i ▁is ▁fragment ed ▁and ▁limited ▁to ▁less ▁dist urbed ▁areas . ▁Lar ge ▁decl ines ▁in ▁numbers ▁or ▁local ised ▁ext in ctions ▁are ▁thought ▁to ▁have ▁occurred ▁in ▁the ▁Welcome , ▁Mont agu , ▁Rub icon , ▁Don , ▁Br id , ▁Bo ob yal la , ▁P ip ers , ▁Ring aro oma , ▁D uck , ▁Little ▁and ▁Great ▁For ester ▁R ivers ▁and ▁Clay tons ▁Riv u let . ▁Eastern ▁populations ▁are ▁particularly ▁reduced . ▁ ▁Hab itat ▁A . ▁g ould i ▁inhab it ▁slow - mov ing ▁rivers ▁and ▁streams ▁of ▁several ▁sizes ▁including ▁head w aters ▁and ▁riv u lets . ▁Water ▁should ▁be ▁of ▁high ▁quality ▁with ▁high ▁dissol ved ▁o xygen ▁content , ▁little ▁susp ended ▁sed iment , ▁and ▁water ▁temper atures ▁between ▁, ▁although ▁relatively ▁low ▁temper atures ▁are ▁preferred . ▁Ad ult s ▁need ▁still , ▁deep ▁po ols ▁with ▁sub mer ged ▁decay ing ▁logs ▁and ▁over h anging , ▁but ▁not ▁er oding , ▁banks ▁to ▁shelter ▁beneath . ▁ ▁Ju ven iles ▁prefer ▁shall ow , ▁faster - flow ing ▁stream ▁habit ats ▁with ▁distinct ▁cav ities ▁to ▁hide ▁under ▁and ▁higher ▁port ions ▁of ▁b older ▁substr ate ▁and ▁m oss ▁cover . ▁ ▁Ex cell ent ▁habitat ▁requires ▁int act , ▁native ▁rip arian ▁veget ation ▁which ▁is ▁dens ely ▁can op ied ▁and ▁sh ades ▁the ▁water ways . ▁However , ▁the ▁species ▁has ▁been ▁recorded ▁in ▁conf ines ▁of ▁non - native ▁rip