The present paper is an account of some of the investigations on the biology of the perch (Perca fluviatilis Linn.) in Windermere, which are being conducted in connexion with a trap-fishery experiment (Worthington, 1950). This experiment is mainly a study of populations, but it has been necessary simultaneously to investigate the general biology of the perch, particularly the growth and related aspects. The computation of a formula to express the length,weight relationship and provide a means of interconverting measurements of length and weight, revealed the relative complexity of the interrelationships of length, weight and condition. Condition in turn was found to be correlated with the seasonal changes in gonad development and growth, and the importance of the effect of stomach contents on weight had also to be assessed. It was decided, therefore, to combine these separate but interrelated aspects in one paper. The main part of the paper is devoted to the questions of length-weight relationship and condition. A brief review of the fundamental bases for the concepts of length-weight relationship and condition and of some of the methods of analysis of length-weight data precedes an account of the application of the chosen methods to the present material and its results. This is followed by an account of seasonal changes in gonad weights. A brief account is then given of the rather scanty data available on the weight of stomach contents. The seasonal changes in condition are then described and, finally, some of the results are summarized, combined and discussed as a picture of the seasonal cycle in the Windermere perch. In the statistical analysis of the length-weight relationship the data for only one group of fish are given in full (Tables i and 2) as an example of the method of computation used for all the groups. Again, in the section on seasonal changes in gonad weight and condition Figs. 2-7 are based partly on tables of data which are not published. The full tables have been deposited with the Freshwater Biological Association, from whom copies can be obtained.

http://www.britishecologicalsociety.org/100papers/100_Ecological_Papers/100_Influential_Papers_069.pdf

The length-weight relationship and seasonal cycle in gonad weight and condition in the perch (perca fl uvia tilis)

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.

/pdf/cube-law-condition-factor-and-weight-length-relationships-57z29c0cnv.pdf

Cube law, condition factor and weight-length relationships: history, meta-analysis and recommendations

Behavioral ecologists might often benefit by the ability to directly measure an animal's body condition as an estimate of foraging success, and ultimately fitness. Here we compare the reliability and effectiveness of three indices of body condition that have been heavily used in the morphometrics literature. We examined the ratio index (body mass/body size), the slope-adjusted ratio index (based on regression slopes generated from a reference population), and the residual index (the residuals of a regression of body mass on body size). We present the results of tests performed in the field and laboratory on two ecologically and evolutionarily divergent spider species : the vagrant wolf spider Pardosa milvina (Araneae, Lycosidae), and the colonial orb-weaver Metepeira incrassata (Araneae, Araneidae). The ratio index correlated with body size, which weakened the strength of conclusions that could be drawn. The slope-adjusted ratio index requires an independent and large data set with which to generate the expected values, and was likewise sensitive to body size. The residual index, with appropriate transformations to achieve homoscedasticity, was the most reliable index because it did not vary with body size, and we recommend its general use in behavioral studies that require a condition estimate.

http://www.jstor.org/stable/pdfplus/3545585.pdf

Estimating fitness : a comparison of body condition indices

SUMMARY 1. Streams and their adjacent riparian zones are closely linked by reciprocal flows of invertebrate prey. We review characteristics of these prey subsidies and their strong direct and indirect effects on consumers and recipient food webs. 2. Fluxes of terrestrial invertebrates to streams can provide up to half the annual energy budget for drift-feeding fishes such as salmonids, despite the fact that input occurs principally in summer. Inputs appear highest from closed-canopy riparian zones with deciduous vegetation and vary markedly with invertebrate phenology and weather. Two field experiments that manipulated this prey subsidy showed that it affected both foraging and local abundance of stream fishes. 3. Emergence of adult insects from streams can constitute a substantial export of benthic production to riparian consumers such as birds, bats, lizards, and spiders, and contributes 25–100% of the energy or carbon to such species. Emergence typically peaks in early summer in the temperate zone, but also provides a low-level flux from autumn to spring in ice-free streams. This flux varies with in-stream productivity, and declines exponentially with distance from the stream edge. Some predators aggregate near streams and forage on these prey during periods of peak emergence, whereas others rely on the lower subsidy from autumn through spring when terrestrial prey are scarce. Several field experiments that manipulated this subsidy showed that it affected the short-term behaviour, growth, and abundance of terrestrial consumers. 4. Reciprocal prey subsidies also have important indirect effects on both stream and riparian food webs. Theory predicts that allochthonous prey should increase density of subsidised predators, thereby increasing predation on in situ prey and causing a negative indirect effect via apparent competition. However, short-term experiments have produced either positive or negative indirect effects. These contrasting results may be due to characteristics of the subsidies and individual consumers, but could also result from differences in experimental designs. 5. New study approaches are needed to better determine the direct and indirect effects of reciprocal prey subsidies. Experiments coupled with comparative research will be required to measure their effects on individual consumer fitness and population demographics. Future work should investigate whether reciprocal prey fluxes stabilise linked stream–riparian ecosystems, explore how landscape context affects the magnitude and importance of subsidies, and determine how impacts of human disturbance can propagate between streams and riparian zones via these trophic linkages. Study of these

