mudflat ecosystem (Tanzania).(2010) Bonga, Sjoerd W.; Mgaya, Yunus D.; Lugendo, Blandina; Nagelkerken, Ivan; Kruitwagen, G.Mangroves function as important shelter and feeding habitats for marine fauna, but the degree to which mangrove-derived carbon contributes to local food webs has long been debated. In this study, stable isotope analysis was used as a technique to elucidate the role of mangrove carbon in the diets of the macroinvertebrate and fish fauna of an intertidal fringing mangrove forest and adjacent intertidal/subtidal mudflats in a macrotidal Tanzanian estuary. The expectation was that sessile species and those with low motility depend to a larger extent on local carbon sources than highly motile species. A clear distinction in δ13C was present between primary producers from mangrove and mudflat habitats. Macroinvertebrates revealed a gradient in their δ13C where Sesarma crabs were the only species that directly utilised mangrove carbon by feeding on mangrove leaves/detritus. Uca crabs and the gastropod Littoraria scabra showed a higher dependence on microphytobenthos from the mangrove substratum. Among the fish fauna, the amphibious mudskipper was the only species to which the mangroves were accessible during low tide. Consequently this was the only fish species for which it was clear that it fed in the mangrove habitat, most commonly on mangrove-associated Uca crabs. All other species of sessile as well as motile macroinvertebrates and fish from the mangrove and mudflat habitat showed a high degree of utilisation of mudflat carbon. Overall, mangrove carbon thus contributed little to the mangrove and mudflat food webs, despite the high tidal amplitude and the resulting potential for exchange of carbon and fauna in the estuary studied here. Utilisation of mangrove carbon appears to depend more on the ecology of the species in consideration (e.g., species-specific use of zones within the mangrove habitat) than on their potential motility or tolerance to exposure during low tide.Item The Importance of Mangroves, Mud and Sand Flats, and Seagrass Beds as Feeding Areas for Juvenile Fishes in Chwaka Bay, Zanzibar: Gut Content and Stable Isotope Analyses(Wiley, 2006) Lugendo, Blandina R.; Nagelkerken, Ivan; Van der Velde, Gerard; Mgaya, Yunus D.The relative importance of bay habitats, consisting of mangrove creeks and channel, seagrass beds, and mud and sand flats, as feeding grounds for a number of fish species was studied in Chwaka Bay, Zanzibar, Tanzania, using gut content analysis and stable isotope analysis of carbon and nitrogen. Gut content analysis revealed that within fish species almost the same food items were consumed regardless of the different habitats in which they were caught. Crustaceans (mainly copepods, crabs and shrimps) were the preferred food for most zoobenthivores and omnivores, while fishes and algae were the preferred food for piscivores and herbivores, respectively. The mean d13C values of fishes and food items from the mangrove habitats were significantly depleted to those from the seagrass habitats by 6 9 and 9 7% for fishes and food items, respectively, and to those from the mud and sand flats by 3 5 and 5 8%, respectively. Fishes and food items from the mud and sand flats were significantly depleted as compared to those of the seagrass habitats by 3 4 and 3 9%, for fishes and food, respectively. Similar to other studies done in different geographical locations, the importance of mangrove and seagrass themselves as a primary source of carbon to higher trophic levels is limited. The different bay habitats were all used as feeding grounds by different fish species. Individuals of the species Gerres filamentosus, Gerres oyena, Lethrinus lentjan, Lutjanus fulviflamma, Pelates quadrilineatus and Siganus sutor appeared to show a connectivity with respect to feeding between different habitats by having d13C values which were in-between those of food items from two neighbouring habitats. This connectivity could be a result of either daily tidal migrations or recent ontogenetic migration. # 2006 The Authors Journal compilation # 2006 The Fisheries Society of the British IslesItem Influence of Morphology and Amphibious Life-Style on the Feeding Ecology of the Mudskipper Periophthalmus Argentilineatus(2007) Kruitwagen, Guus; Nagelkerken, Ivan; Lugendo, Blandina; Pratap, Harish B.; Brown, Sjoerd W.The potential feeding advantages that are offered to the barred mudskipper Periophthalmus argentilineatus by its amphibious life-style were investigated. To this end the feeding ecology of these fish, the position they occupy in the mangrove food web and the importance of different morphological factors for their diet were studied. Analysis of gut contents showed that the major component of the barred mudskipper diet changes during growth from small crustaceans (e.g. copepods and amphipods) to polychaetes to mangrove crabs. This dietary shift was found to