Single and joint effects of regional- and local-scale variables on tropical seagrass fish assemblages

Aller, Elisa Alonso; Gullström, Martin; Maarse, Floriaan K J Eveleens; Gren, Michaela; Nordlund, Lina Mtwana; Jiddawi, Narriman; Eklöf, Johan

doi:10.1007/s00227-014-2514-7

Cited by 22 publications

(19 citation statements)

References 56 publications

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“…The important role of seagrasses as fish habitats has been studied primarily in temperate areas, but also in the tropics, where seagrass habitat complexity can play an important role. A recent study conducted around the nearby island Zanzibar (Tanzania) found a clear, positive effect of the cover of the larger, structurally more complex seagrass species Thalassodendron ciliatum on seagrass fish communities [ 25 ]. Moreover, presence and areal cover of seagrass beds has been shown to be highly important for fish biomass not only in seagrass beds [ 5 , 6 , 21 ], but also in nearby coral reefs [ 26 , 51 ].…”

Section: Discussionmentioning

confidence: 99%

“…In contrast to coral reefs, seagrass beds have only more recently been acknowledged as important providers of ecosystem services [ 5 , 6 , 21 , 22 ], including fisheries [ 23 , 24 ]. Even though many seagrass fish species are less sedentary and territorial than coral reef fish, seagrass cover affects fish communities both on the local [ 25 ] and regional scale [e.g. 26 ].…”

Section: Introductionmentioning

confidence: 99%

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Community- and government-managed marine protected areas increase fish size, biomass and potential value

Chirico¹,

McClanahan²,

Eklöf³

2017

PLoS ONE

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Government-managed marine protected areas (MPAs) can restore small fish stocks, but have been heavily criticized for excluding resource users and creating conflicts. A promising but less studied alternative are community-managed MPAs, where resource users are more involved in MPA design, implementation and enforcement. Here we evaluated effects of government- and community-managed MPAs on the density, size and biomass of seagrass- and coral reef-associated fish, using field surveys in Kenyan coastal lagoons. We also assessed protection effects on the potential monetary value of fish; a variable that increases non-linearly with fish body mass and is particularly important from a fishery perspective. We found that two recently established community MPAs (< 1 km2 in size, ≤ 5 years of protection) harbored larger fish and greater total fish biomass than two fished (open access) areas, in both seagrass beds and coral reefs. As expected, protection effects were considerably stronger in the older and larger government MPAs. Importantly, across management and habitat types, the protection effect on the potential monetary value of the fish was much stronger than the effects on fish biomass and size (6.7 vs. 2.6 and 1.3 times higher value in community MPAs than in fished areas, respectively). This strong effect on potential value was partly explained by presence of larger (and therefore more valuable) individual fish, and partly by higher densities of high-value taxa (e.g. rabbitfish). In summary, we show that i) small and recently established community-managed MPAs can, just like larger and older government-managed MPAs, play an important role for local conservation of high-value fish, and that ii) these effects are equally strong in coral reefs as in seagrass beds; an important habitat too rarely included in formal management. Consequently, community-managed MPAs could benefit both coral reef and seagrass ecosystems and provide spillover of valuable fish to nearby fisheries.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Community- and government-managed marine protected areas increase fish size, biomass and potential value

Chirico¹,

McClanahan²,

Eklöf³

2017

PLoS ONE

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“…In tropical reef environments, spatial heterogeneity is a strong driver of distribution and diversity patterns of reef fish (Chabanet et al 1997;Sabater and Tofaeono 2007;Messmer et al 2011;Samoilys et al 2018), where characteristics such as structural complexity and rugosity are important predictors of fish assemblage structure and abundance (Bell and Galzin 1984;Gratwicke and Speight 2005;Graham and Nash 2013). In submerged macrophyte habitats, canopy height and cover have been shown to structure fish assemblages in both tropical seagrass meadows (Gullström et al 2008;Alonso Aller et al 2014) and macroalgal beds (Wenger et al 2018;van Lier et al 2018). However, environmental factors as such may impact coral fish communities on multiple spatial and temporal scales as some fish species might have shifting habitat preferences during different ontogenetic stages and hence utilize alternative habitats like seagrass meadows, mangroves and/or macroalgal beds during their juvenile life stage (Nagelkerken et al 2000;Wilson et al 2010;Berkström et al 2012).…”

