5-31 



Settlement of barnacle spat was similar in 1977 at New Haven 

 Harbor to previous years. Observations on settlement are not complete 

 for each species because barnacle spat are difficult to identify. In 

 1977, settlement of Balanus spp. on short-term panels was first observed 

 in April with a second, more intense set occurring in June through 

 October, and peaks in June, July and September (variable) . Balanus 

 improvisus was identified in the April set and comprised one-half of the 

 July set. B. eburneus was positively identified only in mid- June, but 

 as the majority of the juveniles in June and September were unidentified 

 it is likely that there were more B. eburneus than indicated. Grave 

 (1933) observed B. eburneus setting at Woods Hole in mid- June through 

 July with a small September set. 



The apparent recent increase in Balanus improvisus beginning 

 in 1975 probably reflects a series of more successful spawnings for 

 the species in New Haven Harbor but it may be related to improved iden- 

 tification of juvenile forms from Balanus spp. to Balanus improvisus . 

 B. improvisus occurred in slightly greater numbers at Long Wharf than 

 the other stations but did not show a substantially greater percent 

 occurrence at this lower salinity station. Hydrographic data for New 

 Haven Harbor do not indicate any temperature changes that could be the 

 basis for species composition shifts. The shift to Balanus improvisus 

 does not appear to be a Long Island Sound phenomenon because data from 

 Millstone 1975 and 1977 indicate high numbers of B. eburneus (Battelle, 

 1977, 1978). Millstone data for 1973 showed only B. eburneus and B. 

 crenatus on long-term panels although B. crenatus was excluded at the 

 effluent station (Battelle, 1977) . Short-term panels at Millstone showed 

 S. eburneus settling in July, August and September and B. improvisus in 

 August; no Balanus crenatus were seen on 1973 short-term panels. In New 

 Jersey, B. eburneus was reported to set throughout the summer and into 

 September; larvae of B. improvisus and B. crenatus began settling after 

 September (Hoagland et al . , 1978). Fall population reductions of B. 

 eburneus (Figure 5-9) seen most years at all stations in New Haven 

 Harbor corresponds to observations of high mortality rates of balanoids 

 in September and October (Fuller, 1946, in TRIGOM, 1973) . 



