Emerging market carry trades are taking off again, as currency volatility subsides amid signs President Donald Trump’s aggressive tariffs may not get fully enacted. An index of carry returns — for which a trader borrows in a low-yielding currency and then invests in another offering higher returns — hit a seven-year high in late May. Asset managers have boosted long positions in developing-nation currencies in recent weeks, with those on Mexico’s peso reaching a nine-month high, based on CME Group Inc. data.“Carry trades at this juncture, they do make sense,” said...