Spatial predictability of juvenile fish species richness and abundance in a coral reef environment

Abstract Coastal zones are ecosystems of high economic value but exposed to numerous disturbances, while they represent nurseries for many fish species, raising the issue of the preservation of their functions and services. In this context, the juvenile fish assemblages of all types of habitats present in shallow coastal zones were studied on the south-east coast of France using underwater visual censuses. The abiotic and biotic descriptors of the 14 habitat types individualized did not vary with time, except for a higher cover percentage and canopy height of macrophytes in the warm period, which increased the three-dimensional structure of some habitats. The taxonomic composition and density of juvenile fish assemblages were analyzed using both multivariate and univariate descriptors, after grouping the 57 fish species recorded into 41 well-individualized taxa. Juvenile fishes were recorded in all habitat types, with higher mean species richness and abundance during the warm than the cold period. The richest habitats in terms of both species richness and abundance were the natural rocky substrates and the interfaces between Posidonia beds and the other habitats. Although juvenile fish assemblages differed among habitat types and between periods, the most abundant fish species (Atherina sp., Sarpa salpa, Gobiidae, Symphodus spp., Pagellus spp. and several Diplodus species) colonized different habitat types (from 7 to 14) during their juvenile life. This study provided evidence of the role of all types of shallow coastal habitats as fish nurseries and their varying pattern of occupation in space and time by the different juvenile stages. It highlighted the importance of the mosaic of habitats and interfaces for the complete development of all juvenile life stages of fishes, and for the preservation of a high diversity of coastal fish assemblages and fisheries resources in the Mediterranean Sea.

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All shallow coastal habitats matter as nurseries for Mediterranean juvenile fish

Scientific Reports ◽

10.1038/s41598-021-93557-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Adrien Cheminée ◽

Laurence Le Direach ◽

Elodie Rouanet ◽

Patrick Astruch ◽

Adrien Goujard ◽

...

Keyword(s):

Species Richness ◽

Fish Species ◽

Fish Assemblages ◽

Juvenile Fish ◽

Posidonia Oceanica ◽

Dimensional Structure ◽

Coastal Zones ◽

Habitat Types ◽

Coastal Habitats ◽

Species Richness And Abundance

AbstractCoastal zones are ecosystems of high economic value but exposed to numerous disturbances, while they represent nurseries for many fish species, raising the issue of the preservation of their functions and services. In this context, the juvenile fish assemblages of all types of habitats present in shallow coastal zones were studied on the south-east coast of France using underwater visual censuses in warm (June–July 2014) and cold (April 2015) periods. A total of fourteen habitat types were characterized, which could be grouped into three broad categories, rocky substrates (natural and artificial), sedimentary bottoms with all levels of granulometry, and seagrass beds including Cymodocea nodosa and Posidonia oceanica meadows; the ecotones or interfaces between the three broad habitat categories were individualized as particular habitat types. The abiotic and biotic descriptors of the 14 habitat types individualized did not vary with time, except for a higher cover percentage and canopy height of macrophytes in the warm period, which increased the three-dimensional structure of some habitats. The taxonomic composition and density of juvenile fish assemblages were analyzed using both multivariate and univariate descriptors, after grouping the 57 fish species recorded into 41 well-individualized taxa. Juvenile fishes were recorded in all habitat types, with higher mean species richness and abundance during the warm than the cold period. The richest habitats in terms of both fish species richness and abundance were the natural rocky substrates and the interfaces between Posidonia beds and the other habitats. Although juvenile fish assemblage composition differed among habitat types and between periods, the most abundant fish species were Atherina sp., Sarpa salpa, Gobiidae, Symphodus spp., Pagellus spp. and several Diplodus species, which colonized 7 up to 14 different habitat types (depending on taxa) during their juvenile life. Most species settled in one or a few specific habitats but rapidly colonized adjacent habitats when growing. This study provided evidence of the role of all types of shallow coastal habitats as fish nurseries and their varying pattern of occupation in space and time by the different juvenile stages. It highlighted the importance of the mosaic of habitats and interfaces for the complete development of all juvenile life stages of fishes, and for the preservation of a high diversity of coastal fish assemblages and fisheries resources in the Mediterranean Sea.

