The importance of sponges and mangroves in supporting fish communities in degraded coral reefs in Caribbean Panama

Fish communities associated with coral reefs worldwide are threatened by overexploitation and other human impacts such as bleaching events that cause habitat degradation. We assessed the fish community on coral reefs on the Caribbean coast of Panama, as well as those associated with mangrove and seagrass habitats, to explore the influences of habitat cover, connectivity and environmental characteristics in sustaining biomass, richness and trophic structure in a degraded tropical ecosystem. Overall, 94 % of all fishes across all habitat types were of small body size (≤11 cm), with communities dominated by fishes that usually live in habitats of low complexity, such as Pomacentridae (damselfishes) and Gobiidae (gobies). Moreover, total fish biomass was very low, small fishes from low trophic levels were over-represented, and top predators were under-represented relative to other Caribbean reefs. For example, herbivorous/omnivorous/detrivorous fishes (trophic level 2-2.7) comprised 37 % of total fish biomass, with the diminutive parrotfish Scarus iseri comprising 72 % of the parrotfish biomass. However, the abundance of sponges and proximity of mangroves were found to be important positive drivers of reef fish richness, biomass and trophic structure on a given reef, presumably by promoting functional processes of ecosystems. The masked goby (Coryphopterus personata) was a strong indicator of reef degradation, apparently benefiting from the reduced density of large predators on local reefs. The damselfish Abudefduf saxatilis was more common on reefs with high sponge cover, and also to proximity to mangroves. Our study suggests that a diverse fish community can persist on degraded coral reefs, and that the availability of habitat forming organisms other than corals, including sponges and mangroves, and their arrangement on the landscape, is critical to the maintenance of functional processes in these ecosystems.

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The importance of sponges and mangroves in supporting fish communities on degraded coral reefs in Caribbean Panama

PeerJ ◽

10.7717/peerj.4455 ◽

2018 ◽

Vol 6 ◽

pp. e4455 ◽

Cited By ~ 8

Author(s):

Janina Seemann ◽

Alexandra Yingst ◽

Rick D. Stuart-Smith ◽

Graham J. Edgar ◽

Andrew H. Altieri

Keyword(s):

Species Richness ◽

Coral Reefs ◽

Trophic Structure ◽

Small Body ◽

Fish Communities ◽

Trophic Levels ◽

Fish Biomass ◽

Seagrass Meadows ◽

Total Fish ◽

The Caribbean

Fish communities associated with coral reefs worldwide are threatened by habitat degradation and overexploitation. We assessed coral reefs, mangrove fringes, and seagrass meadows on the Caribbean coast of Panama to explore the influences of their proximity to one another, habitat cover, and environmental characteristics in sustaining biomass, species richness and trophic structure of fish communities in a degraded tropical ecosystem. We found 94% of all fish across all habitat types were of small body size (≤10 cm), with communities dominated by fishes that usually live in habitats of low complexity, such as Pomacentridae (damselfishes) and Gobiidae (gobies). Total fish biomass was very low, with the trend of small fishes from low trophic levels over-represented, and top predators under-represented, relative to coral reefs elsewhere in the Caribbean. For example, herbivorous fishes comprised 27% of total fish biomass in Panama relative to 10% in the wider Caribbean, and the small parrotfishScarus isericomprised 72% of the parrotfish biomass. We found evidence that non-coral biogenic habitats support reef-associated fish communities. In particular, the abundance of sponges on a given reef and proximity of mangroves were found to be important positive correlates of reef fish species richness, biomass, abundance and trophic structure. Our study indicates that a diverse fish community can persist on degraded coral reefs, and that the availability and arrangement within the seascape of other habitat-forming organisms, including sponges and mangroves, is critical to the maintenance of functional processes in such ecosystems.

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Fishing degrades size structure of coral reef fish communities

10.7287/peerj.preprints.2118 ◽

2016 ◽

Author(s):

James PW Robinson ◽

Ivor D Williams ◽

Andrew M Edwards ◽

Jana McPherson ◽

Lauren Yeager ◽

...

