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Biol Bull 141: 189-201. (August 1971)
© 1971 Marine Biological Laboratory
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AGE AND GROWTH OF LOLIGO PEALEI, A POPULATION STUDY OF THE COMMON ATLANTIC COAST SQUID

WILLIAM C. SUMMERS 1

1 Marine Biological Laboratory, Woods Hole, Massachusetts 02543

1. This paper describes the population size structure, inferred age, growth, reproduction and longevity of the common Atlantic Coast squid, Loligo pealei.

2. The sampling includes records of size (dorsal mantle length), sex and sexual maturity of 15,132 squid taken from 1967-1970. Nearly half of these were collected offshore between Cape Hatteras and Georges Bank in the late winters of 1967 and 1968. The remainder, including planktonic, young-of-the-year squid were trawled in the vicinity of Woods Hole, Massachusetts between May and November of all three years.

3. Size classes were identified and weighted through the use of size frequency analysis and arrayed to provide an empirical growth model. Mean sizes of individuals appeared to increase smoothly to 16 and 18 cm at one year and 27 and 32 cm at two years for females and males, respectively.

4. Two broods arise each year, a ubiquitous July brood (probably delayed north of Cape Cod) and a November brood which probably originates in the southern mid-Atlantic Bight. Sexual maturity and breeding have not been observed at less than one year of age; at Woods Hole these features occur at different ages and slightly different dates for the two broods. Competition for females may postpone the breeding of some males and exaggerate the population sexual dimorphism.

5. The stock is basically annual, though a significant proportion of the squid hatching near Woods Hole appear to be the product of two year olds. A breeeding induced mortality is consistent with the growth scheme for both sexes. This mechanism is evoked to explain the dynamics of age structure and sexual maturity during the inshore season.

6. Maximum longevity is understood tentatively to be 36 months for males (more frequently 20-24 months) and months for females. Sex ratios were consistently close to 1:1 though not necessarily balanced in older age groups.

7. The proposed growth scheme provides an hypothesis for latitudinal variations in the stock of L. pealei.

8. The results are compared with Verrill's influential treatment of the species and found to differ principally in the interpretation of data. The proposed growth scheme appears to be applicable to published data for the European squid, L. vulgaris. and is contrasted with records from other loliginid squid.






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Copyright © 1971 by the Marine Biological Laboratory.