McBride et a\ Larval and settlement periods of Pnonotiis carolinwi and P evolam 



McBride et al.. 1998). Because few other .species use both 

 estuarine and shelf habitats lor spavvninj^. such pallcrns 

 arc not commonly obser\i'(l. 



Linking metamorphosis and settlement 



Prionotus carollniis are otten ranked as among the most 

 abundant species in regional trawling surveys for adult 

 fish or plankton sui-veys for larval fish (McBride and Able, 

 1994). The results from the small-mesh beam trawl used 

 in our experiment demonstrate that the juvenile stages 

 of P. caroliniift are also very abundant offshore. Age-0 Pri- 

 onotus spp. are found in estuaries, as discussed above for 

 the southern New England region, but our observation of 

 high densities of juvenile Prionotus in shelf habitats off- 

 shore of New Jersey suggest that neither species requires 

 estuarine nursery habitats during their life cycle. Most 

 searobins complete their life cycle in continental shelf hab- 

 itats (Hoff, 1992), with the notable exception of P. scitulus 

 whose young are concentrated in lower salinity, estuarine 

 habitats (Ross, 1978). 



Our findings of age and size at settlement largely agree 

 with Yuschak and Lund's (1984) and Yuschak's (1985) de- 

 scriptions of early development of cultured specimens. The 

 developmental rate of cultured specimens of P. carolinus 

 and P. evolans-^ did not differ notably from our obsei-va- 

 tions of field-collected individuals, which further supports 

 our conclusion that neither species delays settlement. Pri- 

 onotus evolans. cultured at 20°C, were all at prefiexion 

 and flexion stages after 11-13 days; they were at flexion 

 and newly postflexion stages after 18-20 days; 

 and all were at the postflexion stage at 25 days. 

 All available P. carolinus specimens, cultured at 

 15°C, were less than 20 days old; they followed 

 a similar, if slightly slower, rate of development 

 compared with P. evolans. Fin-ray development, 

 which greatly facilitates locomotion, is complete 

 in postflexion individuals. Prehensile, chemosen- 

 sory pectoral rays, which would facilitate benthic 

 feeding, are completely separated by 11.5 mm SL. 

 Thus, on the basis of cultured and field-caught 

 specimens, both species are well developed (i.e. 

 are similar to adults) and well-suited for a bottom- 

 feeding and swimming life style as they complete 

 flexion. Other species delay metamorphosis to set- 

 tle during favorable lunar phases (Sponaugle and 

 Cowen, 1994), but settlement by Prionotus was so 

 concentrated in a single month (i.e. September) 

 that we could not test spawning or settlement cy- 

 cles in more than one month. Nevertheless, be- 

 cause larvae o{ Prionotus species commonly bury 

 themselves in loose substrate (Bardach and Case, 

 1965), and this material was common to all our 

 sampling stations (Hales et al.M, competent lar- 

 vae are likely not habitat limited (one mechanism 

 identified with the delay of settlement). 



The variation of P. carolinus sizes and ages along a 

 depth gradient could be caused by one or a combination 

 of three processes. There could be differential larval survi- 

 vorship, juvenile movements, or adult reproduction rates 



This material was cultured by P. Yuschak (see Yuschak and 

 Lund 119841 and Yuschak 11985]) and has been examined by 

 R.S.M. 



