Intra-annual and long-term patterns in the reproductive cycle of giant scallops Placopecten magellanicus (Bivalvia: Pectinidae) from Passamaquoddy Bay, New Brunswick, Canada

Abstract

The reproductlve cycle of glant scallops Placopecten magellan~cus was examlned over a 13 yr perlod from 1978 to 1990 at several sltes wlthln Passamaquoddy Bay New Brunswick Gonosomatlc Index (GSI) and gonad weight were obtalned from scallops sampled approximately monthly From 1985 to 1990 samples were collected every 2 wk durlng the gonad r l p e n ~n g and about weekly durlng the spawning perlod Scallops In Passamaquoddy Bay had one main spawnlng perlod between July and September wlth peak spawning occurnng durlng August Spawnlng was not a cont~nuous and complete process but was ~ntermlttent, wlth 2 to 3 spawnlng events There was concordance between these spawnlng events and the lunar/tldal cycle s u g g e s t ~n g a tldally related spabvnlng cue Spawnlng was h ~g h l y synchronous wlthln local populatlons between sexes, and wlthln the bay Onset duratlon and penodlclty of spawnlng were also slmllar between years The long-term GSI pattern and maxlmum level In the reproduct~ve cycle of glant scallops from Passamaquoddy Bay were annually consistent Thelefore ~t appears that In Passamaquoddy Bay changes In potential reproductlve output (Independent of s u e and numbers) may not be as Important In the determlnatlon of recruitment for scallops as factors operating at other llfe-hlstory stages