be facilitated through enlargement of the mouth, as well as elongation of the gut. The use of stable isotope analysis revealed that barred mudskippers had a similar trophic position as other zoobenthivore fish species, but that their diet did not appear to be affected by competition for food with other zoobenthivores. The amphibious habits of the barred mudskipper provide specific advantages to its feeding ecology, such as access to an abundant food source of mangrove crabs, which are mostly inaccessible for other fish species. # 2007 The Authors Journal compilation # 2007 The Fisheries Society of the British IslesItem Mangrove Fish Production is Largely Fuelled by External Food Sources: A Stable Isotope Analysis of Fishes at the Individual, Species, and Community Levels from Across the Globe(2013) Mgaya, Yunus D.; Van der Velde, Gerard; Nagelkerken, Ivan; Igulu, MathiasCoastal ecosystems are energetically connected through passive transport of nutrients but also by migrations of motile organisms. Mangroves are highly productive tropical ecosystems that replenish offshore populations of many species, but we know little about the degree to which this production is fuelled by prey from mangroves, especially in the cases in which mangroves are only accessible at high tide. Different results have been obtained on the importance of mangroves as feeding habitats, confounded by differences in species composition, seascape configuration, and methodology. In the present study, we took a more holistic approach by exploring reliance by fishes on mangroves as a feeding habitat at multiple ecological levels: from individuals to species to communities in mangrove ecosystems from across the globe, using a stable isotope approach. A two end-member mixing model showed a wide range (12–72%) in degree of reliance on mangrove food sources by fishes from different studies across the globe. However, analyzed at the levels of individual fish and species, reliance was low (for example, <25% for 55% of the species worldwide, or <50% for 85% of species, respectively) even though they were collected from sites that differed in geographical location, tidal regime, seascape structure, and species composition. The high fisheries productivity of mangroves appears to be energetically supported largely by food sources from adjacent habitats. In light of the ongoing rapid demise and fragmentation of mangrove and adjacent ecosystems, loss of ecosystem connectivity is likely to affect the productivity and functioning of tropical coastal ecosystems and the services they proItem The mangrove nursery paradigm revisited: otolith stable isotopes support nursery-to-reef movements by Indo-Pacific fishes.(2013-06-12) Kimirei, Ismael A.; Nagelkerken, Ivan; Mgaya, Yunus D.; Huijbers, Chantal M.Mangroves and seagrass beds have long been perceived as important nurseries for many fish species. While there is growing evidence from the Western Atlantic that mangrove habitats are intricately connected to coral reefs through ontogenetic fish migrations, there is an ongoing debate of the value of these coastal ecosystems in the Indo-Pacific. The present study used natural tags, viz. otolith stable carbon and oxygen isotopes, to investigate for the first time the degree to which multiple tropical juvenile habitats subsidize coral reef fish populations in the Indo Pacific (Tanzania). Otoliths of three reef fish species (Lethrinus harak, L. lentjan and Lutjanus fulviflamma) were collected in mangrove, seagrass and coral reef habitats and analyzed for stable isotope ratios in the juvenile and adult otolith zones. δ13C signatures were significantly depleted in the juvenile compared to the adult zones, indicative of different habitat use through ontogeny. Maximum likelihood analysis identified that 82% of adult reef L. harak had resided in either mangrove (29%) or seagrass (53%) or reef (18%) habitats as juveniles. Of adult L. fulviflamma caught from offshore reefs, 99% had passed through mangroves habitats as juveniles. In contrast, L. lentjan adults originated predominantly from coral reefs (65–72%) as opposed to inshore vegetated habitats (28–35%). This study presents conclusive evidence for a nursery role of Indo-Pacific mangrove habitats for reef fish populations. It shows that intertidal habitats that are only temporarily available can form an important juvenile habitat for some species, and that reef fish populations are often replenished by multiple coastal habitats. Maintaining connectivity between inshore vegetated habitats and coral reefs, and conserving habitat mosaics rather than single nursery habitats, is a major priority for the sustainability of various Indo Pacific fish populations.Item Meta-analysis reveals that utilization of mangrove and seagrass nursery habitats across the globe is related to tidal regime rather than biogeographic region.