Effect of marine protected areas (MPAs) on consumer diet: MPA fish feed higher in the food chain

Dell, Claire L. A.; Montoya, Joseph P.; Hay, Mark E.

doi:10.3354/meps11487

Cited by 23 publications

(18 citation statements)

References 28 publications

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“…Indeed, bold or high-performance individuals may have a greater propensity to locate prey across broader spatial scales, whereas shy or low-performance individuals may remain within smaller home-ranges and rely exclusively on ambush rather than roaming foraging tactics5457. A disproportionate reduction in high-performance coral grouper in the Indo-Pacific may reduce the existing diversity in home-range size across individuals39 and modify inter- and intraspecific trophic interactions585960. While these ideas would be technically challenging to investigate, they would broaden our understanding of trophic dynamics beyond the interspecific level.…”

Section: Discussionmentioning

confidence: 99%

Rising temperatures may drive fishing-induced selection of low-performance phenotypes

Messmer

Tobin

Hoey

et al. 2017

Sci Rep

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Climate warming is likely to interact with other stressors to challenge the physiological capacities and survival of phenotypes within populations. This may be especially true for the billions of fishes per year that undergo vigorous exercise prior to escaping or being intentionally released from fishing gear. Using adult coral grouper (Plectropomus leopardus), an important fisheries species throughout the IndoPacific, we show that population-level survival following vigorous exercise is increasingly compromised as temperatures increase from current-day levels (100-67% survival at 24-30 °C) to those projected for the end of the century (42% survival at 33 °C). Intriguingly, we demonstrate that high-performance individuals take longer to recover to a resting metabolic state and subsequently have lower survival in warm water compared with conspecifics that exercise less vigorously. Moreover, we show that postexercise mortality of high-performance phenotypes manifests after 3-13 d at the current summer maximum (30 °C), while mortality at 33 °C occurs within 1.8-14.9 h. We propose that wild populations in a warming climate may become skewed towards low-performance phenotypes with ramifications for predator-prey interactions and community dynamics. Our findings highlight the susceptibility of phenotypic diversity to fishing activities and demonstrate a mechanism that may contribute to fishinginduced evolution in the face of ongoing climate change.Anthropogenic carbon emissions and modified land use have directly contributed to increases in the surface temperature of the planet since the beginning of the industrial revolution 1 . Aquatic systems have absorbed the majority of the excess heat added to the atmosphere, which has led to a warming of the global sea surface by 0.4 °C in the past century with an additional 0.6-2.0 °C expected by 2100 1,2 . Concomitant with the background warming, there is evidence that extreme shorter-term temperature spikes (e.g., daily, seasonal) are becoming more frequent in many aquatic systems, presenting a more immediate thermal challenge for aquatic organisms 1,3-5 . While the direct effects of environmental warming on the survival, ecology and physiology of aquatic organisms are becoming clearer 3,6-8 , it is generally accepted that other stressors can work interactively with temperature to increase stress and reduce survival 9,10 . The future performance of aquatic organisms is therefore dependent upon the combined impacts of multiple stressors working simultaneously as the environment continues to change.Exercise is critical for optimising fitness through processes such as food capture, predator avoidance and reproduction. Nevertheless, exercise often induces physiological, biochemical and behavioural disturbances that require significant durations to recover to baseline levels [11][12][13][14][15] . Thus, the interplay between climate warming and exercise is a critical consideration in helping to understand long-term climate impacts on animal populations, yet one that has received ...

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Section: Discussionmentioning

confidence: 99%

Rising temperatures may drive fishing-induced selection of low-performance phenotypes

Messmer

Tobin

Hoey

et al. 2017

Sci Rep

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“…The lower nitrogen content in S. polycystum from the non-MPAs could be caused by greater competition among algae for nutrients in those locations as isotopic studies from these sites indicate that nitrogen sources for paired MPAs and non-MPAs at each village did not differ (Dell et al 2015). Macroalgal cover in the non-MPAs is 27 to 61 times greater than in the MPAs (Rasher et al 2013), so increased competition for nutrients could occur and limit nutrient content in non-MPA algae.…”

Section: Discussionmentioning

confidence: 99%

“…This difference in macroalgal cover is not the result of differing physical conditions between the MPA and non-MPA areas; caged recruitment and reciprocal transplant experiments between the MPA and non-MPA areas demonstrate that algae recruit and grow as well or better (depending on the village) in the MPA, where seaweeds are scarce, than the non-MPA, where they are abundant, if they are protected from herbivorous fishes (Rasher et al 2012, Dell et al 2016). Additionally, isotopic investigations of seaweeds from the sites indicate that MPA and non-MPA areas within a village do not differ in sources of nitrogen (Dell et al 2015). Despite the similar physical conditions between MPAs and non-MPAs at each village, there is now considerable difference in the selective pressure imposed by the higher densities and diversities of herbivorous fishes in MPA as opposed to non-MPA areas (Rasher et al 2013).…”

