Food, fishing and seabirds in the Benguela upwelling system

Crawford, Robert J. M.

doi:10.1007/s10336-007-0228-z

Cited by 73 publications

(55 citation statements)

References 29 publications

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“…For example, sandeels (Ammodytes marinus) are targeted by the largest single-species fishery in the North Sea, and declining sandeel abundance can cause severely reduced breeding success in seabirds (37). Other studies suggest similar sensitivity to a few small fish species across a range of seabirds and pinnipeds (38)(39)(40). Even though short-lived species may recover more quickly from collapse than other fishes (41), collapses in small, low trophic-level species can last from years to decades (17).…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Unexpected patterns of fisheries collapse in the world's oceans

Pinsky

Jensen

Ricard

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

215

157

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Understanding which species are most vulnerable to human impacts is a prerequisite for designing effective conservation strategies. Surveys of terrestrial species have suggested that largebodied species and top predators are the most at risk, and it is commonly assumed that such patterns also apply in the ocean. However, there has been no global test of this hypothesis in the sea. We analyzed two fisheries datasets (stock assessments and landings) to determine the life-history traits of species that have suffered dramatic population collapses. Contrary to expectations, our data suggest that up to twice as many fisheries for small, low trophic-level species have collapsed compared with those for large predators. These patterns contrast with those on land, suggesting fundamental differences in the ways that industrial fisheries and land conversion affect natural communities. Even temporary collapses of small, low trophic-level fishes can have ecosystem-wide impacts by reducing food supply to larger fish, seabirds, and marine mammals.body size | ecosystem-based management | food webs | life-history theory | marine conservation O verfishing is one of the most serious conservation concerns in marine ecosystems (1), but understanding which species are most at risk remains a challenge. On land, life-history traits are strong predictors of extinction risk (2), and vulnerable species often have large body size and high trophic level (2, 3). In marine ecosystems, the well-publicized declines of large predatory fishes (4, 5) suggest that similar trends may also be common in the sea. However, research to date has found or proposed a wide range of life-history characteristics that cause high vulnerability, including large body size (6-9), late maturity (6, 9), long lifespan (6, 8-11), low fecundity and high parental investment in offspring (11, 12), or high trophic level (2, 13). Understanding which traits, or combinations of traits, are most useful for predicting vulnerability has been difficult because analyses have been limited to regional comparisons or narrow species groups, and because reliable global data have not been available to more broadly test which types of fishes are most likely to suffer fisheries collapse.In addition, there are reasons to believe that regional or terrestrial life-history trends might not apply globally in the ocean. For example, fishery biologists often recommend higher harvest rates for fast-growing, highly productive species, and lower harvest rates for species with lower productivity (14). Where implemented, these adjustments might reduce the resilience of fastgrowing species and put all harvested species at similar risks of decline. In addition, economic forces or management regime may be more important than life history in determining whether fishing effort is successfully controlled (15,16). Small pelagic species, although often possessing a rapid growth rate, are also highly catchable, and therefore susceptible to overfishing (17). Finally, the conflict with human development that is ...

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Section: Discussionmentioning

confidence: 99%

“…Even though short-lived species may recover more quickly from collapse than other fishes (41), collapses in small, low trophic-level species can last from years to decades (17). These durations are long enough to have substantial impacts on the food web (37,39,40).…”

Section: Discussionmentioning

confidence: 99%

Unexpected patterns of fisheries collapse in the world's oceans

Pinsky

Jensen

Ricard

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

215

157

View full text Add to dashboard Cite

show abstract

“…Although seabird parameters may be strongly correlated with measures of fish abundance (e.g. Crawford et al 2006a, Crawford 2007, and hence be indicators of fish abundance, it is not always clear which factor is driving the changes in the forage fish populations, whether it is fishing or the climate. In such instances, examination of the responses of a suite of predators (and other organisms) may provide greater insight into the controlling factors than consideration of a single predator.…”

Section: Need For Seabirds As Indicatorsmentioning

confidence: 99%

Pros and cons of using seabirds as ecological indicators

Durant¹,

Hjermann²,

Frederiksen³

et al. 2009

Clim. Res.

110

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Climate change and overfishing are increasingly causing unanticipated changes in marine ecosystems (e.g. shifts in species dominance). In order to understand and anticipate these changes, there is a crucial need for indicators that summarise large quantities of information into a few relevant and accessible signals. Seabirds have been suggested as good candidates for ecological indicators of the marine environment; however, few studies have critically evaluated their value as such. We review the role of seabirds as ecological indicators, and discuss their limitations and drawbacks, as compared to other types of indicators. In addition, we highlight the statistical consequences of inverse inference when using seabird data as indicators. We discuss the use of integrated indices and the use of seabirds as autonomous samplers of the marine environment. Finally, we highlight the necessary steps preceding the use of seabirds as indicators. We conclude that, in order to use seabird time series properly, the use of recent advances both in statistics and in remote sensing is a way to move forward. This, along with the assessment of their usefulness, should enable us to use seabird indicators appropriately for managing urgent conservation problems.

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“…Seabirds are attracted to trawl vessels to feed on fish bycatch or offal that is discarded (Williams & Capdeville 1996, Crawford 2007. Aggressive competition for this food off the stern of the vessel places seabirds in the area where the warp cables (the 2 steel cables used to tow trawl nets) enter the ocean, and at increased risk of harmful interactions.…”

Section: Introductionmentioning

confidence: 99%

Industry-based development of effective new seabird mitigation devices in the southern Australian trawl fisheries

Koopman¹,

Boag²,

Tuck³

et al. 2018

Endang. Species. Res.

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Incidental mortality of seabirds caused by interactions with the warp wires of trawl vessels in Australia's Commonwealth-managed Southern and Eastern Scalefish and Shark Fishery has been reported by on-board observers. Seabird mortality as a result of fishery interactions is an issue of global conservation concern. This paper describes an industry-led study that developed and tested the effectiveness of 2 experimental mitigation devices for trawl vessels: a baffler and a water sprayer. These were tested against a control which was previously the only prescribed device (a warp deflector called a pinkie). Seabird interactions were observed during 69 shots comparing the sprayer against the control, and 55 shots comparing the baffler against the control. The seabird mitigation device employed alternated between the trial device (either the water sprayer or baffler) and the control device. Both experimental mitigation devices showed significant reductions in heavy interaction rates (interactions per shot) compared with the pinkie (83.7 and 58.9%). On stern trawlers, both new devices are deployed at the start of fishing and retrieved at the end of fishing operations, whereas pinkies need to be deployed and retrieved for each shot. This results in time savings and reduced risks to crew. Based on the findings from this study, the Australian Fisheries Management Authority now allows vessels to meet seabird bycatch mitigation requirements through use of either new device. The outcomes of this research and subsequent uptake of the new mitigation devices will greatly contribute to the reduction of incidental fishing mortality in Australian, and potentially other trawl fisheries.

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Food, fishing and seabirds in the Benguela upwelling system

Cited by 73 publications

References 29 publications

Unexpected patterns of fisheries collapse in the world's oceans

Unexpected patterns of fisheries collapse in the world's oceans

Pros and cons of using seabirds as ecological indicators

Industry-based development of effective new seabird mitigation devices in the southern Australian trawl fisheries

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