Figure 2. — Etropus muro^tomus early larvae; a) 2.0 mm NL; bt 2.2 mm NL. 



Joseph, formed or the inelanophores migrated 

 ventrally to form all or part of the band. The mid- 

 caudal band was found in larvae as early as 2.1 

 mm in our collections; it was never observed in 

 larvae still displaying the posterior dorsal finfold 

 spot. The finfold markings appear to have been 

 lost in the 2.5 mm SL (standard length) specimen 

 illustrated by Richardson and Joseph due to 

 finfold mutilation but do appear in their illustra- 

 tions of 3.5 and 4.5 mm specimens. 



The smallest specimen containing pigmenta- 

 tion on the gas bladder in our collections was 2.4 

 mm. Preopercular spines were first observed at 

 about 2.3 mm. Gas bladder pigmentation and pre- 

 opercular spines were described by Richardson 

 and Joseph (1973) for their smallest specimen (2.5 

 mm). 



Occurrence 



Etropus microstonitis eggs were found in our 

 Block Island Sound samples from 11 June until 10 

 September 1975; sampling was weekly through 

 August, monthly thereafter. Samples taken again 

 on 140ctober 1975did notcontain£. microstomus 

 eggs. Surface water temperatures during this 

 period ranged from a low of 15.3" C in June to a 

 high of 22.3 C in early August. Larvae were taken 

 from 9 July to 14 October 1975 at which time 

 water temperatures were 15.6° C. 



In our weekly 1976 collections, eggs were taken 

 beginning 1 June, larvae beginning 17 June. Both 

 eggs and larvae were found regularly until 26 

 August when sampling ended. Surface water 

 temperatures averaged 11.9° C on 1 June, 13.2° C 

 on 17 June, and 20.0 C on 26 August. 



Similar Species 



Prior to formation of the distinctively pig- 

 mented embryo in E. microstomus . some confu- 

 sion may occur in separating similar stage eggs of 

 the fourbeard rockling, Enchelyopus cimbnus; 

 hakes, Urophycis spp.; and butterfish, Peprilus 

 /nacanthiis. According to Scotton et al. ( 1973), E. 

 cimbnus spawns from Nova Scotia to Block Island 

 and Urophycis spp. spawn from Nova Scotia to 

 South Carolina, depending upon the species. Pep- 

 rilus triacanthus spawns from Nova Scotia (Scot- 

 ton et al. 1973) to Chesapeake Bay (Peai-son 1941). 

 We regularly collected eggs and larvae of these 

 species in Block Island Sound at the same time 

 that Etropus microstomus eggs were taken. Most 

 early and middle stage E. microstomus eggs may 

 be distinguished on the basis of their smaller egg 

 and oil globule diameters. Although ranges over- 

 lap to some extent (Table 2) mean values for egg 

 and oil globule diameters are fairly distinctive. 

 Only 2'Z of the 794 eggs we measured contained oil 

 globule diameters 3=0.13 mm, the smallest oil 



711 



