Book•
On the Dynamics of Exploited Fish Populations
30 Jun 1993-
TL;DR: Pitcher and Pauly as mentioned in this paper used a simple theory of fishing, illustrated by analysis of a trawl factoy, to give the annual yield in weight from a fishery in a steady state.
Abstract: Series foreword AJ Pitcher Foreword D Pauly Part One: Fundamentals of the theory of fishing, illustrated by analysis of a trawl factoy Introduction:- theoretical methods in the study of fishery dynamics The basis of a theoretical model of an exploited fish population and definition of the primary factors Mathematical representation of the four primary factors Recruitment Natural mortality Fishing mortality Growth A simple model giving the annual yield in weight from a fishery in a steady state Adaptation of the simple model to give other characteristics of the catch and population Part Two: Some extensions of the simple theory of fishing Recruitment and egg-production Natural mortality Fishing mortality and effort Growth and feeding Spatial variation in the values of parameters movement of fish within the exploited area Mixed populations:- the analysis of community dynamics Part Three: Estimation of parameters Relative fishing power of vessels and standardisation of commercial statistics of fishing effort Estimation of the total mortality coefficient (F + M), and the maximum age, t* Seperate estimation of fishing and natural mortality coefficients Recruitment and egg-production Growth and feeding Part Four: The use of theoretical models in a study of the dynamics and reaction to exploitation of fish populations Application of population models of part one Application of population models of part two Principles and methods of fishery regulation Requirements for the regulation of the North Sea Demersal fisheries Appendices Bibliography and author index Subject index List of amendments compiled by the American Fisheries Society
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TL;DR: A historical review, a meta-analysis, and recommendations for users about weight–length relationships, condition factors and relative weight equations are presented, indicating a tendency towards slightly positive-allometric growth (increase in relative body thickness or plumpness) in most fishes.
Abstract: Summary This study presents a historical review, a meta-analysis, and recommendations for users about weight–length relationships, condition factors and relative weight equations. The historical review traces the developments of the respective concepts. The meta-analysis explores 3929 weight–length relationships of the type W ¼ aL b for 1773 species of fishes. It shows that 82% of the variance in a plot of log a over b can be explained by allometric versus isometric growth patterns and by different body shapes of the respective species. Across species median b ¼ 3.03 is significantly larger than 3.0, thus indicating a tendency towards slightly positive-allometric growth (increase in relative body thickness or plumpness) in most fishes. The expected range of 2.5 < b < 3.5 is confirmed. Mean estimates of b outside this range are often based on only one or two weight–length relationships per species. However, true cases of strong allometric growth do exist and three examples are given. Within species, a plot of log a vs b can be used to detect outliers in weight–length relationships. An equation to calculate mean condition factors from weight–length relationships is given as Kmean ¼ 100aL b)3 . Relative weight Wrm ¼ 100W/ (amL b m ) can be used for comparing the condition of individuals across populations, where am is the geometric mean of a and bm is the mean of b across all available weight–length relationships for a given species. Twelve recommendations for proper use and presentation of weight–length relationships, condition factors and relative weight are given.
3,227 citations
Book•
01 Jan 1986
TL;DR: In this article, the authors argue that scientific understanding will come from the experience of management as an ongoing, adaptive, and experimental process, rather than through basic research or the development of ecological theory.
Abstract: The author challenges the traditional approach to dealing with uncertainty in the management of such renewable resources as fish and wildlife. He argues that scientific understanding will come from the experience of management as an ongoing, adaptive, and experimental process, rather than through basic research or the development of ecological theory.
The opening chapters review approaches to formulating management objectives as well as models for understanding how policy choices affect the attainment of these objectives. Subsequent chapters present various statistical methods for understanding the dynamics of uncertainty in managed fish and wildlife populations and for seeking optimum harvest policies in the face of uncertainty. The book concludes with a look at prospects for adaptive management of complex systems, emphasizing such human factors involved in decision making as risk aversion and conflicting objectives as well as biophysical factors. Throughout the text dynamic models and Bayesian statistical theory are used as tools for understanding the behavior of managed systems. These tools are illustrated with simple graphs and plots of data from representative cases.
This text/reference will serve researchers, graduate students, and resource managers who formulate harvest policies and study the dynamics of harvest populations, as well as analysts (modelers, statisticians, and stock assessment experts) who are concerned with the practice of policy design.
3,131 citations
TL;DR: The body size is one of the most important attributes of an organism from an ecological and evolutionary point of view as mentioned in this paper, and it has a predominant influence on an animal's energetic requirements, its potential for resource exploitation, and its susceptibility to natural enemies.
Abstract: Body size is manifestly one of the most important attributes of an organism from an ecological and evolutionary point of view. Size has a predominant influence on an animal's energetic requirements, its potential for resource exploitation, and its susceptibility to natural enemies. A large literature now exists on how physiological, life history, and population parameters scale with body dimensions (24, 131). The ecological literature on species interactions and the structure of animal communities also stresses the importance of body size. Differences in body size are a major means by which species avoid direct overlap in resource use (153), and size-selective predation can be a primary organizing force in some communities (20, 70). Size thus imposes important constraints on the manner in which an organism interacts with its environment and influences the strength, type, and symmetry of interactions with other species (152, 207). Paradoxically, ecologists have virtually ignored the implications of these observations for interactions among species that exhibit size-distributed populations. For instance, it has been often suggested that competing species
3,129 citations
TL;DR: Zoning the oceans into unfished marine reserves and areas with limited levels of fishing effort would allow sustainable fisheries, based on resources embedded in functional, diverse ecosystems.
Abstract: Fisheries have rarely been 'sustainable'. Rather, fishing has induced serial depletions, long masked by improved technology, geographic expansion and exploitation of previously spurned species lower in the food web. With global catches declining since the late 1980s, continuation of present trends will lead to supply shortfall, for which aquaculture cannot be expected to compensate, and may well exacerbate. Reducing fishing capacity to appropriate levels will require strong reductions of subsidies. Zoning the oceans into unfished marine reserves and areas with limited levels of fishing effort would allow sustainable fisheries, based on resources embedded in functional, diverse ecosystems.
2,896 citations
TL;DR: A compilation of values for the exponential coefficient of natural mortality (M) is given for 175 different stocks of fish distributed in 84 species, both freshwater and marine, and ranging from polar to tropical waters as mentioned in this paper.
Abstract: A compilation of values for the exponential coefficient of natural mortality (M) is given for 175 different stocks of fish distributed in 84 species, hath freshwater and marine, and ranging from polar to tropical waters. Values of Loo(LT, em), W\",,(g, fresh weight), K (l/year) and T (ec, mean annual water temperature) were attributed to each value of M, and the 175 sets of values plotted such that:
2,649 citations