Scallop growout using a new bottom-culture system

A new bottom-culture system was tested at a commercial level to grow catari na scallops (Argopecten ventricosus) in the Rancho Bueno tidal channel in B ahia Magdalena, Mexico. The system consisted of a 50 x 1-m sleeve of 19-mm mesh polyethylene netting placed on the sea floor of selected growout areas . A total of 448 sleeves were deployed at various times from October 1994 t o April 1995 in four zones from the mouth to the head of the tidal channel. Each sleeve contained 10,000 scallops (initially 32 mm shell height) at a density of 200 scallops/m(2). Fifty-four percent of the spat were produced in a hatchery and the rest were collected using onion-bag collectors. Hatch ery and wild spat were deployed separately. Water parameters were measured monthly in each zone: temperature, salinity, dissolved oxygen and total sus pended solids. There were better water conditions towards the mouth of the channel. The scallops were harvested from 27 July to 18 August 1995: a tota l of 2.87 million scallops from the original 4.48 million. Their mean shell height was 56.2 mm and the mean weight of their adductor muscles was 6.8 g . The production was 19.3 t of adductor muscles. Statistically significant differences in mean shell height and mean adductor weight were found betwee n scallops grown in different zones, but no statistically significant diffe rences were found comparing yields from hatchery vs. wild scallops. To find the best culture conditions, a scallop relative value (SRV) was calculated by multiplying survival by adductor muscle weight and relative market pric e, and dividing by the growout duration. There were higher SRVs for scallop s cultured in zones closer to the channel mouth. The highest SRV was found in a group from this zone, with 86% survival, 6.25 g mean adductor weight, and a growout duration of only 3.6 months. A new successful method for grow ing scallops in shallow areas is, thus presented here. It gave better resul ts than suspension methods tested in the same area. (C) 2000 Elsevier Scien ce B.V. All rights reserved.