A comparison between fish assemblages in mangrove forests and on intertidal flats at Ungwana Bay, Kenya

AbstractMangrove forests are important habitats for fish. However, their utilisation by fish, and the specific values they confer, are still not fully understood. This study describes how fish use mangrove forests in an Indo-Pacific mangrove-coral reef seascape. Sampling was conducted using underwater video cameras (UVCs) to describe spatial and temporal variations in fish assemblages across a small-scale (~ 2.5 km2) system, and over the tidal and lunar cycle. UVCs were deployed in the two main component habitats of mangrove forests: at the mangrove forest edge, and inside the forest (5 m from the forest edge), to establish patterns of utilisation of fish across the tidal and lunar cycle. Proximity to coral reefs had a strong influence on the mangrove fish community, as most fish recorded were reef-associated. Juveniles of 12 reef species were observed, including two species classified as vulnerable on the IUCN list, and one endemic species. Fish assemblages on the mangrove edge differed significantly from those inside the forest. Most fish utilised the forest edge, with few species making regular use of in-forest habitats, supporting the contention that most fish species remain on the edge and potentially retreat into the forest for opportunistic feeding, or when threatened by larger predators. Species-specific patterns of utilisation varied across the tidal and lunar cycle. Small differences in depth profiles and substrate across the small-scale system had a significant effect on fish assemblages, highlighting the importance of accounting for spatial heterogeneity in these factors. These data provide important information for managers to implement adequate conservation strategies that include broader interconnected habitat mosaics.

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Contrasting effects of mangroves and armoured shorelines on fish assemblages in tropical estuarine seascapes

ICES Journal of Marine Science ◽

10.1093/icesjms/fsz007 ◽

2019 ◽

Vol 76 (4) ◽

pp. 1052-1061 ◽

Cited By ~ 7

Author(s):

Christopher J Henderson ◽

Ben L Gilby ◽

Thomas A Schlacher ◽

Rod M Connolly ◽

Marcus Sheaves ◽

...

Keyword(s):

Fish Assemblages ◽

Urban Expansion ◽

Ecological Impacts ◽

Spatial Context ◽

Fish Diversity ◽

Mangrove Forests ◽

Habitat Types ◽

Tropical Estuarine ◽

Eastern Australia ◽

Close Proximity

Abstract Coastal seascapes are composed of a diversity of habitats that are linked in space and time by the movement of organisms. The context and configuration of coastal ecosystems shapes many important properties of animal assemblages, but potential seascape effects of natural and artificial habitats on nearby habitats are typically considered in isolation. We test whether, and how, the seascape context of natural and urban habitats modified fish assemblages across estuaries. Fish were sampled with underwater videos in five habitat types (mangroves, rock bars, log snags, unvegetated sediments, armoured shorelines) in 17 estuaries in eastern Australia. Different habitats supported distinct fish assemblages, but the spatial context of mangroves and armoured shorelines had pervasive ecological effects that extended across entire estuaries. In most estuarine habitats, fish diversity and abundance was greatest when they were in close proximity of mangroves, and decreased due to the proximity of armoured shorelines. Many cities are centred on estuaries, and urban expansion is often associated with the fragmentation of mangrove forests. Our findings emphasize that these transformations of urban estuarine landscapes are likely to propagate to broader ecological impacts detectable in multiple habitats beyond mangrove forests.

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Assessing the contribution of mangrove carbon and of other basal sources to intertidal flats adjacent to one of the largest West African mangrove forests

Marine Environmental Research ◽

10.1016/j.marenvres.2021.105331 ◽

2021 ◽

pp. 105331

Author(s):

Mohamed Henriques ◽

José Pedro Granadeiro ◽

Theunis Piersma ◽

Seco Leão ◽

Samuel Pontes ◽

...

