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Hogger, John B. (1984) A study of aspects of the biology and distribution of freshwater crayfish in the Thames catchment. Doctoral thesis, City of London Polytechnic.
The results presented in this thesis concern an examination of the biology and distribution of freshwater crayfish in the Thames Catchment. Studies of the distribution of both the native (Austropotamobius pallipes. Lereb.), and an introduced (Pace as acus leniusculus. Dana.) species have been undertaken and attempts to evaluate some of the factors controlling distribution have been made. The specific influences of river engineering works on populations of A. pallipes have been studied in more detail.
Data concerning A. pallipes at the population level has been obtained by sampling a single lacustrine population. A comparison has been made with crayfish from a riverine population. Information concerning life-history, growth, density and trophic position is discussed and is related to similar information from elsewhere in the Thames Catchment and the U.K. The morphology of A. alli es in this area has been quantified and an assessment made of sexually dimorphic features and hence the size at maturity of A. pallipes in southern England. The collection of information regarding diseases and parasites of A. pallipes in the Thames Catchment has been undertaken throughout the study and the incidence and importance of these is discussed.
Comparable information has been obtained from a population of the introduced P. leniusculus. Survival of implants, growth and life-history of this alien species in a single population are discussed in detail and compared with information collected from other introduced populations in the Thames Catchment. The morphometry of P. leniusculus has been investigated and their size at maturity calculated. The data collected concerning P. leniusculus forms the only known study of this species in -the U. K., to date, and the results are compared with information from Scandinavia and North America.
The results from both parts of this thesis are discussed in terms of the ecological and economic importance of crayfish populations and the effects that introductions of alien species may have on native populations. It is intended that this thesis should provide a full and accurate assessment of the status of freshwater crayfish in the Thames Catchment at a time when increasing pressures may result in serious alterations to stocks of both species.
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