companied in this space by a second pterygiophore, 

 which carries a single spine (the third). The succeeding 

 several pterygiophores alternate one on one with neural 

 spines. The first and second neural spines lie close 

 together and often point forward, in contrast to the diver- 

 gent angle between neural spines two and three neces- 

 sary to accommodate the anterior two pterygiophores. In 

 several genera a single, short predorsal bone was ob- 

 served immediately before the first neural spine; this 

 bone is more readily seen on cleared and stained 

 specimens than on radiographs. 



The number of principle caudal rays (those supported 

 by hypurals and the parhypural according to our defini- 

 tion) in most scorpaenid fishes is 8 -I- 7 = 15. The number 

 of branched rays is either 6 -H 6 (Sebastes, Ectre- 

 posebastes) or 6 -I- 5 (Sebastolobus, Helicolenus, Scor- 

 paenodes, Scorpaena, Pontinus). Hence in these scor- 

 paenid genera there are two unbranched principal rays 

 associated with the upper lobe of the caudal fin, and 

 either one or two associated with the lower lobe — one un- 

 branched if the branched ray count of the lower lobe is 

 six, two unbranched if the branched ray count is five. 

 The principal rays of both lobes of the caudal fin are sup- 

 ported exclusively by hypural bones (we include the 

 parhypural as a hypural). The primitive condition, 

 which we have observed in Ectreposebastes imus, is the 

 retention of three superior and three inferior hypurals 

 (including the parhypural). Among the genera included 

 in this guide, Scorpaenodes and Pontinus retain the 

 primitive complement of three superior hypurals, but 

 have the inferior complement reduced to two. In the 

 other four genera there are two superior and two inferior 

 hypurals. The primitive complement of three epurals is 

 retained by all scorpaenids studied. Only one pair of 

 uroneurals was observed on specimens examined. The 

 neural spine on the vertebral centra immediately an- 

 terior to the ural is markedly reduced or lacking. The 

 haemal spine on this vertebra is autogenous, as is the 

 haemal spine on the vertebra immediately anteriad. 



Since changes in body shape during larval develop- 

 ment are illustrated and are emphasized in the descrip- 

 tions, we will discuss them only briefly here. Newly 

 hatched larvae of all scorpaenids studied are more slen- 

 der, often markedly more slender, than are later larval 

 stages. Larvae of Sebastes and Helicolenus are usually 

 more slender in later larval stages than are those of the 

 other genera. The eastern Pacific Sebastes with the slen- 

 derest body is S. jordani; in postflexion larvae the 

 average relative body depth is less than 25% standard 

 length (range of 22 to 26''p). Relative body depth for post- 

 flexion larvae of other species ranges from 30 to 37%. 

 Average relative body depth for postflexion specimens in 

 the other genera is as follows: Sebastolobus, 35 and 41% 

 for its two species; Scorpaenodes, 39%; Scorpaena, 38 to 

 40% for two species; Pontinus, 39 and 42% for two species; 

 and Ectreposebastes up to 55%. 



A knowledge of the sizes at initiation of major develop- 

 mental events such as hatching, notochord flexion, and 

 transformation aids in identifying scorpaenid larvae. 

 There is a major dichotomy between Sebastes and the 



other genera in the size at hatching — Sebastes hatches at 

 3.8 to 7.5 mm body length and the other genera hatch at 

 1.8 to 2.8 mm (Table 4). Sebastes larvae are also longer 

 at notochord flexion (6 to 12 mm) than the tropical 

 genera Scorpaenodes, Scorpaena, Pontinus, and Ec- 

 treposebastes (4 to 6 mm) and the other temperate- 

 boreal genera, Sebastolobus and Helicolenus, are inter- 

 mediate (6 to 8 mm). Size at transformation from larva 

 to pelagic juvenile is highly variable among genera and 

 species of scorpaenids (Table 4). 



Also essential for identification of scorpaenid larvae is 

 the locality of collection. Three of the seven genera dealt 

 with here are cold-water forms, temperate to subarctic in 

 distribution (Sebastes, Sebastolobus, and Helicolenus) 

 and the other four genera are tropical to subtropical. 

 Trachyscorpia will probably be shown to occur only in 

 the deep coastal waters of the southeast Pacific. The 

 single known specimen was taken from 580 to 600 m 

 (Chirichigno 1974) and listed as Trachyscorpia sp. 



Over much of the California Current (CalCOFI) area, 

 the genera that commonly cooccur are Sebastes and 

 Sebastolobus. Although adults of Sebastolobus have 

 been taken as far south as Cape San Lucas, Sebastolobus 

 larvae are seldom taken south of California (Moser 1974). 

 Larvae of some species of Sebastes (e.g., S. macdonaldi) 

 are distributed primarily off Baja California (Moser 

 1972), but larvae of most species of Sebastes have a more 

 northern distribution. 



In the area covered on EASTROPAC and STOR 

 cruises, between lat. 20°N and lat. 20°S, the larvae com- 

 monly taken are those of Pontinus and Scorpaenodes, 

 with larvae of Scorpaena collected occasionally and lar- 

 vae of Ectreposebastes found in equatorial waters as far 

 offshore as long. 126°W. To the south of the EAS- 

 TROPAC area, three temperate genera (Helicolenus, 

 Sebastes, and Trachyscorpia) occur. Larvae of Scorpaena 

 guttata are occasionally taken off southern California 

 and occur along Baja California south to Magdalena 

 Bay, hence cooccur commonly with Sebastes larvae. Lar- 



Table 4- Length (rm) at hatching, notochord flexion, transformation into pelagic 

 juveniles, and known lengths of pelagic juveniles of scorpaenid 

 fishes included in this guide. 



