TY - JOUR
T1 - Inter-colony and inter-annual variation in discard use by albatross chicks revealed using isotopes and regurgitates
AU - Kuepfer, Amanda
AU - Catry, Paulo
AU - Bearhop, Stuart
AU - Sherley, Richard B.
AU - Bell, Olivia
AU - Newton, Jason
AU - Brickle, Paul
AU - Arkhipkin, Alexander
AU - Votier, Stephen C.
N1 - Funding Information:
This study had the support of the Fundação para a Ciência e a Tecnologia (FCT) I.P. through the strategic project UIDB/04292/2020, UIDP/04292/2020 and DivRestore/0012/2020 awarded to MARE and ISPA, and LA/P/0069/2020 granted to the Associate Laboratory ARNET. Further funding was provided by Fortuna Ltd., the Falkland Islands Government through the Environmental Studies Budget, as well as by the National Environmental Research Committee (NERC) through grants-in-kind (EK316-03/19, 2264.0420).
Funding Information:
We are thankful to Ludovic Goyot, Brendon Lee, and Rebecca Piontek of the Falkland Islands Fisheries Department for collection of prey samples and assistance with sample processing. We are grateful for generous support from Falklands Conservation who enabled data collection at Steeple Jason Island, and to the New Island Conservation Trust and Wildlife Conservation Society for granting us site access.
Publisher Copyright:
© 2023, The Author(s).
PY - 2023/4
Y1 - 2023/4
N2 - Effective marine ecosystem monitoring is critical for sustainable management. Monitoring seabird diets can convey important information on ecosystem health and seabird–fishery interactions. The diet of breeding black-browed albatross (Thalassarche melanophris) has previously been assessed using stomach content analysis (SCA) or stable isotope analysis (SIA), but not both methods together. Combining dietary sampling approaches reduces biases associated with using single methods. This study combines SCA and SIA to study the diet of black-browed albatross chicks, with a specific focus on fishery discard consumption, at two Falkland Islands colonies (New Island 51°43′S, 61°18′W and Steeple Jason Island 51°01′S, 61°13′W) during two consecutive breeding seasons (2019 and 2020). SCA provided high taxonomic resolution of short-term diet and priors for stable isotope mixing models, with multiple measures of dietary items (e.g. numeric frequency N%, frequency of occurrence FO%). By contrast, SIA of down feathers provided a single and more integrated dietary signal from throughout chick development. Although the two methods disagreed on the dominant prey group (SCA—crustacean; SIA—pelagic fish), the complementary information suggested a chick diet dominated by natural prey (SCA: 74%–93% [FO], 44%–98% [N]; SIA: minimum 87%–95% contribution). Nonetheless, SCA revealed that a high proportion of breeding adults do take discards. We detected consistent colony-specific diets in relation to prey species, but not in relation to higher discard use. Overall, discard consumption was highest in 2020, the year characterised by the poorest foraging conditions. Our results have implications for fisheries management and future dietary studies assessing discard use.
AB - Effective marine ecosystem monitoring is critical for sustainable management. Monitoring seabird diets can convey important information on ecosystem health and seabird–fishery interactions. The diet of breeding black-browed albatross (Thalassarche melanophris) has previously been assessed using stomach content analysis (SCA) or stable isotope analysis (SIA), but not both methods together. Combining dietary sampling approaches reduces biases associated with using single methods. This study combines SCA and SIA to study the diet of black-browed albatross chicks, with a specific focus on fishery discard consumption, at two Falkland Islands colonies (New Island 51°43′S, 61°18′W and Steeple Jason Island 51°01′S, 61°13′W) during two consecutive breeding seasons (2019 and 2020). SCA provided high taxonomic resolution of short-term diet and priors for stable isotope mixing models, with multiple measures of dietary items (e.g. numeric frequency N%, frequency of occurrence FO%). By contrast, SIA of down feathers provided a single and more integrated dietary signal from throughout chick development. Although the two methods disagreed on the dominant prey group (SCA—crustacean; SIA—pelagic fish), the complementary information suggested a chick diet dominated by natural prey (SCA: 74%–93% [FO], 44%–98% [N]; SIA: minimum 87%–95% contribution). Nonetheless, SCA revealed that a high proportion of breeding adults do take discards. We detected consistent colony-specific diets in relation to prey species, but not in relation to higher discard use. Overall, discard consumption was highest in 2020, the year characterised by the poorest foraging conditions. Our results have implications for fisheries management and future dietary studies assessing discard use.
KW - Original Paper
KW - Fishery discards
KW - Seabird diet
KW - Stomach content analysis
KW - Stable isotope analysis
KW - Thalassarche melanophris
UR - http://www.scopus.com/inward/record.url?scp=85150857421&partnerID=8YFLogxK
U2 - 10.1007/s00227-023-04191-7
DO - 10.1007/s00227-023-04191-7
M3 - Article
SN - 0025-3162
VL - 170
JO - Marine Biology
JF - Marine Biology
IS - 4
M1 - 46
ER -