@article{fdi:010040927,
  title = {{I}sotopic evidence of distinct feeding ecologies and movement patterns in two migratory predators (yellowfin tuna and swordfish) of the western {I}ndian {O}cean},
  author = {{M}{\'e}nard, {F}r{\'e}d{\'e}ric and {L}orrain, {A}nne and {P}otier, {M}ichel and {M}arsac, {F}rancis},
  editor = {},
  language = {{ENG}},
  abstract = {{E}cologists primarily use delta {N}-15 values to estimate the trophic level of organisms, while delta {C}-13, and even recently delta {N}-15, are utilized to delineate feeding habitats. {H}owever, many factors can influence the stable isotopic composition of consumers, e.g. age, starvation or isotopic signature of primary producers. {S}uch sources of variability make the interpretation of stable isotope data rather complex. {T}o examine these potential sources of variability, muscle tissues of yellowfin tuna ({T}hunnus albacares) and swordfish ({X}iphias gladius) of various body lengths were sampled between 2001 and 2004 in the western {I}ndian {O}cean during different seasons and along a latitudinal gradient (23 degrees {S} to 5 degrees {N}). {B}ody length and latitude effects on delta {N}-15 and delta {C}-13 were investigated using linear models. {B}oth latitude and body length significantly affect the stable isotope values of the studied species but variations were much more pronounced for delta {N}-15. {W}e explain the latitudinal effect by differences in nitrogen dynamics existing at the base of the food web and propagating along the food chain up to top predators. {T}his spatial pattern suggests that yellowfin and swordfish populations exhibit a relatively unexpected resident behaviour at the temporal scale of their muscle tissue turnover. {T}he body length effect is significant for both species but this effect is more pronounced in swordfish as a consequence of their different feeding strategies, reflecting specific physiological abilities. {S}wordfish adults are able to reach very deep water and have access to a larger size range of prey than yellowfin tuna. {I}n contrast, yellowfin juveniles and adults spend most of their time in the surface waters and large yellowfin tuna continue to prey on small organisms. {C}onsequently, nitrogen isotopic signatures of swordfish tissues are higher than those of yellowfin tuna and provide evidence for different trophic levels between these species. {T}hus, in contrast to delta {C}-13, delta {N}-15 analyses of tropical {I}ndian {O}cean marine predators allow the investigation of complex vertical and spatial segregation, both within and between species, even in the case of highly opportunistic feeding behaviours. {T}he linear models developed in this study allow us to make predictions of delta {N}-15 values and to correct for any body length or latitude differences in future food web studies.},
  keywords = {},
  booktitle = {},
  journal = {{M}arine {B}iology},
  volume = {153},
  numero = {2},
  pages = {141--152},
  ISSN = {0025-3162},
  year = {2007},
  DOI = {10.1007/s00227-007-0789-7},
  URL = {https://www.documentation.ird.fr/hor/fdi:010040927},
}