Small pelagic fish, trawling discards and breeding performance of the critically endangered Balearic shearwater: improving conservation diagnosis

Louzao, Maité; Igual, José Manuel; McMinn, Miguel; Aguilar, Juan Salvador; Triay, Rafel; Oro, Daniel

doi:10.3354/meps318247

Cited by 38 publications

(37 citation statements)

References 34 publications

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“…At least as important as the effects of global climate change are fishery-seabird interactions that have aroused concern worldwide. Population sizes of many seabirds have been found to reflect changes of fish stocks or amounts of discards provided by fisheries (Garthe & Hüppop 1994, Garthe et al 1996, Oro & Ruiz 1997, Oro 1999, Louzao et al 2006a). …”

Section: Introductionmentioning

confidence: 99%

Fatty acid signature analysis confirms foraging resources of a globally endangered Mediterranean seabird species: calibration test and application to the wild

Käkelä¹,

Käkelä²,

Martínez‐Abraín³

et al. 2010

Mar. Ecol. Prog. Ser.

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Dietary studies of seabirds provide information on food webs and oceanographic variability. Studying fatty acid signatures (FAS), which reflect changes in the composition of the diet, has several advantages over traditional methods. In the context of the Mediterranean marine ecosystem, we studied tissue FAS in captive-fed and wild seabirds. Yellow-legged gulls Larus michahellis were experimentally fed either pelagic (sardine Sardina pilchardus) or demersal (spotted flounder Citharus linguatula) fish for 8 wk, and FAS in the birds' plasma and adipose tissue were studied. The FAS developed patterns characteristic of the sardine or flounder diet, showing the reliability of both types of samples. In addition, plasma samples of 20 endangered wild Balearic shearwaters Puffinus mauretanicus and their most likely prey items from the Mediterranean Sea were collected and analyzed for FAS. Based on FAS of Mediterranean fish, and the results from the feeding experiment, the diet of the endangered wild shearwaters was estimated. In terms of the composition of polyunsaturated fatty acids, the plasma FAS of the shearwaters resembled those of the captive gulls kept on a sardine diet, suggesting that pelagic feeding resources dominate shearwater diet. However, the high level of 20:1n-11, likely metabolized from 22:1n-11 by the birds themselves, suggested that the diet also contained a demersal component rich in 22:1n-11. Contrary to the situation in the open oceans, the levels of the C20 and C22 monounsaturated fatty acids are low in the Mediterranean food web and characteristic of most demersal species. Our results support the findings of previous field studies that the diet of the shearwaters is frequently supplemented by demersal fish from fishery discards.

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Section: Introductionmentioning

confidence: 99%

Fatty acid signature analysis confirms foraging resources of a globally endangered Mediterranean seabird species: calibration test and application to the wild

Käkelä¹,

Käkelä²,

Martínez‐Abraín³

et al. 2010

Mar. Ecol. Prog. Ser.

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“…This situation is especially true in the western Mediterranean ecosystem, where trawling discards have an impact on the foraging behaviour, breeding performance and population dynamics of opportunistic seabirds, including endangered species (Oro 1999;Arcos and Oro 2002a;Oro et al 2004b;Louzao et al 2006b). The Balearic shearwater (PuYnus mauretanicus) is one of the rarest seabirds in the world, currently listed as Critically Endangered by the IUCN (Oro et al 2004a;BirdLife International 2008).…”

Section: Introductionmentioning

confidence: 99%

“…During the breeding season, the species mainly forages over the eastern Iberian continental shelf (Louzao et al 2006a), a highly productive and spawning area for small pelagic Wsh such as anchovies (Engraulis encrasicolus) and pilchards (Sardina pilchardus) and where important Wshing Xeets operate (Abad et al 1998;Agostini and Bakun 2002;Palomera et al 2007). Although the Balearic shearwater appears to primarily forage on shoals of small pelagic Wsh, mainly anchovies and pilchards, diVerent ecological models have also shown the importance of demersal and pelagic Wsh provided by trawling discards (Arcos and Oro 2002a;Abelló et al 2003;Louzao et al 2006b). Similarly, trawling discards also seem to improve the breeding performance of this and other endangered seabirds in the Mediterranean (Oro 1999;Louzao et al 2006b).…”

Section: Introductionmentioning

confidence: 99%

Seasonal changes in the diet of a critically endangered seabird and the importance of trawling discards

et al. 2009

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Pelagic seabirds obtain food from oceans where the availability of their prey changes rapidly both seasonally and spatially. Here, we investigated changes in the trophic habits of the critically endangered Balearic shearwater (PuYnus mauretanicus) through the breeding season and tested for dietary diVerences between sexes and age classes. We analysed & 15 N and & 13 C values in blood of adults during the pre-incubation, incubation and chick-rearing periods and of their chicks. Using a two-isotope mixing model, we estimated dietary contributions based on isotope values from potential prey species which included small pelagic species available naturally and demersal Wsh species available only from trawling discards. Balearic shearwaters showed clear isotopic and dietary variation through the breeding season. During pre-incubation, breeding adults appeared to exploit demersal Wsh, whereas during the incubation and chick-rearing period, they fed mainly on pelagic anchovies (Engraulis encrasicolus) and pilchards (Sardina pilchardus). Similarly, chicks were fed mainly with anchovies, a resource with a high energetic value. This variation in the dietary habits of adult shearwaters during the breeding season was probably related to both natural and Wsheryinduced seasonal changes in the availability of potential prey species within their main feeding grounds. However, changes in the nutritional requirements of the shearwaters could also play an important role. Indeed, diet diVered between sexes during pre-incubation: females fed less on trawling discards and more on small pelagic Wsh than males. This sexual segregation in diet could be the consequence of higher nutritional requirements of females during this period. Our study reveals the diVerential importance of both trawling discards and small pelagic Wsh species for a pelagic seabird depending on the breeding period and illustrates the importance of considering the entire breeding season when making inferences about the importance of speciWc prey in seabird dietary studies.

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“…Selected models are in bold. CHL: chl a; np: number of parameters estimated in the model species (Oro et al 2004, Louzao et al 2006b), in addition to removing threats related to introduced predators in some accessible colonies. Unfortunately, not much effort has been directed at obtaining detailed local information on seabird mortality at national or European levels and, in turn, the spatio-temporal window of the interaction between bottom longlines and Balearic shearwaters is not well known.…”

mentioning

confidence: 99%

Exploiting the closest productive area: geographical segregation of foraging grounds in a critically endangered seabird

Louzao¹,

Navarro²,

Forero³

et al. 2011

Mar. Ecol. Prog. Ser.

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Small pelagic fish, trawling discards and breeding performance of the critically endangered Balearic shearwater: improving conservation diagnosis

Cited by 38 publications

References 34 publications

Fatty acid signature analysis confirms foraging resources of a globally endangered Mediterranean seabird species: calibration test and application to the wild

Fatty acid signature analysis confirms foraging resources of a globally endangered Mediterranean seabird species: calibration test and application to the wild

Seasonal changes in the diet of a critically endangered seabird and the importance of trawling discards

Exploiting the closest productive area: geographical segregation of foraging grounds in a critically endangered seabird

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