Section: Methodsmentioning

confidence: 99%

“…These were rinsed vigorously in seawater to remove particulates and epibiota and frozen at −20°C until they were dried at 70°C to a constant weight, ground into a fine powder with a pestle and mortar, and analysed by mass spectrometer for carbon and nitrogen content. Further processing methods are detailed in Dell et al (2015).…”

Section: Methodsmentioning

confidence: 99%

“…Modified from Dell et al (2015). Study sites located between 18° 11’ 23” S, 177° 37’ 15” E (Namada’s MPA) and 18° 12’ 58” S, 177° 43’ 01”E (Votua’s MPA).…”

Section: Figmentioning

confidence: 99%

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Induced defence to grazing by vertebrate herbivores: uncommon or under-investigated?

Dell

Hay

2016

Mar. Ecol. Prog. Ser.

Self Cite

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There are many examples of macroalgae inducing defence in response to small invertebrate herbivores like amphipods, isopods, and gastropods but few cases of induction in response to vertebrate macrograzers like herbivorous fishes. This may be because larger grazers rapidly consume large quantities of seaweed before induction can occur, thus selecting for constitutive rather than induced defences. Alternatively, the pattern could occur because induction due to feeding by macrograzers is less commonly investigated. In Fiji, field assays with the brown macroalga Sargassum polycystum demonstrated that thalli growing in marine protected areas (MPAs) with abundant herbivorous fishes were significantly less palatable than those growing in adjacent fished areas (non-MPAs) with few herbivorous fishes. This significant preference occurred in 11 of 13 trials over 5 time periods and across 3 pairs of MPAs and spatially associated non-MPAs. This preference was not positively associated with algal nitrogen content or with the toughness of algal fronds. When S. polycystum ramets were taken from the non-MPA and half were partially grazed by fishes while the other half were protected from grazing, new growth from the controls was strongly preferred to new growth from the previously grazed ramets although these fronds originated from the same holdfast. This suggests that S. polycystum upregulates defences (probably chemical) in response to grazing by herbivorous fishes. This is one of the few published examples of induction of macroalgal defence in response to feeding by large, mobile grazers. It is unclear whether induced defences against fishes are rare or just under-investigated.

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Shortened food chain length in a fished versus unfished coral reef

Young,

McCauley,

Micheli

et al. 2024

Ecological Applications

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Direct exploitation through fishing is driving dramatic declines of wildlife populations in ocean environments, particularly for predatory and large‐bodied taxa. Despite wide recognition of this pattern and well‐established consequences of such trophic downgrading on ecosystem function, there have been few empirical studies examining the effects of fishing on whole system trophic architecture. Understanding these kinds of structural impacts is especially important in coral reef ecosystems—often heavily fished and facing multiple stressors. Given the often high dietary flexibility and numerous functional redundancies in diverse ecosystems such as coral reefs, it is important to establish whether web architecture is strongly impacted by fishing pressure or whether it might be resilient, at least to moderate‐intensity pressure. To examine this question, we used a combination of bulk and compound‐specific stable isotope analyses measured across a range of predatory and low‐trophic‐level consumers between two coral reef ecosystems that differed with respect to fishing pressure but otherwise remained largely similar. We found that even in a high‐diversity system with relatively modest fishing pressure, there were strong reductions in the trophic position (TP) of the three highest TP consumers examined in the fished system but no effects on the TP of lower‐level consumers. We saw no evidence that this shortening of the affected food webs was being driven by changes in basal resource consumption, for example, through changes in the spatial location of foraging by consumers. Instead, this likely reflected internal changes in food web architecture, suggesting that even in diverse systems and with relatively modest pressure, human harvest causes significant compressions in food chain length. This observed shortening of these food webs may have many important emergent ecological consequences for the functioning of ecosystems impacted by fishing or hunting. Such important structural shifts may be widespread but unnoticed by traditional surveys. This insight may also be useful for applied ecosystem managers grappling with choices about the relative importance of protection for remote and pristine areas and the value of strict no‐take areas to protect not just the raw constituents of systems affected by fishing and hunting but also the health and functionality of whole systems.

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Effect of marine protected areas (MPAs) on consumer diet: MPA fish feed higher in the food chain

Cited by 23 publications

References 28 publications

Rising temperatures may drive fishing-induced selection of low-performance phenotypes

Rising temperatures may drive fishing-induced selection of low-performance phenotypes

Induced defence to grazing by vertebrate herbivores: uncommon or under-investigated?

Shortened food chain length in a fished versus unfished coral reef

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