Tangled webs: reciprocal flows of invertebrate prey link streams and riparian zones

BACKGROUND Global aquatic environments are changing profoundly as a result of human actions; consequently, so too are the ways in which organisms are distributing themselves through space and time. Our ability to predict organism and community responses to these alterations will be dependent on knowledge of animal movements, interactions, and how the physiological and environmental processes underlying them shape species distributions. These patterns and processes ultimately structure aquatic ecosystems and provide the wealth of ecosystem services upon which humans depend. Until recently, the vast size, opacity, and dynamic nature of the aquatic realm have impeded our efforts to understand these ecosystems. With rapid technological advancement over the past several decades, a suite of electronic tracking devices (e.g., acoustic and satellite transmitters) that can remotely monitor animals in these challenging environments are now available. Aquatic telemetry technology is rapidly accelerating our ability to observe animal behavior and distribution and, as a consequence, is fundamentally altering our understanding of the structure and function of global aquatic ecosystems. These advances provide the toolbox to define how future global aquatic management practices must evolve. ADVANCES Aquatic telemetry has emerged through technological advances in miniaturization, battery engineering, and software and hardware development, allowing the monitoring of organisms whose habitats range from the poles to the tropics and the photic zone to the abyssal depths. This is enabling the characterization of the horizontal and vertical movements of individuals, populations, and entire communities over scales of meters to tens of thousands of kilometers and over time frames of hours to years and even over the entire lifetimes of individuals. Electronic tags can now be equipped with sensors that measure ambient physical parameters (depth, temperature, conductivity, fluorescence), providing simultaneous monitoring of animals’ environments. By linking telemetry with biologgers (e.g., jaw-motion sensors), it is possible to monitor individual feeding events. In addition, other devices on instrumented animals can communicate with one another, providing insights into predator-prey interactions and social behavior. Coupling telemetry with minute nonlethal biopsy allows understanding of how trophic dynamics, population connectivity, and gene-level basis for organismal health and condition relate to movement. These advances are revolutionizing the scope and scales of questions that can be addressed on the causes and consequences of animal distribution and movement. OUTLOOK Aquatic animal telemetry has advanced rapidly, yet new challenges present themselves in coordination of monitoring across large-spatial scales (ocean basins), data sharing, and data assimilation. The continued advancement of aquatic telemetry lies in establishing and maintaining accessible and cost-effective infrastructure and in promoting multidisciplinary tagging approaches to maximize cost benefits. A united global network and centralized database will provide the mechanism for global telemetry data and will promote a transparent environment for data sharing that will, in turn, increase global communication, scope for collaboration, intellectual advancement, and funding opportunities. An overarching global network will realize the potential of telemetry, which is essential for advancing scientific knowledge and effectively managing globally shared aquatic resources and their ecosystems in the face of mounting human pressures and environmental change.

