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Chapter 9 - Large Pelagic FishBlue Marlin (Makaira nigricans)Blue marlins are found throughout the Atlantic Ocean inoffshore areas mostly between 45 o N and 35 o S (Nakamura1985). They are highly migratory and seasonal movementsare correlated to changes in sea surface temperature (especiallythe 24 o C isotherm). Blue marlin are solitary anddo not typically school (Nakamura 1985). ICCAT (2001)considers there to be a single Atlantic stock of blue marlin.Blue marlins spawn outside the Northwest Atlantic regionin marine habitats (Nakamura 1985). Female bluemarlin mature when they reach 104 to 134 lbs, while malesmature at smaller weights, from 77 to 97 lbs (NMFS1999). Pelagic eggs and fast-growing larvae are found inthe same habitat as the spawning region. Larvae are foundin marine waters with a temperature of >24 o C and aregenerally bounded by 100-2000m isobath or to the EEZ(NMFS 1999). Pelagic juveniles are obligate marine andfound within temperatures ranging between 22 and 31 o C.From Jan-April adult blue marlins are found in the SWAtlantic (5-30 o N) and from June-Oct. in NW Atlantic(10-35 o N). Maximum total length recorded for bothmales and females is 500 cm (NMFS 1999). Maximumweight of males is 170-175 kg, while females grow largerand faster than males, and can reach a maximum weightof over 900kg (NMFS 1999). Blue marlin feed at a widevariety of depths and their diet consists of other mediumsized oceanic organisms like tuna and squid (Collette andKlein-MacPhee 2002).White Marlin (Tetrapturus albidus)Atlantic white marlin are distributed widely in the AtlanticOcean, in coastal and offshore areas, mostly ranging from45 o N to 45 o S (NMFS 2009). Animals are generally foundalone, but can be found in small schools grouped by sizeor sex (Nakamura 1985). This species follows the thermoclineand is usually found in the upper 20 to 30 m of thewater column, but may dive to depths of 200 to 250 m inwarmer areas. White marlin are only found at the higherlatitudes of their range in the warmer months. Taggingdata has shown that white marlin undergo extensive migrations;maximum movement has been 6523 km, with amean displacement of 719 km (Orbesen et al. 2008).Spawning occurs outside the Northwest Atlantic in marinewaters of the Caribbean during early summer atwater temperatures greater than 68 o F (NMFS 2008).Known spawning areas include the area northeast of LittleBahama Bank, northwest of Grand Bahama Island, andsouthwest of Bermuda (NMFS 1999). Spawning activityoccurs during the spring (March through June) in northwesternAtlantic tropical and sub-tropical waters markedby relatively high surface temperatures (20° to 29°C) andsalinities (> 35 ppt). When female white marlin reach 20kg and 130 cm in length, they become sexually mature(NMFS 2009). Females spawn by releasing eggs andmay do so up to four times a year (NMFS 2009). Bothlarvae and juveniles are oceanic and pelagic. Adult whitemarlin can grow larger than 300 cm and weight 82 kg(Nakamura 1985). Females grow larger than males. Whitemarlin are known to stun or kill their prey with theirbill, but also consume prey whole (Nakamura 1985). Themajority of their prey consists of fishes, crustaceans, andcephalopods.Bigeye Thresher (Alopias superciliosus)Bigeye thresher sharks are coastal and oceanic and foundthroughout the world in tropical and temperate seas(NMFS 2009). Within the Western Atlantic, bigeyethreshers range from New York to Florida (Compagno2001). They are found in waters over the entire continentalshelf, in both shallow and deep waters (Gruberand Compagno 1981). Recent studies have determinedthat bigeye threshers may not have the thermoconservingmechanisms, the ability to maintain a body temperatureabove ambient water temperature, that the thresher sharkhas (Sepulveda et al. 2005).Male bigeye thresher males mature at about 279 to 300cm in length when they reach between 9 and 10 yearsof age and live up to about 19 years (Compagno 2001).Females mature at approximately 294 to 355 cm in lengthwhen they reach between 12 and 13 years of age and livefor 20 years (Compagno 2001). The exact location ofbreeding grounds has not yet been identified for thesesharks (NMFS 2009). These sharks are ovoviviparousand births may occur through the year, although in theNorthwest Atlantic Marine Ecoregional Assessment • Phase 1 Report 9-31