Lure-assisted visual census: a new method for quantifying fish abundance, behaviour, and predation risk in shallow coastal habitats

2010 ◽  
Vol 61 (12) ◽  
pp. 1349 ◽  
Author(s):  
Claudia Kruschel ◽  
Stewart Schultz
Keyword(s):  
Predation Risk ◽  
Structural Complexity ◽  
Marine Ecology ◽  
Fish Abundance ◽  
Coastal Habitats ◽  
Field Methods ◽  
Bare Sediment ◽  
Faunal Abundance ◽  
Abundance And Diversity ◽  
Ambush Predators

Understanding the causes of variation in faunal abundance and diversity across shallow coastal habitats is a fundamental goal of marine ecology. Field methods for inferring a habitat effect on population density and predation risk are informative only if method biases are equal across habitats and species. We hypothesised that observation of fixed lures has a species by bias interaction if sampled species have different modes of predation, and that these biases are overcome by use of moving lures. We tested this hypothesis by observation of fixed and moving lures within seagrass and bare sediment in the Novigrad Sea, Croatian Adriatic. Both methods showed that ambush predators peaked in seagrass, wait–chasers peaked over bare sediment, and move–chasers were abundant in both. Stationary lures underestimated wait–chase and wait–ambush predators relative to moving lures, whereas moving lures did not underestimate the density of predators. These results indicate that stationary lures can underestimate both fish abundance and predation risk in the presence of waiting predators, and that if waiting predators are more abundant in structured habitat, then stationary lures will underestimate the predation risk within such habitats. Use of moving lures may be preferable for comparing habitats differing in structural complexity and frequency of predation modes.

Assemblages of fish along a mangrove - mudflat gradient in temperate Australia

2009 ◽  
Vol 60 (1) ◽  
pp. 1 ◽  
Author(s):  
Nicholas Leslie Payne ◽  
Bronwyn May Gillanders
Keyword(s):  
Fish Species ◽  
Fish Assemblages ◽  
Structural Complexity ◽  
Fish Abundance ◽  
Fish Distribution ◽  
Individual Species ◽  
Total Abundance ◽  
Total Fish ◽  
Abundance And Diversity ◽  
Habitat Scale

Mangroves are considered to support rich assemblages of fish and invertebrates. Fishes inhabiting mangrove habitats and at various distances from mangroves across mudflats were sampled to: (1) compare fish assemblages between habitats; and (2) determine the influence of mangrove proximity on fish abundance and diversity in three southern Australian estuaries between November 2005 and January 2006. Based on their distribution, fish species were classified as mangrove residents, mudflat residents, generalists or rare species. The assemblage structure of fish in mangroves differed from assemblages 500 m away; however, neither total abundance nor species richness differed significantly between mangroves and mudflats. Mangrove residents and Aldrichetta forsteri (yellow-eyed mullet) displayed strong associations with mangrove habitats, whereas mudflat residents were associated with mudflat habitats. No other fish groups or individual species occurred in higher abundances in either habitat. Total fish abundance, mangrove residents and A. forsteri were positively correlated with pneumatophore density, indicating that the structural complexity of the mangroves might influence the distributions of certain fish species. The current study demonstrated that mangrove habitats in temperate Australia support no greater abundance or diversity of fish than adjacent mudflat habitats and that mangrove proximity does not influence fish distribution at a habitat scale.

scholarly journals Convolutional Neural Networks Predict Fish Abundance from Underlying Coral Reef Texture

2018 ◽  
Author(s):  
Grace Young ◽  
Vassileios Balntas ◽  
Victor Prisacariu
Keyword(s):  
Spatial Scales ◽  
A Priori ◽  
3D Structure ◽  
Three Dimensional ◽  
Structural Complexity ◽  
3D Models ◽  
Fish Abundance ◽  
Ecological Patterns ◽  
Abundance And Diversity ◽  
First Time

Coral reefs are among the most biodiverse ecosystems on Earth in large part owing to their unique three-dimensional (3D) structure, which provides niches for a variety of species. Metrics of structural complexity have been shown to correlate with the abundance and diversity of fish and other marine organisms, but they are imperfect representations of a surface that can oversimplify key structural elements and bias discoveries. Moreover, they require researchers to make relatively uninformed guesses about the features and spatial scales relevant to species of interest. This paper introduces a machine-learning method for automating inferences about fish abundance from reef 3D models. It demonstrates the capacity of a convolutional neural network (ConvNet) to learn ecological patterns that are extremely subtle, if not invisible, to the human eye. It is the first time in the literature that no a priori assumptions are made about the bathymetry–fish relationship.