(2014-12-14) Igulu, Mathias M.; Nagelkerken, Ivan; Dorenbosch, Martijn; Grol, Monique G. G.; Harborne, Alastair R.; Kimirei, Ismael A.; Mumby, Peter J.; Olds, Andrew D.; Mgaya, Yunus D.Identification of critical life-stage habitats is key to successful conservation efforts. Juveniles of some species show great flexibility in habitat use while other species rely heavily on a restricted number of juvenile habitats for protection and food. Considering the rapid degradation of coastal marine habitats worldwide, it is important to evaluate which species are more susceptible to loss of juvenile nursery habitats and how this differs across large biogeographic regions. Here we used a meta-analysis approach to investigate habitat use by juvenile reef fish species in tropical coastal ecosystems across the globe. Densities of juvenile fish species were compared among mangrove, seagrass and coral reef habitats. In the Caribbean, the majority of species showed significantly higher juvenile densities in mangroves as compared to seagrass beds and coral reefs, while for the Indo-Pacific region seagrass beds harbored the highest overall densities. Further analysis indicated that differences in tidal amplitude, irrespective of biogeographic region, appeared to be the major driver for this phenomenon. In addition, juvenile reef fish use of mangroves increased with increasing water salinity. In the Caribbean, species of specific families (e.g. Lutjanidae, Haemulidae) showed a higher reliance on mangroves or seagrass beds as juvenile habitats than other species, whereas in the Indo-Pacific family-specific trends of juvenile habitat utilization were less apparent. The findings of this study highlight the importance of incorporating region-specific tidal inundation regimes into marine spatial conservation planning and ecosystem based management. Furthermore, the significant role of water salinity and tidal access as drivers of mangrove fish habitat use implies that changes in seawater level and rainfall due to climate change may have important effects on how juvenile reef fish use nearshore seascapes in the futureItem Ontogenetic habitat use by mangrove/seagrass-associated coral reef fishes shows flexibility in time and space.(2011) Mgaya, Yunus D.; Wagner, Coen; Griffioen, Ben; Nagelkerken, Ivan; Kimirei, IsmaelTropical shallow-water habitats such as mangroves and seagrass beds are widely acknowledged as important juvenile habitats for various coral reef fish species, most of which are commercially important to fisheries. Spatio-temporal variability in ontogenetic habitat use by fish among these tropical coastal ecosystems has rarely been investigated, yet there are sufficient reasons to believe that this plays an important role. In the present study, we test the spatio-temporal variability in patterns of ontogenetic habitat use by some mangrove/seagrass-associated coral reef fishes (Lethrinus harak, Lethrinus lentjan, Lutjanus fulviflamma and Siganus sutor). Abundances of these four species were investigated during two years in Tanzanian coastal waters, using underwater visual census in mangrove, seagrass, shallow and deep mudflat, and shallow and deep coral reef habitats. The study covered four distinct seasons of the year and was done at two spatially separated (>40 km) locations. Averaged across locations, seasons and years, juveniles (<=10 cm length) of the four study species had significantly higher relative densities in shallow-water (mangroves and seagrass beds) than in deep-water habitats (deep mudflats or coral reefs), whereas the opposite pattern was found for the adults (>15 cm). These findings suggest a strong and general pattern of ontogenetic habitat shifts from shallow- to deep-water habitats. However, specific habitat-use patterns of juveniles as well as adults differed significantly in time and space. Various species showed subtle to considerable flexibility in juvenile as well as adult habitat use across seasons, years, or at different locations. Furthermore, for some species the data suggest presence of ontogenetic habitat shifts at one location but lack thereof at the other location. In summary, ontogenetic habitat use needs to be considered at various spatial and temporal scales for the interpretation of habitat utilization by fish during different life stages. This is important for conservation and management of these habitats, as essential habitats or seasons may be ignored or over-emphasized with respect to their importance for fish during different parts of their life cycle.Item Orientation from open water to settlement habitats by coral reef fish: behavioral flexibility in the use of multiple reliable cues(2013) Igulu, Mathias; Nagelkerken, Ivan; van der Beek, M.; Schippers, M.; van Eck, R.; Mgaya, Yunus D.Most coastal marine organisms have a dispersive oceanic larval stage, during which they must be able to distinguish and respond to relevant environmental cues when settling into their first benthic habitat. Chemical stimuli emanating from