Notes On The Use Of Theoretical Models In The Study Of The Dynamics Of Exploited Fish Populations

Among the fishes, a remarkably wide range of biological adaptations to diverse habitats has evolved. As well as living in the conventional habitats of lakes, ponds, rivers, rock pools and the open sea, fish have solved the problems of life in deserts, in the deep sea, in the cold antarctic, and in warm waters of high alkalinity or of low oxygen. Along with these adaptations, we find the most impressive specializations of morphology, physiology and behaviour. For example we can marvel at the high-speed swimming of the marlins, sailfish and warm-blooded tunas, air-breathing in catfish and lungfish, parental care in the mouth-brooding cichlids, and viviparity in many sharks and toothcarps. Moreover, fish are of considerable importance to the survival of the human species in the form of nutritious, delicious and diverse food. Rational exploitation and management of our global stocks of fishes must rely upon a detailed and precise insight of their biology. The Chapman & Hall Fish and Fisheries Series aims to present timely volumes reviewing important aspects of fish biology. Most volumes will be of interest to research workers in biology, zoology, ecology and physiology but an additional aim is for the books to be accessible to a wide spectrum of non-specialist readers ranging from undergraduates and postgraduates to those with an interest in industrial and commercial aspects of fish and fisheries.

This book is presented in seven Chapters. Chapter 1 describes the basic assumptions underlying the optimal allocation of natural resources and the inherent characteristics of fisheries that determine, under unrestricted access, the failure to allocate resources, economic inefficiency and overfishing. To mitigate these undesired effects, the bioeconomic literature invokes the allocation of property rights, which in turn must be implemented within a management context. Thus, in this Chapter we suggest some guidelines to conduct management plans. Static and dynamic bioeconomic models are presented in Chapter 2 as a theoretical framework for the design of intelligent management schemes aiming at sustainable use of fish stocks. Classic models are shown, such as the Gordon-Schaefer based on the logistic. We also develop new bioeconomic approaches, such as a distributed-delay model to add realism to Smith's fleet dynamics approach. Chapter 2 also includes an introductory version of a bioeconomic yield-mortality model, and dynamic age-structured models. A comparison of the dynamic and static trajectories is stressed. The price of time and its implications for optimal resource allocation over time is also discussed. For the sake of adding realism to the above models, the systems approach is used in Chapter 3 to model different technological and ecological complexities that occur in marine fisheries. Ecological interdependencies (competition, predation), as well as technological interdependencies resulting from fleets with different fishing power and/or gear types, operating on components of a stock, or on different target species of a "mixed stock", are specified and modelled.

Fish Physiology