Table I. Size-age groups used to discuss much of the biological and fisheries data 

 for Atlantic bluef'in tuna in this report. 



Group 



Length Weight Approximate Age 



(cm) (in) (kg) (lbs) (years) 



Very small < 50 <20 



Small 50-120 20-48 



Medium 120-185 48-76 



Large or Giant >185 >76 



the snout (tip of upper jaw) to the pos- 

 terior medial margin of the caudal fin 

 (Figure 2). In this paper, length mea- 

 surements exceeding 12 cm are fork 

 lengths unless defined otherwise. An 

 alternative method of measuring fork 

 length is with a tape and following the 

 lateral contour of the body. Lengths 

 measured by this method have been 

 referred to as tape lengths, curved 

 lengths or flank lengths. The slope of a 

 linear regression which Schuck and 

 Mather fitted by inspection to a plot of 

 straight lengths against curved lengths 

 for each of a series of western north 

 Atlantic bluefin tuna from 35 to 270 

 cm longindicated that the straight length 

 was 0.958 times the curved length. Sev- 

 eral other authors have published con- 

 version factors for these parameters. 

 Of course this relationship would vary 

 slightly with the length-girth (or length- 

 weight) ratio of the fish. 



The lengths of juvenile specimens 

 less than 1 2 cm long and of larvae are 

 usually measured in standard length 

 (SL). This is the length from the snout 

 to the end of the vertebral column. In 

 this paper, length measurements of blue- 

 fin tuna less than 12 cm long are stan- 

 dard lengths unless defined otherwise. 



b. Weight 



Weight data for fish are presented 

 in this paper in terms of round, whole, 

 or live weight (the weight of the entire 

 fish) unless othenvise stated. In some 

 fisheries, it is necessary to collect weight 

 data for fish in the condition in which 

 they are sold. This may be in several 

 forms depending on the extent to wh ich 



the fish have been butchered. Conver- 

 sion factors for obtaining round weights 

 from weights in the various other con- 

 ditions are available in the literature 

 and at the Woods Hole Oceanographic 

 Institution. 



Weights of individual fish and av- 

 erage weights of fish are recorded in 

 kilograms, unless otherwise stated. 

 Weights of landings and catches (of 

 numerous fish) are recorded in metric 

 tons unless otherwise stated. 



2. Size- Age Groups 



Much of the biological and fisher- 

 ies data for the Atlantic bluefin tuna 

 will be discussed in terms of the size- 

 age groups shown in Table 1 . The lim- 

 its of these groups were selected to 



correspond as closely as possible to 

 sizes and estimated ages at which the 

 migratory and distributional patterns 

 of the species undergo distinct changes 

 (Mather 1 964b). The ages for the re- 

 spective sizes are from Mather and 

 Schuck ( 1 960). These size groups were 

 set up on the basis of data from the 

 summer fisheries in the northwestern 

 Atlantic and the spring fishery off the 

 Bahamas. They appear, however, to be 

 reasonably applicable to bluefin in the 

 eastern Atlantic and the Mediterranean 

 Sea. 



3. Trap Fishery Terminology 



Specialized terms have been used 

 to describe the bluefin tuna trap fisher- 

 ies of the eastern Atlantic and the Medi- 

 terranean Sea. Since these terms are 

 often misunderstood or poorly trans- 

 lated in the literature, an explanation of 

 them seems desirable. 



The true bluefin tuna traps are very 

 large, complex installations set at spe- 

 cial locations to harvest runs (periodic 

 migratory passages) related to the 

 spawning of these fish. "Arrival" fish 

 are essentially fat, maturing individu- 

 als, generally traveling eastward in late 

 April, May, and June. "Return" fish are 

 essentially lean, spent individuals, gen- 



Table 2. A glossarN' of some of the more important tuna fishery terms in English. 

 French, Italian, Portuguese, and Spanish. 



English 



French 



Italian Portuguese 



Spanish 



Irue Tuna Trap 



Madrague 

 Thonaire' 



Tonnara' 



Minor Tuna Trap Petite Madrague Tonnarella 

 Thonaire Mixle 



' The words thonaire and tonnara arc also used locally for oilier gears which catch tunas 

 or tuna-like fishes 



