Morphological differences among females of four species of stickleback (Gasterosteidae) from New Brunswick and their possible ecological significance

Abstract

Fifteen morphological characters were measured from females of four species of stickleback (Gasterosteidae) collected from the east coast of Canada. Significant differences were found between the species for 12 of these characters. All four species were found to differ significantly in their gill raker number. Gasterosteus had the greatest number of gill rakers followed by Pungitius and Apeltes. A significant negative correlation between gill raker number and prey size was demonstrated; Gasterosteus fed to a greater extent on smaller, planktonic prey, while Pungitius and Apeltes fed on larger, benthic prey. Gasterosteus were found also to have larger pectoral and caudal fin areas, and shorter but wider caudal peduncles, than Pungitius and Apeltes. The larger fins of Gasterosteus are probably a reflection of their increased swimming ability in response to the pelagic phase of their life histories. The longer, narrower caudal peduncles of Pungitius and Apeltes are probably an adaptation to life in weedy habitats where high manoeuverability is desired. The significance of these characters, as well as mouth height, pelvic fin length, body depth, gut length, head length, and pectoral fin length, are further discussed with respect to observed differences in diet, habitat, and life histories.