/pdf/aquatic-animal-telemetry-a-panoramic-window-into-the-3bw494f0ls.pdf

Aquatic animal telemetry: A panoramic window into the underwater world

The estimation of the size and other parameters of populations of animals has long been a central problem for ecologists and several different methods have been used that mostly fall into two categories, (a) mark-recapture experiments (e.g. De Lury 1958; Parker 1963; Seber 1965), and (b) the effect on the population of catches of random size but known effort (e.g. Leslie & Davis 1939; De Lury 1947; Beverton & Holt 1957; Ricker 1958; and many others)-Zippin (1956, 1958) calls this the removal method. The aim of the following paper is to investigate the removal method more fully and, in particular, to consider its application to situations in which it is possible to catch a significant proportion of the population present (see, for example, Junge & Libosvairsky 1965). The method was developed for estimating fish populations in small rivers where capture by electricity was easy but where marking experiments had drawbacks. The method may, however, be found to be useful in quite different situations where it could, for example, provide a check on mark-recapture methods and perhaps in the sorting of animals out of samples of mud, soil or grain. The paper is written throughout in terms that are used in fishing as not only are there few suitable alternatives in non-technical language, but previous work in this subject has been pioneered mostly by fishery biologists. A description of the method of calculating population size from two catches is first presented, followed by the estimation of its variance, the verification of the method by several repeated catches and the information available from single catches. The estimation of mortality rates from successive population estimates and combined catch and mark-recapture experiments are also discussed. The methods described are illustrated with examples taken from actual fishing experiments. In these examples most numbers are written to just one or two decimal places for simplicity.

http://www.jstor.org/stable/pdfplus/2818.pdf

Estimating Population Parameters from Catches Large Relative to the Population

The fact that many fish show rings on such skeletal structures as scales, bones, otoliths and fin rays, has, been known for a long time. In many cases these rings have been shown to be annual in formation and to be probably due to seasonal fluctuations in growth. They thus provide a very useful method for assessing the ages of fish, and as such have been extensively used by many workers. In fact, age determination, usually from the rings on the scales, has become one of the standard methods in fishery research. Age determinations are very useful in practical fishery management as they can lead to assessments of mortality rates and by calculations of the mean sizes of the age groups to a knowledge of the growth rates of the fish. Additional information on the growth of fish can also be ascertained from the scales and similar skeletal structures by calculating the length of a fish at each year of its life from the proportional width of the rings laid down each year. These methods have been very widely used and a large proportion of the extensive modern research on fish ecology and fishery management is based on age and growth studies using the 'scale method'. There is also a large literature on the validity of the use of these methods, which discusses whether the rings are true annual formations and whether they provide accurate estimates of past growth. Although there is relatively little substantial direct evidence of the soundness of age and growth determinations from scales, the sum of indirect evidence leaves no doubt that in general their use is justified. At the same time the practice of many workers, who have published accounts of age and growth based on the scale method without attempting to substantiate the validity of its application to the species or problem studied, is to be deprecated. The present paper is a preliminary to an account of the study of perch (Perca flutviatilis L.) in Windermere, and its aim is to demonstrate that the methods used to determine age and growth are valid. The literature on the method and the investigations towards proving its correctness has been discussed by several workers, and the papers of Graham (I 929) and Van Oosten (I929, 1941) give detailed reviews. It is not intended here to enter into a general discussion on the scale method and its validity. In the perch, some age and growth studies have been made by Scandinavian and German workers, and recently the ecology of the closely related yellow perch (P. flavescens Mitchill) has been investigated in many North American waters. In nearly all cases the scales have been used, but Nilsson (I92I) concluded that in practice the opercular bone was more accurate and easier to use than the scales. Roper (1936) used scales and operculars in a study of perch in Germany, and found that infra-red photography helped to reveal the obscure inner annual rings on the operculars. The opercular bone has also been used by Nikolsky & Evtiukhov (I940) to determine the age of P. shrenki Kessler. Segerstrale (I933) has studied the use of the scales of the perch in detail, has shown the need for correcting back-calculated readings of growth made by direct proportion, and has constructed a curve for this purpose. When data were collected from the perch in Windermere in connexion with the current trap fishery experiment (Worthington, I94), Mr H. J. Buchanan-Wollaston tried using the opercular bones and compared them with scales from various parts of the perch. He discovered that the use of polarized light often clarified the rings on the operculars, and that by projection the width of these rings could easily be measured. He found that in general the

The Determination of the Age and Growth of the Perch (Perca fluviatilis) from the Opercular Bone

Observations on the Growth of Perch (Perca fluviatilis L.) Over Twenty-Two Years with Special Reference to the Effects of Temperature and Changes in Population Density

E. D. Le Cren

Papers

The length-weight relationship and seasonal cycle in gonad weight and condition in the perch (perca fl uvia tilis)

Estimating Population Parameters from Catches Large Relative to the Population

The Determination of the Age and Growth of the Perch (Perca fluviatilis) from the Opercular Bone

Observations on the Growth of Perch (Perca fluviatilis L.) Over Twenty-Two Years with Special Reference to the Effects of Temperature and Changes in Population Density

Trout Biomass and Production@@@The Horokiwi Stream: A Study of a Trout Population