vertebrae 11, caudal vertebrae 13 (these vertebral differentiations 

 into precaudal and caudal elements are clear [see Nakamura, 

 1938 and Pis. 4-5 of 1955 translation] and no variant is known for 

 any species). 2. The bill is proportionately longer in juveniles 

 than in adults vs. the opposite condition (this is independent of 

 the ultimate length of the bill of any species). 3. Size relatively 

 small, less than 200 lbs., except for T. audax which sometimes ex- 

 ceeds 400 lbs. (as previously noted [Robins and de Sylva, 1961: 

 403] the world-record 692-lb. striped marlin is misidentified and 

 is really Makaira nigricans, the blue marlin) vs. size very large, 

 both species approaching 2000 lbs. 4. Anterior lobe of dorsal fin 

 high, equal to or exceeding the body depth at this point us. 

 anterior lobe of dorsal low, less than the body depth at this point. 



Robins and de Sylva (1960, 1963) assign, as a result 

 of their work, five distinct species to the genus Tetrap- 

 turus — T. angustirostris, T. belone, T. pfluegeri, T. 

 albidus, and T. audax — with a transition running 

 from Tetrapturus of the angustirostris type to that of 

 the audax type consecutively. Specific differences are 

 discussed in Robins and de Sylva, 1963, p. 100-102, 

 Tables 6 and 7. 



Specific 



Type specimen: No type specimen exists. 



Type locality: North coast of Cuba (Poey, 1861). 



Diagnosis: Fishes of the family Istiophoridae are dis- 

 tinguished from all others by the extension of the up- 

 per jaw into a short pointed spear of nearly round 

 cross section, and a pair of small cartilaginous keels 

 on either side of the base of the caudal fin. In the most 

 closely related family, Xiphiidae, the upper jaw is ex- 

 tended into a long sword, much flattened vertically 

 and sharp at the horizontal edges; there is a single 

 large fleshy keel on either side of the base of the 

 caudal fin, and the ventral fins, present in the 

 Istiophoridae, are lacking. 



In its adult form, T. albidus is easily distinguished 

 from the other Istiophoridae. It differs from the 

 Makaira species in: vertebral count — 12 + 12 vs. 11 + 

 13; maximum height of first dorsal fin — more than 

 depth of body vs. less than depth of body; body 

 ehape — slender (depth less than length of pectoral 

 fin) vs. stout (depth usually greater than length of 

 pectoral fin); lateral line — distinct, single vs. obscure, 

 single or complex; lobes of first dorsal and first anal 

 fins — strongly rounded at extremities vs. pointed at 

 extremities; spear — long and slender vs. short and 

 stout; size — small (less than 100 kg) vs. large (ap- 

 proaching 1,000 kg). The above characters are from 

 Nakamura (1949), LaMonte (1955), and Robins and 

 de Sylva (1960, 1963). Tetrapturus albidus is easily 

 distinguished from Istiophorus by the size and shape 

 of the first dorsal fins. The first dorsal of T. albidus is 

 distinctly peaked anteriorly, and its height tapers 

 posteriorly. Its maximum height is less than twice the 

 body depth. The dorsal fin of Istiophorus is highest in 

 the middle portion of its length, and its maximum 

 height is much more than twice the body depth. 



Tetrapturus albidus may be distinguished from T. 

 belone, T. pfluegeri, and T. angustirostris by the 

 strongly rounded lobes of its first dorsal and first anal 

 fins, the shape of its dorsal fin, and the location of its 

 anus. The anterior distal extremities of the first 

 dorsal and first anal fins of the latter three species are 

 pointed rather than rounded; their first dorsal fins are 

 not as distinctly peaked anteriorly, and are higher in 

 their middle portion than that of T. albidus, making 

 the height of the fin more nearly uniform. The anus of 

 T. albidus is near (4.8-5.8% of body length) the anal 

 fin origin, but in the other three species, it is from 6.3 

 to 11% of the body length from the anal fin origin. The 

 spear of T. albidus (26-35% of body length) is longer 

 than that of T. pfluegeri (19-25% of body length) and 

 much longer than those of T. belone and T. 

 angustirostris. These data are from Robins and de 

 Sylva (1963). 



Tetrapturus audax is the species most similar in ex- 

 ternal appearance to T. albidus. Although the former 

 is an Indo-Pacific species, the ranges of the two 

 overlap at least off South Africa (Talbot and Penrith, 

 1962). The main difference noted by LaMonte (1955) 

 was the lateral line — conspicuous in T. albidus, and 

 invisible or very inconspicuous in T. audax. Robins 

 and de Sylva (1960) separate these species on the 

 basis of the strongly rounded tips of the spinous dor- 

 sal, anal, and pectoral fins, and the red flesh of T. 

 albidus, and the pointed tips of these fins, and pale 

 flesh, of T. audax. The experience of the senior author 

 has been that roundedness vs. pointedness of pectoral 

 fins is a very unreliable character in separating scom- 

 broid fishes and that the tip of the spinous dorsal of T. 

 audax is not always sharply pointed. The best 

 character in separating these species probably is the 

 shape of the anal fin. In fact, this character easily 

 separates T. albidus from all the other Istiophoridae. 



The diagnosis of larval and juvenile T. albidus is lit- 

 tle known. We can only reproduce the key of de Sylva 

 (1963) for young specimens (50-500 mm in length) of 

 the istiophorid species known in the western Atlantic. 



A provisional key is presented to assist identification of young 

 specimens of known istiophorid species in the western Atlantic, 

 based upon published data and the writer's material . . .; this key 

 should suffice for specimens from about 50 to 500 mm in length: 



la. Anus placed far forward, approximately midway between 

 bases of anal and pelvic fins; pelvic fins short, not reaching nearly 

 to base of anal fin; dorsal fin unspotted or mottled; dorsal spine 

 count high, 45-53, modally 49 (see Robins and de Sylva, 1963, 

 Table 5) Longbill spearfish, Tetrapturus pfluegeri 



lb. Anus placed close to anal fin base; pelvic fins long, reaching 

 nearly to base of anal fin; dorsal fin variously spotted or mottled; 

 dorsal spine count relatively low, 38-49 2 



2a. Lateral line complex, partly forming a reticulated pattern 

 (see Gehringer, 1957, Fig. 25; LaMonte, 1958, PI. 75, Fig. 2; de 

 Sylva, 1958, PI. 81, Figs. 1-3; Caldwell, 1962, Fig. 1); bill short, 



only slightly longer than the mandible 



Blue marlin. Makaira nigricans 



57 