Keyword(s):

Coral Reef ◽

Reef Fish ◽

Fish Community ◽

Size Structure ◽

Fish Communities ◽

Fish Biomass ◽

Community Size ◽

Size Spectra ◽

Coral Reef Ecosystems ◽

Total Fish

Fishing pressure on coral reef ecosystems has been frequently linked to reductions of large fishes and reef fish biomass. Associated impacts on overall community structure are, however, less clear. In size-structured aquatic ecosystems, fishing impacts are commonly quantified using size spectra, which describe the distribution of individual body sizes within a community. We examined the size spectra of coral reef fish communities at 38 US-affiliated Pacific islands, spanning from near pristine to highly human populated. Reef fish community size spectra slopes ‘steepened’ steadily with increasing human population and proximity to market due to a reduction in the relative biomass of large fishes and an increase in the dominance of small fishes. In contrast, total fish community biomass was substantially lower on inhabited islands than uninhabited ones, regardless of human population density. Comparing the relationship between size spectra and reef fish biomass, we found that on populated islands size spectra steepened linearly with declining biomass, whereas on uninhabited islands size spectra and biomass were unrelated. Size spectra slopes also were steeper in regions of low sea surface temperature but were insensitive to variation in other environmental and geomorphic covariates. In contrast, reef fish biomass was highly sensitive to biophysical conditions, being influenced by oceanic productivity, sea surface temperature, island type, and habitat complexity. Our results suggest that community size structure is more robust than total fish biomass to increasing human presence and that size spectra are reliable indicators of exploitation impacts across regions of different fish community compositions, environmental drivers, and fisheries types. Size-based approaches that link directly to functional properties of fish communities, and are relatively insensitive to abiotic variation across biogeographic regions, offer great potential for developing our understanding of fishing impacts in coral reef ecosystems.

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Fishing degrades size structure of coral reef fish communities

10.7287/peerj.preprints.2118v1 ◽

2016 ◽

Author(s):

James PW Robinson ◽

Ivor D Williams ◽

Andrew M Edwards ◽

Jana McPherson ◽

Lauren Yeager ◽

...

Keyword(s):

Coral Reef ◽

Reef Fish ◽

Fish Community ◽

Size Structure ◽

Fish Communities ◽

Fish Biomass ◽

Community Size ◽

Size Spectra ◽

Coral Reef Ecosystems ◽

Total Fish

Fishing pressure on coral reef ecosystems has been frequently linked to reductions of large fishes and reef fish biomass. Associated impacts on overall community structure are, however, less clear. In size-structured aquatic ecosystems, fishing impacts are commonly quantified using size spectra, which describe the distribution of individual body sizes within a community. We examined the size spectra of coral reef fish communities at 38 US-affiliated Pacific islands, spanning from near pristine to highly human populated. Reef fish community size spectra slopes ‘steepened’ steadily with increasing human population and proximity to market due to a reduction in the relative biomass of large fishes and an increase in the dominance of small fishes. In contrast, total fish community biomass was substantially lower on inhabited islands than uninhabited ones, regardless of human population density. Comparing the relationship between size spectra and reef fish biomass, we found that on populated islands size spectra steepened linearly with declining biomass, whereas on uninhabited islands size spectra and biomass were unrelated. Size spectra slopes also were steeper in regions of low sea surface temperature but were insensitive to variation in other environmental and geomorphic covariates. In contrast, reef fish biomass was highly sensitive to biophysical conditions, being influenced by oceanic productivity, sea surface temperature, island type, and habitat complexity. Our results suggest that community size structure is more robust than total fish biomass to increasing human presence and that size spectra are reliable indicators of exploitation impacts across regions of different fish community compositions, environmental drivers, and fisheries types. Size-based approaches that link directly to functional properties of fish communities, and are relatively insensitive to abiotic variation across biogeographic regions, offer great potential for developing our understanding of fishing impacts in coral reef ecosystems.

