officially named tributaries
... that a 2001 survey found that only one of the officially named tributaries of Mahanoy Creek had fish, but that tributary had 20 fish species?
... that a 2001 survey found that only one of the <b id="mwAnQ"><a href="./List_of_tributaries_of_Mahanoy_Creek" id="mwAnU" rel="mw:WikiLink" title="List of tributaries of Mahanoy Creek">officially named tributaries</a></b> of <a href="./Mahanoy_Creek" id="mwAnY" rel="mw:WikiLink" title="Mahanoy Creek">Mahanoy Creek</a> had fish, but that tributary had 20 fish species?