settlement habitats and being dispersed by water plumes could enable long-distance navigation by larval reef fish, but we know little about the cues responsible and their interactive effects. In the present study, we tested this by conducting several ex situ choice experiments in which the response of the coral reef fish Lutjanus fulviflamma towards different chemical cues from coastal habitats was tested close to their settlement stage. Fish preferred seagrass habitat water over that from coral reef and mangrove habitats. Furthermore, fish were attracted to chemical cues from their own species (conspecifics) and other fish species, as well as vegetation of 4 different seagrass species, when offered in isolation (i.e. soaked in neutral water), but a strong response remained only towards cues from conspecifics and seagrass leaves when these cues were mixed with seagrass habitat water that naturally contains other cues. Hierarchical effects were observed as fish preferred chemical cues from seagrass leaves over those from conspecifics when both were offered at the same time. The importance of visual habitat cues only overruled that of chemical cues when it concerned preferred cues (i.e. seagrass as opposed to mangrove cues). Our findings indicate that pelagic fish and settlers possess the ability to use multiple reliable chemical cues to locate suitable early life stage habitats, although the importance of these cues is context-dependent. Nevertheless, this flexibility in choice behavior is probably an adaptive strategy to enhance fitness by increasing successful orientation towards preferred settlement habitats.Item The potential role of visual cues for microhabitat selection during the early life phase of a coral reef fish (Lutjanus fulviflamma).(2011) Mgaya, Yunus D.; Ligtenberg, H.; van Hintum, R.; Fraaije, Rob; Nagelkerken, Ivan; Igulu, MathiasPelagic larvae of various coral reef fish species are known to be active swimmers that can carefully select preferred microhabitat during settlement. Fish larvae may use visual, environmental, or chemical cues to orient and settle in shallow-water habitats such as coral reefs, mangroves, and seagrass beds. In the present study, we investigated in dual-choice laboratory experiments the visual attraction of recent settlers of a reef fish (Lutjanus fulviflamma) towards different microhabitats, conspecifics, and heterospecifics, and the interactive effects among these cues. Fish preferred seagrass and coral above mangrove roots. Fish were more attracted towards a combination of conspecifics or heterospecifics and seagrass microhabitats than to seagrass microhabitats alone, but showed a significantly stronger preference for conspecifics than for heterospecifics when placed in preferred seagrass or non-preferred mangrove microhabitats. However, the preference for conspecifics disappeared when choice was given between conspecifics placed in non-preferred mangrove microhabitat versus heterospecifics placed in preferred seagrass micro habitat. A multiple choice experiment further showed that recent settlers preferred conspecifics of equal or about 1cm larger body size, but not of 2 or 3cm larger body size. The higher attraction towards the combination of seagrass microhabitats and conspecifics/heterospecifics shows an additive effect of the latter, which could be explained by the fact that presence of resident fish in preferred habitat may indicate favorable conditions in the field and may offer an increased safety through schooling. However, (1) attraction towards conspecifics of (nearly) similar body size and not larger, (2) stronger attraction towards conspecifics in a non-preferred than in a preferred microhabitat, and (3) equal attraction towards conspecifics in non-preferred microhabitat vs. heterospecifics in preferred microhabitat all indicate that the importance of schooling with conspecifics is highly context-dependent. This may have significant effects on the habitat selection and distribution of early-stage fish (and thus also on consecutive life stages) in coastal habitats. Our findings point to the potential ecological significance of various visual cues, and their interactive effects, for early juvenile coral reef fishes while settling into shallow-water habitats and/or selecting early post-settlement habitats.Item Relative Importance of Mangroves as Feeding Habitat for Juvenile Fish: A Comparative Study on Mangrove Habitats with Different Settings(2007-01) Lugendo, Blandina R.; Nagelkerken, Ivan; Kruitwagen, Guus; Van der Velde, Gerard; Mgaya, Yunus D.The importance of mangroves as feeding grounds for fish and other macrozoob-enthos in the Indian Ocean and elsewhere has been a subject of debate. This could partly be due to the fact that studies describing this role have been conducted in mangrove systems that differed in their settings. By using stable isotope analysis of carbon and nitrogen, we investigated two different