Keyword(s):

West African ◽

Mangrove Forests ◽

Intertidal Flats

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study fish assemblages of Intertidal flats in Iraqi marine water

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/779/1/012122 ◽

2021 ◽

Vol 779 (1) ◽

pp. 012122

Author(s):

Ahmed Chasib Al-Shamary

Keyword(s):

Fish Assemblages ◽

Marine Water ◽

Intertidal Flats

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Hypoxia in mangroves: occurrence and impact on valuable tropical fish habitat

Biogeosciences ◽

10.5194/bg-16-3959-2019 ◽

2019 ◽

Vol 16 (20) ◽

pp. 3959-3976 ◽

Cited By ~ 2

Author(s):

Alexia Dubuc ◽

Ronald Baker ◽

Cyril Marchand ◽

Nathan J. Waltham ◽

Marcus Sheaves

Keyword(s):

Mangrove Forest ◽

Fish Assemblages ◽

Fish Habitat ◽

Environmental Parameters ◽

Detailed Examination ◽

Quality Parameter ◽

Tropical Fish ◽

Water Quality Parameter ◽

Mangrove Forests ◽

Low Do

Abstract. Intertidal mangrove forests are harsh environments that can naturally experience hypoxia in association with low tide. However, we know relatively little about dissolved oxygen (DO) fluctuations and DO-induced responses by fish, although DO is a fundamental water quality parameter. This study examines DO as a potential factor regulating the utilisation of intertidal mangrove forests by fish and consequently their widely recognised feeding, refuge and nursery values. We deployed underwater video cameras, coupled with DO and depth loggers, in a mangrove forest to record changes in fish assemblages in response to tidal variations in DO and other associated environmental parameters. Our results indicate that DO underwent extreme tidal fluctuations, reaching levels as low as 14 % saturation. As DO was identified as a significant factor for explaining variability in fish assemblage composition, we further investigated fish responses to DO fluctuations. Higher taxonomic richness and frequencies of occurrence were observed once DO reached 70 %–80 % saturation. More detailed examination revealed species-specific responses. Three distinct patterns of mangrove utilisation in response to DO were identified, driven by apparent taxa's behavioural DO avoidance thresholds. Most taxa did not display any behavioural avoidance, including presence at the lowest DO levels, while other taxa were not observed either below 50 %–60 % saturation or below 70 %–80 % saturation. This implies that tidal migrations, often observed in intertidal environments, could be the result of differential DO tolerances and are not simply initiated by changes in water depth. Taxa remaining in the mangrove forest even at low DO were on average more frequently observed than the other taxa and were mostly species commonly associated with mangrove habitats. This suggests that being adapted to withstand low DO might be an important condition for using mangrove habitats extensively. The need of being tolerant to low DO could constrain fish utilisation and explain the relatively low species richness often observed in other intertidal mangrove forests.

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Seascape heterogeneity modifies estuarine fish assemblages in mangrove forests

ICES Journal of Marine Science ◽

10.1093/icesjms/fsab022 ◽

2021 ◽

Author(s):

Christopher J Henderson ◽

Ben L Gilby ◽

Edward Stone ◽

Hayden P Borland ◽

Andrew D Olds

Keyword(s):

Fish Community ◽

Fish Assemblages ◽

Estuarine Fish ◽

Mangrove Forests ◽

Fish Community Structure ◽

Estuary Mouth ◽

Urban Structures ◽

Catchment Size ◽

Subtropical Estuaries ◽

Species Richness And Abundance

Abstract Mangroves are a dominant structural habitat within tropical and subtropical estuaries that provide a number of ecosystem services, including habitat for a range of crustaceans and fish. However, mangroves are one of the most threatened estuarine habitats globally, having been severely reduced in extent, and replaced by urban structures. Here, we test for the effects of both natural (e.g. seagrass, rock and mangroves habitat extent, and connectivity) and human (e.g. extent of urban area) landscape variables on the number and type of fish inhabiting mangroves forests. We used remote underwater video stations to quantify fish assemblages within mangroves at 150 sites in 30 estuaries across Queensland, Australia. Fish community structure was best explained by the extent of mangroves and seagrasses within an estuary, the distance to the estuary mouth, and the size of the estuary and catchment. Moderate catchment size and proximity to the estuary mouth increased species richness and abundance of harvestable fish at individual mangrove sites. In order to maintain mangrove fish assemblages and the functions they provide, management initiatives should focus on maintaining natural estuarine seascapes that are located closer to the mouth of estuaries, in particular, focusing on estuaries that have lower levels of catchment urbanization.

