81 research outputs found
Fishing gear experiments in Finland
A comparison of some different European methods of estimating the numbers of fish in a lake using different fishing gear is described. The different gears used were 1. surface trawl used by night 2. bottom trawl used by day 3. trammel nets, set in the evening and lifted in the morning 4. surface seine net used by night 5. bottom seine net used by day 6. Fyke nets, emptied each morning and evening 7. gill nets, set in the evening and lifted in the morning. The most variable catches were from those gears used by day on the bottom and the least variable were those used by night at the surface. The work continued by examining the use of acoustic systems for pelagic fish stock assessment. This gear gave reasonable population estimates for pelagic fish 10m and more below the surface. The advantage of the accoustic method is that it is quick and requires little labour. Its disadvantage is that it is not possible to identify the species and so it must be supplemented by another, conventional method
Cube law, condition factor and weight-length relationships: history, meta-analysis and recommendations
This study presents a historical review, a meta-analysis, and recommendations for users about weightâlength relationships, condition factors and relative weight equations. The historical review traces the developments of the respective concepts. The meta-analysis explores 3929 weightâlength relationships of the type W = aLb 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 = 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 weightâlength 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 weightâlength relationships. An equation to calculate mean condition factors from weightâlength relationships is given as Kmean = 100aLbâ3. Relative weight Wrm = 100W/(amLbm) 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 weightâlength relationships for a given species. Twelve recommendations for proper use and presentation of weightâlength relationships, condition factors and relative weight are given
Fecundidade da manjuba Curimatella lepidura (CURIMATIDAE) na represa de TrĂȘs Marias, rio SĂŁo Francisco, MG
Reprodução da piranha-amarela Serrasalmus spilopleura Kner, 1858, em lagos de vårzea, Amazonas, Brasil
Responses of zooplankton and fish to restoration in eutrophic Lake TuusulanjÀrvi in southern Finland
Length-weight and length-length relationships of some small indigenous fish species from the Mathabhanga River, southwestern Bangladesh
Reproductive biology of the East African lungfish (Protopterus aethiopicus) in Mwanza Gulf, Lake Victoria
Breeding and larval rearing of threatened, endemic fish stonesucker, Garra ceylonensis (Bleeker)
The annual cycle of intraovarian egg size and fecundity of the barbel Barbus barbus in the River Severn
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