Section: Introductionmentioning

confidence: 99%

“…The majority of herbivoremacroalgae-coral studies have been performed in Kenya (see, e.g., McClanahan et al 1999McClanahan and Arthur 2001), where top-down control in the form of herbivory has been identified as an important predictor for macroalgae abundance on coral reefs Mörk et al 2009). Likewise, a study in seagrass meadows from Zanzibar has shown that both top-down (fishing) and bottom-up (seagrass density) control explained fish assemblage structure (Alonso Aller et al 2014). However, patterns as such might vary across the WIO region, in different habitat types and with different fishing pressure.…”

Section: Introductionmentioning

confidence: 99%

Contrasting distribution and foraging patterns of herbivorous and detritivorous fishes across multiple habitats in a tropical seascape

et al. 2019

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Understanding drivers behind patterns of functionally important groups of fishes is crucial for successful management and conservation of tropical seascapes. Herbivorous fishes are the most prominent consumers of marine primary production which can have profound effects on reef resilience. We explored environmental variables affecting distribution and foraging patterns of herbivorous and detritivorous fish assemblages (siganids, acanthurids and parrotfish) across distinct shallow-water habitats (coral reefs, macroalgae beds and seagrass meadows) during September-November 2016 at Mafia Island, Tanzania (8°00′S, 39°41′E). We performed underwater visual census to quantify fish assemblages, measured habitat features, deployed macroalgal assays and conducted inventories of grazing scars. Multi-dimensional scaling and mixed-effects linear models were used to evaluate differences in fish assemblages and environmental variables influencing abundance and foraging patterns of fishes. Fish communities of focal functional groups differed among habitats. Abundance of herbivores and detritivores as well as relative browsing and scraping was highest on coral reefs compared to macroalgae and seagrass meadows. Adult fish were more abundant on coral reefs while juveniles were abundant in macroalgal beds. Coral cover and crustose coralline algal cover had a positive effect on the abundance of fish in coral reef areas, while macroalgal cover had a negative effect. Contrastingly, in macroalgae habitats, macroalgal cover had a positive effect on the abundance of parrotfish. These results highlight the importance of considering connectivity between macroalgal beds and coral reefs through ontogenetic shifts in habitat use by primarily microphagous parrotfish and of incorporating a range of habitats within coastal management plans.

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“…In both tropical and temperate regions, seagrass structural complexity (e.g. cover, shoot density, height) can strongly affect associated fish communities [ 36 – 38 ]. As the growth, and therefore cover and distribution of seagrasses, often changes with season [ 39 – 41 ], seasonality can indirectly affect fish communities through changes in habitat extent and quality [ 42 ].…”

Section: Introductionmentioning

confidence: 99%

Marine protected areas increase temporal stability of community structure, but not density or diversity, of tropical seagrass fish communities

2017

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Marine protected areas (MPAs) have been shown to increase long-term temporal stability of fish communities and enhance ecosystem resilience to anthropogenic disturbance. Yet, the potential ability of MPAs to buffer effects of environmental variability at shorter time scales remains widely unknown. In the tropics, the yearly monsoon cycle is a major natural force affecting marine organisms in tropical regions, and its timing and severity are predicted to change over the coming century, with potentially severe effects on marine organisms, ecosystems and ecosystem services. Here, we assessed the ability of MPAs to buffer effects of monsoon seasonality on seagrass-associated fish communities, using a field survey in two MPAs (no-take zones) and two unprotected (open-access) sites around Zanzibar (Tanzania). We assessed the temporal stability of fish density and community structure within and outside MPAs during three monsoon seasons in 2014–2015, and investigated several possible mechanisms that could regulate temporal stability. Our results show that MPAs did not affect fish density and diversity, but that juvenile fish densities were temporally more stable within MPAs. Second, fish community structure was more stable within MPAs for juvenile and adult fish, but not for subadult fish or the total fish community. Third, the observed effects may be due to a combination of direct and indirect (seagrass-mediated) effects of seasonality and, potentially, fluctuating fishing pressure outside MPAs. In summary, these MPAs may not have the ability to enhance fish density and diversity and to buffer effects of monsoon seasonality on the whole fish community. However, they may increase the temporal stability of certain groups, such as juvenile fish. Consequently, our results question whether MPAs play a general role in the maintenance of biodiversity and ecosystem functioning under changing environmental conditions in tropical seagrass fish communities.

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Single and joint effects of regional- and local-scale variables on tropical seagrass fish assemblages

Cited by 22 publications

References 56 publications

Community- and government-managed marine protected areas increase fish size, biomass and potential value

Community- and government-managed marine protected areas increase fish size, biomass and potential value

Contrasting distribution and foraging patterns of herbivorous and detritivorous fishes across multiple habitats in a tropical seascape

Marine protected areas increase temporal stability of community structure, but not density or diversity, of tropical seagrass fish communities

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