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Mangrove-associated fish assemblages off the southern Panama Bight region (tropical eastern Pacific)

Neotropical Ichthyology ◽

10.1590/1982-0224-2021-0025 ◽

2021 ◽

Vol 19 (4) ◽

Author(s):

Gustavo A. Castellanos-Galindo ◽

Rodrigo A. Baos ◽

Luis A. Zapata

Keyword(s):

Fish Species ◽

Fish Assemblages ◽

Spatial Dynamics ◽

Ecological Factors ◽

Eastern Pacific ◽

Trophic Relationships ◽

Mangrove Forests ◽

Artisanal Fishery ◽

Fish Community Structure ◽

Tropical Eastern Pacific

ABSTRACT The Panama Bight ecoregion (PBE) in the eastern Pacific contains probably the best developed mangrove forests in the American continent. Fishes inhabiting the mangrove-estuary mosaic play fundamental ecological roles and sustain the artisanal fishery operating there. Here, using data collected along ~300 km between 2012 and 2017, we examine the spatial dynamics of mangrove fish assemblages that undertake intertidal migrations in the southern part of the PBE (southern Colombian Pacific coast), where the largest and least disturbed mangroves of Colombia are located. Sixty-one fish species used intertidal mangrove habitats in these areas, constituting ~30% of all fishes inhabiting the whole mosaic of mangrove habitats in this ecoregion. Species within Clupeidae, Ariidae, Centropomidae and Tetraodontidae, all common in mangroves of the eastern Pacific, were the most dominant. Half of the fish species found are commercially important to the artisanal fishery. Differences in fish community structure could be related to salinity differences, but other environmental and ecological factors could also play a role in explaining these differences. A better understanding of the ecological role of mangrove fishes in the region could be gained by examining the ichthyofauna of other habitats within the mosaic and their trophic relationships.

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Hypoxia in mangroves: occurrence and impact on valuable tropical fish habitat

10.5194/bg-2019-178 ◽

2019 ◽

Cited By ~ 1

Author(s):

Alexia Dubuc ◽

Ronald Baker ◽

Cyril Marchand ◽

Nathan J. Waltham ◽

Marcus Sheaves

Keyword(s):

Mangrove Forest ◽

Fish Assemblages ◽

Fish Habitat ◽

Environmental Parameters ◽

Detailed Examination ◽

Quality Parameter ◽

Tropical Fish ◽

Water Quality Parameter ◽

Mangrove Forests ◽

Low Do

Abstract. Intertidal mangrove forests are harsh environments that can naturally experience hypoxia in association with low tide. However, we know relatively little about dissolved oxygen (DO) fluctuations and DO-induced responses by fish, although DO is a fundamental water quality parameter. This study examines DO as a potential factor regulating the utilisation of intertidal mangrove forests by fish, and consequently their value. We deployed underwater video cameras, coupled with DO and depth loggers, in a mangrove forest to record changes in fish assemblages in response to tidal variations in DO and other associated environmental parameters. Our results indicate that DO underwent extreme tidal fluctuations, reaching levels as low as 14 % saturation. As DO was identified as a significant factor to explain variability in fish assemblage composition, we further investigated fish responses to DO fluctuations. Higher taxonomic richness and frequencies of occurrence were observed once DO reached 70–80 % saturation. More detailed examination revealed species-specific responses. Three distinct patterns of mangrove utilisation in response to DO were identified, driven by apparent taxa’s behavioural DO avoidance thresholds. Most taxa did not display any behavioural avoidance, including presence at the lowest DO levels, while other taxa were not observed either below 50–60 % saturation, or below 70–80 % saturation. This implies that tidal migrations, often observed in intertidal environments, could be the result of differential DO tolerances, and not simply initiated by changes in water depth. Taxa remaining in the mangrove forest even at low DO were on average more frequently observed than the other taxa, and were mostly species commonly associated with mangrove habitats. This suggests that being adapted to withstand low DO might be an important condition to use mangrove habitats extensively. The need of being tolerant to low DO could constrain fish utilisation and explain the relatively low species richness often observed in other intertidal mangrove forests.

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