Seabird consumption and production in the Benguela and Western Agulhas ecosystems

Crawford, Robert J. M.; Ryan, P G; Williams, Alan

doi:10.2989/025776191784287709

Cited by 50 publications

(40 citation statements)

References 13 publications

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“…McLaren & Peterson 1994, Caro & Durant 1995. For example, 1s seabird predation on fish capable of limiting fisheries production (Wiens & Scott 1975, Furness 1978, Crawford et al 1991?…”

Section: Introductionmentioning

confidence: 99%

“…Estimates of the amount of fish production taken by seabirds globally suggest that this is not usually the case. Seabirds consume between 0.8% (Sanger 1972) and 30% (Crawford et al 1991) of marine tertiary productivity. This range is quite large, and it has been suggested that the impact depends on a number of factors, including proximity to large colonies (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Furness 1978, Diamond et al 1993), whether consumption is averaged or calculated for individual prey types (e.g. Furness & Cooper 1982, Crawford et al 1991, whether birds are resident or migratory (Woehler 1997), and the presence of oceanographic factors such as upwelling (e.g. Haney 1986, Vermeer et al 1987, Duffy 1989, downwelling (Hoffman et al 1981), fronts or eddies (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Salmon fry predation by seabirds near an Alaskan hatchery

Scheel¹,

Kr²

1997

Mar. Ecol. Prog. Ser.

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ABSTRACT-We est~mated the mortality of hatchery-raised pink Oncorhynchus gorbuscha and chum 0 keta salmon fry from seabird predation near a salmon hatchery In Lake Bay, Prince William Sound, Alaska, USA. Fleld counts of seabirds and observations of feeding rates for plunge-diving seabirds were obtained durlng salmon fry releases between Apnl and June 1995. Several hundred birds of 7 piscivorous species aggregated in front of the hatchery. Consumption rates were determined from focalanimal sampling and energetic models. For most species, per capita consumption rates based on behavioral data were lower than those calculated from energetic considerations. From energetic models and fry movement rates, w e estimated that 2.7 to 5.9 million juvenile salmon (1.1 to 2.4 "" of released fry) were consumed during the study period. Differences between the energetics models accounted for 64 % of this range; assumptions about fry movement rates accounted for the remainder. Gulls recorded during aerial surveys throughout Prince William Sound were significantly associated with s p a w n~n g herring and hatchery sites, but not with miles of coast with herring spawn present. The correlation of bird aggregations with the presence of these small fish indicates that concentrations of prey fish have an important influence on the distribution of birds at sea during this time of the year. Bird numbers in both boat counts and aerial surveys declined from early May to early June. Taken together, these results lndlcate that salmon fry just entering the marine environment were not especially susceptible to avlan predation Thelr vulnerability to predation was apparently buffered by the presence of other attractlve food patches within seabird foraging range early in our study period, and by declines in the numbers of seabirds foraging along the shoreline later In the study.

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“…McLaren & Peterson 1994, Caro & Durant 1995. For example, 1s seabird predation on fish capable of limiting fisheries production (Wiens & Scott 1975, Furness 1978, Crawford et al 1991?…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Salmon fry predation by seabirds near an Alaskan hatchery

Scheel¹,

Kr²

1997

Mar. Ecol. Prog. Ser.

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“…The initial estimates of seabird consumption showed that it was negligible in terms of total mortality of pelagic fish (Crawford et al 1991). However, in-depth analysis of regular collections of stomach samples and indices of reproductive success allowed Crawford and Dyer (1995) to link changes in bird populations and diets to variations in the population strength of pelagic fish.…”

Section: Top Predators Within the Ecosystemmentioning

confidence: 99%

“…In order to understand the integrated flows within the ecosystem, studies of diets and associated trophic roles were expanded to include a wide range of predators (e.g. Armstrong et al 1991, Crawford et al 1991, Ebert et al 1991, Meyer and Smale 1991a, b, Sauer and Lipiński 1991, Punt et al 1995). Many of the important feeding interactions in the ecosystem were quantified (e.g.…”

Section: Ecosystem Research: Emergent Propertiesmentioning

confidence: 99%

Contributions of the Benguela ecology programme to pelagic fisheries management in South Africa

Moloney

Lingen²,

Hutchings³

et al. 2004

African Journal of Marine Science

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The economic tradeoffs and ecological impacts associated with a potential mesopelagic fishery in the California Current

Chapman

Koehn

Hoagland

2022

Ecological Applications

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The ocean's mesopelagic zone (200–1000 m) remains one of the most understudied parts of the ocean despite knowledge that mesopelagic fishes are highly abundant. Apex predators from the surface waters are known to consume these fishes, constituting an important ecological interaction. Some countries have begun exploring the potential harvest of mesopelagic fishes to supply fishmeal and fish oil markets due to the high fish abundance in the mesopelagic zone compared with overfished surface waters. This study explored the economic and ecological implications of a moratorium on the harvest of mesopelagic fishes such as lanternfish off the US West Coast, one of the few areas where such resources are managed. We adapted a bioeconomic decision model to examine the tradeoffs between the values gained from a hypothetical mesopelagic fishery with the potential values lost from declines in predators of mesopelagic fishes facing a reduced prey resource. The economic rationale for a moratorium on harvesting mesopelagics was sensitive both to ecological relationships and the scale of the nonmarket values attributed to noncommercial predators. Using a California Current‐based ecological simulation model, we found that most modeled predators of mesopelagic fishes increased in biomass even under high mesopelagic harvest rates, but the changes (either increases or decreases) were small, with relatively few predators responding with more than a 10% change in their biomass. While the ecological simulations implied that a commercial mesopelagic fishery might not have large biomass impacts for many species in the California Current system, there is still a need to further explore the various roles of the mesopelagic zone in the ocean.

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Seabird consumption and production in the Benguela and Western Agulhas ecosystems

Cited by 50 publications

References 13 publications

Salmon fry predation by seabirds near an Alaskan hatchery

Salmon fry predation by seabirds near an Alaskan hatchery

Contributions of the Benguela ecology programme to pelagic fisheries management in South Africa

The economic tradeoffs and ecological impacts associated with a potential mesopelagic fishery in the California Current

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