778 



Abstract— Lengths and ages of sword- 

 fish (Xiphias gtadius) estimated from 

 increments on otoliths of larvae col- 

 lected in the Caribbean Sea, Florida 

 Straits, and off the southeastern United 

 States, indicated two growth phases. 

 Larvae complete yolk and oil globule 

 absorption 5 to 6 days after hatching 

 (DAH). Larvae <13 mm preserved 

 standard length (PSD grow slowly 

 (-0.3 mm/d); larvae from 13 to 115 mm 

 PSL grow rapidly (-6 mm/d). The accel- 

 eration in growth rate at 13 days fol- 

 lows an abrupt (within 3 days) change 

 in diet, and in jaw and alimentary canal 

 structure. The diet of swordfish larvae 

 is limited. Larvae <8 mm PSL from 

 the Caribbean, Gulf of Mexico, and 

 off the southeastern United States eat 

 exclusively copepods, primarily of one 

 genus, Corycaeus. Larvae 9 to 11 mm 

 eat copepods and chaetognaths; larvae 

 >11 mm eat exclusively neustonic fish 

 larvae. This diet indicates that young 

 larvae <11 mm occupy the near-surface 

 pelagia, whereas, older and longer 

 larvae are neustonic. Spawning dates 

 for larvae collected in various regions of 

 the western North Atlantic, along with 

 the abundance and spatial distribution 

 of the youngest larvae, indicate that 

 spawning peaks in three seasons and 

 in five regions. Swordfish spawn in the 

 Caribbean Sea, or possibly to the east, 

 in winter, and in the western Gulf of 

 Mexico in spring. Elsewhere swordfish 

 spawn year-round, but spawning peaks 

 in the spring in the north-central Gulf 

 of Mexico, in the summer off southern 

 Florida, and in the spring and early 

 summer off the southeastern United 

 States. The western Gulf Stream fron- 

 tal zone is the focus of spawning off the 

 southeastern coast of the United States, 

 whereas spawning in the Gulf of Mexico 

 seems to be focused in the vicinity of 

 the Gulf Loop Current. Larvae may use 

 the Gulf of Mexico and the outer con- 

 tinental shelf off the east coast of the 

 United States as nursery areas. Some 

 larvae may be transported northward, 

 but trans-Atlantic transport of larvae 

 is unlikely. 



The early life history of swordfish (Xiphias gladius) 

 in the western North Atlantic 



John Jeffrey Govoni 



Elisabeth H. Laban 



Jonathan A. Hare 



Center for Coastal Fisheries and Habitat Research 



National Oceanic and Atmospheric Administration 



101 Rivers Island Road 



Beauloa North Carolina 28516-9722 



E-mail address (for J, J, Govoni): Jeff Govoni(5>noaa gov 



Manuscript approved for publication 

 17 April 2003 by Scientific Editor 



Manuscript received 26 June 2003 at 

 NMFS Scientific Publications Offfice. 



Fish. Bull. 101:778-789 (2003). 



Swordfish (Xiphias gladius) live in 

 warm waters of the world's oceans, as 

 well as in large enclosed basins such 

 as the Caribbean and Mediterranean 

 seas, and the Gulf of Mexico (Berkeley, 

 1983). Swordfish are highly migratory 

 throughout their global range. The 

 worldwide population structure, as 

 currently understood, has at least three 

 breeding units: Mediterranean, north- 

 western Atlantic to the tropical South 

 Atlantic, and Indo-Pacific (Kotoulas et 

 al., 1995; Chow and Takeyama, 2000; 

 Reeb et al., 2000). For the purpose of 

 fishery management, the International 

 Commission for the Conservation of 

 Atlantic Tunas (ICCAT) recognizes 

 only North Atlantic and South Atlan- 

 tic stocks. Possible genetic exchange 

 between eastern and western North 

 Atlantic populations is incompletely 

 documented. 



Swordfish reportedly spawn year- 

 round in the western North Atlantic in 

 different seasons and regions. Spawn- 

 ing season and location has been 

 inferred from the abundance of small 

 larvae (Gorbunova, 1969; Richards 

 and Potthoff, 1980; Potthoff and Kel- 

 ley, 1982; Grail et al, 1983; Govoni et 

 al., 2000), gonad maturation (LaMonte, 

 1944; Beckett, 1975), or oocyte cytol- 

 ogy (Taylor and Murphy, 1992; Arocha, 

 1997; Arocha, 2002). The observation of 

 live females with running eggs, hooked 

 on long-lines, and followed to the fishing 

 vessel by several smaller males (Lee^; 

 Berkeley''^) corroborates spawning in 

 some seasons and locations. Although 

 gonad condition and oocyte status can 

 indicate spawning season, the resolu- 

 tion of spawning location can be am- 

 biguous with these methods because 



mature gonads and hydrated oocytes 

 can be found in several seasons within 

 the range of these highly migratory 

 fishes. The determination of age and 

 the distribution of young larvae, along 

 with realistic estimates of water veloc- 

 ity and trajectory, help to resolve this 

 ambiguity. 



Beyond spawning, the early life his- 

 tory of swordfish in any ocean is incom- 

 pletely described (Palko et al., 1981). 

 Larvae undergo a stark change in 

 physical appearance between ~8 and 13 

 mm preserved standard length (PSL), 

 from a typical scombroid larval form to 

 a juvenile istiophorid one (Collette et 

 al., 1984). At this juncture in develop- 

 ment, larvae develop characteristic 

 preorbital, supraorbital, posttemporal, 

 and preopercular spines; enlarged and 

 spinous dorsal, ventral, and lateral 

 scale anlagen; and a continuous long 

 dorsal fin that extends along most of 

 the dorsal aspect. Swordfish retain 

 these larval characters until they are 

 at least 188 mm PSL (Arata, 1954; Pot- 

 thoff and Kelley, 1982), a size at which 

 most fishes are considered juveniles. 

 By using the ages and lengths of larvae 

 hatched in the laboratory and reared 

 through yolk and oil globule absorp- 

 tion (Sanzo, 1910; Yasuda et al., 1978), 

 along with length frequencies of larvae 

 caught in the western North Atlantic, 



' Lee, D. J. 1995. Personal commun. 

 Southeast Fisheries Science Center, 

 NMFS, 75 Virginia Beach Drive, Miami, 

 FL 33149. 



'^ Berkeley, S. A. 1998. Personal commun. 

 Long Marine Laboratory, Univ. California, 

 Santa Cruz, 100 Shaffer Road, Santa Cruz, 

 CA 95060. 



