This is the introduction including citations to the study I am currently working on, I will post the whole paper when I am finished with it. I am convinced the the main reason that most (normally Large) fish kept in aquariums or in small aquariums do not obtain their maximum size or out grow the small tanks is the way their fed. I was approached at an LFS with a question about why Oscars kept in a 55 gallon tank only reached about 4 inches long after 3 years. When I asked what they were being fed, I was told flake food. The question then becomes: Are Large fish (ie, Oscars, comets, ect.) kept in small aquariums fed like small aquarium fish (ie: swordtails, mollies, bettas, ect.) which does not allow for the nutritional resources for proper growth?
Bluegills are important components of freshwater communities and are numerically dominant in many freshwater lakes throughout North America (Aday et al, 2002). Bluegill populations exhibit complex social structures and the life histories of individuals can be shaped by social interactions within the population showed that the presence of large mature males delayed the maturation of immature males (Aday et. al, 2003). The tremendous reproductive ability of bluegills can cause problems for the fish pond owner. Bluegills often produce more young than the pond can support. When this happens, bluegill growth is very poor and few fish reach sizes desired by the pond owner.
The rate of growth in a bluegill depends on the amount of food it eats. According to the Indiana Department of Natural Resources, slow growing bluegill populations are the most severe problem in Indiana fish ponds (INDNR). This slow growth is commonly referred to as stunting. Stunting is a common phenomenon in fish populations and can be the result of a variety of mechanisms. Stunted populations are defined as occurring when only a few of the fish present in the pond have been able to obtain a legal size (Swingle & Smith, 1942).Fish growth is often controlled by environmental conditions such as food and space (Murnyak et al, 1984). There are various degrees of stunting; the principle causes of such a condition are as follows: (1) overstocking, (2) absence of sufficient carnivorous fish, and (3) heavy weed growth in ponds (Swingle & Smith, 1942).
In determining whether or not a population is stunted, population estimates that are derived from direct counts, from catch statistics, from marking-and-recapture techniques, and by various combinations of these methods (Koster, 1955); must be done to ensure that the population is viable and the sample is representative of the whole population and not young of the year. The preferred method in small ponds seems to be the marking-and-recapture technique, where a certain amount of fish are caught, tagged, and then released back into the pond. The researcher then waits a given amount of time (depends on the research) and goes back to the pond to recapture fish, all fish not just the fish with the tags. The number of fish is counted and wrote down; the number of tagged fish is counted and wrote down. It is then calculated as follows:
Total population = total size of 2nd sample X marked # in 1st catch
marked # recaptured in 2nd catch
The total population will also held to figure the extent of schooling, and the composition of the schools as regards to sex, size, age of the individuals, and the inclusion of other species (Koster, 1955). Many factors influence the demography of natural populations, making the detection of causal factors very difficult (Vanni, 1986). In the case of fish populations, researchers have used comparative studies to attribute this variability to environmental and geographic factors, such as latitude of water bodies, thermal regime, length of growing season, productivity of food availability, predation, and degree of environmental fluctuation (Fox, 1994).
Habitat use by bluegill often depends on prey availability and predator avoidance. The process of prey selection by visually foraging fish depends heavily on the visual capabilities of the predator, which affect its ability to detect and recognize potential prey (Kao et al, 1985). Food habits studies suggest that bluegills consume benthic and epiphytic macroinvertebrates and may also consume zooplankton when predation risk is limited and foraging efficiency is greater in open-water habitats (Paukert and Willis, 2002). Since bluegills capture prey individually and swallow them intact, the size and type of prey consumed by a foraging fish are easily determined from gut contents (Mittelbach, 1981). Analysis of stomach contents of bluegills from stunted populations reveal that starving individuals will eat fish eggs of both their own and other species (Swingle and Smith, 1942).
Numerous studies have been made of bluegill age and growth based on the scale method (Reiger, 1962). Many species of fish lay down concentric annual growth rings, or annuli, in bony structures and scales. When a fish is captured, its age can be determined by counting the annuli; information can be obtained by measuring the distance between annuli, which is thought to vary with more interesting physical characteristics such as length (Weisberg, 1986). Gerking (1954) figured out that the length of individual fish at each annulus can be calculated as follows:
Fork Length of fish at time = 20 + (scale radius at year x) (fork length 20)
of annulus formation total scale radius
Bony fish have three pairs of ear stones, or otoliths, that record age and other important events in their lives. The sagitta is usually the largest otolith and is the one that is studied most often, but the lapillus and asteriscus can also be informative (Bell, 2001). Otoliths of larval and juvenile fish provide a record of age, size, growth, and development (Fey et al, 2005). Seasonal variation in growth rate results in annual patterns, or annuli, in otoliths, because the thickness of daily increments is related to body growth (Bell, 2001). In a 2005 study by the South Dakota Department of Wildlife and Fisheries Sciences, it was found that bluegill age estimates for scales were less precise than those for otoliths (Edwards et al, 2005) which confirmed a 2001 study in Illinois (Hoxmeier et al, 2001). All ages for each species must be validated (Beamish & McFarlane, 1983) due to the inconsistencies in the annuli. Validating a method of age determination is as important in fisheries biology as standardizing solutions or calibrating instruments are in other sciences (Beamish & McFarlane, 1983). Validation of the scale method is as easy as using the otolith method and comparing the two.
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Yes, I find the MILF comment about you offensive as well. And you're right people should do some research in books and online before making claims.
