NATURAL HISTORY OF THE BAY SCALLOP 1 
& 
By James S. Outsell, Ph. D. 
Associate Aquatic Biologist, United States Bureau of Fisheries 
CONTENTS 
Page 
Introduction 569 
Economic importance 570 
Literature 570 
Classification and relationship 571 
Habitat and distribution 572 
Organization and mode of life 573 
Shell 573 
Mantle 574 
Gills 580 
Lips 586 
Alimentary tract 586 
Foot 589 
Adductor muscle 590 
Circulatory system 591 
Nervous system and sense organs 592 
Urinogenital system 594 
Feeding 595 
Ciliary currents of the mantle, vis- 
ceral mass, etc 595 
Pigmentation of the visceral mass 595 
Swimming 597 
Page 
Reproduction and development 599 
Spawning period 599 
Spawning 601 
Fertilization and embryonic devel- 
opment 602 
Larval development 602 
Postlarval development 605 
Growth, age at maturity, and length of 
life (annual growth line) 606 
Environmental factors 614 
Bottom 614 
Depth of water 614 
Current 615 
Salinity 616 
Temperature 620 
Enemies and parasites 621 
Importance of a knowledge of scallop 
biology for conversation 623 
Summary 624 
Bibliography 626 
INTRODUCTION 
The bay scallop, Pecten irrcidians, 2 is one of the few commercial, edible bivalves 
of our Atlantic coast. In North Carolina, where it is of considerable national and 
very great local importance, it had received almost no scientific study previous to these 
investigations. Accordingly an investigation was undertaken at the United States 
Bureau of Fisheries station, Beaufort, N. C., which is in the heart of the scallop- 
producing area in this State. Work was begun in the summer of 1925 and continued 
into 1928. 3 
Effort was concentrated on those aspects of life history which it was thought 
would yield knowledge of greatest usefulness for conservation. However, during 
certain periods, time was found for anatomical and other studies. Because of the 
i Submitted to the faculty of Cornell University in partial fulfillment of the requirements for the degree of doctor of philosophy. 
Submitted for publication Nov. 13,1929. 
J Also known as Pecten gibbus. See discussion under “ Classification and relationship.” 
8 1 wish to thank Capt. John A. Nelson, commissioner, and others of the division of commercial fisheries, Department of Con 
servation and Development, North Carolina, for much helpful service during these investigations. 
569 
