Hand harvesting quickly depletes intertidal whelk populations

摘要

With the collapse of the offshore whelk trawl fishery in Georgia, interest has increased in harvesting whelk from inshore areas where trawling is prohibited. This study examines the effects of hand harvesting on local intertidal populations of whelk. Over a 34 day period from 27 February to 1 April 2006, 1,824 whelk were hand harvested at low tide: 91.2% knobbed, Busycon carica (Gmelin, 1791); 4.7% lightning, Busycotypus sinistrum (Hollister, 1958); 4.1% channeled, Busycotypus canalicalatus (Linnaeus, 1758); and one pearwhelk, Busycotypus spiratus (Lamarck, 1816). Significantly greater numbers of knobbed and lightning female whelk were found than males. Mean shell lengths for females were consistently larger than males of all species. The study period was divided into three collection periods that were separated by approximately one week. The numbers of whelk harvested and their mean shell lengths significantly decreased between sampling periods as stocks were depleted. All species and sexes were active in both daytime and nighttime; however, significantly more knobbed and channeled whelk were harvested when sampling occurred closer to the middle of the night and significantly fewer toward the middle of the day. Nocturnal feeding is likely a cryptic adaptation to avoid predation and desiccation, and many whelk presumably remain buried on the intertidal flats during diurnal exposure. This study was conducted in the period leading up to copulation and egg-laying on the intertidal sandy-mud flats in inshore areas in coastal Georgia. Nocturnal hand harvesting at this time of the year could very quickly have detrimental impacts to local whelk stocks. Further implications of this work for an intertidal hand harvest supplemental whelk fishery are discussed.