Comyns and Grant Urophycis and Phycis larvae and pelagic |uveniles 



213 



Results 



Identification of Urophycis and Phycis larvae 

 and juveniles 



Meristics 



Epibranchial gill rakers (Table 3) A complete size- 

 series of all species was not available, but size (mm) at 

 which U. regia, U. chuss, and U. tenuis larvae attain 

 the adult complement of epibranchial gill rakers and 

 other meristic elements is shown in App. Table 2. The 

 following sections are abbreviated to avoid repeating 

 in the text what the tables and figures succinctly show. 

 Phycis chesteri does not attain the adult complement 

 of epibranchial gill rakers until 16-18 mm (Methven 

 1985), but by 13 mm the third gill raker has developed 

 and serves to separate larvae of this species from U. 

 tenuis, U. earlli, and U. floridana. Occasionally U. chuss 

 and U. regia possess two or four epibranchial gill rak- 

 ers on one side, but most of these specimens have the 

 normal complement of three gill rakers on the other 

 side. Urophycis tenuis occasionally possesses a 3rd 

 epibranchial gill raker, but only very rarely is this 

 third gill raker found on both sides of a specimen. 



Caudal-fin rays (Table 3) All but two specimens of 

 U. tenuis (rc=195) had more caudal-fin rays than all 

 other species of Urophycis. Numbers of caudal-fin rays 

 of U. tenuis overlapped those of P. chesteri, but more 

 than half of our U. tenuis were distinct in having >36 

 rays, and over 40% of P. chesteri (n-56) differed from 

 U. tenuis in having <34 rays. As few as 28 caudal-fin 

 rays have been reported in P. chesteri (Wenner 1983) 

 and U. cirrata (J.A. Musick, VA Inst. Mar. Sci., pers. 

 commun.), but this may be because some of the small 

 procurrent rays are not easily seen in radiographs of 

 larger fish. 



No U. earlli specimens (n=31) possessed >31 caudal- 

 fin rays, while all other hake commonly have >31 rays. 



Dorsal-fin rays (Table 3) Despite overlapping ex- 

 tremes, numbers of first dorsal-fin rays helped distin- 

 guish U. floridana from other species of hake. In our 

 material, U. regia and U. earlli never possessed >10 

 and 11 first dorsal-fin rays, respectively, while over 

 80% of U. floridana (ra=45) had >11 rays. One-third of 

 U. floridana specimens examined possessed 13 first 

 dorsal-fin rays, delimiting these from all other hake 

 taxa. 



The relatively low number of second dorsal-fin rays 

 in U. regia separated this species from P. chesteri and 

 other Urophycis species with little overlap. Urophycis 

 chuss and U. regia with incomplete development of 

 second dorsal-fin rays were delimited by numbers of 

 pterygiophores supporting these rays at sizes as small 

 as 6mm (Fig. 2). Although extremes in numbers of 



second dorsal-fin rays overlapped in all other taxa, 

 many of the available specimens of U. earlli and U. 

 cirrata were distinct in possessing >63 rays. 



Abdominal vertebrae (Table 3) Numbers of ab- 

 dominal vertebrae cannot be used alone to identify 

 individual specimens because of overlapping extremes, 

 but this meristic character is useful when identifying 

 collections comprised entirely off/, tenuis or U. chuss. 

 Urophycis tenuis larvae, identified by numbers of 

 epibranchial gill rakers and caudal-fin rays, were found 

 in the MAB only in spring and accounted for 99% of 

 the Urophycis collected at this time ( U. regia juveniles 

 accounted for the other 1%). Urophycis larvae <10mm 

 (n=154) that were present in spring collections had 

 not yet developed the adult complement of caudal-fin 

 rays, but these larvae (>4 mm) had developed the adult 

 complement of abdominal vertebrae and were identi- 

 fied as U. tenuis because their frequency-distribution 

 of numbers of abdominal vertebrae was identical to 

 that found in larger U. tenuis; 88% of the larvae had 

 16 abdominal vertebrae, and no specimens were found 

 with <15. It is unlikely that any of these small larvae 

 were U. floridana or U. cirrata, two other species with 

 similar numbers of abdominal vertebrae, because these 

 two southern species were found only in offshore 

 winter collections and most specimens were pelagic 

 juveniles. 



Urophycis chuss >4 mm (n=448) possessed 14-16 ab- 

 dominal vertebrae, but the majority of specimens 

 (n=391) had 15. In all other species of Urophycis the 

 count of 15 occurred in <20% of the specimens; and 

 although extremes of U. chuss and P. chesteri were 

 similar, P. chesteri commonly had 14 or 16 abdominal 

 vertebrae (17%). Consequently, in the MAB during late 

 summer when U. chuss larvae are extremely abun- 

 dant (and, in this study, were the only species of hake 

 found at this time), complete meristic counts to check 

 for species other than U. chuss need be performed only 

 on those specimens that do not have 15 abdominal 

 vertebrae. If species other than U. chuss are found in 

 late-summer collections, numbers of abdominal verte- 

 brae are no longer taxonomically useful and complete 

 meristic counts are necessary to identify larvae. 



Urophycis regia (n=698) had 13-15 abdominal ver- 

 tebrae, but only eight specimens had 15, and seven of 

 these specimens had an anomalous 15th abdominal 

 vertebra. This anomalous vertebra possessed one short 

 transverse process characteristic of abdominal verte- 

 brae and one long transverse process typical of caudal 

 vertebrae. Because 99.9% of U. regia examined had 

 <15 normal abdominal vertebrae, it was assumed that 

 specimens with >15 abdominal vertebrae were not U. 

 regia. This meristic character aided in the separation 

 of small (<6mm) U. chuss and U. regia in fall collec- 



