38 



Fishery Bulletin 89(1). 1991 



there were apparent tem- 

 perature-related differences 

 in the percent frequency of 

 chaetognath species in the 

 two habitats. Cold-temper- 

 ate species were less fre- 

 quent at the surface than in 

 the underlying water col- 

 umn, while warm-temper- 

 ate or subtropical species 

 were either equally frequent 

 in the two habitats or more 

 frequent in the hyponeuston. 

 The idea for T-S-P dia- 

 grams apparently origin- 

 ated with Pickford's (1946) 

 study of the cephalopod 

 Vampyroteuthis, and was 



first applied to chaetognaths by Bary (1959, 1963). 

 T-S-P diagrams have since been used to relate abun- 

 dance of chaetognaths to hydrography by numerous 

 authors, including Sund (1961, 1964), Aurich (1971), 

 Kotori (1976), Michel and Foyo (1976), O'Brien (1977), 

 Nagasawa and Marumo (1982), and Andreu (1984). 

 Flaccisagitta enflata, abundant in the Middle Atlantic 

 Bight in warmer temperatures (averaging 18.6°C) and 

 in various salinities (<32 to 36%o), occurred through- 

 out the temperature and salinity ranges sampled by 

 Nagasawa and Marumo (1982) and was apparently 

 limited only by depth in the Caribbean (Michel and Foyo 

 1976). Sund (1961) also recorded F. enflata from 

 13-28°C and 32.6-35°/.*. T-S-P diagrams for Para- 



sagitta elegans have been plotted by Bary (1963), who 

 included the species in his "coastal (neritic) group," by 

 O'Brien (1977) for populations to the west of Ireland, 

 and by Kotori (1976) with ranges of temperature and 

 salinity close to those in the present study. All agree 

 in showing higher occurrence and abundance in colder 

 water and an apparent tolerance for reduced salinity. 

 Although the ranges of surface salinity in which Mid- 

 dle Atlantic Bight species were found were very 

 similar, it is noteworthy that the five species with the 

 lowest weighted means were the same five species 

 recorded from within Chesapeake Bay (Grant 1977b) 

 and in approximate inverse order of their estuarine 

 abundance (Sagitta tenuis, x S = 32.6"A». and the most 



