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Title: Growth history patterns in squid in assessed by gladius structure
Author: Hughes, Shirley
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 1998
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Increments on the internal shell, the gladius (or pen) of squids were used to investigate the growth histories of these pelagic marine animals both at the individuals level and at the population level. The gladius structure is unique because it is inextricably linked to the mantle length of the animals and provides a record of the growth of the animal at a resolution impossible to achieve with other methods. Since the technique is relatively new this thesis was concerned with the developments, validation and use of the technique for three squid species in the north-east Atlantic. The following areas were investigated: 1. The structure of the gladius and the dynamics of its deposition in hatchling and adult squid. 2. The development of gladius reading methods and the preliminary growth analysis for three species; Loligo forbesi, Allotheuthis subulata (Family Loliginidae) and Todarodes sagittatus (Family Ommastrephidae). 3. An estimate of chitin production (g m-2 yr-1) from the gladius of squid for the seas west of Scotland. 4. Maintenance of captive squid (Todarodes pacificus) to determine the periodicity of increment formation using a chemical marker, the factors driving increment formation (temperature / feeding regime) and the effects of these factors on the overall growth of animals. 5. A hypothesis of increment formation is proposed. 6. The use of techniques to examine biology and ecology of the main UK fishery species, Loligo forbesi. The differences in growth histories between sexes, population cohorts and ecological phenomena such as multiple size modes at maturity were examined. In addition, the effects of maturity stage, reason and the presence of periodic components in the data were analysed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available