  For a graph $G$, the edge Mostar index of $G$ is the sum of
$|m_u(e|G)-m_v(e|G)|$ over all edges $e=uv$ of $G$, where $m_u(e|G)$ denotes
the number of edges of $G$ that have a smaller distance in $G$ to $u$ than to
$v$, and analogously for $m_v(e|G)$. This paper mainly studies the problem of
determining the graphs that maximize the edge Mostar index among tricyclic
graphs. To be specific, we determine a sharp upper bound for the edge Mostar
index on tricyclic graphs and identify the graphs that attain the bound.
