Let $S_n$ denote the network of all RNA secondary structures of length $n$, in which undirected edges exist between structures $s$, $t$ such that $t$ is obtained from $s$ by the addition, removal or shift of a single base pair. Using context-free grammars, generating functions and complex analysis, we show that the asymptotic average degree is $O(n)$ and that the asymptotic clustering coefficient is $O(1/n)$, from which it follows that the family $S_n$, $n = 1, 2, 3,\ldots$ of secondary structure networks is not small-world.