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Dryad

Data From: Shortened food chain length in a fished versus unfished coral reef

Data files

Apr 19, 2024 version files 77.91 KB

Abstract

Direct exploitation through fishing is driving dramatic declines in 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 often high dietary flexibility and numerous functional redundancies, especially in diverse ecosystems such as coral reefs, it is important to establish if web architecture is strongly impacted by fishing pressure, or if 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 find that even in a high diversity system with relatively modest fishing pressure, there are strong reductions in the trophic position of the three highest trophic position consumers examined in the fished system but no effects on the trophic position of lower-level consumers. We see no evidence that this shortening of these affected food webs is being driven by changes in basal resource consumption, e.g., through changes in spatial location of foraging by consumers. Instead, this likely reflects 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 ecosystems 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.