464 
Fishery Bulletin 113(4) 
R 
Figure 6 
Illustration of the caudal skeleton of the single posttransi- 
tion juvenile (13.1 mm in body length) of Acanthistius pa- 
tachonicus that was examined for this study; this specimen 
was caught near Mar del Plata, Argentina, in December 
1963: raylets (R), epurals 1-3 (EP), uroneural (UN), neural 
spines (NS), hypurals 1-4 (HY), branched rays (BR), ante- 
penultimate vertebra (APU), penultimate vertebra (PU), 
urostyle (UR), haemal spines (HS), and parahypural (PH). 
of the preopercle in preflexion larvae <3.1 mm BL. In 
the larger posttransition juvenile (13.1 mm BL), the 
preopercle and the opercle allowed linkage from the 
postflexion stage to the adult stage, because both 
bones in this juvenile matched the osteological descrip- 
tion for adult fish (Gosztonyi and Kuba 5 ; Irigoyen et 
ah, 2008). 
Head spination and pigmentation were useful for 
distinguishing larvae of A. patachonicus from other, 
morphologically somewhat similar species described 
for the Argentine Sea (Sanchez, 1991). Rough scad 
(Trachurus lathami) has a higher number of spines on 
the preopercular margin (Sanchez-Rann'rez and Flores- 
Coto, 1993), and larvae of cabrilla ( Sebastes oculatus ) 
have visible parietal spines by 5.3 mm BL (Sanchez 
and Acha, 1988). The pigmentation pattern of larvae 
of A. patachonicus also differed from those of rough 
scad, cabrilla, and wreckfish (Polyprion americanus ). 
5 Gosztonyi, A. E., and L. Kuba. 1996. Atlas de huesos cra- 
neales y de la cintura escapular de peces costeros patagonic- 
os. Inf. Tec. 4, 29 p. Fundacion Patagonia Natural, Chubut, 
Patagonia, Argentina. [Available at website.] 
Rough scad has numerous melanophores on the 
head and along the dorsal and ventral midlines 
(Sanchez-Ramirez and Flores-Coto, 1993), cabrilla 
has heavy pectoral-fin pigmentation throughout 
larval development (Sanchez and Acha, 1988), and 
wreckfish has strongly pigmented larvae with stel- 
late melanophores all over the body (Sparta, 1939). 
The wreckfish also has a large, oblique mouth that 
reaches the posterior margin of the eye, another 
difference from A. patachonicus (Fig. 3). Finally, 
larvae of dusky grouper (Epinephelus marginatus) 
have serrate and pigmented dorsal and pelvic 
spines that distinguish this species from A. pata- 
chonicus (Cunha et ah, 2013). 
The spawning season of A. patachonicus lasts 
for about 4 months (September-December) during 
the austral spring, between ~36°S and 43°S. The 
presence of its planktonic larvae, which were col- 
lected from November through March, 2008-2013, 
was slightly delayed in relation to the spawning 
season. Because the surveys conducted were not 
specifically designed to study the spatial or tempo- 
ral distribution of this species outside of the SJG 
where a 2-year systematic survey was conducted, 
only limited inference about their distribution 
and abundance patterns can be derived from the 
data available. Analyzing an extensive database 
of fisheries surveys, Irigoyen (2006) reported high 
concentrations of A. patachonicus in shelf areas 
(depths: <90 m) during the reproductive season. 
The occurrence of larvae in coastal areas, to the 
east and north of the mouth of the SMG, was co- 
incident with the reported distribution patterns of 
ripe adults (Irigoyen 2 ). 
Although A. patachonicus is the most abundant 
rocky-reef fish in Northern Patagonia, between 
~40°S and 45°S (Irigoyen et ah, 2008), its larvae 
have been scarce: overall, they were present in only 
17% of the tows conducted between November and 
March in 2009-2013. Only a single individual was cap- 
tured in most of the tows, with few exceptions (Table 
1, Fig. 1). This patchy distribution is consistent with 
the occurrence of spawning aggregations of adults of 
this species (Irigoyen 2 ). However, the small size of the 
larvae collected may also indicate a short pelagic life. 
Indeed, larvae longer than 8.4 mm BL were not found 
(see also Acha et al., 2012), and the juvenile fish that 
was 13.1 mm BL had already metamorphosed, indicat- 
ing that individuals of this species could adopt a de- 
mersal habit at around 13 mm BL. 
Similarly, the mean planktonic larval duration of 
some serranid fishes of the genera Paralabrax, Epi- 
nephelus, and Serranus, for example, ranges between 
18 and 33 days (McClean, 1999; Macpherson and 
Raventos, 2006; Allen and Block, 2012), and 3 species 
of Paralabrax settle to the bottom as larvae between 
9.1 and 10.2 mm BL (Allen and Block, 2012). Further, 
Baldwin and Neira (1998) stated that western wir- 
rah would settle between 10.5 and 23.0 mm BL, and 
Brownell (1979) registered one koester taking up a 