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Littoral Fish Communities in Southern Quebec Lakes: Relationships with Limnological and Prey Resource Variables

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f94-112 ◽

1994 ◽

Vol 51 (5) ◽

pp. 1128-1138 ◽

Cited By ~ 27

Author(s):

Clay L. Pierce ◽

Joseph B. Rasmussen ◽

William C. Leggett

Keyword(s):

Species Richness ◽

Fish Species ◽

Yellow Perch ◽

Fish Communities ◽

Principal Component ◽

Lepomis Gibbosus ◽

Fish Biomass ◽

Littoral Fish ◽

Total Fish ◽

Invertebrate Biomass

We assessed species richness, biomass, and community type of littoral fish in 10 southern Quebec lakes in relation to several limnological and prey resource variables. Lake, yearly, and seasonal variation in biomass was evaluated by quantitative, replicated seining. Species richness averaged 12.8 in our lakes, and 24 species were collected overall. Total littoral fish biomass averaged 13.5 g∙m−2 overall and varied significantly among lakes (range 6.1–26.9 g∙m−2) and between early and late summer. Yellow perch (Perca flavescens), golden shiner (Notemigonus crysoleucas), and pumpkinseed (Lepomis gibbosus) occurred in all lakes and were the most abundant species overall, averaging 57% of the total fish biomass. Principal component ordination of littoral fish communities showed little evidence for aggregation of community types. Species richness was positively correlated with lake surface area (r2 = 0.62), as has been shown in other studies. Total fish biomass was positively correlated with biomass of chironomids (r2 = 0.57), which constituted 24% of the littoral invertebrate biomass in our lakes and are important prey of many fish species. We found no significant correlation between total fish biomass and total invertebrate biomass or between biomass of any of the dominant fish species and limnological or prey variables.

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Does rapid scavenging hide non-predation mortality in coral-reef communities?

Marine and Freshwater Research ◽

10.1071/mf10194 ◽

2011 ◽

Vol 62 (5) ◽

pp. 510 ◽

Cited By ~ 7

Author(s):

Andrew Rassweiler ◽

Thomas Rassweiler

Keyword(s):

Coral Reefs ◽

Fish Community ◽

Juvenile Fish ◽

Trophic Levels ◽

Fish Mortality ◽

Adult Fish ◽

Predation Mortality ◽

Reef Fish Community ◽

Main Pathway

Predation is assumed to be a principal cause of adult fish mortality on coral reefs, and therefore a main pathway by which biomass is passed to higher trophic levels. However, the strength of predation has mostly been demonstrated on juvenile fish, and even with juveniles, when predators are excluded, substantial mortality still occurs. Mortality from causes other than predation is rarely considered, because carrion is not common on coral reefs, but the strength of this inference depends crucially on the rate of scavenging. We tested the hypothesis that removal of carrion through scavenging may be very rapid by placing undamaged fish carcasses of a range of species and sizes on reefs in Curaçao, monitoring their rate of disappearance. All carrion was consumed within 24 h and at such rapid rates that, if non-predation mortality were occurring, it would leave little evidence on the reef. Carcasses were consumed almost exclusively by fish, mainly reef-associated piscivores, indicating that scavenged biomass is tightly recycled within the reef fish community. The results of this study suggest that more attention should be paid to quantifying the role of non-predation sources of fish mortality in reef ecosystems.

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Biodiversity–ecosystem functioning relationships in fish communities: biomass is related to evenness and the environment, not to species richness

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2019.1189 ◽

2019 ◽

Vol 286 (1906) ◽

pp. 20191189 ◽

Cited By ~ 5

Author(s):

Aurore Maureaud ◽

Dorothee Hodapp ◽

P. Daniël van Denderen ◽

Helmut Hillebrand ◽

Henrik Gislason ◽

...

Keyword(s):

Species Richness ◽

Ecosystem Functioning ◽

Structural Equation ◽

Fish Assemblages ◽

Current Knowledge ◽

Marine Ecosystem ◽

Experimental Studies ◽

Fish Communities ◽

Trophic Levels ◽

Fish Biomass

The relationship between biodiversity and ecosystem functioning (BEF) is a topic of considerable interest to scientists and managers because a better understanding of its underlying mechanisms may help us mitigate the consequences of biodiversity loss on ecosystems. Our current knowledge of BEF relies heavily on theoretical and experimental studies, typically conducted on a narrow range of spatio-temporal scales, environmental conditions, and trophic levels. Hence, whether a relationship holds in the natural environment is poorly understood, especially in exploited marine ecosystems. Using large-scale observations of marine fish communities, we applied a structural equation modelling framework to investigate the existence and significance of BEF relationships across northwestern European seas. We find that ecosystem functioning, here represented by spatial patterns in total fish biomass, is unrelated to species richness—the most commonly used diversity metric in BEF studies. Instead, community evenness, differences in species composition, and abiotic variables are significant drivers. In particular, we find that high fish biomass is associated with fish assemblages dominated by a few generalist species of a high trophic level, who are able to exploit both the benthic and pelagic energy pathway. Our study provides a better understanding of the mechanisms behind marine ecosystem functioning and allows for the integration of biodiversity into management considerations.