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Evaluating the feasibility and advantage of a multi-purpose submerged breakwater for harbor protection and benthic habitat enhancement at Kahului Commercial Harbor, Hawai‘i: case study

SN Applied Sciences ◽

10.1007/s42452-020-04072-4 ◽

2021 ◽

Vol 3 (2) ◽

Author(s):

Yuko Stender ◽

Michael Foley ◽

Ku’ulei Rodgers ◽

Paul Jokiel ◽

Amarjit Singh

Keyword(s):

Coral Reef ◽

Coral Cover ◽

Ecological Impact ◽

Coastal Protection ◽

Benthic Habitat ◽

Engineering Structures ◽

Camera System ◽

Reef Environment ◽

Submerged Breakwater ◽

Coral Reef Environment

AbstractConstruction of breakwaters provides an engineering solution for coastal protection. However, little effort has been made toward understanding the ecological impact on local coral reef ecosystems and developing engineering structures that would enhance the coral reef environment. A submerged breakwater proposed for Kahului Commercial Harbor, Hawai‘i, provided an opportunity to design a multi-purpose ‘reef structure’ to mitigate wave impacts while providing new coral reef habitat. This design involved ecological and environmental considerations alongside engineering principles, serving as a model for environmentally sound harbor development. This field study evaluated environmental conditions and reef community composition at the proposed site in a gradient extending outward from the harbor, using in situ data with multivariate analyses. Benthic and topographic features in the area were assessed using a towed drop camera system to relate to biological factors. Results that support breakwater topography should follow the natural spur and groove and depth of the adjacent reef and orient with wave direction. A deep area characterized by unconsolidated substrata and low coral cover would be replaced with the shallow, sloping hard bottom of the breakwater, and provide an exemplary area for corals to flourish while protecting the harbor from large ocean swells. Surfaces on shallow sloping hard bottoms receive higher levels of irradiance that benefits coral growth. Optimal levels of water motion facilitate sediment removal and promote coral recruitment and growth. The design of the Kahului Harbor submerged multi-purpose structure serves as a model for design of shoreline modification that enhances, rather than degrades, the local coral reef environment.

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Estimation of Sand Distribution in Coral Reef Environment using Colour Segmentation and Colour Thresholding Methods

Universiti Malaysia Terengganu Journal of Undergraduate Research ◽

10.46754/umtjur.v1i3.83 ◽

2019 ◽

Vol 1 (3) ◽

pp. 96-104

Author(s):

Pauleen Ong ◽

Muhammad Suzuri Hitam ◽

Zainuddin Bachok ◽

Mohd Safuan Che Din

Keyword(s):

Coral Reef ◽

Extraction Methods ◽

Colour Difference ◽

Reef Environment ◽

Still Images ◽

Point Count ◽

Automatic Computer ◽

Computer Based ◽

Coral Reef Environment ◽

Colour Segmentation

At present, marine scientists employ manual method to estimate the components in coral reef environment, where Coral Point Count with Excel extensions (CPCe) software is used to determine the coral reef components and substrate coverage. This manual process is laborious and time consuming, and needs experts to conduct the survey. In this paper, a prototype for estimating the distribution of sand cover in coral reef environment from still images by using colour extraction methods was introduced. The colour segmentation called delta E was used to calculate the colour difference between two colour samples. Another method used was colour threshold by setting the range of sand colour pixels. The system was developed by using a MATLAB software with image processing toolbox. The developed system was semi-automatic computer-based system that can be used by researchers even with little knowledge and experience to estimate the percentage of sand coverage in coral reef still images.

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Change Detection in Coral Reef Environment Using High-Resolution Images: Comparison of Object-Based and Pixel-Based Paradigms

ISPRS International Journal of Geo-Information ◽

10.3390/ijgi7110441 ◽

2018 ◽

Vol 7 (11) ◽

pp. 441 ◽

Cited By ~ 11

Author(s):

Zhenjin Zhou ◽

Lei Ma ◽

Tengyu Fu ◽

Ge Zhang ◽

Mengru Yao ◽

...

Keyword(s):

Coral Reef ◽

Change Detection ◽

Accuracy Assessment ◽

Detection Accuracy ◽

Reef Environment ◽

Object Based ◽

Coral Reef Environment ◽

Study Sites ◽

Object Area ◽

Segmentation Image

Despite increases in the spatial resolution of satellite imagery prompting interest in object-based image analysis, few studies have used object-based methods for monitoring changes in coral reefs. This study proposes a high accuracy object-based change detection (OBCD) method intended for coral reef environment, which uses QuickBird and WorldView-2 images. The proposed methodological framework includes image fusion, multi-temporal image segmentation, image differencing, random forests models, and object-area-based accuracy assessment. For validation, we applied the method to images of four coral reef study sites in the South China Sea. We compared the proposed OBCD method with a conventional pixel-based change detection (PBCD) method by implementing both methods under the same conditions. The average overall accuracy of OBCD exceeded 90%, which was approximately 20% higher than PBCD. The OBCD method was free from salt-and-pepper effects and was less prone to images misregistration in terms of change detection accuracy and mapping results. The object-area-based accuracy assessment reached a higher overall accuracy and per-class accuracy than the object-number-based and pixel-number-based accuracy assessment.

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