Age and Growth of Bluefish 

 Pomatomus saltatrix from 

 the Morthern Gulf of Mexico 

 and U.S. South Atlantic Coast 



Lyman E. Barger 



Panama City Laboratory, Southeast Fisheries Center 



National Marine Fisheries Service, NOAA 



3500 Delwood Beach Road, Panama City, Florida 32408 



The liluefish Pomatomus snltntrix is 

 a migratory coastal pelagic fish 

 generally found in temperate and 

 warm continental shelf waters of all 

 oceans (Briggs 1960). The species 

 occurs along the east coast of the 

 United States and the coast of the 

 Gulf of Mexico. Important commer- 

 cial and recreational fisheries for 

 bluefish exist throughout the U.S. 

 range (Wilk 1977). 



Age and growth studies have 

 been conducted on bluefish from 

 U.S. Atlantic waters (Hamer 1959, 

 Backus 1962, Lassiter 1962, Rich- 

 ards 1976, Wilk 1977), but not from 

 the Gulf of Mexico. The primary 

 purposes of this study were to eval- 

 uate and use the best of several 

 bony structures to estimate the age 

 and determine growth of bluefish 

 from the northern Gulf of Mexico 

 (hereafter referred to as Gulf) and 

 from the U.S. Atlantic coast. 



Methods 



Bluefish from the northern Gulf gill- 

 net fishery were sampled monthly 

 from 1978 through 1982 (Feb-Nov) 

 and in the Atlantic along the south- 

 ern U.S. east coast in 1980 and 1981 

 (Jan-July). These samples were 

 augmented by catches from the 

 seine and hook-and-line fisheries. 

 The Gulf samples were collected 

 from the coastal waters off north- 

 west Florida and Louisiana, while 

 Atlantic samples were taken along 



the coast from South Carolina to 

 Florida. 



Fork length (FL) to the nearest 

 millimeter (mm), weight (W) to the 

 nearest gram (g), and sex were 

 recorded from 1 190 Gulf and 842 

 Atlantic bluefish, and one or both 

 otoliths (sagittae) were removed, 

 wiped clean, and stored dry in vials. 

 A subsample of 100 fish represent- 

 ing the entire size range of bluefish 

 caught in the Gulf during May and 

 June 1978 was selected for com- 

 parison among ageing structures. 

 From these 100 fish, in addition to 

 otoliths, the tenth vertebra anterior 

 to the hypural plate was removed 

 and scales were taken from the left 

 side under the pectoral fin. Verte- 

 brae were cleaned and air-dried. 

 Both vertebrae and scales were 

 stored dry in envelopes. 



Otoliths were placed in glycerol, 

 sulcus acousticus down, in a black 

 dish and were examined under re- 

 flected light using a binocular-dis- 

 secting microscope with an ocular 

 micrometer. The most legible oto- 

 lith from each fish was examined for 

 age marks. The second otolith from 

 25 of the bluefish was sectioned to 

 allow interior examination. Tlie 

 otoliths were embedded in Lakeside 

 70C thermoplastic cement and, to 

 include the locus, 2 or 3 thin sec- 

 tions (0.15 mm) were cut along the 



Reference to trade names does not imply en- 

 dorsement by the National Marine Fisheries 

 Service, NOAA. 



transverse plane, using a Buehler 

 isomet slow-speed saw. The cement 

 was dissolved with isopropyl alco- 

 hol, and then the otolith sections 

 were mounted on glass slides and 

 examined on a black background in 

 the manner of whole otoliths. 



On whole or sectioned otoliths an 

 opaque zone (mark) preceded by a 

 translucent (hyaline) zone (Fig. la) 

 was assumed to be an age mark. 

 Measurements (OR) were made 

 along the longitudinal axis of the 

 rostrum from the focus to the distal 

 edges of the marks and of the 

 otolith. A determination of the 

 edge character (opaque or translu- 

 cent) was made, and marks were 

 counted. A mark was not consid- 

 ered complete, so not counted or 

 measured, unless the portion of the 

 otolith distal to it was translucent. 

 The rostrum was selected for ex- 

 amination because the postrostrum 

 had an uneven edge which proved 

 difficult to measure. 



Vertebrae were stained with crys- 

 tal violet following the technique of 

 Johnson (1979). To facilitate the ob- 

 servation of age marks, the verte- 

 brae were cut in half, anterior- 

 posteriorly, with a Dremel saw. 

 Both halves of the vertebrae were 

 examined under a binocular-dissect- 

 ing microscope using reflected light. 

 The most legible posterior centrum 

 was used. 



An age mark on the vertebral 

 cone surface was counted if a prom- 

 inent concentric ridge preceded by 

 a depression was observed (Fig. lb). 

 Measurements were made from the 

 vertex (focus) of the centrum to the 

 distal edge of each mark as well 

 as to the terminal edge of the 

 vertebra. 



Scales were cleaned in a weak 

 solution of water and liquid deter- 

 gent, then mounted between two 

 glass slides. Scales from 15 blue- 

 fish were also impressed on plastic 

 slides with a cold roller press. Both 



Manuscript accepted Hi Ma.v 1990. 

 Fishery Bulletin. U.S. 88:80.5-809. 



805 