Community dynamics in Fijian coral reef fish communities vary with conservation and shark-based tourism

2019 ◽  
Vol 25 (4) ◽  
pp. 363
Author(s):  
Mallory G. McKeon ◽  
Joshua A. Drew
Keyword(s):  
Community Dynamics ◽  
Local Community ◽  
Census Data ◽  
Fish Abundance ◽  
Full Potential ◽  
Community Members ◽  
Composition And Structure ◽  
Feeding Methods ◽  
Abundance And Diversity ◽  
Unprotected Area

Marine protected areas (MPAs) effectively improve the biomass and diversity in heavily exploited marine systems, but often fail to reach their full potential because they require more space, time, and consistency of regulation. Recently, shark-based tourism, which utilises some of the remaining shark strongholds as tourism hotspots, has brought about increased awareness to exploited reef systems. In Fiji, specifically, shark diving companies include local community members in their operations to promote better understanding of their reefs. We seek to investigate whether seemingly denser shark populations during feeding times influence community composition and structure. Visual census data were collected from 50-m belt transects at four different reefs in Fiji: two MPAs with shark-based ecotourism with food provisioning, one MPA without shark-based ecotourism, and one unprotected area without shark-based tourism. Paradoxically, indices of evenness and diversity were highest in the non-protected site. However, there was significantly higher fish abundance and species diversity within reserves than outside of reserves. Within reserves, sites with shark feeding had lower fish abundance and higher richness, diversity, and evenness. Mean trophic level was highest at sites with shark feeding. Use of chum increased average fish abundance and diversity within shark-dive sites. These results indicate that there are evident differences between MPAs that do and do not offer trophic supplementation for shark-based ecotourism. Thus, tourism may be facilitating a shift of ecosystem composition in such areas. Furthermore, the results suggest that feeding methods may augment the impacts of shark-based tourism on the reef at large.

Structural Complexity and Distance from Source Habitat Determine Invertebrate Abundance and Diversity

Biotropica ◽  
2011 ◽  
Vol 43 (6) ◽  
pp. 738-745 ◽  
Author(s):  
Roger P. Mormul ◽  
Sidinei M. Thomaz ◽  
Alice M. Takeda ◽  
Rômulo D. Behrend
Keyword(s):  
Structural Complexity ◽  
Invertebrate Abundance ◽  
Abundance And Diversity

scholarly journals The comparative effects of habitat complexity on faunal assemblages of northern temperate artificial and natural reefs

2009 ◽  
Vol 66 (4) ◽  
pp. 691-698 ◽  
Author(s):  
W. R. Hunter ◽  
M. D. J. Sayer
Keyword(s):  
Habitat Complexity ◽  
Artificial Reef ◽  
Structural Complexity ◽  
Marine Species ◽  
Rocky Reef ◽  
Faunal Assemblages ◽  
Faunal Abundance ◽  
Concrete Blocks ◽  
Belt Transect ◽  
Natural Reefs

Abstract Hunter, W. R., and Sayer, M. D. J. 2009. The comparative effects of habitat complexity on faunal assemblages of northern temperate artificial and natural reefs. – ICES Journal of Marine Science, 66: 691–698. Several north temperate marine species were recorded on subtidal hard-substratum reef sites selected to produce a gradient of structural complexity. The study employed an established scuba-based census method, the belt transect. The three types of reef examined, with a measured gradient of increasing structural complexity, were natural rocky reef, artificial reef constructed of solid concrete blocks, and artificial reef made of concrete blocks with voids. Surveys were undertaken monthly over a calendar year using randomly placed fixed rope transects. For a number of conspicuous species of fish and invertebrates, significant differences were found between the levels of habitat complexity and abundance. Overall abundance for many of the species examined was 2–3 times higher on the complex artificial habitats than on simple artificial or natural reef habitats. The enhanced habitat availability produced by the increased structural complexity delivered through specifically designed artificial reefs may have the potential to augment faunal abundance while promoting species diversity.