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Hybridisation on coral reefs and the conservation of evolutionary novelty

Current Zoology ◽

10.1093/czoolo/61.1.132 ◽

2015 ◽

Vol 61 (1) ◽

pp. 132-145 ◽

Cited By ~ 39

Author(s):

Zoe T. Richards ◽

Jean-Paul A. Hobbs

Keyword(s):

Coral Reefs ◽

Habitat Degradation ◽

Human Impacts ◽

Incomplete Lineage Sorting ◽

Reef Fishes ◽

Evolutionary Novelty ◽

Lineage Sorting ◽

Conservation Policies ◽

Alternative Hypotheses ◽

Reverse Speciation

Abstract Hybridisation was traditionally considered rare on coral reefs. However, a rapid increase in hybrid studies over the last 20 years has revealed that hybridisation on coral reefs is common and widespread. In this review, we summarise the growing body of evidence arising from studies on stony corals and reef fishes to verify the occurrence of hybridisation, and we examine the influence hybridisation has had on the enormous level of biodiversity present on coral reefs. We discuss the challenges of distinguishing hybridisation from alternative hypotheses (e.g. incomplete lineage sorting). This review also explores the evolutionary consequences of hybridisation, which range from increasing genetic diversity and the production of novel lineages that may outperform the parent species, to reverse speciation and extinction by genetic swamping. Instances of hybridisation can be natural or occur as a result of human impacts (e.g. habitat degradation) and distinguishing between these two very different causal mechanisms is important for management. Currently, the legislative status of hybrids is unclear and hybrids are rarely protected in conservation programs. Failing to adequately manage hybridisation and hybrid lineages may lead to potential losses of evolutionary novelty, declines in phylogenetic diversity or species extinctions. To conserve existing coral reef biodiversity, and the processes that generate biodiversity, conservation policies must be re-defined and instances of hybridisation must be assessed and managed on a case-by-case basis.

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Gravity of human impacts mediates coral reef conservation gains

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1708001115 ◽

2018 ◽

Vol 115 (27) ◽

pp. E6116-E6125 ◽

Cited By ~ 55

Author(s):

Joshua E. Cinner ◽

Eva Maire ◽

Cindy Huchery ◽

M. Aaron MacNeil ◽

Nicholas A. J. Graham ◽

...

Keyword(s):

Coral Reefs ◽

Human Impacts ◽

Global Analysis ◽

Marine Reserves ◽

Relative Difference ◽

Ecosystem Functions ◽

Fish Biomass ◽

High Compliance ◽

Top Predators ◽

Trade Offs

Coral reefs provide ecosystem goods and services for millions of people in the tropics, but reef conditions are declining worldwide. Effective solutions to the crisis facing coral reefs depend in part on understanding the context under which different types of conservation benefits can be maximized. Our global analysis of nearly 1,800 tropical reefs reveals how the intensity of human impacts in the surrounding seascape, measured as a function of human population size and accessibility to reefs (“gravity”), diminishes the effectiveness of marine reserves at sustaining reef fish biomass and the presence of top predators, even where compliance with reserve rules is high. Critically, fish biomass in high-compliance marine reserves located where human impacts were intensive tended to be less than a quarter that of reserves where human impacts were low. Similarly, the probability of encountering top predators on reefs with high human impacts was close to zero, even in high-compliance marine reserves. However, we find that the relative difference between openly fished sites and reserves (what we refer to as conservation gains) are highest for fish biomass (excluding predators) where human impacts are moderate and for top predators where human impacts are low. Our results illustrate critical ecological trade-offs in meeting key conservation objectives: reserves placed where there are moderate-to-high human impacts can provide substantial conservation gains for fish biomass, yet they are unlikely to support key ecosystem functions like higher-order predation, which is more prevalent in reserve locations with low human impacts.

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