Une solution est de modifier la commande `\maketitle`. On peut, par exemple, utiliser la commande `\xpatchcmd`.
`\xpatchcmd\maketitle{\docsvlist{french,english}}{\docsvlist{french}}{}{\err}`
`\xpatchcmd\maketitle{\docsvlist{french,english}}{\docsvlist{french}}{}{}`
**ECM**
\documentclass[12pt,version=final]{yathesis}
\usepackage{lmodern}
\usepackage[T1]{fontenc}
\usepackage{pgfplots}
\usepackage{floatrow}
\usepackage{listings}
\usepackage[autostyle]{csquotes}
\usepackage{biblatex}
\usepackage{hyperref}
\addbibresource{biblatex-examples.bib}
\nocite{*}
%-------------------------------------------------
\xpatchcmd\maketitle{\docsvlist{french,english}}{\docsvlist{french}}{}{\err}
\begin{document}
%-------------------------------------------------
\author[aa@zygo.fr]{Alphonse}{Allais}
\title[Laugh's Chaos]{Le chaos du rire}
\academicfield[Mathematics]{Mathématiques}
\date{1}{1}{2015}
\institute[url=http://www.univ-littoral.fr/]{ULCO}
\doctoralschool[url=http://edspi.univ-lille1.fr/]{ED Régionale SPI 72}
\laboratory[
telephone=(33)(0)3 21 46 55 86,
fax=(33)(0)3 21 46 55 75,
email=secretariat@lmpa.univ-littoral.fr,
url=http://www-lmpa.univ-littoral.fr/
]{LMPA Joseph Liouville}{%
Maison de la Recherche Blaise Pascal \\
50, rue Ferdinand Buisson \\
CS 80699 \\
62228 Calais Cedex \\
France}
\supervisor[professor,affiliation=ULCO]{Michel}{de Montaigne}
\cosupervisor[associateprofessor*,affiliation=ULCO]{Charles}{Baudelaire}
\comonitor[associateprofessor,affiliation=ULCO]{Étienne}{de la Boétie}
\referee[professor,affiliation=IHP]{René}{Descartes}
\referee[seniorresearcher,affiliation=CNRS]{Denis}{Diderot}
\committeepresident[professor,affiliation=ENS Lyon]{Victor}{Hugo}
\examiner[associateprofessor,affiliation=Université de Paris~13]{Sophie}{Germain}
\examiner[juniorresearcher,affiliation=INRIA]{Joseph}{Fourier}
\examiner[juniorresearcher*,affiliation=CNRS]{Paul}{Verlaine}
\guest{George}{Sand}
\keywords{chaos, rire}{chaos, laugh}
%-------------------------------------------------
\maketitle
%-------------------------------------------------
\begin{abstract}
bar baz
\end{abstract}
\begin{abstract}
foo foo
\end{abstract}
\makeabstract
%-------------------------------------------------
% Sommaire
\tableofcontents[depth=chapter,name=Sommaire]
\mainmatter
\chapter{Introduction}
%-------------------------------------------------
\printbibliography
\backmatter
\tableofcontents
\end{document}