scholarly journals Associations between Benthic Cover and Habitat Complexity Metrics Obtained from 3D Reconstruction of Coral Reefs at Different Resolutions

2020 ◽  
Vol 12 (6) ◽  
pp. 1011 ◽  
Author(s):  
Atsuko Fukunaga ◽  
John H. R. Burns ◽  
Kailey H. Pascoe ◽  
Randall K. Kosaki
Keyword(s):  
Fractal Dimension ◽  
Coral Reefs ◽  
Habitat Structure ◽  
Coral Cover ◽  
Three Dimensional ◽  
Structural Complexity ◽  
Coralline Algae ◽  
Crustose Coralline Algae ◽  
Surface Areas ◽  
Abundance And Diversity

Quantifying the three-dimensional (3D) habitat structure of coral reefs is an important aspect of coral reef monitoring, as habitat architecture affects the abundance and diversity of reef organisms. Here, we used photogrammetric techniques to generate 3D reconstructions of coral reefs and examined relationships between benthic cover and various habitat metrics obtained at six different resolutions of raster cells, ranging from 1 to 32 cm. For metrics of 3D structural complexity, fractal dimension, which utilizes information on 3D surface areas obtained at different resolutions, and vector ruggedness measure (VRM) obtained at 1-, 2- or 4-cm resolution correlated well with benthic cover, with a relatively large amount of variability in these metrics being explained by the proportions of corals and crustose coralline algae. Curvature measures were, on the other hand, correlated with branching and mounding coral cover when obtained at 1-cm resolution, but the amount of variability explained by benthic cover was generally very low when obtained at all other resolutions. These results show that either fractal dimension or VRM obtained at 1-, 2- or 4-cm resolution, along with curvature obtained at 1-cm resolution, can effectively capture the 3D habitat structure provided by specific benthic organisms.

Comparative cleaning behaviour of Pederson's cleaner shrimp (Ancylomenes pedersoni) between geographically close yet ecologically dissimilar coral reef habitats

2020 ◽  
Vol 100 (7) ◽  
pp. 1093-1106
Author(s):  
Joseph J. Romain ◽  
Dan A. Exton ◽  
David J. Smith ◽  
Amelia Rose ◽  
Clayton Vondriska ◽  
...  
Keyword(s):  
Coral Reef ◽  
Coral Cover ◽  
Fish Population ◽  
Fish Abundance ◽  
Environmental Drivers ◽  
Variable Nature ◽  
Total Fish ◽  
Abundance And Diversity ◽  
Lutjanus Apodus ◽  
Cleaner Shrimp

AbstractCleaning mutualisms are important interactions on coral reefs. Intraspecific variation in cleaning rate and behaviour occurs geographically and is often attributed to local processes. However, our understanding of fine-scale variation is limited, but would allow us to control for geography and region-specific behavioural patterns. Here, we compare the cleaning activity of Pederson's cleaner shrimp (Ancylomenes pedersoni) on two neighbouring, yet ecologically dissimilar, reef systems in Honduras: Banco Capiro, an offshore bank close to significant land runoff with high coral cover but a depleted fish population, and an oligotrophic fringing reef around the island of Utila, with lower coral cover but high fish abundance and diversity. The proportion of realized to potential fish clientele was <60% at both sites, and the composition of clientele was neither reflective of the demographics of the resident assemblages at each site nor similar between sites. Parrotfishes represented 13–15% of total fish abundance at both sites yet accounted for >50% (Banco Capiro) and 10% (Utila) of all cleans. Conversely, the schoolmaster snapper (Lutjanus apodus) represented ~1% of total fish abundance at both sites yet accounted for 40% (Utila) and 1% (Banco Capiro) of all cleans. After standardizing our cleaning rate data by clientele abundance, we find that clientele at Banco Capiro engage in over four times as many cleaning encounters per hour with A. pedersoni than at Utila. Our study highlights the variable nature of coral reef cleaning interactions and the need to better understand the ecological and environmental drivers of this biogeographic variation.

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