BILLFISH, including three species of marlin, sailfish, blackfin and yellowfin tuna, dorado and even wahoo are chomping on lines year-round off the coast of Quepos and Manuel Antonio, on the central Pacific coast. Their activity dwindles during the rainy season, May to November, and surges during the dry season, peaking December through February, fishermen report.If that news makes you wish you had left your golf clubs at home and brought a fishing rod, dozens of companies will lend you their boats, fully equipped and most piloted by captains who either grew up on these shores or migrated here years ago. Inshore varieties include roosterfish, amber jack, snapper and others.The offshore goods are the billfish and others mentioned, all of which are caught and released. Visiting fishermen can sometimes take home a tuna or a dorado, said Ana Arguedas of Sportfishing Wahoo (777-0832), but most of the trophy fish will be immortalized only in photos.Arguedas and her husband Olman Ramos have run Wahoo for more than 10 years, and are looking this year to upgrade to a tiny fleet by adding a second boat in December. They run all-inclusive trips for one to four people, throwing in everything from food to poles for a flat rate of $500 per day.BLUEFIN Sport Fishing Charters and Tours (777-2222, 398-2222, www.bluefinsportfishing.com), a family-owned company operating in Costa Rica for more than 15 years, runs three charter boats on half-, three-quarter and full-day trips. It offers all-inclusive inshore, offshore and fly-fishing trips for discounted rates during the rainy season.“The sailfish season is solid this time of year, and the mahi-mahi, snapper and tuna that you catch on your charter are ready to be grilled for you at several local hot spots,” Bluefin said in a statement. Its management calls September to March the peak billfish season and warned it is already halfway booked for those months. In one “stellar” day recently, the company’s three boats reported catching 12 yellowfin tuna, five blackfin tuna, one dorado, four wahoo, seven sailfish and one 350-pound black marlin.Rivers and deltas are muddied by rainy-season runoff, limiting the availability of solid inshore fishing. Bluefin runs up the coast to estuaries and coral reefs but does not enter the rivers with its big boats, it said. The catch there is snook, six kinds of snapper, wahoo and others.For offshore excursions, Bluefin’s boats go 20-30 miles out to sea, “where the water is crystal clear and calm for sportfishing,” it said.“Just let us know what type of charter you would like and what boat size, and we will take care of the rest at your convenience,” it said. Prices range from $480-900.LUNA Tours Sportfishing (777-0725 www.lunatours.net) owns three sportfishing boats and represents other boats, all ranging in size from 24-45 feet. It charters boats by the day, with discounts during the rainy season, and runs half- and full-day tours. Prices vary according to the boat, from the lowest half-day inshore price of $400 to the highest full-day offshore price of $850.According to the company’s Web site, during the dry season, December through April, catching and releasing more than a dozen sailfish in a day is not unusual, while May to November is the best time to catch yellowfin tuna, marlin and mahi-mahi. Boats can be snatched up quickly, especially during the dry season, so reservations are recommended.