BUENOS AIRES, July 31 (Reuters) - Argentina's stock, currency and bond market trends on Friday:
* The MerVal stock index .MERV rose 1.39 percent to 1,719.87, its highest since September, on the strength of energy-related shares that shot up with crude oil prices.
* The index gained 8.31 percent in July and is up almost 60 percent since the start of the year.
* Shares of steelmaker Tenaris TENA.BA TS.N, a leading producer of pipes for the energy sector that accounts for almost half of the MerVal, climbed 2.29 percent to 58 pesos.
* On the broad market, volume was brisk at $17.3 million. Among active issues, 73 rose, 14 fell and 16 were unchanged.
* Prices for government bonds traded over-the-counter in Buenos Aires climbed 1.4 percent on average. Bonds have posted an 8.0 percent gain since the start of the month.
* Bond prices have been rising since last week, when the economy minister said he would seek to swap and buy back the inflation-indexed bonds that account for at least a third of the country's sovereign debt.
* The peso-denominated Par bond was among the day's winners, rising 3.4 percent ARPARP=RASL to an ask price of 23.80.
* In formal trade between banks, the peso held steady at 3.8275/3.8300 per U.S. dollar ARS=RASL in light trade, as the central bank intervened to hold the currency stable. The peso weakened a total of 0.85 percent in July.
* In informal trade between foreign exchange houses as measured by Reuters, the peso strengthened 0.13 percent to 3.865/3.8700 per dollar ARSB=. (Reporting by Walter Bianchi; Writing by Dana Ford; Editing by James Dalgleish)