settings of mangroves along the Tanzanian coast, to establish if mangrove setting influences the extent to which this habitat is utilized as a potential feeding ground by fish. The two mangrove settings were: mangrove-lined creeks which retain water during low tides and fringing mangroves that drain completely during low tides. The δ13C signatures of most fishes from the mangrove-lined creeks were similar to those of food items from the mangrove habitat, which suggests that these fishes feed from the mangrove habitats. In contrast, the overlap in δ13C of some food items from the fringing mangroves with those from adjacent habitats, and the more enriched δ13C signatures of fishes from the fringing mangroves with respect to most typical food items from the mangrove habitat could be an indication that these fishes feed from both habitats but to a lower extent from the fringing mangroves. The results suggest that fishes feed more from the mangrove-lined creeks as compared to fringing mangroves which is probably related to differences in the degree of mangrove inundation. The more or less continuous access provided more time for fishes to stay and feed in the mangrove-lined creeks compared to fishes from the fringing mangroves, which have access to these mangroves only during high tide and have to migrate to adjacent habitats with the ebbing tide.Item Relative Importance of Mangroves as Feeding Habitats for Fishes: A Comparison between Mangrove Habitats with Different Settings(2007) Lugendo, Blandina R.; Nagelkerken, Ivan; Kruitwagen, Guus; Van der Velde, GerardThe importance of mangroves as feeding grounds for fish and other macrozoob-enthos in the Indian Ocean and elsewhere has been a subject of debate. This could partly be due to the fact that studies describing this role have been conducted in mangrove systems that differed in their settings. By using stable isotope analysis of carbon and nitrogen, we investigated two different settings of mangroves along the Tanzanian coast, to establish if mangrove setting influences the extent to which this habitat is utilized as a potential feeding ground by fish. The two mangrove settings were: mangrove-lined creeks which retain water during low tides and fringing mangroves that drain completely during low tides. The δ13C signatures of most fishes from the mangrove-lined creeks were similar to those of food items from the mangrove habitat, which suggests that these fishes feed from the mangrove habitats. In contrast, the overlap in δ13C of some food items from the fringing mangroves with those from adjacent habitats, and the more enriched δ13C signatures of fishes from the fringing mangroves with respect to most typical food items from the mangrove habitat could be an indication that these fishes feed from both habitats but to a lower extent from the fringing mangroves. The results suggest that fishes feed more from the mangrove-lined creeks as compared to fringing mangroves which is probably related to differences in the degree of mangrove inundation. The more or less continuous access provided more time for fishes to stay and feed in the mangrove-lined creeks compared to fishes from the fringing mangroves, which have access to these mangroves only during high tide and have to migrate to adjacent habitats with the ebbing tide.Item What drives ontogenetic niche shifts in reef fishes? Ecosystems(2013) Kimirei, Ismael A.; Nagelkerken, Ivan; Trommelen, M.; Blankers, P.; van Hoytema, N.; Hoeijmakers, D.; Huijbers, Chantal.m; Mgaya, Yunus D.; Rypel, Andrew LeeOntogenetic niche shifts are taxonomically and ecologically widespread across the globe. Consequently, identifying the ecological mechanics that promote these shifts at diverse scales is central to an improved understanding of ecosystems generally. We evaluated multiple potential drivers of ontogenetic niche shifts (predation, growth, maturation, diet shifts, and food availability) for three fish species between connected coral reef and nearshore habitats. In all cases, neither diet compositional change nor sexual maturity functioned as apparent triggers for emigration from juvenile to adult habitats. Rather, the fitness advantages conferred on reef inhabitants (that is, enhanced growth rates) were primarily related to high prey availability on reefs. However, there exists a clear trade-off to this benefit as survival rates for small fishes were significantly reduced on reefs, thereby revealing the potential value of (and rationale behind high juvenile abundances in) nearshore habitat as predation refugia. We ultimately conclude that predation risk functions as the primary early life stage inhibitor of ontogenetic niche shifts towards more profitable adult habitats in these systems. Furthermore, this study provides a case study for how complex, meta-dynamic populations and ecosystems might be better understood through the elucidation of simple ecological trade-offs. © 2013 The Author(s).