File:American malacological bulletin (1988) (17968446080).jpg

Title: American malacological bulletin
Identifier: americanmal6719881990amer (find matches)
Year: 1983 (1980s)
Authors: American Malacological Union
Subjects: Mollusks; Mollusks
Publisher: (Hattiesburg, Miss. ?) : (American Malacological Union)
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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Fig. 1. Location of shallow water and deep water sea scallop sampl- ing sites in the Gulf of Maine.
Text Appearing After Image:
Fig. 2. Sea scallop shell conformation and dimensions. of recapture as well as measuring the height of rings formed during that time (Naidu, 1975; Posgay, 1981). Shell height at age was determined using the technique of Merrill era/. (1966) and a table of mean height-at-age was constructed for both groups. Since ring formation occurs during the winter and scallops spawn in the late summer, the age at first ring for- mation is taken as 6 months with subsequent rings found at 18 months, 30 months, etc. Deep water scallops from 170 m depth in the Gulf of Maine were collected annually in August using a fine mesh, 32 ft. (9.8 m) chain footrope, semi-balloon otter trawl. Two deep water locations provided continuous records between 1976 and 1983 except in 1980 when samples were unavailable. These were: ^32 km (20 miles) South of Boothbay Harbor (43°26.5'N, 69°33.3'S) and Jeffrey's Basin (43°04.25'N, 70° 11.33'S). Height frequency distributions over time were deter- mined from shell heights measured to the nearest millimeter (Figs. 3, 4). The increment in shell height of a predominant year class (1975) from one year to the next was used as a measure of growth. The shell heights are for August, and since scallops spawn in August, the first height frequency is taken as scallops at one year of age, with subsequent annual col- lections representing scallops at 2 years, 3 years, etc. This assumption of age is based on examination of the shells from the first sample which showed one ring on each shell in- dicating that they had survived one winter. Controversy still exists over the most accurate method of determining the correct age of scallops (Merrill era/., 1966; Krantz et a/., 1984). Unfortunately, our data do little to clarify

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