Condition and Health Indicators of Exploited Marine Fishes

This book is based on the methodologies and examples given in the previous book by two of the three present authors (Shulman & Love 1999). One of the main aims of the former book was to show how fish can be assessed for harvesting at the best time in their life cycles and in the correct condition for marketing. In contrast, the main goal of the present book is the assessment of condition indicators of fish stocks for their sustainable management in a variable environment subjected to climate change and increased anthropogenic pressure. This book does not concentrate on the usual parameters of fish stocks, such as population size, spawning stock biomass, growth rate, demographic composition and reproductive potential, but on fish condition (including mainly physiological and biochemical indicators) as an important predictor of the population status.

The first author of this book, Dr Josep Lloret, is a fisheries and marine biologist from the University of Girona (Spain); the second author, Dr Professor Georgiy Shulman, is a well-known marine zoologist and physiologist from the Institute of Biology of the Southern Seas (Sevastopol, Ukraine); and the third author, Dr R. Malcolm Love, is a world-renowned fish biochemist from Scotland, deceased in 2006.

The book begins with a foreword including the brief reviews of seven scientists, and their opinions on the book quality are extremely positive. The book is organized into seven chapters, and each chapter is supplied with a brief summary. The first five chapters describe the condition indicators, methods of their assessment, and the effect of the environment on their variability. The two last chapters are devoted to more applied aspects of the assessment of environmental status (based on fishes as biological indicators) and fish stock monitoring and management.

The following condition indicators are described in Chapter 1: Fulton's condition factor K, Le Cren's relative condition factor, relative weight, hepatosomatic index, fat index and digestive index. The first three parameters are called ‘morphometric indicators’ but that seems incorrect. The length-weight measurement can partly describe the shape of the fish, but morphometry is the quantitative measurement of the form, especially of morphological structures of the organisms. Although the limitations of Fulton's K are analysed in the chapter, the units of measurements are not given in the formula; in addition, the parameter L is indicated as the total length. Murza & Khristoforov (2009) suggest applying the unified condition index (at least, for salmonid fishes) using the formula K = (W/L³) × 100 where W is the total body weight (g) and L is the fork length (cm).

Chapter 2 is devoted to the description of physiological and biochemical indicators. Following a comprehensive analysis of metabolism in fishes and a description of indicators such as oxygen consumption, ATPase activity, erythrocyte concentration in the blood and haemoglobin content, the role of the main chemical components and methods for their evaluation are described.

In Chapter 3 the analysis of functional activity indicators begins with a table, ‘Scheme of biological evolution and biodiversity’, where two alternative strategies (expansion and specialization) are mentioned. The table, most likely, is based on the evolutionary concept of A. N. Severtsov on ‘aromorphosis’ (adaptations of a wide importance that raise the level of organization of a species and enable it to adapt to life under new conditions) and ‘idioadaptation’ (a period in which individual adaptive changes take place). However, these evolutionary changes are not related to the subsequent text of the chapter, where the differences in oxygen consumption, muscle composition, as well as in neutral lipids and fatty acid content, are analysed in fishes with different levels of locomotor activity.

The central and most essential chapter (4) of the book describes the change in fish condition over the whole life cycle and the link between fish condition and life-history traits. Despite the references to several Russian scientists including S. G. Kryzhanovskii, the ontogenetic intervals are not clearly defined, and terms such as ‘embryonic, larval, and juvenile stages’ or ‘fry’ are applied. Strict definitions of life-history intervals and related terminology were developed by Kryzhanovskii and his well-known follower, Eugene Balon (Balon 1990), where stages were characterized as certain events in development, embryo, larva and juvenile periods were clearly defined, and the term ‘fry’ was regarded as inappropriate. The changes in the chemical content and oxygen uptake of the organism during its ontogeny are analysed in the book based on a large number of sources. (An error in the legend to Figure 4.1: ‘total yolk respiration’ should be read as ‘total yolk resorption’.) The section analysing the impact of fish condition on life-history traits seems the most important. It is shown that reproductive potential is substantially determined by the condition of the fish and cannot depend entirely on spawning stock biomass. A strong connection between maternal condition (in particular, Fulton's K and lipid content), incidence of sexual maturity, egg and larval quality and natural mortality is demonstrated. The authors illustrate the linkage between condition of spawners and progeny quality, but indicate that ‘the most critical period (bottleneck) in the life history of fish is undoubtedly the wintering period, especially for juveniles’ (p. 102). Such a statement can be reasonable in certain situations. However, as is known, the main critical intervals are registered in the early ontogeny of the fish.

