Virginia Institute of Marine Science
Eighteen species of chaetognaths were identified from shelf waters in the Middle Atlantic Bight. Species composition in the water column and the hyponeuston was nearly identical, but the percent frequencies of the more common cold-temperate species were generally lower in surface collections. Mean surface salinity, weighted for abundance of individual chaetognath species in the hyponeuston collections, varied from 32.6 and 32.8 parts per thousand for the coastal- and estuarine-inhabiting Sagitta tenuis and Parasagitta elegans, to 34.8 and 34.9 for the offshore Pterosagitta draco and Krohnitta pacifica. Weighted mean temperatures ranged from below 14-degrees-C for Mesosagitta minima, P. elegans, and Serratosagitta tasmanica to over 24-degrees-C for K. pacifica. Overall association among Middle Atlantic Bight chaetognaths, measured for the 15 most frequent species in 716 collections by variance ratio, was significantly positive. Association between pairs of species was therefore also largely positive, with the important exception of Parasagitta elegans. This species, with a unique regional niche in low salinities and temperatures, was negatively associated (p < 0.01) with five warm-water species (Krohnitta pacifica, Ferosagitta hispida, Sagitta tenuis, Sagitta helenae, and Flaccisagitta enflata). Most species reached maximum abundance at the surface near midnight. Exceptions included Sagitta helenae, with daylight maxima, and Krohnitta pacifica, Ferosagitta hispida and Serratosagitta serratodentata, showing crepuscular increases in abundance.
Temporal Abundance Patterns; Western North-Atlantic; Oceanic Chaetognaths; Bay
Grant, George C., Chaetognatha From The Central And Southern Middle Atlantic Bight - Species Composition, Temperature-Salinity Relationships, And Interspecific Associations (1991). Fishery Bulletin, 89(1), 33-40.