NOTE McBnde: Spawning, growth, and overwinter size of Pnonotus camlinus and P evolans 



643 



t' P. camlinus 

 oP. evolans 

 DBoth 



76° 74° 72° 70° 68° 66° 



77° 76° 75° 74° 73° 72° 



Figure 1 



(A) Locations of all sampling during February-April 1993. Locations are indicated where 

 searobins were and were not collected in tows. (B) Sample locations for age-0 searobins used 

 for estimating overwintering size. Locations are for cruise dates during February- March 

 1993. No age-0 Pnonotus spp. were collected during April 1993, and sampling areas covered 

 during April (north of 40°N) are not shown. 



the sagittal plane, and viewed under a binocular scope 

 (typically at 20x) to check for the presence (e.g. age-1) 

 or absence (e.g. age-0) of an annulus. Annulus formation 

 occurs in March for both species (Wong, 1968; McEachran 

 and Davis, 1970), and an annulus on the otolith margin 

 was not counted. 



Results and discussion 



Otolith microstructure 



Two pairs of otoliths (the sagittae and lapilli) were pres- 

 ent prior to hatching in cultured embryos, having formed 

 at the same time as the optic vesicles. No asterisci were 

 observed in cultured yolksac larvae and, from personal 

 observations of field-caught specimens, the asterisci 

 form after flexion of the notochord. First ring deposition 

 in sagittae was contemporaneous with eye pigmentation 

 and yolksac absorption, although this process was not 

 observed directly. Instead, it was observed that the diam- 

 eter of the sagittal core (=primordium) steadily increased 

 during yolksac absorption but that no microincrements 

 were evident. I conclude that the laboratory specimens 

 would have laid down their first ring at yolk absorption 

 had they survived because the diameters of their sagittae 

 were similar to the sagittal core diameters of wild fish (i.e. 

 the diameter of the first microincrement). The maximum 

 sagittal diameter of laboratory-cultured P. carolinus 

 larvae was 26.3 pm and the mean sagittal core diameter 

 of field-caught fish was 27.0 or 26.8 pm (n=8 flexion stage 

 and n=6 postflexion specimens, respectively). 



Yolksac absorption occurred approximately six days af- 

 ter fertilization and four days after hatching at 22-26°C; 

 therefore four days were added to the average number of 

 microincrements counted for both species, although this 

 developmental pattern was observed only for P. carolinus. 

 The rate of larval development observed in the present 

 study is consistent with other reports of P. carolinus 

 cultured at 15-22°C. Yuschak and Lund (1984) observed 

 yolksac absorption by P. carolinus larvae at 3.4 mm NL 

 and first feeding at 3.5-5 days after hatching. Kuntz and 

 Radcliffe ( 1917) reported P. carolinus hatching at about 60 

 hours (2.5 days) and starvation 5-6 days after hatching. 



Sagittal microincrement deposition occurred daily in 

 chemically marked P. carolinus juveniles cultured in the 

 laboratory. Data from four replicate aquaria (75 fish) were 

 pooled because an ANCOVA did not indicate a significant 

 difference by either the interaction of treatments (slope- 

 replicate interaction: P=0.48) or the covariate (replicate: 

 P=0.12). The resulting relationship was 



Y= 1.23 + 0.94 (X), 



where Y = the number of microincrements after the tetra- 

 cycline mark; and 

 X = the number of days following marking. 



A test of statistical power (i.e. 1 - beta, as in Dixon and 

 Massey [1951] and Cohen and Cohen [1975]) indicated a 

 99.9% confidence that microincrement deposition did not 

 deviate from unity by more than 0.02 rings/d. McBride 

 (1994) presented preliminary evidence of daily sagittal 

 microincrements in P. evolans. 



