The effects of fishing on the diversity, biomass and trophic structure of Seychelles’ reef fish communities

Jennings, Simon; Grandcourt, Edwin; Polunin, Nicholas V. C.

doi:10.1007/bf00334346

Cited by 155 publications

(80 citation statements)

References 29 publications

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“…), and hence that it is relatively easy for 'artisanal' fisheries to impact local fish resources. Similar observations have been made for fisheries in the Seychelles (Jennings et al 1995) and in the Philippines (Russ and Alcala 1996). The implication is that low-level artisanal fisheries might have impacted fish stocks for millennia elsewhere in the world, well before the onset of intensive and industrialised fishing during the 19th and 20th centuries.…”

Section: The Relatively Large Impact Of 'Small-scale' Fishingsupporting

confidence: 69%

The ‘shifting baseline’ phenomenon: a global perspective

Pinnegar

Engelhard

2007

Rev Fish Biol Fisheries

269

199

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In this paper we demonstrate that low level 'artisanal' fishing can dramatically affect populations of slow-growing, late-maturing animals and that even on remote oceanic islands, stocks have been depleted and ecosystems degraded for millennia. Industrialised fisheries have developed during different decades in different regions of the world, and this has almost always been followed by a period of massive stock decline. However, ecosystems were not pristine before the onset of industrial fishing and it is difficult to assess the 'virgin' state of a population given that it may have been subject to moderate or even high levels of fishing mortality for many centuries.A wide range of information is available to help define or deduce historic marine population status. These include 'traditional' written sources but also less conventional sources such as archaeological remains, genetic analyses or simple anecdotal evidence. Detailed information, collected specifically for the purpose of determining fish stock biomass tends to exist only for recent decades, and most fishery assessments around the world (and thus time-series of biomass estimates), are less than 30 years long. Here we advocate using a wider range of multidisciplinary data sources, although we also recognise that it can be difficult to separate natural variability associated with changing climatic conditions from human-induced changes through fishing. We consider whether or not recovery of degraded ecosystems is ever possible and discuss a series of one-way ratchet like processes that can make it extremely difficult to return to a former ecosystem state.

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Section: The Relatively Large Impact Of 'Small-scale' Fishingsupporting

confidence: 69%

The ‘shifting baseline’ phenomenon: a global perspective

Pinnegar

Engelhard

2007

Rev Fish Biol Fisheries

269

199

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“…Natural variations in recruitment, preferred habitat for larval settlement, ontogenetic changes in habitat use, fishing intensity (Jennings et al 1995), and habitat degradation together shape a fishery, affecting the numbers, sizes, and species of fishes caught, and where they are caught. Why did traps set in algal plain contain the greatest number of fish, including the preferred food species?…”

Section: Discussionmentioning

confidence: 99%

The habitats exploited and the species trapped in a Caribbean island trap fishery

Garrison

Rogers²,

Beets

et al. 2004

Environmental Biology of Fishes

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SynopsisWe visually observed fish traps in situ to identify the habitats exploited by the U.S. Virgin Islands fishery and to document species composition and abundance in traps by habitat. Fishers set more traps in algal plains than in any other habitat around St. John. Coral reefs, traditionally targeted by fishers, accounted for only 16% of traps. Traps in algal plain contained the highest number of fishes per trap and the greatest numbers of preferred food species. Traps on coral reefs contained the most species, 41 of the 59 taxa observed in the study. Acanthurus coeruleus was the most abundant species and Acanthuridae the most abundant family observed in traps. Piscivore numbers were low and few serranids were observed. Traps in algal plain contained the most fishes as a result of: ecological changes such as shifts in habitat use, mobility of species and degradation of nearshore habitat (fishery independent); and, catchability of fishes and longterm heavy fishing pressure (fishery dependent). The low number of serranids per trap, dominance of the piscivore guild by a small benthic predator, Epinephelus guttatus, and dominance of trap contents overall by a small, fast-growing species of a lower trophic guild, Acanthurus coeruleus, all point to years of intense fishing pressure.

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“…For example, Jennings et al (1995) looked at patterns of fish abundance along a gradient of fishing intensity in the Seychelles. They found that while the abundance of targeted species (piscivores and invertebrate feeders) declined with higher fishing intensity, there was no apparent pattern among the unfished species.…”

Section: Trophic Cascadesmentioning

confidence: 99%

Marine fisheries as ecological experiments

2011

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There are many examples of ecological theory informing fishery management. Yet fisheries also provide tremendous opportunities to test ecological theory through large-scale, repeated, and well-documented perturbations of natural systems. Although treating fisheries as experiments presents several challenges, few comparable tests exist at the ecosystem scale. Experimental manipulations of fish populations in lakes have been widely used to develop and test ecological theory. Controlled manipulation of fish populations in open marine systems is rarely possible, but fisheries data provide a valuable substitute for such manipulations. To highlight the value of marine fisheries data, we review leading ecological theories that have been empirically tested using such data. For example, density dependence has been examined through meta-analysis of spawning stock and recruitment data to show that compensation (higher population growth) occurs commonly when populations are reduced to low levels, while depensation (the Allee effect) is rare. As populations decline, spatial changes typically involve populations contracting into highdensity core habitats while abandoning less productive habitats. Fishing down predators may result in trophic cascades, possibly shifting entire ecosystems into alternate stable states, although alternate states can be maintained by both ecological processes and continued fishing pressure. Conversely, depleting low trophic level groups may affect central-place foragers, although these bottom-up effects rarely appear to impact fish-perhaps because many fish populations have been reduced to the point that they are no longer prey limited. Fisheries provide empirical tests for diversity-stability relations: catch data suggest that more diverse systems recover faster and provide more stable returns than less diverse systems. Fisheries have also provided examples of the tragedy of the commons, as well as counter-examples where common property resources have been managed successfully. We also address two barriers to use of fisheries data to answer ecological questions: differences in terminology for similar concepts and misuse of records of fishery landings (catch data) as a proxy for biomass trends.

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The effects of fishing on the diversity, biomass and trophic structure of Seychelles’ reef fish communities

Cited by 155 publications

References 29 publications

The ‘shifting baseline’ phenomenon: a global perspective

The ‘shifting baseline’ phenomenon: a global perspective

The habitats exploited and the species trapped in a Caribbean island trap fishery

Marine fisheries as ecological experiments

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