In Chapter 5, the influence of food quantity and quality, fish density, parasitic infections and abiotic factors on fish condition are reviewed. Finally, the effects of pollution and fishing on fish condition are examined, and some examples of interactions between farmed and wild fishes are described. The role of fish condition indices as indicators of habitat quality is discussed in Chapter 6. The importance of the assessment of the condition of small pelagic species as a valuable indicator of environmental state is demonstrated. It should be noted that the Black Sea has become the exclusive water body where parameters such as water temperature, phytoplankton and zooplankton abundance, fishing pressure, pollution level, biomass of stocks and biochemical content of the fish have been followed for several exploited stocks from the 1960s to the present time. The examples of the use of fish condition indicators to improve stock assessment and management are described in Chapter 7. It should be noted that the content of this chapter (as well as of the whole book) represents an extremely valuable addition to the book by Jakobsen et al. (2009) (the second edition is in preparation).

The book by Lloret et al. concentrates mainly on the physiological and biochemical components of fish condition, but the structural (morphological) characteristics remain mainly beyond its scope. As is known, numerous biomarkers (sub-lethal biological measures of response to habitat degradation and pollutants) including histological and cellular parameters can be assessed with simple and inexpensive techniques. Among different target organs used in assessing fish health, the cellular quality of the gonads provides an accurate evaluation of the reproductive potential because the reproductive system is very sensitive to environmental changes. Some examples of reduced fecundity (due to oocyte resorption) and skipped spawning (as a result of gonadal destruction) are given in the book. However, various types of gonadal abnormalities (not necessarily leading to termination of spawning) as an indication of environmental changes are known for a large number of freshwater and marine fishes and could be reviewed in more detail.

The book includes a large number of good-quality graphs and histograms. Unfortunately, many of the photographs are of poor quality (possibly the contrast and brightness of colour images were not adjusted after their conversion to black-and-white copies), and some of the photographs are not very informative. An ‘ichthyometer’ consisting of a simple board with a scale is shown in Figure 1.2, but information on digital calipers or electronic measuring boards currently used for fish body length measurement is absent. The maximum total length after stretching of the caudal fin (but not natural total length most often used for measurements) is shown in Figure 1.8. A histological section of the ovary is illustrated in Figure 4.7, but the scale bar and designations of the elements are not included. The scale bars are also absent on the images of histological sections of abnormal gonads (Figure 4.15). Eviscerated fishes are shown in several photographs, but the organs are not indicated.

An obvious advantage of the book is the inclusion of an extensive citation of Russian literature, which is totally ignored in many publications. However, the use of an extremely large number of references to sources in Russian from the Soviet Union period seems unreasonable.

Overall, the quality of this book is very good, and it represents an excellent source for a reading course for advanced undergraduate and postgraduate students with basic knowledge in the branches of fish biology, physiology and biochemistry. As indicated in the preface, fish condition indicators have important biological and ecological links with the productivity of fish stocks and the quality of their habitats. This book represents an essential contribution to the biology of marine fishes and will be an extremely valuable guide for the monitoring, conservation and sustainable exploitation of fish stocks.

Dimitri A. Pavlov

Principal Scientist

Department of Ichthyology, Faculty of Biology, Moscow State University, Moscow, Russia

E-mail: [email protected]

© 2014 Dimitri A. Pavlov