The Growth of Brown Trout (Salmo Trutta Linn.)

Abstract

1. Groups of trout fry of the same parentage were grown in environments where the following factors were controlled: temperature, amount and intensity of illumination, rate of water flow, aeration and chemical composition of the water, amount of living space and quality of food supply. They were allowed to eat as much as they would, and individual weights were recorded during the first 8 months after the beginning of feeding. 2. There was soon an increase in the range of individual weight in each group of fry, and thereafter the larger fry grew faster than smaller ones. When the larger fry were removed, the smaller ones grew at an increased specific rate, and when larger fry were added, the smaller ones grew more slowly. It is suggested that a ‘size hierarchy’ was established within each group, and an individual's specific growth rate depended on its position in the order of decreasing weight. 3. There was an optimum degree of crowding for maximum productivity. Compared with the fry in this group, the specific growth rates of individuals in larger, more crowded groups depended on the number of fish of larger size, while in smaller, less crowded groups, individuals grew at rates depending on the proportion of fish which were larger and smaller. 4. Alevin weight had little effect on the specific growth rates of fry. 5. There were differences between the growth histories of fry derived from alevins of the same weight and descended from the same father but different mothers (all of the same stock, age and size). 6. The specific growth rates decreased as the fry grew older, but there was no correlation between body weight and specific growth rate, except for the size hierarchy effect within each group. This effect had a greater influence on the size of individual fry than had either alevin weight or heredity.

Determination of the growth performance and reproductive season of wild Channa lucius (Cuvier, 1831) populations of genus Channa (Channidae, Perciformes) in the Mekong Delta, Vietnam

“…The CF value is often used in length‐weight relationships to assess the effects of conditions such as environment, food supply and infection degree. In addition, the seasonal change in fish is determined by the combination of condition factors (Brown, 1946). In the present study, the CF value was used to investigate environmental impacts in relation to the gonad cycles.…”

Sex-dependent growth regulation in monogamous pairs of a cichlid fish

“…In fishes with size hierarchies, growth regulation of subordinates typically occurs via the use of aggression by the dominants (Brown, 1946;Koebele, 1985;Allen, 1972;Ochi, 1986;Hattori, 1991;Booth, 1995) or interception of food resources (Magnusson, 1962;Coates, 1980;Forrester, 1991). In J. transcriptus pairs, the dominance index of larger individuals in pairs was usually higher than that of their partner, indicating that larger individuals were dominant in both pair types.…”

The Effect of Raceway Grading on Return to Creel for Catchable‐Sized Hatchery Rainbow Trout

“…Indeed, grading effectively decreased the variation in size and increased the mean size of hatchery Yellow Perch Perca flavescens (Wallat et al. ), and it also increased the growth of hatchery Brown Trout Salmo trutta (Brown ) and Atlantic Salmon S. salar (Gunnes ). However, other studies have found grading to have no growth benefit for Arctic Char Salvelinus alpinus (Wallace and Kolbeinshavn ) or for Brown Trout, Brook Trout Salvelinus fontinalis , and Rainbow Trout Oncorhynchus mykiss (Pyle ).…”

“…Size grading is one method that could be used to select for larger fish from a given rearing unit. Literature on fish grading and its effect on hatchery rearing date back to the mid‐1900s (e.g., Brown ; Mullan ; Pyle ), and grading practices continue to be used as a tool for rearing hatchery trout by some state agencies (Mark Clifford, State of California Department of Fish and Game, personal communication; Kris Urquhart, Nevada Division of Wildlife, personal communication). Hatcheries grade fish to achieve a uniform size, to reduce cannibalism in certain species, and to increase the accuracy of weight estimates by reducing size variation during sample counts.…”